This contribution will focus on the conversion of CO2 to carbon-based fuels and chemicals, with a focus on electrified processes. As atmospheric concentrations of carbon dioxide (CO2) continue to rise, innovative approaches are needed to develop technologies capable of producing fuels and chemicals in a renewable, sustainable manner. This talk will describe efforts involving electrocatalytic approaches, with several points of emphasis: (1) tandem/cascade approaches to improve selectivity, (2) operando approaches to understand the dynamics of materials and interfaces in real-time, and (3) a focus on durability to understand mechanisms of degradation that can ultimately inform the design and development of more stable systems. This talk will cover fundamental studies on model surfaces and extend insights from those systems toward more applied technological platforms.

The extensive use of fossil fuels has significantly raised atmospheric CO₂ levels, leading to serious environmental concerns. Direct electroreduction of captured CO₂ (CO₂ER) into value added chemicals and fuels using renewable electricity is raising great interest as a way to mitigate CO₂ emissions.

Copper (Cu) is one of the most promising electrocatalytsts for converting CO₂ to value-added multicarbon (C₂₊) chemicals and fuels. However, CO₂ER technology is facing various scientific challenges mainly related to (a) the lack of selectivity of cathode Cu electrocatalysts and (b) the lack of in-depth studies in electrolyzers at high current density (i.e. high reaction rates). In this work, we demonstrate that dilute alloys – an underexplored class of electrocatalytic materials – can be tuned to control the selectivity toward C₂₊ products in zero-gap electrolyzers.

Dilute alloys employ trace amounts of a secondary metal (like Pd, Ag) in a primary metal matrix (like Cu or Au), resulting in localized strain and electronic effects that improve selectivity toward C₂₊ products and optimize intermediate binding energies (1).

Preparation methods are crucial in dilute alloys as they dictate the surface composition of as-prepared alloys which can directly influence their catalytic performance (2). Yet the influence of preparation methods on dilute alloys for CO₂ electroreduction is underexplored and underexploited.

In this work, PdCu dilute alloys were prepared via two different wet-chemical methods, namely co-reduction and sequential reduction. In the co-reduction method, Cu and Pd precursors are introduced and reduced simultaneously to obtain PdCu dilute alloy nanoparticles. In the sequential reduction method, Cu nanoparticles are prepared first, and Pd is added via galvanic replacement. A narrow size distribution of ca 4 nm was obtained and the Pd composition was varied and controlled at 2, 4, and 6 at.% for both methods. The dilute alloys were characterized using a combination of techniques such as HR-TEM, XPS, and in situ IR to elucidate the structure of the as-prepared catalysts.

Electrocatalytic tests were carried in zero-gap electrolyzers at high current density (>100 mA cm²). An important finding is that the selectivity for C₂₊ products and notably ethylene is highest for PdCu with 4 at.% Pd. Investigation of the effect of the preparation method and composition on the catalytic activity and selectivity of CuPd dilute alloys will be discussed in details.

This study aims at elucidating the effect of preparation methods on the synergetic effect of Cu-based dilute alloys for CO₂ electroreduction.

The electrochemical reduction of CO₂ (CO₂RR) into ethylene represents a crucial strategy for carbon utilization and integration with renewable energy sources, offering a pathway toward carbon neutrality. Current limitations, primarily sluggish kinetics and mass transport constraints, necessitate the design of advanced hybrid catalyst architectures.

A multifunctional hybrid catalyst system integrating graphene oxide–modified metal–organic frameworks (MOFs, HKUST-1) with CeO₂-promoted Cu₂O oxides was developed to address these challenges. The parent Cu₂O–CeO₂ catalyst demonstrated efficient C–C coupling with ethylene faradaic efficiencies approaching 73% under optimized hydrophobic and gas flow conditions. Incorporating the MOFs establishes a synergistic interface where the high porosity and tunable surface chemistry of the MOF facilitates the local CO₂ enrichment, enhancing reactant availability and selectivity. The hybrid system achieved ethylene faradaic efficiencies of up to ≈75%, alongside a notable reduction in hydrogen evolution.

Two electrode configurations—bilayer and mixed—were examined to understand how catalyst architecture influences CO₂ accessibility and interfacial contact. The bilayer design improved CO₂ adsorption and diffusion through the MOF layer, while the mixed configuration provided superior interfacial connectivity and simultaneous CO₂ activation, resulting in more balanced product distribution. Evaluation in 0.5 M KHCO₃ electrolyte further offered insights into CO₂ transport and catalyst behavior under near-neutral, scalable conditions.

The electrochemical CO₂ reduction reaction (CO₂RR) is one of the chemists’ tools for contributing to environmental remediation through low-impact methods. Its complexity relies on the stability of the CO₂ molecule and the multiple potential products derived from this reaction [1]. There is a necessity to develop new CO₂RR electrocatalysts due to the lack of selectivity of the current solutions. Recently, the potential of Cu-nitrogen-doped carbon composites has been demonstrated to be effective for the selective conversion of CO₂ [2]. Similarly, our research group has been able to demonstrate that the addition of a second heteroatom (P), contributes to improving the efficiency of these nanocomposites for obtaining C₂₊ compounds, especially ethylene [3]. However, little changes in the synthetic procedure showed us unexpected behaviours, allowing us to modulate the electrocatalyst activity from a hydrogen evolution predominance to the obtention of more than 50% C₂₊ products passing through catalysts capable of transforming CO₂ into methane with an efficiency of around 30%.

This contribution approaches the preparation of N, P-doped carbon-Cu nanocomposites by solvothermal characterization and its optimization for the obtainment of ethylene. During this process, it was possible to observe that slight variations in synthesis parameters led to remarkable differences in electrocatalytic activity. In order to find a justification for this change in behaviour, a complete physicochemical characterization was carried out to gain a deeper understanding of the environment and transformations of catalytic centers before, during, and after the electrochemical reaction. STEM studies revealed a change in the dispersion of metal when the heteroatom presence or the pyrolytic treatment is modified. In situ XAS experiments demonstrated a change in the oxidation state under catalytic conditions, a modification that only occurs for the catalysts with the presence of P in their structure. Thus, it is fair to affirm that this synthetic procedure allows us to control the selectivity of CO₂RR through the fitting of these little changes.

Accurate activity normalization remains a central challenge in electrocatalysis. Current densities are routinely reported per unit surface area. However, this requires a clear distinction between the real surface area (RSA) and the electrochemically active surface area (ECSA). Furthermore, uncertainties in these area determinations propagate directly into the reported current densities, restricting fair comparisons of electrocatalytic activity across studies.

In this contribution, we examine the structure of real electrode surfaces and argue which surface regions should be counted as part of the RSA and which subset contributes to the ECSA. We provide measurement protocols to probe the electrode surface using double-layer capacitance and adsorption-limited faradaic reactions. We show that representative reference values per unit area are required to convert these measurements into quantitative surface areas. Depending on how they are applied, these reference values yield estimates of either RSA or ECSA. As the reference values are condition-dependent, we outline how to construct them to enable consistent and rational current normalization.

Finally, we outline best practices and protocols for current normalization that support rigorous comparison of emerging electrocatalytic transformations central to sustainable fuels and chemicals.

The separate electrolysis of CO₂ and nitrate and their co-electrolysis to produce urea are environmentally and industrially promising processes yet to be optimized. Indeed, the large number of electron transfers and bonds broken and made in every catalytic cycle render them visibly inefficient.

