The conversion of CO₂ via electrochemical processes is a promising technology to close the carbon cycle, especially when combined with renewable energy sources. Given their high market value and energy density, significant efforts are currently dedicated to designing copper (Cu)-based catalysts for converting CO₂ into multicarbon molecules. By integrating concepts from molecular catalysts, the engineering of Cu-based catalysts aims to finely tailor the behavior of active sites on metallic surfaces, which remains a long-standing interest for the controlled design of novel electrocatalytic materials. In this context, we have recently explored strategies to enhance the conversion of CO₂ into hydrocarbon molecules with two or more carbon atoms (C₂₊) via molecular doping or metal alloying.

Despite impressive progress achieved through the development of flow cells with improved gas/liquid/solid interfaces, the realistic development of CO₂ electrolyzers is still hindered by several fundamental challenges. These include understanding the local microenvironment, reducing the large operating voltage, and improving CO₂ utilization efficiency.

In my presentation, I will review our recent progress in understanding and controlling the interface at various levels within CO₂ electrolyzers, from the molecular scale to the complete electrolysis system.

Electrochemical CO₂ conversion can result in a variety of products, often as a mixture, and controlling the product selectivity remains a key challenge. It has been shown that pulsing the electrochemical potential can lead to altered product distributions, influenced by effects on, e.g., transport, double-layer rearrangement, adsorption/desorption, and changes to electrode structure and composition [1].

Herein we report our observations using metal electrodes normally selective for the 2-electron formation of CO as major product under steady-state (potentiostatic) conditions, finding that they can produce significant amounts of higher-order products (including methane and ethylene) under the application of pulse potential waveforms. We confirm this is not due to metal impurities in the system, but is significantly affected by phenomena such as surface restructuring and accumulation of liquid products. Furthermore, time-resolved differential electrochemical mass spectrometry (DEMS) measurements reveal distinctly different transient behaviors between the different gaseous products, providing key new mechanistic insight for clarifying the roles of pulsing.

Electrolysis is usually performed under constant potential or current, but pulsed electrolysis has received growing attention over the last years, especially in the context of CO₂ reduction where favourable impacts on product selectivity are observed. However, the mechanism at play remains under debate.^1,2 Among the most often reported contributions are the modified mass-transport of reactants at the electrode, the oxidation of metal catalyst during anodic steps or the morphological reconstruction of the surface under dynamic conditions. Much less explored are the (micro-)kinetics events during transient operation. Herein, we address some specific cases following classical theory of electron transfer and chemical reaction rate. Upon conditions where mass-transport effect, metal oxidation and surface reconstruction are not interfering, we predict large selectivity improvements (exceeding 5000% for some cases), resulting only from (micro-)kinetics effects. For the specific reaction framework investigated, we provide rational explanations for the selectivity switch, derive a method for pulsed program optimization and show that the high selectivity improvements are compatible with high current density operation, relevant for commercially-viable CO₂ reduction.

Correlating activity, selectivity and stability with the structure and composition of catalysts is crucial to advance the knowledge in chemical transformations which are essential to move towards a more sustainable economy. Among these, the electrochemical CO2 reduction reaction(CO2RR) and, more recently, CO reduction reaction (CORR) hold the promise to close the carbon cycle by storing renewable energies into chemical feedstocks. Although notable progress has been made in understanding the parameters which govern activity and selectivity in CO2RR, CORR is still in its infancy. Catalyst stability remains a less explored property for both reactions.

In this talk, I will show how well-defined copper nanocrystals (NCs) synthesized via colloidal synthesis can be used as model system to establish unambiguous structure/property relations in CO2RR and CORR.

First of all, I will illustrate how tailor made copper NCs have revealed synergy between shape and size, thus the importance of facet ratio in CO2RR.[1] Secondly, I will show that these relationships hold when these catalysts are integrated in a gas-fed electrolyzers at technologically relevant conditions with currents up to 300 mA/cm2.[2]

I will then present our recent advancement in understanding structural dependence relationship in CORR. Specifically, I will discuss about the importance of lattice strain for the production of alcohols in this reaction as revealed by a combination of theoretical simulation and advanced characterization techniques. I will close with a discussion of stability of these catalysts and compare CO2RR/CORR conditions. [3]

Carbon capture, utilization, and storage (CCUS) strategies are gaining attention as effective methods to achieve carbon dioxide neutrality while creating value-added products through CO₂ conversion. Among these strategies, electrochemical CO₂ reduction stands out due to its low temperature and pressure requirements and its ability to store energy from renewable sources like solar and wind in the form of valuable chemicals such as formic acid or formate [1].

The “Development of Chemical Processes and Pollution Control” (DePRO) research group at the University of Cantabria, Spain, has been actively working on the continuous electrochemical reduction of CO₂ to formate. Various electrocatalysts for both the cathode and anode, along with different electrode configurations, have been investigated. This communication focuses on the recent advancements and challenges in the lab’s research on continuous CO₂ electrocatalytic reduction to formate. The experiments were conducted using a consistent setup and operating conditions, with variations in cathodic electrocatalysts, including Pb-, Sn-, and Bi-based materials, and different cathode configurations like plate electrodes, particulate electrodes (PE), Gas Diffusion Electrodes (GDE), Catalyst Coated Membrane Electrodes (CCME), and Membrane Electrode Assembly (MEA). We have also explored various anodes, such as DSA/O₂ and Ni-based electrodes, and different ion exchange membranes, including Nafion cationic exchange membranes (CEM) and Sustainion anionic exchange membranes (AEM), while performing the Oxygen Evolution Reaction in the anodic compartment [2].

Notable achievements were made using a Bi MEA configuration with a CO₂-humidified input stream [3]. These results include formate concentrations of up to 337 g·L^-1, Faradaic Efficiencies of 89 %, and energy consumption values as low as 180 kWh·kmol^-1, representing one of the best trade-offs reported in the literature, marking noteworthy progress in this field.

Further research is essential to scale up this process industrially by developing more stable electrocatalysts for both the cathode and anode. Recent work by the research group has focused on optimizing the manufacturing of GDEs for CO₂ electroreduction to formate using the automatic spray pyrolysis technique [4]. This approach has yielded valuable insights into creating more efficient electrodes for CO₂ reduction.

