Electrochemical CO₂ reduction (CO₂R) has emerged as a key enabling technology for establishing sustainable carbon cycles and defossilizing the chemical industry by converting renewable electricity and captured carbon dioxide into value-added chemicals and fuels. Despite tremendous advances in catalyst development over the past decade, the translation of promising laboratory-scale concepts into industrially relevant electrolysis technologies remains one of the major bottlenecks preventing large-scale implementation. While significant efforts have been devoted to the development of novel catalyst materials, industrial deployment requires a much broader perspective that simultaneously addresses electrode architecture, membrane-electrode assemblies, mass transport phenomena, and reactor engineering. Performance metrics obtained under idealized laboratory conditions frequently fail to translate into practical devices operating at elevated current densities and under realistic process conditions.

Herein, we present an integrated approach that bridges catalyst development with application-oriented CO₂ electrolysis technologies. Using representative examples from materials-based electrocatalysis, we demonstrate how catalyst design principles can be transferred into functional gas diffusion electrodes and subsequently implemented in zero-gap electrolyzers operating at industrially relevant current densities. Particular emphasis is placed on the interplay between catalyst properties, catalyst integration strategies, electrode formulation, and membrane-electrode assembly optimization. We further discuss how transport limitations, local reaction environments, and reactor configurations govern activity, selectivity, energy efficiency, and long-term stability under practical operating conditions.

Recent advances in high-pressure CO₂ electrolysis, scale-up methodologies, and the integration of electrolysis units with downstream chemical processes will be highlighted alongside. In addition, practical challenges associated with realistic CO₂ feed streams and the transition from laboratory screening platforms to pilot-scale demonstrators will be addressed.

By connecting catalyst development with engineering-driven device design, this contribution outlines a pathway towards application-ready CO₂ electrolysis technologies and identifies the key scientific and technological barriers that must be overcome for industrial implementation. Ultimately, the presentation aims to stimulate discussion on how interdisciplinary approaches can accelerate the deployment of scalable, efficient, and economically viable carbon conversion technologies.

A decarbonized society is essential to maintain and further improve the standard of living for humankind. However, the chemical industry still requires carbon-based fuels as a resource, hindering decarbonization [1]. One carbon-neutral technology to produce base chemicals is electrochemical carbon dioxide electrolysis (CO₂E), powered by renewable electricity. CO₂E targets multiple base chemicals, ranging from carbon monoxide (CO) and ethylene (C₂H₄) [2].

CO₂E is well established at lab-scale, normally utilizing gas-fed membrane electrode assembly (MEA) cells. However, lab-scale MEA CO₂ electrolysers are suffering from limited runtimes far below industry requirements of >10.000 h [3]. De facto, most CO₂ MEA cells lose their carbon product selectivity within a couple of hours of operation under industry-relevant conditions.

Extensive flooding and salt formation are the main bottlenecks for the operation runtime in the current state of the art, often occurring at the same time or briefly after each other [4]. Both limit the access of CO₂ at the cathodic catalyst layer and impede the cell's selectivity [5]. While salt mitigation strategies are more understood [6,7], a deeper understanding of flooding and the underlying water management within the MEA cell and especially at the cathodic reaction environment, where the CO₂ reduction takes place, is still absent. Hence, in this work, we present model-aided experimental work, investigating the dominant water transport mechanism and its effect on product selectivity to extend the system's lifetime.

To do so, experiments in an AEM-based MEA cell using sputtered Ag as the cathode-side catalyst partnered with an oxygen-evolving IrO₂ catalyst at the anode are executed to reduce CO₂ to CO. We perform a model-guided sensitivity analysis for industry-relevant conditions under current density up to 500 mA cm^-2 in a temperature corridor from 25°C to 65°C, using CsHCO₃ as anolyte varying from 0.01 M to 0.5 M to understand the impact of the different water transport mechanisms. Our data, combined with the model predictions, indicate that diffusive water drag driven by ion gradients across the membrane is the dominating mechanism for water transport to the cathode. Based on the above operation conditions regarding membrane thickness, anolyte concentration, current density and temperature, are determined to flatten ion profiles and mitigate flooding. That way, stable selectivity under current density of up to 500 mA cm^-2  for the investigated timeframe of 24h is achieved. Using the above findings, we hope to contribute to the mitigation of water management-related and underlying ion management-related bottlenecks for CO₂E on the pathway to industrial application. 