In this talk, I will first discuss some common pitfalls in the DFT-based modelling of these reactions and how to overcome them [1-3]. Moreover, I will expose the systematicity of cation effects on a wide variety of C₁ species adsorbed on numerous metal electrodes and illustrate their combined effect on CO₂ reduction [4]. Finally, I will show how Cu-O-I surface ensembles catalyze the electrocatalytic dimerization of acetylene to produce 1,3-butadiene [5].

References

[1] Urrego-Ortiz, Builes, Calle-Vallejo. ACS Catal. 2022, 12, 4784-4791.

[2] Urrego-Ortiz, Builes, Illas, Bromley, Figueiredo, Calle-Vallejo. Commun. Chem. 2023, 6, 196.

[3] Urrego-Ortiz, Builes, Illas, Calle-Vallejo. EES Catal. 2024, 2, 157-179.

[4] Sargeant, Rodriguez, Calle-Vallejo. ACS Catal. 2024, 14, 8814-8822.

[5] Teh, Romeo, Xi, Rowley, Illas, Calle-Vallejo, Yeo. Nat. Catal. 2024, 7, 1382-1393.

Electrochemical CO₂ reduction (CO₂R) offers a path to mitigate global greenhouse emissions by converting atmospheric and waste CO₂ into widely used chemicals such as syngas, formic acid, methane, ethanol, and ethylene, among others, using renewable and low carbon electricity. However, CO₂ electrolysis continues to be limited by key challenges, including the formation of unwanted carbonates under alkaline conditions and relatively low selective efficiency throw multi-carbon. In our work, a tandem CO₂ electrolyser was engineered for acetate production. This integrated system shows improved potential in both efficiency and selectivity, using a bicarbonate solution to in situ generate CO₂ which is then converted into highly selective carbon monoxide (CO) with high faradaic efficiency (>90%) and a cell potential of around 3 V. The resulting CO stream is coupled to a second step that produces and concentrates acetate. Acetate partial current density above 120 mA/cm² and cell potential below 3 V were achieved. Finally, we discuss an integration of an efficient route for converting CO₂ into biodegradable plastics (PHA) by engineering upgrading pathways in microbial systems.

The traditional chemical industry relies on thermal catalytic processes, using fossil fuels as both raw materials and energy sources, to produce valuable chemicals. However, there's a growing interest in electrochemical conversion of waste CO2 using renewable energy.1 This shift is driven by two key factors: first, the rapidly decreasing cost of renewable energy suggests that electrochemical processes will soon become commercially viable.2 This economic advantage is further enhanced by using freely available CO2 as a raw material, contrasting with the energy-intensive and polluting extraction of fossil fuels. Second, achieving carbon neutrality in large-scale chemical processes is crucial for meeting climate goals by 2050.3 Electrocatalytic CO2 conversion offers a promising strategy to efficiently transform CO2 into valuable products, characterized by high activity, stability, and selectivity. Especially, the fixation of CO2 via electrochemical carboxylation is a green and promising approach in the synthesis of a variety of organic compounds especially carboxylic acid derivatives.4

This electrocarboxylation processes are of high scientific and commercial interest as only one or two electrons is required per CO2 molecule. However, electrochemical carboxylation processes are currently limited by some serious drawbacks that hinder the development of these technologies towards industrial scale deployment.4 One of the main drawbacks is the use of sacrificial anodes, which necessitate batch mode operation with periodic complex and labour intensive anode replacement procedures.5 In this context, here we demonstrate the electrochemical dicarboxylation of 1,3-butadiene with CO2 for the production of  3-hexenedioic acid (3-HDA), a key precursor for adipic acid. The current industrial synthesis of adipic acid relies heavily on nitric acid oxidation of cyclohexanol or cyclohexanone, generating significant nitrous oxide emissions, a potent greenhouse gas.6 Our approach offers a potentially greener alternative by integrating carbon fixation with C–C bond formation, eliminating the need for harsh oxidants and operating under milder conditions. The electrochemical carboxylation is carried out using nickel (Ni) cathode and by replacing typical aluminium (Al, sacrificial anode) with platinum (Pt, non-sacrificial anode) in the presence of organic electrolyte acetonitrile (ACN). We study how operating parameters such as applied potential, electrode materials, and supporting electrolyte and substrate concentration affect the overall process and the reaction product distribution. 

Beyond the synthesis of 3-hexenedioic acid, this methodology serves as a platform for the broader application of electrochemical carboxylation strategies to other conjugated dienes and unsaturated hydrocarbons.

Urea sits at the intersection of food security and hard-to-abate chemistry. Produced at the megaton scale via fossil-fed Haber–Bosch and the Bosch–Meiser processes, its manufacture is tightly coupled to CO₂ emissions and centralized infrastructure. Against this backdrop, Electrochemical Urea Synthesis (EUS) has been proposed as a way to electrify both carbon and nitrogen management. The basic concept goes way back: in 1995 Shibata and co-workers reported urea formation from the coreduction of CO₂ and nitrate/nitrite on Cu-based gas diffusion electrodes¹, but only in the last few years the topic has grown into a fast-expanding research field.

The resulting literature, however, rests on a fragile foundation, flanked by urea detection and quantification issues^2–4. In a recent Viewpoint⁵, we argued that EUS lies at the crossroad between two problematic areas: CO₂ reduction tested in batch H-cells at low current density, and nitrogen electrochemistry hampered by false positives and weak analytical practice. Widely used urea quantification protocols—urease/indophenol blue, DAMO–TSC colorimetry, and ¹H NMR—are each prone to specific artefacts, from nitrite interference to time-dependent color evolution and detection limits misaligned with realistic production rates. At the same time, many EUS studies employ non-scalable cell designs and weakly buffered electrolytes, where pH drift and mass-transport limitations decouple reported metrics from any industrially relevant scenario.

Our own work on EUS began in October 2022, when experiments deliberately inspired by Shibata’s conditions appeared to indicate promising urea formation on copper. This observation triggered a systematic effort to understand whether we were truly synthesizing urea, or simply probing the limits of our analytical tools. Building on our initial “UREAlity Check”⁵, we developed an HPLC/UV–vis method to separate and quantify urea in typical EUS electrolytes, and re-examined modified DAMO–TSC protocols with nitrite suppression⁶. Together, these tools improved sensitivity while exposing how easily common procedures can misreport urea in complex matrices.

With this toolbox in place, we revisited CO₂ + NO₃^- coreduction on polycrystalline Cu—the first EUS-active catalyst ever reported—in both H-cells and a three-compartment flow cell, using near-neutral KHCO₃ + KNO₃ electrolytes. Extensive chronopotentiometry across relevant current densities and potential windows yielded rich product distributions in CO₂ reduction and nitrate reduction, but no HPLC-detectable urea. Only trace signals appeared in modified colorimetric assays, at levels incompatible with the high Faradaic efficiencies reported in the 1990s.

This experience also reshaped our perspective on where the field should go next. It is now evident that improving analytics, while necessary, is not sufficient. Cell and process engineering—gas-fed architectures, membrane and electrolyte choice, pH management and buffering, current density, and single-pass conversion—are as central to the credibility of an EUS claim as the catalyst itself. At the same time, emerging oxidative EUS routes, in which urea is formed by coupling CO with NH₃ at the anode rather than by co-reducing CO₂ and nitrate at the cathode, remind us that EUS spans distinct chemistries and device concepts.