Additionally, replacing the Oxygen Evolution Reaction at the anode with more valuable oxidation reactions is crucial. The research group has explored the coupling of the Glycerol Oxidation Reaction with CO₂ electroreduction to formate, resulting in valuable products in both compartments of the electrochemical reactor. Recent results include high formate concentrations of up to 359 g·L⁻¹ with Faradaic efficiencies up to 95% at the cathode, along with dihydroxyacetone production at a rate of 0.434 mmol·m⁻²·s⁻¹ [5]. This represents a significant advancement in the development and application of this technology.

The most challenging deal we face these years is the need to lower greenhouse gas (GHG) emissions and tackle climate change; though calls to reduce it are growing louder yearly, emissions remain high. CO₂ is the key contributor. For this reason, synthesising high-added-value products from CO₂ conversion is a promising approach to mitigate the problem. [1] Among the different alternatives, exploiting CO₂ via electrochemical reduction under mild conditions (ambient pressure and temperature) represents an opportunity to support a low-carbon economy.[2] The electrocatalytic (EC) CO₂ reduction (CO₂R) driven by renewable energy can be exploited for the future energy transition, for the carbon storage into valuable products like syngas (H₂/CO mixtures), organic acids (formic acid) and chemicals/fuels (C₁₊ alcohols). A big challenge for the industrialisation of this technology is to find low-cost electrocatalysts, efficient reactors and process conditions. In the efforts to develop efficient, selective and stable materials, we have exploited the current knowledge of thermocatalytic CO₂ hydrogenation to develop noble-metal-free CO₂R electrocatalysts. For instance, Cu/Zn/Al synthesised catalyst producing methanol and CO from the CO₂ thermocatalytic (TC) hydrogenation (at H₂ pressure (P) of 30 bar and temperature (T) > 200 ^oC) promotes the formation of methanol (⁓32% of FE) during the EC CO₂R in a gas-diffusion-electrode system; while operating in the liquid phase, the same catalyst produces syngas with a tunable composition (95% of FE at the most positive applied potential) and other liquid C₂₊ products (in both cases at ambient T, P).[3]  Conversely, Cu/ZnO electrocatalyst has also been tested at industrially relevant current densities in liquid phase configuration.[4]  We demonstrated through ex-situ characterisations that the presence of ZnO nanoparticles in the mixed Cu/ZnO catalyst plays an important role in forming and stabilising mixed oxidation states of copper and Cu¹⁺/Cu⁰ interfaces in the electrocatalyst (in bulk and surface). These interfaces seem to promote CO dimerisation to ethanol. Indeed, ethanol was produced with the Cu/ZnO catalyst, reaching ethanol productivity of about 5.3 mmol∙g_cat^-1∙h^-1 in a liquid-phase configuration at ambient conditions. The Cu/Zn/Al and Cu/ZnO electrocatalysts have also been tested in a catholyte-free configuration with an increased selectivity to ethylene, reaching approx. 60% and 70% of FE, respectively. Here, Cu catalyst structure transformed, on average, completely to metallic with a very thin layer of Cu¹⁺ during testing, which seems to promote the selectivity towards C₂H₄, demonstrating that the reaction pathways for EC CO₂R are determined mainly by transport limitations rather than only by the intrinsic properties of the electrocatalysts. Our results open a promising path for the prospective implementation of metal-oxide nanostructures for CO₂ conversion to the chemicals and fuels of the future.

Previous electrochemical CO₂ reduction studies have shown alkaline electrolytes favor the production of acetaldehyde over acetaldehyde and ethanol, and proposed hypothesis of their generation pathways accordingly [1], [2], [3]. However, our work shows acetate can also come from the fast non-faradaic chemical oxidation of acetaldehyde in alkaline solutions [4]. This could lead to an overestimated acetate productivity and correspondingly an underestimated acetaldehyde productivity, and thus mislead following investigations on the reaction mechanisms of CO₂ reduction reaction conducted in alkaline environment.

In the presented work, we will first systematically demonstrate how and why misleading acetaldehyde and acetate production could be caused, and propose suggestions on accurately measuring their productivities in alkaline electrolytes. In addition, we will present real-time detection of gas (hydrogen, methane and ethylene) and volatile liquid (acetaldehyde) being produced during electrochemical CO reduction on polycrystalline and various single crystal ((100), (110), (111), and (211)) Cu electrodes at low overpotentials (< 0.65 V ). Results reveal that acetaldehyde production as well as the production rate of acetaldehyde to ethylene are both potential- and facet-dependent. The quantified acetaldehyde-to-ethylene production ratio will provide insightful information for understanding the bifurcation point of acetaldehyde/ethylene production from electrochemical CO₂ reduction in a mechanistic perspective.

Highly porous ZIF-8 and ZIF-67 synthesized by an environmentally friendly steam-assisted dry-gel technique are investigated as potential catalysts for electrochemical reductive reactions. The synthesis conditions play a crucial role in the growth of the metal-organic frameworks (MOFs). Tuning water content, in particular, significantly influences the morphological and structural properties of ZIF-8. These properties show significant effects in CO₂ electroreduction, producing syngas with different CO: H₂ ratios. The CO selectivity changed by variation in the volume of water during the synthesis and significantly affects the crystal size and morphology of the ZIF-8 particles. An optimum CO selectivity of 50% is obtained at -1.2 V_RHE by increasing the water content to 20mL during the dry-gel synthesis. The tunability of CO selectivity influenced by the synthesis conditions and the reductive potential used during the CO₂ electroreduction process is advantageous for producing syngas in different CO: H₂ ratios. In addition, despite exhibiting similar textural and structural properties, ZIF-8 and ZIF-67 show distinctive CO₂ electroreductive performance, which is assigned to the vital role of their respective metal center.

Carbon monoxide is an important raw material for the synthesis of different bulk chemicals (e.g., phosgene and different products thereof). Considering that it can be a building block for the synthesis of virtually any organic compound, carbon monoxide might play an important role in the production of synthetic fuels and other typical petrochemical products. This can be achieved at high temperatures and pressure in the Fischer-Tropsch process, rendering this a widely investigated topic. As an alternative, electrochemical methods offer a way of forming different chemicals from carbon monoxide under considerably milder conditions.