CO₂ electrolysis is undergoing a transition from lab-scale research to industrial deployment. However, the route from beaker chemistry to pilot plants remains challenging due to a fundamental mismatch between the objectives of exploratory research and industrial application. While academic efforts often focus on achieving champion performance metrics, industrial stakeholders prioritize reliability, durability, and scalability. Standardization plays a pivotal role in bridging this gap by enabling faster knowledge transfer, ensuring comparability of results, and accelerating the development of robust, industry-ready technologies.
eChemicles is pioneering the industrialization of CO₂ electrolysis technology and places significant emphasis on establishing standardized protocols both internally and at the community level. In this presentation, I will demonstrate how well-developed processes and standardized methodologies accelerate research and development in the CO₂ reduction field. Standardization—encompassing incoming material inspection, electrode preparation, and electrolyzer testing already at the R&D phase—contributes significantly to generating reproducible and reliable measurement data, which in turn accelerates performance imrpovement. I will discuss how this approach supports scale-up processes and evaluate whether the same standards can be applied across differently sized systems.

CO₂ electrolysis is widely recognized as a promising pathway to enable carbon circularity in the chemical industry. However, from the perspective of a manufacturer of membrane electrode assembly components for various electrochemical applications, its industrialization is currently constrained less by fundamental electrochemistry than by a lack of material and system standardization across the value chain. In contrast to established technologies such as PEM water electrolysis, CO₂ electrolysis lacks clearly defined operating conditions, material specifications, and component benchmarks.

In PEM water electrolysis, decades of development have led to a well-converged materials ecosystem: catalyst compositions, membrane specifications, porous transport layers, and bipolar plates are standardized to a high degree, with clearly defined performance, durability, and quality requirements. This enables robust supply chains, reproducible manufacturing, and predictable scale-up. Component suppliers can optimize production processes with confidence in long-term demand and stable specifications.

By comparison, CO₂ electrolysis is characterized by a broad and rapidly evolving landscape of materials and cell concepts. Multiple competing approaches exist for catalysts, membranes (anion exchange, bipolar, hybrid), and gas diffusion electrodes, each operating under different conditions or targeting different products. Companies spearheading the field often use proprietary materials or electrolyzer architecture. This diversity results in fragmented demand profiles and a lack of industrial-grade specifications. Consequently, component manufacturers face challenges in ensuring consistent quality, qualifying materials, and justifying investments in large-scale production capacity.

Furthermore, the absence of harmonized testing protocols and lifetime criteria complicates direct comparison between material solutions. Performance claims are often system-specific, limiting transferability and increasing development risks. Unlike PEM water electrolysis, where material compatibility and durability are well understood, CO₂ electrolysis still lacks consensus on the most viable material combinations for industrial operation.

This contribution highlights the critical need for convergence in material selection, operating windows, and qualification standards. Establishing a more unified framework—similar to what has been achieved in water electrolysis—will be essential to enable reliable component manufacturing, reduce costs, and accelerate the industrial deployment of CO₂ electrolysis technologies.

In this presentation, we will report on recent advances in our design and understanding of electrocatalytic interfaces and devices for efficient electrochemical CO₂ valorization into value-added carbonaceous e-fuels and e-chemicals. We will present new in situ diagnostic tools to recognize and analyze cell failure modes in zero- and one-gap cell designs. Among them is the carbon crossover coefficient (CCC), the N₂ bleed FE value, and the H₂ crossover into the catholyte [1-4].

References:

[1] Brückner, S.; Bondarchuk, O.; Araújo, A.; Ju, W.; Cid, R.; Paz, E.; Krebs, F.; Soares, O.; Amorim, I.; Yu, Z. P.; et al. Failure mode diagnosis and stabilization of an efficient reverse-bias bipolar membrane CO2 to CO electrolyzer. Energ Environ Sci 2025, 18 (13), 6577-6586.