In this contribution, I will place urea synthesis in its historical and industrial context, discuss the availability and sustainability of carbon and nitrogen feedstock, and examine how cell configuration and electrolyte engineering govern both performance and data reliability. I will then draw on our own results to outline practical guidelines for rigorous urea detection and for benchmarking both reductive and oxidative EUS pathways when assessing their prospects as viable technologies.

Electrosynthesis is emerging as a powerful strategy for building C–N bonds using renewable electricity in place of stoichiometric oxidants, reductants, or hazardous reagents. Yet the central challenge in electrifying multi-step organic transformations lies in achieving selective control over reactive intermediates that form and evolve at the electrode interface. Operando infrared (IR) spectroscopy has become a key tool in addressing this challenge. By probing vibrational fingerprints directly during electrochemical operation, IR spectroscopy reveals transient species, parallel pathways, and competing reactions that dictate the efficiency and selectivity of C–N bond-forming electrosynthesis. Across various systems—including alcohol-to-amine conversion, reductive amination, and N-formylation—operando IR studies have provided mechanistic clarity that cannot be obtained from electrochemical data alone.

In electrocatalytic oxidation of alcohols followed by reductive amination, operando IR monitoring enables direct observation of aldehyde formation during the oxidation of benzyl alcohol on nickel oxyhydroxide surfaces. The appearance of the C=O stretching mode of benzaldehyde under controlled potentials allows the reaction sequence to be mapped in real time, capturing the transition from alcohol to aldehyde before further oxidation can occur. IR spectra also help distinguish selective aldehyde formation from overoxidation to carboxylates, which display characteristic carboxylate stretching bands. This information guides the optimization of catalyst loading, potential windows, and electrolyte conditions to maximize aldehyde selectivity. During the subsequent reductive amination step, IR detection of imine-related vibrations confirms formation of the aldimine intermediate and its potential-dependent conversion to the amine product. These spectroscopic signatures connect anodic and cathodic steps, illustrating how paired electrolysis can be tuned for efficient alcohol-to-amine conversion.

IR spectroscopy also plays a decisive role in elucidating mechanistic complexity during the electrochemical N-formylation of amines using methanol as both solvent and carbon source. In these systems, methanol oxidation first produces formaldehyde, which forms a hemiaminal upon reaction with an amine. Operando IR spectra reveal not only the expected aldehyde and hemiaminal features, but also additional bands corresponding to highly reactive intermediates. Detailed comparison of potential-resolved spectra has shown that these features are consistent with the formation of an isocyanide species—an intermediate typically associated with harsh dehydration chemistry. Confirmatory experiments demonstrate that this reactive intermediate can be generated and consumed entirely within the controlled electrochemical environment. Thus, IR spectroscopy establishes the existence of dual mechanistic pathways: direct oxidation of the hemiaminal to the formamide, and an isocyanide-mediated sequence that ultimately converges to the same product. Such mechanistic branching would remain hidden without real-time spectroscopic observation.

More broadly, operando IR spectroscopy provides mechanistic insight that shapes the design principles of sustainable C–N bond formation. It enables differentiation between surface-mediated and solution-phase reactions, helps identify the onset of undesired side processes such as hydrogen evolution or overoxidation, and reveals how pH, electrode material, and applied potential shift intermediate lifetimes and reaction equilibria. By correlating IR signals with faradaic efficiencies and product distributions, reaction conditions can be rationally optimized for selectivity.

Together, these studies show that operando IR spectroscopy is not merely a diagnostic tool but a foundational technique for advancing green electrosynthesis. By illuminating the molecular choreography of intermediates at electrified interfaces, IR spectroscopy enables the development of efficient, selective, and sustainable routes to amines, formamides, and other nitrogen-containing products via C–N bond formation.

I will discuss recent work in our group at DTU. The core of our approach lies in the strategic use of computational descriptors, derived primarily from Density Functional Theory (DFT), to establish robust structure-activity relationships. These descriptors, often related to the binding energies of key intermediates, transform the daunting task of catalyst screening into an efficient, rational, and predictive process.

A major challenge in electrocatalysis is the issue of selectivity. For many beneficial reduction reactions—such as the electrochemical reduction of carbon dioxide CO2RR to fuels and chemicals, or the nitrogen reduction reaction N2RR for sustainable ammonia production—the desired transformation faces direct, thermodynamic competition from the ubiquitous Hydrogen Evolution Reaction (HER). This competition is universally governed by the binding strength of the *H intermediate. A mirror challenge exists in selective oxidation reactions, where the desired transformation may share a common *O intermediate and must outcompete the parasitic Oxygen Evolution Reaction (OER). I will try to discuss both reduction & oxidation reactions, showing similarities and differences.

Finally, I will address the methodological framework for tackling complex, multiple-electron, and multiple-step reactions. We distinguish between scenarios where a robust, data-driven approach can be applied and situations where a chemical intuition approach is necessary. By learning when to rely on scalable data and when to deploy detailed chemical insight, we can guide the future of electrocatalyst design.

Excess greenhouse gas emissions and accelerating global warming pose an escalating risk to society. Among emerging mitigation pathways, electrocatalytic CO₂ reduction (CO₂RR) is widely viewed as a promising option for converting CO₂ into value-added chemicals and fuels. Realising this promise, however, depends critically on the rational selection and optimisation of the anodic reaction, which governs both the overall energy efficiency and the economic viability of the electrolyser. The oxygen evolution reaction (OER) is most often paired with CO₂RR at the anode, yet its high thermodynamic onset (≈1.23 V vs SHE) and sluggish kinetics make it energetically costly; in typical cells, OER can consume >90% of the electrical input while producing no salable co-product.

As an alternative, ethylene glycol (EG)—obtained by hydrolysing poly(ethylene terephthalate) (PET)—has gained attention as an anodic feedstock. PET is ubiquitous in packaging and textiles, with global consumption of ~28.45 Mt per year and a recycling rate of only ~23%, underscoring the need for more sustainable end-of-life routes [1]. Conventional mechanical recycling is energy-intensive and tends to downgrade material quality, whereas hydrolysis depolymerises PET back to monomers suitable for true recycling and even upcycling [2]. Coupling CO₂RR with EG oxidation (EGOR) offers a pathway to lower cell voltages while creating value on both electrodes [3]. Nevertheless, the literature on integrated CO₂RR + EGOR systems still faces key hurdles, including insufficient current densities and limited operational stability, highlighting the need for better anode/cathode interface engineering, transport management, and durability strategies.

We present a single, integrated electrolyser that co-processes hydrolysed PET and CO₂ to co-produce formate at ampere-scale rates. The anode employs a three-dimensional nickel-foam architecture to oxidise ethylene glycol (EG) obtained from PET hydrolysis [4]. By prioritizing mass transport and interfacial engineering rather than catalyst discovery alone, this anode delivers formate formation at 1.2 A·cm⁻²—to our knowledge, among the highest reported for non-noble metal systems. On the cathode, a Bi₂O₂CO₃-based gas-diffusion electrode (GDE) enables selective CO₂ electroreduction to formate, completing a closed-carbon valorisation loop within a single device.

The integrated design sustains 100 h of continuous operation at 0.50 A·cm⁻², maintaining Faradaic efficiencies of 93.7% at the anode (EG oxidation to formate) and 86.0% at the cathode (CO₂-to-formate). Operating membrane-free, the cell achieves a 2.91 V full-cell voltage at 1.0 A·cm⁻², corresponding to an energy input of ~0.10 kWh·mol⁻¹, a ~65% reduction relative to conventional benchmarks. These outcomes arise from deliberate electrode structuring—high-surface-area current collectors, controlled wettability, and optimised gas–liquid pathways—that collectively minimise concentration polarisation and ohmic losses.