In this study, we aimed to explore the effect of different experimental parameters on the rate and selectivity of the electrochemical reduction of CO (CORR), using cell components and catalysts available from commercial sources. Studying the reaction in different electrolyzers, we highlight the dual effect of the electrolyte solution that separates the membrane and the catalyst layer. On the one hand, it limits the product crossover to the anode, but on the other hand, gives ground to electrode flooding, hence also limiting the maximum achievable current density. The zero-gap electrolyzer structure is therefore most beneficial in terms of both achievable reaction rate and energy efficiency, but product accumulation in the anolyte is a hurdle to get over, as will be further discussed in my talk.

The phase boundary between the catalyst particles, the liquid phase, and the gas reactant can be engineered by using functional catalyst layer additives. In the second part of my talk the effect of the used gas diffusion layer, the catalyst layer composition, and the catalyst additive will be discussed. Various, systematically chosen polymeric materials were tested as catalyst binders to reveal any possible contribution of certain molecular motifs (e.g., functional groups, fluorinated backbone, etc.), present in the polymer additives. The electrochemical results are contrasted with the detailed physico-chemical characterization of the catalyst layers. Building on these optimization studies, experiments were also performed in a scaled-up electrolyzer stack (3×100 cm² geometric area) to evaluate the possible industrial applicability of this process.

Global warming has received a lot of attention from all over the world. The development of earth-abundant catalysts for highly selective electrochemical CO₂ reduction reaction (CO₂ RR) is a  promising way to mitigate the increasing amount of CO₂ in the atmosphere. Here, we have obtained non-noble metals consisting of Cu and Sn for the highly selective reduction of CO2 through a facile method. The morphology and particle size of the as-prepared CuSn catalyst were very different from the Cu catalyst, which was transformed into nanometers after Sn doping. Compared to the faradic efficiency of Cu₂O, the total selectivity of the nanocatalyst towards CO₂ RR was improved by 25% at a current density of −200 mA cm⁻² in 1 M KOH electrolyte, and its selectivity was shifted towards formate. The high performance is attributed to the synergistic catalytic effect between Cu and Sn, which is still under investigation. This approach could also be used to design and develop high performance electrocatalysts for the selective conversion of CO₂ to other products.

Theoretical atomic scale calculations of the electrochemical reduction of CO₂ and the competing hydrogen evolution reaction are presented. The calculations include evaluation of the activation energy of the various elementary steps as a function of applied voltage based on efficient methods for finding saddle points on the energy surface that represent transition states for the reactions. The energy and atomic forces are calculated using density functional theory (DFT). Copper is found to be special among the transition metals in that the activation energy for CO₂ reduction becomes lower than that of hydrogen evolution reaction (HER) within a certain window of applied voltage [1]. The fact that the onset potential of formate and CO formation is similar can be explained by the fact that the energy barrier for these two competing processes turns out to be similar [2]. The most likely step for reduction of CO, which also turns out to be the rate limiting step for methane formation, involves a Heyrovsky mechanism to form COH, rather than formation of CHO. The rate of C-C bond formation is strongly dependent on the surface structure, Cu(100) being the most active facet, and it can be affected by H-adatom coverage. The optimal mechanism for C-C bond formation is found to involve a nearly simultaneous electron-proton transfer to form *OCCOH. Calculations of CO adsorption on doped copper surfaces reveal multiple CO molecules adsorbed on a single surface impurity [3]. The calculations have mostly been carried out by explicitly including a few (4 or 5) water molecules around the reacting surface species while the rest of the electrolyte is described with an implicit solvent approach. Proper inclusion of a liquid electrolyte at the surface of the electrode is a challenge as it makes the DFT calculations too heavy. Ongoing methodology development based on a hybrid simulation approach where the liquid electrolyte is fully represented will be introduced [4].

Multi-physical transport processes on multiple scales occur in electrochemical devices and components for CO₂ electroreduction. These complex coupled transport processes determine the local environment in the catalyst layer and subsequently also the reaction rates at the catalytic sites. Experiments have difficulties to provide locally resolved information within a working cell, but can provide important insight into catalytic mechanisms or provide macroscopic performance characteristics (current-voltage behaviour, selectivity’s, etc.). The multi-physics and multi-scale models can provide locally resolved insights, starting from the double layer [1,2], the pore-scale [2,3], all the way to the volume-averaged continuum-scale [4], but typically rely on experimental input for model parameters or validation. Operational conditions (e.g. steady state vs. transient) can further provide interesting insights into limiting phenomena. I will discuss how combined experimental and computational approaches can help provide relevant insights into (photo)electrochemical CO₂ reduction to improve activity and selectivity utilizing multi-scale and transient models that are fed by dedicated experimental data.

Copper-based electrocatalysts are showing great promise for converting CO2 into valuable products through electrochemical processes. However, achieving high selectivity for higher carbon number (C2+) products is still a major hurdle for their commercial use. In our study, we have developed a range of electrocatalysts using octadecylamine (ODA) coated Cu2O nanoparticles. High-resolution transmission electron microscopy (HRTEM) has shown that these coatings vary in thickness from 1.2 to 4 nanometers. Density functional theory (DFT) calculations indicate that with low coverage, ODA molecules tend to spread out on the surface of Cu2O, exposing hydrophilic areas. In contrast, at higher coverage, the ODA molecules pack closely together, which can hinder mass and charge transfer. This variation in the arrangement of ODA molecules on the nanoparticles significantly impacts the selectivity of the products.

Further insights were gained through in situ Raman spectroscopy, which demonstrated that the ideal ODA thickness helps stabilize important intermediates in the production of C2+ products, particularly ethanol. Additional tests using electrochemical impedance spectroscopy and pulse voltammetry have shown that thicker ODA coatings increase resistance to charge transfer, whereas thinner ODA layers facilitate quicker desorption of intermediates. The optimal thickness of the ODA layer results in the slowest rate of intermediate desorption, correlating with the highest observed concentration of these intermediates via in situ Raman spectroscopy. Consequently, this leads to a Faradaic efficiency exceeding 73% for ethanol and ethylene production. This study highlights the critical role of molecular coating thickness in tuning the performance of Cu-based electrocatalysts for efficient and selective CO2 conversion.