[2] Brückner, S.; Ju, W.; Strasser, P. Efficient Forward‐Bias Bipolar Membrane CO2 Electrolysis in Absence of Metal Cations. Advanced Energy Materials 2025, 15, 2500186.

[3] Brückner, S.; Feng, Q.; Ju, W.; Galliani, D.; Testolin, A.; Klingenhof, M.; Ott, S.; Strasser, P. Design and diagnosis of high-performance CO2-to-CO electrolyzer cells. Nature Chemical Engineering 2024, 1 (3), 229-239.

[4] Filippi, M.; Galotti, E.; Sahin, B.; Wiesner-Fleischer, K.; Magori, E.; Simon, E.; Fleischer, M.:  Strasser, P.; H2 Crossover as a Descriptor for Degradation and Mass Transport in CO2 Electrolyzers, in review, 2026

The electrochemical reduction of carbon dioxide (CO₂) represents a promising strategy to mitigate anthropogenic emissions while producing high-value chemicals and fuels. Membrane electrode assembly (MEA) electrolyzers employing anion exchange membranes are among the most industrially relevant configurations for CO production^[1]. However, their large-scale deployment remains constrained by limited operational stability, with salt formation in the cathode compartment representing one of the most critical bottlenecks^[2]. Under applied negative potentials, alkali metal cations migrate from the anode to the cathode. There, they react with CO₂ and hydroxide ions to form carbonate and bicarbonate salts. These deposits progressively accumulate within the gas diffusion electrode and microporous layer, obstructing CO₂ transport, promoting the hydrogen evolution reaction, and ultimately leading to electrolyzer failure.

In this work, we present a novel mitigation strategy based on the integration of tuned low-frequency ultrasound into a zero-gap MEA CO₂ electrolyzer (Sono-MEA). The ultrasonic probe (26 kHz) is mechanically coupled to the cathode side and operated to induce controlled acoustic cavitation while minimizing temperature variations. Acoustic cavitation and microstreaming disrupt salt nucleation and growth, while promoting the continuous detachment and removal of crystalline deposits during operation.

The approach was validated using a 5 cm² MEA electrolyzer operating at industrially relevant current densities (300 mA cm⁻²) under ambient conditions. To rigorously assess its effectiveness, experiments were deliberately conducted under challenging, salt-promoting conditions using potassium-based electrolytes. Compared to conventional MEA operation, pulsed ultrasound leads to improved stability, maintaining CO selectivity over extended operation and delaying performance degradation. Elemental analysis, combining inductively coupled plasma measurements and EDX-FESEM characterization, confirms a reduced accumulation of alkali cations within the cathode compartment and enhanced transport of salt-forming species toward the outlet stream.

These findings demonstrate that ultrasound-assisted operation provides a continuous and non-invasive cleaning mechanism, directly addressing a key bottleneck in CO₂ electrolyzers without requiring system interruption. This approach complements existing mitigation strategies and offers a scalable pathway to improve the durability and long-term performance of MEA-based CO₂ electrolyzers.

The industrial deployment of electrochemical CO₂ reduction is no longer limited only by catalyst activity, but by the ability to maintain selectivity, stability and energy efficiency while gas transport, water management, ion crossover and pressure gradients evolve with electrode area. These challenges become even more critical for integrated CO₂ capture–conversion schemes, where captured or CO₂-rich streams could reduce separation costs but impose additional constraints on electrolyte compatibility, membrane operation and reactor design.[1]

Here, we present a scalable Cu-based gas-diffusion-electrode platform that provides the electrochemical and engineering basis for translating CO₂ electrolysis toward captured-stream syngas production. CRM-lean Cu₂O/SnO₂-derived catalytic layers were fabricated by scalable spray coating and integrated into flow and zero-gap electrolyzer architectures. The platform was evaluated across active areas of 5, 25 and 120 cm², with ongoing scale-up toward 500 cm², reaching current densities up to 500 mA cm⁻². By tuning catalyst-layer architecture, membrane/ionomer pairing, electrolyte composition and operating current density, the product distribution was directed toward CO-rich syngas and formate as complementary C1 routes, with Faradaic efficiencies toward syngas up to 80%.[2-3]