Beyond demonstrating a practical route for simultaneous PET upcycling and CO₂ utilisation, this work clarifies design rules for integrated electrolysers: (i) choosing anodic reactions that generate value while lowering overall cell energy; (ii) engineering transport-centric electrodes to sustain high current densities; and (iii) leveraging cathode GDEs that stabilise key intermediates for selective CO₂-to-formate conversion. The platform provides a blueprint for coupling waste-derived organics with CO₂ electroreduction to manufacture commodity chemicals efficiently, offering a scalable pathway toward circular-carbon manufacturing.

Electrochemical conversions offer an alternative path towards producing chemicals and fuels while using renewable energy. Emerging electrochemical reactions are gaining interest due to their potential to produce complex molecules and small-scale on-site feedstocks. Many of these reactions occur in near-neutral pH conditions due to the intrinsic nature of the reactants and feedstocks, or to avoid unwanted competing reactions such as hydrogen evolution. Furthermore, the acidification or alkalization of feedstocks may incur higher balance of plant costs, corrosion issues or destabilization of the electrocatalysts and formed liquid products¹. Thus, operating under near-neutral pHs can be desired and even sometimes a restriction of the system. However, we hypothesize that near-neutral pH conditions will lead to inherent and non-negligible voltage penalties, decreasing the energy efficiency and economic viability of the process. 

Here we use the simplest case of water electrolysis to demonstrate how current-dependent pH conditions at the surface of electrodes in near-neutral pH systems results in ~1 V cell voltage increases from a reaction’s thermodynamic potential. In aqueous electrochemical reactions, the consumption or generation of H⁺ and OH^-, results in considerable pH swings at the electrodes^2,3. While these effects are neglected in extreme pH scenarios, under near-neutral pH conditions these local concentration gradients give rise to Nernstian shifts of 0.5-1 V when current densities increase beyond ~50 mA cm^-2. Elaborating on this knowledge, we show how and why the cell voltages of semi-mature electrochemical reactions, such as CO₂ or NO₃^- reduction, are limited to much higher minimum thermodynamic potentials than expected. Lastly, we extend this knowledge to emerging electrochemical reactions which also utilize near-neutral pH conditions, and provide specific scenarios to avoid substantial Nernstian penalties. 

Lignocellulose, the non-edible part of biomass, is considered an attractive source of renewable carbon.[1] Its breakdown can produce a range of platform compounds, including furfural. Two of the main valorization products of furfural are furfuryl alcohol (FOH; a binder for the foundry industry) and, to a smaller extent, 2-methylfuran (2MF), which has been proposed as a drop-in biofuel[2] and high-density biofuel precursor[3]. Electrocatalytic hydrogenation appears to be a promising synthesis route for 2MF owing to the direct use of (renewable) electricity, mild operating conditions (ambient temperature and pressure) and eased separation of the product thanks to a low solubility of 2MF in water. Through preliminary techno-economic analysis, we recently demonstrated the beneficial aspects of this approach compared to other decarbonization pathways.[4]

Still, there are challenges to this approach, including (i) achieving sufficient faradaic efficiency (FE) toward furfural conversion (vs the competing Hydrogen Evolution Reaction) and (ii) reaching high selectivity toward 2MF at high current densities. Recent notable studies managed to improve FE_2MF up to 75% at pH 2.9 and -0.58 V vs RHE through the use of a bimetallic CuPd catalyst while the use of a surfactant like butyltrimethylammonium bromide in a pH 1 electrolyte switched selectivity from S_FOH : 83.8% to S_2MF : 80.1% at 15 mA.cm^-2 on electrodeposited Cu on Cu foam.

To address these challenges, we investigated the performance of Cu₂O nanocubes as well-defined model pre-catalysts (Cu₂O-p) for the electrocatalytic hydrogenation of furfural toward 2MF. Well-dispersed particles with diameters of 62.5±39.2 nm were produced on the carbon support via immersion in an acidic electrolyte followed by a redeposition step. In light of a recent report, the morphology of the particles was monitored in situ by transmission electron microscopy (TEM) to help establish structure-activity relationships in our system.[5]

In various electrocatalytic systems, an effective strategy to steer the selectivity of a reaction is through electrolyte engineering.[6] From this perspective, we conducted an evaluation of the effects of cations (Li⁺, Na⁺, K⁺, Cs⁺) and anions (SO₄^2-, PO₄^3-) in acidic conditions (pH 2) using Cu₂O-p. At a fixed potential of -0.5 V vs RHE, in 0.5 M KH₂PO₄ (pH 2) and 40 mM furfural, a selectivity toward 2MF of 72.1±3.4% (FE_2MF: 82.3±3.3%) was measured as opposed to a lower selectivity of 54.8±4.5% in 0.5 M K₂SO₄ (FE_2MF: 65.1±5.4%). In addition to a favorable selectivity toward 2MF in phosphate, we found (i) a noticeable influence of cations on FE_2MF in sulfate and (ii) a limited influence of cations on selectivity in both electrolytes.

To examine the interplay between anions and the observed selectivity change, we utilized time-resolved in-situ surface-enhanced Raman spectroscopy (TR-SERS). In 0.5 M KH₂PO₄ + 40 mM furfural (pH 2) and at open-circuit potential (OCP), a stronger redshift of the adsorbed carbonyl bond was observed in comparison to the same experiment in sulfate. We associated this shift with a stronger interaction of phosphate anions with furfural through hydrogen bonding. Upon the application of cathodic potentials, a local increase in pH was linked to the proton donor behavior of phosphate. We posit those interactions allow for an enhanced cleavage rate of the C=O bond under operating conditions, resulting in selectivity toward 2MF comparable to state-of-the-art results.

Electrochemical reactions occur at specific potentials which are characteristic of the specific molecules involved in the redox processes. In this work I will explore the application of impedance spectroscopy to identify the states at which the charges accumulate in the  surface of the electrodes and how the charge transfer is activated in the the transformation of biomass derived organic molecules.[1] Electrochemical biomass transformation in the process to move from a fuel-based economy to a carbon neutral one, and also in the development of new and sustainble ways of storing excess green power generation by renewables. This work will be focussed in  studing reactions like nitrobenzene reduction and  hydroxymethyl furfural oxidation and reduction. and how they can be combined with hydrogen storage. [2-4] I will show how the analysis of  the capacitance may help to identify surface coverage, potentials of activation of the reaction and absorption processes occurring at the surface of the electrodes, while charge transfer provides information about the kinetics of the process. This information is key to understand the processes that limit the operation of our devices and for the optimization of their performance 

In the transition towards Net-Zero, there is significant interest in phasing out fossil fuels as both the energy source and precursor for petrochemicals. Biomass is recognised as an ideal CO₂ neutral, abundant and renewable resource substitute to fossil fuels. The rich proton content in most biomass-derived materials endows it to be an effective hydrogen carrier.¹ The inherent chemical structure allows them to be easily catalysed to produce valuable commodity chemicals that can be used in applications such as biodegradable polymers and pharmaceuticals. Although historically biomass has been regarded as a waste stream, recent years have seen increasing attention in valorising it into useful products.