It is experimentally known that electrochemical CO₂ reduction (eCO₂R) does not take place on Cu, Ag and Au without a cation near the electrode surface, and that both organic and inorganic cations modulate eCO₂R activity and selectivity. The rational optimization of microenvironments in eCO₂R requires understanding of the intricate chemical and transport phenomena taking place across length scales.

We modeled CO₂ reduction to CO on Ag via a multiscale approach, accounting for the role of the cation at all scales. The transport is modeled by generalized modified Poisson-Nernst-Planck equations and a microkinetic model is used to calculate the current densities of CO₂ reduction to CO and the competing reduction of water (H₂OR) and H⁺ to H₂ based on the local conditions. Kinetic rate constants are obtained from atomic-scale calculations (DFT and AIMD). In particular, the number of active sites (the microenvironments) depends on the local cation concentration.

We considered different buffers, including alkali (Li⁺, K⁺ and Cs⁺), alkali-earth (Mg²⁺ and Ba²⁺) and organic (tetramethylammonium - TMA⁺) cations, and we evaluated different concentrations (from 1 mM to 2 M) over a large potential window (-0.4 to -1.6 V vs RHE). We observed consistent behaviors across cations of different nature: at slightly negative applied potentials, higher cation concentration leads to improved activity, despite the lower CO₂ solubility in higher ionic strength buffers. At strongly negative applied potentials, cation accumulation due to double layer charging leads to transport limitations and the CO current density is lower at higher cation concentrations. Cs⁺ leads to higher CO current density and high CO selectivity for a combination of favorable chemical and transport properties. We applied the same framework to a TMA⁺ - based anion exchange membrane (AEM) in the vicinity of an Ag electrode and evaluated the effect of a fixed background charge at different hydration levels on eCO₂R activity and selectivity. We showed that, when the AEM is in contact with an electrolyte, the inorganic cation is still present at the AEM-electrolyte interface and contributes to the CO₂R and H₂OR microenvironments.

The model consistently reproduces experimental trends and helps to elucidate optimal local condition for eCO₂R on Ag in aqueous electrolytes and ionomers. Our work paves the way for a coupled multiscale electrolyte and ionomer design for electrochemical interfaces.

Local CO₂ availability at the catalyst is an important limitation for low temperature CO₂ electroreduction in aqueous media. Integrated CO₂ capture and electrochemical utilization is energetically and economically advantageous, as it combines sorptive and electrolytic functions [1]. Previously chemicals used as sorbent and organic electrolyte include monoethanolamine and ionic liquids [2]. Improved uptake capacity, kinetics, and selectivity as well as good chemical and thermal stability are essential criteria in the sorbent electrolyte selection process [3]. A common employed strategy to overcome the mass transport-limited CO₂ supply in liquid electrolyte systems is to provide CO₂ in its gaseous form to the electrode, leading to record performances in such systems [4].

Integration of sorbents in gas-fed electrolyzers enables to locally increase CO₂ availability and thereby boost the maximum reduction rate [5]. Typical Membrane Electrode Assembly (MEA) designs are composed of multiple layers (e.g., hydrophobic porous transport layer, carbon nanoparticles or fibers, ionomer, catalyst nanoparticles, …). Studying the effect of the sorbent and its integration in the assembly is impeded by the stack complexity and therefore hard to decouple from other phenomena. In this work, a planar interdigitated electrode assembly was developed to test sorbent electrolytes for CO­₂ reduction in gas-fed environments under well-defined conditions. Ionic liquid-silica nanocomposites were successfully tested as sorbent electrolyte coatings for CO₂ reduction in such a gas-fed model system, providing a proof-of-concept for the enhanced CO₂ electroreduction by increasing reactant availability . Next to the experimental approach, kinetic parameters for the CO₂ uptake, transport and electroreduction were modeled in a multiphysics model and compared to experiments. The extracted kinetic parameters obtained from the interdigitated electrode model system were implemented in a model of a MEA configuration to determine optimum sorbent placement.

Basic and industrial research are at present spending a lot of effort to reach the goal of mitigating the global energy crisis by proposing alternative technologies. In this framework, the production of carbon-based chemicals and fuels by exploiting anthropogenic CO₂ is nowadays considered a way-out to leave the traditional oil-based technology and to valorize CO₂. In fact, renewable and green approaches to CO₂ valorisation are aimed at minimizing the worrying impact of its emission to the environment, and to drive the transition to a new circular economy approach in chemistry and energy production. To this aim, electrochemical reduction of CO₂ is expected to be a very promising technology. In order to design efficient catalysts for CO₂ reduction reaction (CO2RR) with high activity, selectivity and stability, it is important to understand the fundamental mechanisms involved in the electrochemical processes. In this framework, in situ/operando characterization techniques provide insight into the correlation between physical-chemical properties and the electrochemical performance. Specifically, electrochemical liquid phase transmission electron microscopy (EC-LPTEM) can provide temporally and spatially resolved morphological, structural and chemical information regarding catalytic materials under electrochemical stimulation [1]. Additional characterizations such as operando Raman spectroscopy, can be complementary tools to EC-LPTEM, supporting it with additional information on the reaction intermediates or chemical-physical properties of the catalyst. Within this framework, in this paper, EC-LPTEM experiments on molecular Re@Cu₂O/SnO₂ catalysts for CO2RR are presented and compared to the lab-scale experiments, shading light on the changes the material undergoes during electrocatalytic activity. In addition, thanks to optimized microfluidic setup [2], it was possible to study this catalyst at conditions which are close to those of interest for the applications.

Understanding and controlling electronic properties at solid/liquid interfaces is crucial for optimizing catalytic materials, particularly in electro- and photo-catalytic processes. Accurate monitoring of changes in electronic properties, such as oxidation states and the formation of transient species, is essential for advancing our understanding of key chemical reactions.