In this talk, I present biomass electrolysis, specifically glycerol (the waste by-product from the bio-diesel industry), as an alternative route to produce hydrogen and value-added chemicals, lactic acid. The process resembles water electrolysis, with H2 produced on the cathode via the hydrogen evolution reaction. On the anode, however, instead of oxidising water, a combined electrochemical & chemical process takes place that transforms glycerol into lactic acid. Her,e I present the fundamental knowledge on how a multi-component tandem catalyst system Pt/C-Al2O3 can tune the selectivity towards lactic acid, acquired through advanced material characterisations and DFT calculations.^2,3 At the same time, details on catalyst requirements and recent advances for future strategic design of the processing system will be provided.

Looking beyond, an even more abundant and low-value waste stream than biomass is plastic. Finding a way to upcycle plastic derivatives has become imperative to help tackle this global challenge. Therefore, the last part of my talk will share our recent studies on PET (polyethylene terephthalate) derived ethylene glycol (EG) electrolysis to co-produce hydrogen and glycolic acid. Au-based nanoparticle electrocatalyst has been used to drive the reaction at Ampere-scale with > 85% glycolic acid selectivity, revealing its high potential in industrially relevant applications.

Electrocatalytic biomass conversion offers a sustainable and environmentally friendly approach to producing high-added-value products in a gentler, safer, and greener manner compared to traditional thermochemical or biochemical methods.

Key process in electrochemistry is water splitting, where the oxygen evolution reaction (OER) at the anode provides electrons and protons required for hydrogen generation (HER) at the cathode. However, the economic feasibility of OER is hindered by the low market value of oxygen and the high overpotentials involved. Therefore, there is a growing interest in identifying alternative anode reactions that reduce overpotentials and produce compounds with higher added value for the chemical industry. ^[1,2] In this context, biomass valorization emerges as an attractive substitute for water oxidation.^[3]

Our research group has focused on the electrochemical oxidation of 5-hydroxymethylfurfural (HMF), a biomass-derived molecule, as an alternative reaction to OER. Using nickel electrodes, we successfully oxidized HMF to produce 2,5-furandicarboxylic acid (FDCA),^[4] a valuable building block for pharmaceuticals and polymers.^[5]

Additionally, we explored the electroreduction of HMF, obtaining 2,5-bis-hydroxymethylfuran (BHMF) as the primary product.^[6] BHMF is an essential precursor for polyurethane foams and polyesters. This reduction process was performed using copper and silver electrodes, with superior performance observed when combining the two metals, such as copper foil decorated with silver.

In summary, we have developed processes for both the electrooxidation and electroreduction of HMF in aqueous media under mild, ecological, and safe conditions, yielding value-added products in each case.  

Electrochemical oxidation of biomass-derived furfural (FF) into value-added furoic acid (FA) offers a sustainable and efficient strategy to replace the kinetically sluggish oxygen evolution reaction (OER) at the anode. Herein, we report the in-situ fabrication of nickel-iron layered double hydroxide (NiFe-LDH) catalysts directly grown on carbon cloth, systematically optimizing their electrocatalytic performance. Additional optimization of the Ni:Fe ratio further enhanced the electrocatalytic activity and selectivity for the furfural oxidation reaction (FOR), significantly surpassing those of fluoride-assisted NiFe-LDH and similarly synthesized NiCo-LDH. The optimized NF-0F catalyst achieved exceptional electrocatalytic activity towards FOR, exhibiting a notably low onset potential of 1.39 V vs. RHE. In contrast, the competing OER had a higher onset potential of 1.52 V vs. RHE, highlighting FF oxidation as a substantially more energy-efficient anodic pathway. Detailed mechanistic investigations using in situ Raman spectroscopy revealed an electrochemical-chemical (EC) coupling mechanism through the structural dynamic transformation of catalysts.  Electrochemical impedance spectroscopy coupled with Distribution of Relaxation Time (EIS-DRT) analysis provided quantitative insights into distinct reaction kinetics, clearly demonstrating significantly faster electron transfer and catalytic turnover for FOR compared to OER. This study presents scalable and fluoride-free electrocatalysts, offering a comprehensive mechanistic understanding of biomass-derived substrate oxidation. Such insights pave the way toward integrated and sustainable electrochemical systems that combine biomass valorization and efficient hydrogen production.

Using waste streams as feedstocks for chemical manufacturing creates opportunities for both sustainability and economic resilience. Rather than viewing CO₂ and nitrogen-containing wastes as environmental burdens, they can be transformed into abundant, low-cost raw materials for producing fuels, fertilizers, and other value-added chemicals. This strategy reduces dependence on fossil resources, lowers lifecycle emissions, and strengthens circularity in the chemical sector.

In this talk, we will examine approaches for recycling waste carbon (CO₂) and waste nitrogen (both organic and inorganic) through electrochemical refining. We will focus first on how to use reactor engineering to generate high-volume and energy-efficient syngas from carbon capture feed solutions[1]. We will discuss reactor and system-based design principles, as well as how catalyst engineering at both the anode and cathode can improve system viability. We will also review the economics of integrating carbon capture with electrochemical conversion.

Beyond carbon utilization, we will explore opportunities to convert waste nitrogen into fertilizers[2]. Wastewater treatment plants generate substantial amounts of sewage sludge, much of it stabilized through anaerobic digestion and enriched in organic nitrogen. We will discuss how electrolysis can break down this complex organic matter to produce high-value products such as ammonia and volatile fatty acids.

The electrochemical production of ammonia from dinitrogen and urea from waste CO₂ and nitrate, driven by renewable energy, provides a unique opportunity to both store renewable energy in chemical bonds and produce carbon-neutral artificial fertilizers. Dinitrogen can be electrochemically reduced with lithium as a mediator (Li-NRR) in non-aqueous electrolytes, whereas urea can be produced from CO₂ and nitrate co-reduction.

In this talk, I will first discuss the relationship between the applied potential and Li-NRR performance indicators, such as the FE_NH3, R_NH3 and reaction stability. We identify three potential regimes, where the current response up to -3.2 V vs SHE is the most stable, but at the cost of a relatively low performance. At more negative potentials Li-NRR performance increases, but beyond -4.0 V vs SHE, breakdown of the current response is observed. A strong positive correlation is observed between the FE_NH3 and the LiF concentration, which increases at more negative applied potentials. Thicker and denser SEI morphologies are also beneficial for the FE_NH3, while they can be responsible for the observed current instabilities beyond -4.0 V vs SHE. These findings improve the current understanding of the SEI formation process and sheds light on a new optimization strategy for Li-NRR systems, which contribute to the development of a sustainable ammonia production process.

Second, I will discuss the design of detailed process models for the electrochemical production of NH₃ [1]. These models are used to gain insights into the main bottlenecks of the process and to understand what process conditions are required to reach economic parity with SMR Haber-Bosch. We find that the inherently low energy efficiency (EE) of Li-NRR electrolyzers cause disproportionally high operational costs. The EE can be improved by developing MEA-type electrolyzers to circumvent electrolyte conductivity losses or by implementing an alternative mediator with a more positive plating potential than Li, such as Mg or Al.

Finally, I will discuss the development and optimization of a hybrid flow cell reactor based on a modified membrane electrode assembly configuration for CO₂ and nitrate co-reduction to urea. The results collectively highlight that the performance, selectivity towards urea, and stability of the hybrid flow cell system are governed by the subtle interplay between ion transport, electrolyte composition, and interfacial reaction conditions.

Electrochemical urea synthesis represents a promising pathway toward sustainable nitrogen management and carbon utilization, offering a potential alternative to the energy- and carbon-intensive Haber-Bosch process and conventional urea production from fossil-derived feedstocks. By directly coupling CO₂ and nitrate conversion under mild conditions, this process exemplifies a circular approach to nitrogen fixation. However, the realization of efficient and selective electrochemical urea synthesis is critically hindered by the lack of reliable analytical methods capable of detecting and quantifying urea at sub-micromolar concentrations. This analytical limitation not only impedes accurate benchmarking of catalytic performance but also constrains the predictive design of catalysts and electrochemical systems for sustainable production.

In this work, we systematically assess and optimize existing urea quantification techniques – including high-performance liquid chromatography (HPLC), proton nuclear magnetic resonance (¹H NMR), and colorimetric assays such as urease-based and DAMO–TSC methods – highlighting their inherent limitations in sensitivity, selectivity, and robustness. HPLC and ¹H NMR, while analytically robust, exhibit high limits of quantification (LOQ > 50 μM), making them unsuitable for trace-level detection. Colorimetric methods offer lower LOQs (typically >3 μM), but are highly sensitive to matrix effects and interference from by-products such as nitrite. We address this challenge by introducing sulfamic acid as an effective nitrite scavenger in the DAMO-TSC protocol, significantly improving its reliability in complex reaction matrices. Furthermore, we enhance the urease-based method by replacing conventional UV-vis quantification of ammonia with ion chromatography (IC), which offers improved precision and interference tolerance.

Building upon these insights, we develop a novel analytical framework based on ion chromatography coupled with mass spectrometry (IC–MS), achieving a quantification limit below 5 ppb. This technique provides unparalleled sensitivity and selectivity for urea detection, enabling the rigorous evaluation of catalytic systems that operate at trace production levels. By establishing a robust and interference-free methodology, this work provides a critical analytical foundation for the field of electrochemical urea synthesis. The approach not only facilitates meaningful benchmarking of catalyst activity and selectivity but also enables feedback-driven optimization through quantitative structure-activity relationships and reaction environment design.

These analytical advancements directly support the goals of sustainable catalysis and circular carbon-nitrogen chemistry by bridging analytical precision with materials innovation. We will also offer insights into the implementation of these detection strategies informs the rational design of catalysts and electrolyzer systems, ultimately advancing the development of energy-efficient, selective, and scalable routes for sustainable urea production.

Synthesis of green NH₃ enables the possibility of producing carbon-free, high energy density liquid fuel on the TW scale. The HB reaction is almost thermoneutral, which means hydrogen’s intrinsic energy is largely retained in ammonia, making NH₃ an ideal candidate for storing and transporting renewable H₂. The conversion of NH₃ to electricity via a direct ammonia fuel cell or back to H₂ via electrolysis has received little attention until very recently, however, and is primarily limited by the ammonia oxidation reaction (AOR). This talk will present results from our investigations into homogeneous electrocatalysts to drive the AOR at room temperature and ambient pressure. Our group reported the first example of a homogenous electrocatalyst for ammonia oxidation under mild conditions; [Ru(tpy)(dmabpy)NH₃]²⁺ (tpy = terpyridine; dmabpy = 4,4′-bis(dimethylamino)-2,2′-bipyridine), [Ru(NH₃)]²⁺. Electrocatalytic behavior of [Ru(NH₃)]²⁺ will be presented with complementary spectroscopic (NMR and optical) methods of stoichiometric reactions using isotope labeling to unravel the mechanism(s) of AOR. Recent results of the surprising catalytic behavior of the coordinatively saturated [Ru(Cl)]⁺ complex will also be presented.  The reaction of [Ru(Cl)]²⁺ with NH₃ is surprisingly clean and does not form any [Ru(NH₃)]²⁺ as a side product when carried out in MeCN-_d3. ¹H and ¹⁵N NMR spectroscopy measurements show the products of the reaction are only [Ru(Cl)]⁺ and N₂. Preliminary results of other coordinatively saturated complexes will also be introduced with similar behavior. Taken together, these recent results suggest a third operative pathway of AOR triggered by a one-electron oxidation reaction. In addition, recent efforts to determine the overpotential of the AOR reaction using OCP measurements in a series of non-aqueous solvents titrated with NH₄⁺/NH₃ will be presented. An alternative approach will then be introduced, using differential potentiometric measurements to determine the universal pH abs H 2 O  values aligned to the aqueous pH scale for dilute NH₄⁺/NH₃ solutions in the same solvents: MeCN, THF, DMF, and PC. Knowledge of the pH abs H 2 O  values allows simple determination of the reversible hydrogen potential in any given solvent relative to the aqueous standard hydrogen electrode, SHE. The close agreement of these two methods, as well as calculated potentials from literature values when available, substantiates the new, simpler and more robust approach to determine the reversible hydrogen potential introduced here. We further use the reversible hydrogen potential values established here to report the overpotential for ammonia oxidation as a function of solvent with the ruthenium-based molecular catalysts described above.

Waste carbon- and nitrogen-containing streams can serve as fundamental building blocks for the synthesis of important chemicals for the energy, manufacturing, and agricultural industries. Examples include the integrated capture and conversion of CO2 from various sources directly from capture solution and the generation of fertilizers from damaged water ecosystems. The charged character of reactive species (e.g., bi/carbonates and nitrates) offers new design handles and wide cross-reactivity landscape and access to high-value, complex carbon-nitrogen chemicals through co-electrolysis. Realizing this potential is challenged by overlapping thermodynamics and kinetics involving long sequences of multielectron/proton transfers, and increasing reaction complexity. I will present our recent mechanistic insights on carbonate and nitrate supported reactions, including their coelectrolysis, based on operando probes such as Raman. I will further show how active control of the electrochemical interface and environment in these reactions may enable advances in selectivity and other performance metrics, offering an unifying vision from catalyst-to-device scales.

The pursuit of environmentally sustainable energy solutions has placed significant focus on hydrogen production and storage for industrial applications. Developing efficient technologies for storing and transporting hydrogen is crucial, and Liquid Organic Hydrogen Carriers (LOHCs) present a promising strategy.[1-5] Traditionally, the hydrogenation (loading) and dehydrogenation (releasing) of LOHC pairs rely on costly metal catalysts, often requiring high temperatures and high pressures using molecular hydrogen.

In response to these challenges, a more sustainable approach is being explored using electrocatalysis in aqueous media. Herein we propose the reversible hydrogenation and dehydrogenation of an amine/nitrile pair under mild conditions, establishing this pair as a potentially effective LOHC system.[6] Specifically, a green, selective, and efficient electrochemical synthesis is proposed to convert amines into nitriles. This process avoids harsh reaction conditions and has the significant advantage of producing molecular hydrogen as the sole byproduct. Furthermore, this innovative approach includes the design and synthesis of metallic electrodes specifically optimized to facilitate the reverse reaction: the reduction of nitriles into amines. This comprehensive methodology has demonstrated high efficiency, achieving conversion > 90%. These advancements collectively contribute to a reversible hydrogenation/dehydrogenation cycle, providing a viable, high-efficiency, and potentially scalable solution for industrial hydrogen storage applications.

The use of a well-defined supramolecular cage to encapsulate a catalytic molecule in order to confer an enhancement to its activity is an attractive strategy in chemical catalysis, though functional examples in electrocatalysis are exceedingly rare.

Against this backdrop, this work investigates the microenvironment-confined catalytic activity of a Co-bearing porphyrin encapsulated within a cubic Fe₈L₆ cage with Zn-porphyrin faces. We show that the encapsulated Co-porphyrin exhibits approx. 10-fold enhanced electrocatalytic current densities and much higher Faradaic efficiencies for nitrate reduction to ammonia relative to the free Co-porphyrin analogue. Quantitatively, the supramolecular catalyst attains a reaction selectivity nearing 100% for NH₃, a partial current density of 351 mA cm^–2, a turnover frequency of 742 s^–1 and a turnover number of 108 million, metrics substantially higher than those for the free Co-porphyrin.