Synchrotron radiation-based spectroscopies, including X-ray absorption spectroscopy (XAS) and X-ray photoelectron spectroscopy (XPS), are among the most effective tools for in-situ and operando investigations. These techniques provide valuable insights into electron transfer processes and catalyst behavior under operational conditions, which are critical for developing more efficient and effective catalysts. The Beamline for Advanced Circular diCHroism (BACH) at the Elettra synchrotron facility in Trieste is leading the way in these investigations. BACH utilizes a multi-technique approach to explore a broad spectrum of material properties, including electronic, chemical, structural, and dynamic characteristics.

Recent innovations include the development of electrochemical cells (EC-cells) designed to isolate the liquid electrolyte from the vacuum environment necessary for soft X-ray measurements, featuring a transparent Si₃N₄ window or graphene membranes [1,2]. This setup, equipped with a three-electrode configuration, including an Ag/AgCl reference electrode, a platinum wire counter electrode, and a window serving as the working electrode where the catalytic material is deposited as a thin film, enables real-time collection of s-XAS data during electrochemical experiments. This configuration provides direct insights into the behavior of catalysts during electrochemical and photo-catalytic reactions [3]. The ability to perform cyclic voltammetry (CV), linear sweep voltammetry (LSV), and other electrochemical tests while simultaneously acquiring s-XAS data significantly enhances our understanding of electrochemical processes at solid/liquid interfaces. The flow EC-cell, provided with a liquid flow system, allows for the replacement of the electrolyte during the experiment, enabling the refreshment of the spent solution or adjustment of the solution’s pH as needed. Moreover, a static cell, consisting of a lithium anode and a thin-film cathode material deposited on the window, designed for easy assembly in a glove box, has been specifically developed for the study of rechargeable Li-ion batteries (LIBs).

This comprehensive approach is crucial for the development of new materials with improved activity, selectivity, and performance, which are essential for advancements in chemistry, materials science, and energy technology. Examples of promising Cu nanoparticle (NP) catalysts for CO and CO₂ reduction, investigated using in-operando s-XAS measurements, will be discussed. In particular, the in-situ electrodeposition of Cu NPs and their stability in an alkaline environment during CV and CO₂ reduction reactions will be presented.

Electrochemical CO₂ reduction (ECO2RR) is an attractive technology to produce energy dense carbon products, such as ethylene, alcohols, and syngas from renewable energy and carbon dioxide. Such products are key industrial feedstocks that, if produced renewably, can greatly contribute towards net-zero transition. This is the goal of the Horizon 2020 Ecofuel Project, which aims to optimise the complete process chain from CO₂ direct air capture to electrochemical reduction, oligomerisation and fuel refining, targeting developments up to TRL 4/5.

In this talk I will discuss the CO₂ electrolysis on CuO derived electrodes from atomic to microscale. DFT was used to select suitable dopants for enhancing CuO activity to C₂₊ products. The catalysts were successfully synthesized and characterised using the XRD, TEM and rotating disc electrode to understand the impact of the dopants. Finally, the catalysts were tested at an industrially relevant current density (>200 mAcm^-2) in a 2-Gap flow cell. We performed in-situ TEM studies to understand the catalyst restructuring during reaction and conducted FIB-SEM studies before and after testing to probe the cross-section of the catalyst layer to understand the deactivation mechanism. We believe that achieving an optimal tuning of the entire CO₂ electrolysis process, spanning from catalyst to electrode, holds the key to significantly enhancing performance metrics.

The urgent need to achieve carbon neutrality by 2050 as per the Paris Agreement [1, 2] calls for new strategies to reduce CO₂ in the atmosphere. To this aim a key approach consists of the electrocatalytic reduction of CO₂ (CO₂RR), a process which transforms CO₂ into valuable products such as hydrocarbons and alcohols. However, the thermodynamic stability of CO₂ makes this solution energy-intensive, necessitating the use of catalytic materials to enhance efficiency. Copper (Cu) is known to produce high energy-density products (C₂, C₂₊) but it shows low selectivity, complicating the final product separation [3-5]. To overcome this limitation, Copper bimetallic compounds or alloys have been explored [6]. Along these lines, our study focuses on the realization of Cu-silver (Ag) electrodes to achieve a synergistic effect that improves the performance compared with pure Cu [7-9]. The major advantage of the resulting material is the simple preparation via a sputtering deposition of Cu followed by a spontaneous galvanic displacement reaction. This eliminates the need for applying a potential for Ag deposition onto the Cu substrate. Our Cu-Ag electrodes show enhanced selectivity for C₂ products with respect to the bare Cu ones during the CO₂ electrolysis. To understand the fundamental role of Ag in increasing and stabilizing the production of ethanol and ethylene, in-situ X-ray absorption spectroscopy (XAS) results are presented and analysed.

The European Union (EU) is aiming to reach a 55% reduction of greenhouse gases (GHG) emissions by 2030 compared to 1990 levels, and to reach climate neutrality by 2050. In the last years, dozens of new legislations have been tabled and adopted to drive the climate transition and create a regulatory framework that would enable to reaching those ambitious targets. Delivering on climate targets means decarbonising energy systems, but also defossilising our economy. To reach defossilisation, Carbon Capture and Utilisation (CCU) has been given an unprecedented role in recent EU legislations as one of the levers to reduce our dependency on fossil resources. The European Commission considers in its Industrial Carbon Management Strategy published in February 2024 that “the annual carbon demand for the chemical sector alone in Europe is currently estimated around 125 million tonnes, or about 450 million tonnes CO₂ equivalent, more than 90 % of which is supplied with fossil carbon”. Currently, alternative carbon feedstock (e.g. from recycling, from biomass or from CCU) represents less than 10% of the annual carbon demand for chemicals. Scaling-up the substitution of fossil resources with CCU products is no small task.

CO2 Value Europe is part of two EU-funded projects, VIVALDI and CO2SMOS, which both aim to address the environmental challenge of decreasing the CO2 emissions of bio-based industries by developing innovative CCU solutions to convert CO2 into high-added-value chemicals. Part of the work of those projects is to analyse the current EU regulatory framework and identify what are the opportunities and challenges to scale-up CCU technologies, for example for CCU chemicals or CCU fuels production.

Our work as CO2 Value Europe is to produce recommendations on how current regulations should be interpreted to support the scaling-up of CCU projects such as CO2SMOS and VIVALDI, and inform policy-makers about the environmental benefits of CCU, and how policies will be at the heart of their deployment.