This system is conceptually different to the use of isolated active sites and cage-like catalysts that catalyse reactions outside of the cage without beneficial microenvironment effects. In contrast, by designing a supramolecular cage with the active site solely located inside of the cage, we attained a true catalytic cavity with the microenvironment serving as an orthogonal lever to boost performance. Mechanistic investigations suggest that the activity is enhanced due to: 1) a tandem catalytic mechanism in which the NO₃^– → NO₂^– reduction is carried out preferentially on the Zn sites and the subsequent NO₂^– → NH₃ steps occur on the Co site, and 2) a catalytic microenvironment that substantially accelerates the latter NO₂^– reduction steps.

Electrochemical ammonia synthesis under ambient conditions offers a decentralized, low-carbon alternative to the Haber–Bosch process, which accounts for more than 1% of global CO₂ emissions (1). Among the emerging strategies, the lithium-mediated nitrogen reduction reaction (Li-NRR)—first introduced by Tsuneto et al. in the 1990s (2) and revitalized by Andersen et al. in 2019 (3)—has become one of the most promising. This approach has achieved commercially relevant ammonia production rates alongside high Faradaic efficiencies (4). Nevertheless, significant challenges remain, particularly in controlling and deciphering the complex interfacial processes that dictate selectivity and overall performance.

In this presentation, we highlight recent insights into these interfacial dynamics using in situ infrared spectroscopy, a powerful laboratory-based technique for probing electrochemical interfaces at the molecular level. We demonstrate how a detailed characterization of the electrolyte–electrode interface enables new strategies to regulate proton transfer and solid electrolyte interphase (SEI) formation, ultimately enhancing both the activity and durability of Li-NRR systems.

             Ammonia is a very important chemical compound used across various industries. Due to the large carbon footprint of the traditional method of ammonia synthesis via the Haber-Bosch process, there is urgent need for alternative methods.[1] The direct electrochemical nitrogen reduction reaction (eNRR), which involves direct hydrogen addition to nitrogen via proton coupled electron transfer (PCET) on an electrode or catalyst, is an attractive method due to its small equilibrium potential.[2] However, this method never truly met its potential as direct eNRR in aqueous solution suffers from a low faradaic efficiency and yield rates. The main reason for low eNRR activity is the competition with the hydrogen evolution reaction (HER), where N₂ surface coverage is dominant at only a narrow cathodic potential window due to the different electron transfer nature of N₂ and H surface adsorption.[3]

             One approach to mitigate HER dominance is electrolyte engineering.[4] For example, a methanol-water electrolyte was used to control the local proton concentrations at the electrode-electrolyte interface, resulting in a faradaic efficiency of 75.9%.[5] Another example could be the use of Lewis acid in aqueous solution to increase N₂ solubility and facilitate its surface adsorption.[6]

             In this work, we propose steric hindrance as a new descriptor for proton donors to boost the selectivity of the NRR in non-aqueous electrolytes. Through kinetic studies using DFT calculations and microkinetic modeling, our results show that steric hindrance of proton donors could be leveraged to improve NRR selectivity. The origins of Two different proton donor groups are explored to validate the generality of this descriptor. This research will provide a guide and facilitate new electrolyte designs for electrochemical reactions.

Ammonia production is a cornerstone of modern industry and society, yet the conventional Haber-Bosch process accounts for nearly 2% of the global CO2 emissions. A promising potentially greener alternative ambient temperature, low pressure electrochemical ammonia synthesis, though effective systems in this context have not yet been developed. To this end, this study develops a reactor platform that integrates a palladium membrane reactor coupled with a mono-terpyridine nickel molecular catalyst. This system achieved a peak Faradaic efficiency of 38% for ammonia production at current density of -0.85 mA.cm-2, with H2 detected as a secondary by-product. In-situ spectroscopic analysis, electroanalytical techniques, and computational modelling have revealed a unique catalyst mechanism that entails the formation of a Ni-H species generated from the active hydrogen from the Pd membrane as a key intermediate in the reaction route. The insights gained form this unique system stand to aid the development of practical ammonia production systems while expanding the community’s knowledge base on dinitrogen activation.

The electrochemical nitrate reduction reaction (eNO₃RR) has emerged as a sustainable alternative to the energy-intensive Haber–Bosch process, offering dual benefits of decentralized ammonia production and the remediation of nitrate-rich wastewater. However, achieving high selectivity and activity toward ammonia remains challenging due to sluggish hydrogenation steps and competing hydrogen evolution. In the present work, we explore CuO/CeO₂ heterostructures as efficient catalysts for eNO₃RR, leveraging the oxygen-vacancy-rich nature of ceria to enhance copper–intermediate interactions and promote hydrogenation pathways. CuO/CeO₂ catalysts were synthesized via co-precipitation (CP) and deposition-precipitation (DP) routes.The DP-CuO/CeO₂ catalyst exhibited superior structural features, including higher crystallinity and smaller particle size with significantly enhanced electrochemical performance. Product analysis revealed 46% NO₂⁻ and 28% NH₃ formation while suppressing the competing HER. In parallel, we investigated the small molecule oxidation reaction (SMOR) as the anodic counterpart to create an energy-efficient paired electrolysis system. In case of methanol oxidation, DP-CuO/CeO₂ again outperformed the CP catalyst, showing a 280 mV earlier onset and a fivefold higher current density at 1.8 V. Such bifunctional behaviour highlights the potential of a single catalyst system to simultaneously upgrade nitrate at the cathode and alcohol at the anode. By integrating eNO₃RR with alcohol oxidation, this paired electrolysis strategy aims to lower overall cell potential while generating value-added products on both sides: ammonia at the cathode and formate at the anode. The results showcase DP-CuO/CeO₂ as a promising bifunctional catalyst and lay the groundwork for future demonstration of a fully optimized paired NO₃RR–SMOR electrolyzer.

The production of methanol currently relies on the thermal conversion of methane to syngas, followed by Fischer–Tropsch synthesis. This route operates at high temperatures, is energy-intensive, and suffers from poor selectivity. Electrochemical methane oxidation offers an attractive alternative, enabling single-step conversion under mild conditions with direct integration of renewable electricity. However, major challenges limit its development: methane is difficult to activate due to its stability, and achieving partial oxidation is even harder, as full oxidation to CO₂ is thermodynamically favored.¹

Comparing results and discerning catalytic trends in electrochemical methane oxidation remain difficult because testing conditions vary widely. This highlights an overlooked challenge in the field: the lack of reliable, standardized testing protocols, and the limited understanding of how experimental parameters influence the electrocatalytic behaviour.

In Prof. Escudero-Escribano’s group, we addressed this gap by systematically examining how routine experimental choices affect apparent activity, using IrOₓ in acidic media as a model system.² We analyze the impact of temperature, surface-area normalization, and measurement technique, showing that these factors can drastically alter measured performance. From these insights, we propose practical guidelines to improve reproducibility, including transparent reporting of pre-conditioning, consistent estimation of the electrochemically active surface area (ECSA), replicate measurements with uncertainties, and thoughtful selection of measurement modes.

Electrocatalytic partial oxidation of methane to methanol represents a great opportunity for a sustainable and decentralized valorization of CH₄ using renewable energy sources. Direct electrochemical methane activation and oxidation have been investigated on different electrocatalysts, including metallic surfaces and metal oxides. However, a catalyst capable of carrying out this reaction with high selectivity, efficiency, and stability has not been discovered yet [1]. While results for the electrochemical methane oxidation on metallic surfaces have shown only CO₂ production to date, studying this process on well-defined Pt surfaces allows for gaining key mechanistic insights. Interestingly, a recent study has revealed that methane electro-oxidation exhibits high structure sensitivity for Pt(100) terraces [2]. Herein, we systematically investigate Pt single crystals for electrochemical methane activation and conversion, with a special focus on Pt(100).

Controlling different parameters during electrochemical methane conversion is key to understand the structure-activity-selectivity relationships. We have investigated the effects of the adsorption time and potential, cooling atmosphere, and pH on electrochemical methane oxidation on Pt(100). Our results indicate that the applied activation potential affects the mechanism of the activation step. Interestingly, maximizing the OH coverage seems to enhance methane activation at different pH values. Complementing these results with computational studies allowed us to understand how adsorbed OH species affect the thermodynamics at the electrochemical interface. Our work provides a foundation for more in-depth investigations into the mechanism for electrochemical methane activation and oxidation.

Electrochemical valorization of nitrogen oxides (NOx) provides a powerful framework for converting air and water pollutants into high-value chemicals, addressing environmental challenges while enabling sustainable pathways for industrial nitrogen management. In this talk, I present two independent research directions that explore complementary electroconversion mechanisms within this broader theme. The first study investigates the direct electrochemical reduction of nitrate (NO3-) to ammonia (NH3) using advanced single-atom catalysts, emphasizing how atomically dispersed active sites, and local coordination environments dictate selectivity and efficiency. Through theory-guided catalyst design, we uncover key intermediates, potential limiting steps, and scaling relationships that inform selective NH3 production. The second study examines NOx as a feedstock for electrochemical upgrading into nitric acid (HNO3) using oxygen-functionalized carbon catalysts. We reveal structure-function correlations that govern product distribution, quantify multi-electron oxidation pathways, and identify catalytic motifs that enable high Faradaic efficiency. While distinct in scope and mechanistic direction, one reductive, the other oxidative, these two studies together demonstrate a unified vision for NOx circularity, uncovering design principles and catalytic handles that accelerate the development of clean nitrogen processing and pollutant-to-product conversion technologies.

The artificial nitrogen fixation has revolutionized agriculture and enabled the world population to grow to over 8 billion by 2024.^[1] Currently, 150 Mt of ammonia are produced by the energy-intensive and heavily CO₂-emitting Haber-Bosch process per year, of which 80 % is used for fertilizer production. However, less than 50 % of this ammonia reaches its end-use as nitrogen building block in crops while a high amount leaches into the environment and is present in the wastewater in form of nitrate.^[1,2]

The European environmental quality standard for nitrate in surface waters is at 50 mg l^‑1.^[3] However, in many regions this value is exceeded.^[3] It can seep into drinking water and thus cause health risks for humans.^[1] Using renewable energy, the electrochemical nitrate reduction (NO₃RR) provides an environmentally friendly way to clean wastewater and close the human-induced nitrogen cycle, moving towards a circular nitrogen economy. In the NO₃RR nitrate is employed as an abundant source for ammonia production or converted into the harmless dinitrogen.

Various catalysts have been investigated for NO₃RR. However, among the investigated materials Cu-based catalysts emerged to perform best.^[4] While the catalytic material itself plays a key role in the reaction, another important factor is the reaction environment. The choice of ionomer can affect ion transport, the local pH at the electrode surface, and the electrode porosity, thereby influencing both the activity^[5] and selectivity^[6] of the reaction.

Ionomers are commonly used in electrocatalytic systems as binders or membranes.^[7] Although, the absorption of ammonium and ammonium crossover by cation exchange membranes have been intensively studied in the literature for the electrochemical nitrogen reduction and NO₃RR, the effect of suitable binders has received too little attention.^[8] Furthermore, when choosing a suitable membrane, it is not only important to consider the ammonium crossover, but also other crossover effects. In NO₃RR research, chloride anions are commonly added to the electrolyte as common components of agricultural wastewaters in concentrations between 21-24 mg l^-1.^[9,10] Chloride can be oxidized at the anode to species that lead to the subsequent ammonia decomposition to nitrogen.^[9] Thus, the addition of chloride to the electrolyte is a common strategy to increase the selectivity of NO₃RR towards dinitrogen. However, the interactions between the chlorine species and different membranes, like crossover effects and membrane stability, require further attention.

In this study, the effect of ionomer choice, the correct electrode pre-treatment as well as the choice of membrane in an H-type cell regarding crossover effects of selectivity changing species are investigated. Preliminary results suggest that using a cation exchange ionomer (CEI) as binder and an appropriate pre-treatment of the electrode even in alkaline media increase the NO₃RR activity towards ammonia compared to using an anion exchange ionomer (AIM) binder.

Electrocatalytic nitrate reduction (NO₃RR) offers a sustainable pathway for the synthesis of value-added nitrogen-containing chemicals, such as ammonia, and the remediation of nitrogen contaminants in water systems. Investigating NO₃RR is also essential for understanding fundamental electrochemical C–N coupling processes, where the activation and hydrogenation of nitrogen–oxygen species govern product selectivity and efficiency [1]. For this reason, exploring the fundamental mechanism of this reaction is crucial for advancing sustainable nitrogen conversion technologies. However, NO₃RR is strongly influenced by factors such as electrode material, applied potential, and electrolyte composition [2,3]. Moreover, NO₃RR presents significant challenges, arising from the formation of transient nitrogen–oxygen intermediates, which makes its mechanistic understanding challenging [4]. This complexity underscores the need for combined electrochemical and in situ techniques capable of resolving the elementary steps and active species involved.

In this work, we employ silver as a model electrocatalyst to probe the elementary electron transfer steps of NO₃RR to nitrite in a neutral electrolyte. A combination of electrochemical characterisation techniques, including cyclic voltammetry and scanning electrochemical microscopy, is used to monitor the dynamic evolution of key reaction intermediates [5]. This correlation provides information on the NO₃RR mechanism over silver surfaces and highlights the importance of a rigorous electrochemical characterisation benchmarking. This opens an avenue to accurately compare NO₃RR activity across different electrocatalysts, assessing their role in the rate-limiting nitrate-to-nitrite reduction step.

Fertilizer use and fossil-fuel combustion has increased nitrate concentrations in many wastewaters and watersheds to levels that threaten environmental and human health. Consequently, treatment of nitrate-contaminated water is a growing area of energy consumption. Electrocatalytic nitrate reduction (NO3RR) offers a distributable treatment solution also capable of producing value-added products (e.g. ammonium), using electrons as a reducing agent at ambient temperatures and pressures [1]. However, nitrate reduction occurs at similar electrochemical potentials to water reduction, under conditions where the surface is considered negatively charged. Here we share how the competitive adsorption of nitrate and hydrogen (protons), governed by catalyst electronic structure, influences Faradaic efficiency and selectivity [2]. This understanding, and it's link to catalyst electronic structure, informs our design of alloy catalysts tailored to individual aspects of the reaction network [3]. We will further consider how the identity of alkali cations in the electrolyte influence the kinetic rate of reaction and aspects of reactant transport to the catalyst surface, shedding light on the complex NO3RR reaction mechanism.