Our oral presentation would focus on the learnings from our work in those two EU-funded projects and how current EU regulations are shaping up for CCU: ETS incentives, Renewable Enery Directive, Industrial Carbon Management Strategy, Carbon Removals Certification Framework, Net Zero Industry Act, EU climate target for 2040, all those EU initiatives are at the heart of discussions at EU level and every one of them is impacting definitions, thresholds, requirements, incentives that will help or hinder CCU technologies deployment. It would also look at our recommendations to strengthen that EU regulatory framework and how other projects can help to disseminate a common message on supporting CO2 conversion to chemicals and fuels.

After the EU elections, with a new Parliament and new Commission in place, the EU public policies on climate and CCU are at a defining moment to provide clarity and perspectives to researchers, companies and society as a whole. It is paramount to understand what is the legal grounds for CCU projects, what are the EU objectives for deployment of CCU, and what are the uncertainties and challenges that may impeach future projects from getting off the ground. It is also crucial that researchers and scientists are involved in those discussions to inform local, national and EU policy-makers about the possible consequences of legislations that are being adopted right now.

The development of routes to produce sustainable fuels and chemicals by the integration of renewable energy sources is one of the major challenges for our society, and it is vital to propose disruptive strategies allowing to reach the updated Horizon Europe targets. Artificial Photosynthesis is one of the most promising strategies to decrease the fossil fuels dependence and greenhouse emissions by the transformation of CO₂ and other natural resources (H₂O, N₂, biomass…) into sustainable fuels and chemicals using renewable energy sources. Compared to other CO₂ recycling technologies like electrochemical reduction or thermo-catalytic hydrogenation, photoelectrochemical route offers a promising potential in the medium term for direct solar energy conversion/storage. For this technology to become reality and be transferred into the energy industry chain, a significant enhancement of the process in terms of efficiency and selectivity control is still needed. This enhancement must come by the hand not only of materials science for the development of highly photoactive catalysts/electrodes, but also of device engineering where efficient and scalable solar reactors are needed that maximises the overall efficiency.

This work aims to report the successful validation in the industrial setting (TRL 5) of a new concept of low-cost flow photo-reactor prototype for CO2 reduction and N2 fixation to produce fuels and chemicals (CH4, C2H4, C3H6 and NH3) coupled to the oxidation of microplastics and organic pollutants from wastewater treatment plants. This reactor can be also used in other portable or stationary locations such as chemicals, fertilizers, cement or refinery industries, homes, cements or power plants, among others. It consists of a versatile system with dual configuration: Photocathode vs Dark Anode and PV+EC Cathode vs Dark Anode configuration, overall dimensions of 300x300 mm made of PVDF and  with 20 lighting windows (20x30 mm).  The overall system for industrial validation includes in addition to the reactor, the rest of the equipment such as power source, electrolyte tanks or pumps.  Regarding the instrumentation, different flowmeters, pressure transmitters, COD transmitter, conductivimeter and pHmeter have been included to register all the main operational variables

Advanced computational fluid dynamics techniques have been also performed to optimize the prototype operation, minimizing mass transport limitations in the system. CFD results have shown very good contact properties of the fluid with the electrode surfaces if they use flow rates above 30 l/h (Inlet Re = 700). Finally, the sustainability performance of the proposed system is being assessed through a Life Cycle and Social Analysis (LCSA) perspective.

Hot carriers generated during plasmonic decay in metal nanostructures can improve the efficiency of photocatalytic processes, particularly when combined with metal oxides to drive photochemical reactions. Copper has already proven to be an efficient and selective electrocatalyst, being the only known metal capable of reducing carbon monoxide into significant amounts of hydrocarbons and alcohols over sustained periods at high reaction rates. In our project, we investigate copper-based plasmonic metamaterials as potential photocatalysts for the plasmon-driven catalytic conversion of carbon dioxide. First, we developed a fabrication method for an array of copper nanorods on a glass substrate, which benefits from high uniformity over a large surface area, low cost and scalability. This hyperbolic metamaterial offers several advantages, including a large highly reactive surface area and strong tunable optical properties in the visible range [3]. In this talk, we will also demonstrate the fabrication of a core-shell Cu/Cu₂O metamaterial by controllably growing copper oxide layers with nanometric thickness using anodization and its impact on the optical properties of these nanostructures. This process is monitored optically in real-time using in-situ visible light spectroscopy that infers the current state of the sample and the oxidation state of the copper.  

The photo-electroreduction of CO₂ was performed under laser illumination using Cu and Cu₂O/Cu-based nanostructures as plasmonic photocathodes. We studied the effect of laser intensity on the photocurrent by varying the output power of the light source illuminated on the plasmonic photocatalyst. The presented plasmonic nanostructures show great potential by combining the well-known catalytic behaviour of copper oxides with the plasmonic enhancement of metallic nanostructures offering a promising approach towards highly efficient and potentially selective photo-electroreduction of CO₂.  

The CO2 transformation via electrochemical reduction has been a longstanding target, considering the application of intermitted renewable energy sources. In such a system, the ability of producing liquid fuels is highly desirable due to their high energy density and security in storage and transportation, to which the design of electrocatalytic materials is the main focus. In this direction, Copper-based materials showed great promise to promote selective electroreduction of CO₂ to C₂₊ products with a high conversion efficiency. Research efforts have been made to improve the activity and selectivity of Cu-based electrocatalysts through doping or alloying with other transition metals. Moreover, these electrocatalysts can be coupled to semiconductors to obtain photocathodes. Cuprite (Cu2O) thin films are currently among the most studied p-type semiconductors employed to this aim, however it suffers from severe photo-corrosion and requires multi-step passivation approaches. Generally,  the fine tuning of catalytic properties and selectivity towards the desired products requires an exhausting trial and effort approach, currently representing  the main bottleneck in the realization of performative electrodes.

In the present study Cu-Ti and Cu-Sn alloys are studied for the electro- and photo-electrocatalytic reduction of CO2 (CO2RR) [1][2]. The role of Titanium and Tin relative amount in Cu-based alloys was analyzed in a high-throughput approach. To this aim, lateral concentration gradients of Ti and Sn in copper thin films were prepared by magnetron co-sputtering, producing an entire materials library in a single sample. On the other hand, the  local electrochemical response of limited portion of the sample (about 1mm²), corresponding to a defined atomic ratio, was measured with a scanning flow (photo)electro-chemical cell. High  throughput synthesis and characterization of a materials library, in fact, allowed to drastically reduce experimental effort to find the best configuration. In such a way, it was possible to rapidly select the best atomic concentration for each electrode in terms of electrochemical characteristics ( 5 at.% of titanium and 10 at.% of tin in CuTi and CuSn, respectively). Once the best atomic concentration was obtained, a selectivity analysis has been carried with an HPLC and micro GC in order to reveal, during the CO2 reduction reaction, both the liquid and the gaseous products, respectively.

In addition to that, those catalysts were coupled with a semiconductor, in particular electrodeposited Cu2O electrodes with different passivation layers (TiO2 and AZO), to study their stability and performance under both light and dark configurations.

The most challenging deal we face today is the need to lower greenhouse gas (GHG) emissions and tackle climate change. Though calls to reduce them are growing louder yearly, emissions remain unsustainably high. CO₂ is the key contributor to global climate change in the atmosphere. Electrochemical CO₂ reduction (EC CO₂R) into chemicals or fuels holds great research interest as a promising approach to mitigate CO₂ emissions and reach a carbon-neutral future.¹ In this regard, an extraordinary effort has been made to discover new efficient and sustainable catalysts at the laboratory level over recent years. High-performance electrocatalysts in aqueous electrolytes often rely on noble metals, which may hinder their industrial applications. Herein, we successfully synthesized core-shell Cu₂O/SnO₂ nanoparticles^2–4 functionalized with a silane group, using a simple and versatile methodology based on a three-step scalable synthesis method involving wet precipitation followed by salinization and, finally, a rhenium-based complex has been assembled by electro-polymerization.⁵ The carbon paper-supported Cu₂O/SnO₂-Re electrocatalyst was characterized at 10 cm² scale achieving a CO:H₂ ratio from 3 to 9, and demonstrating an stable syngas production up to 24 hours at -20 mA·cm^-2. To translate those developments from the laboratory level to a higher TRL towards the practical application of CO₂ capture and utilization⁶, an additional chamber was added to the system for the continuous CO₂ capture and electrochemical conversion, increasing the electrode area from 10 cm² to 100 cm². Captured CO₂ co-electrolysis to syngas (H₂:CO ratio of 5) in one step was demonstrated with a high CO₂ conversion at a current up to -2 A, indicating the scale-up potential of this intensified system. The technology is currently under validation in a TRL4 reactor composed of an array of 5 modules (i.e., 4 x 5 cells x 100 cm²) with a total active area of or 0.2m² for direct CO₂ conversion from simulated anthropogenic sources. The design integrates low-cost photovoltaic (PV) cells to provide any required additional bias to drive the reaction, thus, Perovskite PV panels with a cost of up to 5 times lower (10 €/m²) than Si PV cells were used. The TRL5 demonstration of the developed technology is being done with real flue gas emissions since October 2024.

A promising technology to foster the transition to net-zero carbon emissions is the electrochemical reduction of CO₂ (eCO₂R), which can convert CO₂ into climate-neutral fuel and other economically valuable compounds.[1] Despite the potential of eCO₂R, there are numerous areas where electrolyzer and catalyst efficiency and stability could be improved, thereby necessitating further research. eCO₂R yields multiple products both gaseous and liquid at room temperature.[2] The results can be influenced by a variety of factors, including the choice of catalyst, substrate type, applied potential, electrolyte pH, and electrolyzer design.[3] The wealth of experimental data, combined with the complexity of the data formats, often result in the loss of various aspects of precious experimental data. This complexity highlights the importance of having a strong framework for data acquisition and analysis. In this work, we introduce our high-throughput experimental setup for eCO₂R.[4] Our setup comprises 10 parallel electrolyzers, each controlled individually using a dedicated potentiostat channel. The system is equipped with multiple mass flow controllers and meters, temperature sensors, and pressure sensors to monitor experimental conditions. Online GC and LC are also incorporated to periodically analyze the products from the electrolyzers. Our setup generates heterogeneous but rich data in high volumes. To manage this, we have developed an open-source software package that automatically synchronizes multiplexed data chronologically and automates the data analysis.[5] This software ensures that our data adheres to the FAIR principle (findability, accessibility, interoperability, and reusability). Designed with modularity in mind, our software allows us to introduce additional electrolyzers and diagnostic instruments with minimal impact on the analysis workflow. We anticipate that our setup and workflow will inspire the development of other high-throughput experimental setups for eCO₂R, thereby accelerating research in this challenging field.

The electrochemical reduction of CO₂ is a challenging and promising opportunity to fight climate change and to reduce the greenhouse gas concentration in the atmosphere. In the previous work, Zeng et al. [1] deeply investigated the role of copper and antimony-based bimetallic catalysts, optimized the solvothermal microwave-assisted synthesis and greatly demonstrated the electrochemical selective CO production starting from a pure CO₂ feed. To understand how to translate research from laboratory scales (5 cm²) to industrially relevant scale (>100 cm²), this work analyzes different step conditions optimization during the scale up process. This work has the goal to optimize its performance in membrane electrode assembly cell configuration (MEA). Protocols optimizations concern both the catalyst preparation and the cell setup parameters. Regarding the catalyst optimization this work focused on how the ink preparation and the catalyst loading can affect the process selectivity. It was found that, a high catalyst loading and an anionic binder are necessary to obtain high CO production (FE_CO>90%). On the other hand, concerning the cell setup, to decrease the total cell voltage this work focused on the type of membrane, the electrolyte optimal concentration and the nature of the counter electrode (CE). IrOx-based CE was found to have greater performance with respect to Pt-based CE and a huge decrease in terms of potential (> 0.5V) was appreciated during CP=150 mA/cm². To conclude, interesting optimization results were obtained in order to scale up the process and reach TRL4-5. Future developments will concern the scale up to TRL6-7 and stability tests (>150h) to provide industries with an electrochemical cell for CO₂ transformation that ensures high reliability, durability, and selective production of CO.

Turning carbon dioxide (CO₂) into an industrial feedstock is a major challenge, but a necessity for a circular economy. To this end, utilizing an alkaline membrane electrode assembly (MEA) to electrochemically perform the CO₂ reduction reaction (CO₂RR), transforms CO₂ in chemical feedstocks at efficient and industrially relevant reaction conditions. However, the cation crossover through the anion exchange membrane combined with the high local CO₂ concentration and alkalinity yield carbonate salts deposit at the cathode. These salts block CO₂ flow to the catalyst, decreasing the faradaic efficiency and creating a catastrophic pressure buildup. While carbonate formation is an inherent problem in alkaline CO₂RR, cation crossover and salt precipitation can be mitigated.

                Here, we study the effect of operational conditions on the cell failure in alkaline MEA electrolyzers. We derived four key operating conditions to vary, based on solubility products and the Nernst-Plack equation. Focusing on the cation crossover deconvolutes salt-related cell failure from the electrolyzer design, while simultaneously predicting salt-related cell failure, without the need to run a cell to the point of failure. We found a high degree of cation crossover mitigation when using either cesium-based anolytes or elevated cell temperatures. Furthermore, we found an interesting effect of the membrane thickness on the ionic fluxes over the membrane. Our results are both insightful to researchers starting in the field of MEA CO₂ electrolyzers and as guidelines for prolonged cell operation.

The electrochemical conversion of carbon dioxide (CO₂) to value-added products attracts attention in view of closing the carbon cycle and compensating anthropogenic CO₂ emissions, using electricity from renewable source as input. In fact, in recent years, there has been a huge and growing number of papers that published on this topic. All components related to CO₂ electroreduction (CO₂ER) are currently being studied, including catalysts, membranes and electrolytes, but also new set-ups and reactor architectures. However, despite a nascent interest from industry, currently the vast majority of work focuses on studies on a small scale, on the order of few cm². Nevertheless, as the reactor size begins to increase, a whole range of issues (such as long-term stability, flow channel design, separation of the products (downstream), employment of large scale quantities of electrocatalysts) begin to come up that are not present or not relevant on a small scale, limiting process performance and durability, or leading to increased process costs.

In this framework, a systematic analysis of the parameters that can influence the process as the scale increases, may help in further developing the CO₂ER toward industrial application. Therefore, in this work, we analyzed the effect of electrode (morphology, wettability, composition, …), electrolyte (composition and concentration) and membrane on the selectivity and durability of gas-fed zero-gap CO₂ electrolyzer in membrane-electrode assembly configuration while varying the active area from 5 to 100 cm². In particular, silver- and copper-based materials were employed as electrocatalysts on different carbon-based substrates (characterized by diverse morphology and wettability properties) and the electrode features were optimized in terms of composition (catalysts and binder loadings) and fabrication process, aimed at reducing at the same time the production costs.

One of the strategies for reducing CO₂ emissions from industrial sources involves electrochemical conversion and utilization of CO₂ to create valuable products. This method is considered efficient and promising as it allows the storage of excess energy from renewable sources in CO₂-reduced products such as formic acid, formate, methanol, or ethylene. The process occurs in an electrochemical reactor where CO₂ is supplied to the cathode. When an external voltage is applied, the CO₂ molecules undergo transformation over a catalyst surface, while an oxidation reaction occurs at the counter-electrode. Typically, an ion exchange membrane separates both compartments, facilitating the separation of reaction products and increasing the overall system efficiency.[1].

This work aims to develop a prototype of a CO₂ electrolyzer for industrial use, as the first phase in the full-scale implementation of CO₂ electroreduction to formate. The design and testing of the prototype have been a collaborative effort involving the DePRO research group, which has been actively engaged in advancing CO₂ conversion technology in recent years [1-3], and APRIA Systems, a technology supplier company responsible for constructing the CO₂ electrolyzer.

The electrolyzer comprises various components, i) outer closure plates made of stainless steel, ii) the external reactor structure constructed from polypropylene, iii) internal spacers composed of Viton, and iv) titanium current collectors. In the anode compartment, an iridium mixed oxide plate acts as the counter electrode for the water oxidation reaction. As the cathode, a Gas Diffusion Electrode (GDE) is employed, with an active geometric area of 100 cm². This electrode is fabricated by automated spray pyrolysis, a process that has been previously optimized [2]. The catalytic ink consists of the catalyst (commercial Bi₂O₃) and Vulcan, with a mass ratio of 50:50, suspended in ethanol as a solvent and Nafion D-521 as a binder. This ink is applied over a Teflon-coated (50 %) carbon paper. Finally, a Nafion cation exchange membrane (CEM) separates the cathode and anode compartments.

The electrochemical reactor operates in an L-G configuration, a humified CO₂ pure stream is fed to the cathode compartment with a flow rate of 20 mL min^-1 cm^-2, while in the anode an alkaline 1 M KOH anolyte is pumped at 0.57 mL min^-1 cm^-2. Preliminary tests were carried out in the L-G configuration, supplying a current density in a range of 30 to 300 mA cm^-2 to the system.

After construction, the prototype underwent testing to evaluate its performance. In this regard, the system operated continuously for 2 hours with a single pass of CO₂ and electrolyte through the system. The applied current density was varied in a range from 30 to 300 mA cm^-2 in different experiments.  The results of these preliminary tests are shown in Figure 1. The most promising performance is reached working at 200 mA cm^-2, with a formate concentration of 760 g L^-1, an FE of 67 %, and an Energy consumption of 510 kWh kmol^-1. These outcomes improve the performance in prior lab-scale experiences within the research group [3], therefore, the system is demonstrated to be scalable. Nevertheless, ongoing efforts are necessary to improve the system's stability and efficiency, optimizing the electrochemical cell's operational variables, such as the humidity in the cathode feed, the anolyte composition and flowrate, or the CO₂ feed flowrate.

The efforts invested in designing and constructing an industrial demonstrator of a CO₂ electrolyzer have yielded a functional prototype with promising results in preliminary tests, showcasing the scalability of CO₂ electroreduction technology. Future work should be dedicated to maximizing the stability and efficiency of the system in long-term operations.