Rather than focusing only on peak performance, this work identifies the operational bottlenecks that govern scalability. Polarization curves, online gas analysis and Faradaic-efficiency mapping were combined to distinguish ohmic losses, flooding onset, CO₂ starvation, membrane dehydration and catalyst-layer inhomogeneity. Post-operation SEM, TEM, XRD and ICP analyses were coupled with COMSOL-based multiphysics modelling to identify transport and pressure-management limitations and guide electrode and cell redesign.[4]

This work therefore moves beyond performance demonstration and delivers scale-up criteria for stable CO₂ electrolysis: reproducible catalyst-layer manufacturing, controlled triple-phase-boundary formation, membrane/ionomer matching, and diagnostic protocols that connect voltage evolution with product selectivity. The resulting platform provides a concrete bridge between purified-CO₂ electrolysis and integrated capture–conversion concepts based on amine or ionic-liquid media, opening a pathway toward decentralized syngas production from industrially relevant CO₂ streams.

The chemical industry rests almost entirely on fossil carbon, both as the energy that drives its processes and as the raw material from which its products are built. Replacing that foundation is one of the central challenges of the energy transition. Electrochemical carbon oxide conversion offers a direct route: using renewable electricity to transform carbon dioxide or carbon monoxide into the molecules industry already depends on and as such turning a waste emission into a feedstock.

Dioxycle is a carbon utilization company developing electrolyzer technologies with the aim of operating at the industrial scale. The company produces key chemical building blocks without fossil inputs, offering a way to decarbonize sectors that are otherwise difficult to abate. Realizing this potential depends on progress across materials, reactor design, and engineering, and on bridging the gap between promising laboratory results and the durability, efficiency, and cost demanded by real industrial deployment.

This talk introduces Dioxycle's current progress to date.

Electrochemical CO₂ conversion is emerging as a promising route for the electrification of carbon-based chemical production. While high current densities and Faradaic efficiencies are often demonstrated in laboratory-scale cells with active areas of only a few square centimetres, the transition toward larger electrolyzer systems introduces additional challenges. In extended flow cells, reactant depletion, heat management, pressure effects, and mass transport limitations can generate spatial inhomogeneities in current density and product selectivity. As a result, scaled electrolyzers cannot always be treated as spatially uniform systems, and outlet-averaged measurements provide only a black-box description of the underlying local processes.

Previously, we reported spatial gradients in current density and selectivity along the flow direction in a linear CO₂ electrolyzer, showing how CO₂ depletion and changes in the local reaction environment drive a shift from CO formation toward hydrogen evolution. In this work, we extend this concept from one-dimensional flow-direction analysis to two-dimensional X–Y spatial mapping, providing a more complete picture of the reaction environment across the electrode surface.

Using a diagnostic zero-gap CO₂ electrolyzer, we correlate local current density with local product distribution and reveal position-dependent performance under industrially relevant operating conditions. This approach enables the mapping of partial current densities toward different products across the electrode, identifying where parasitic hydrogen evolution emerges and how it relates to local transport limitations. The platform is also used to investigate how different flow-field architectures influence the current density distribution, linking cell design directly to spatially resolved electrochemical performance. Importantly, the system enables long-term operation, allowing the evolution of spatial gradients to be followed over several days.

In this talk, I will discuss how two-dimensional spatial diagnostics can reveal hidden heterogeneities in CO₂-to-CO electrolyzers and how flow-field design affects the distribution of reaction rates across the electrode. These results emphasize that efficient operation must be achieved across the entire electrode area, not only at the outlet, and highlight the importance of local chemical analysis for guiding the design of efficient, stable, and scalable CO₂ electrolysis systems.

Electrolysis-based technologies—such as water splitting, CO2 electroreduction, and other emerging reactions (e.g., reduction of reactive carbon and nitrogen species)—offer sustainable pathways to decarbonize major sectors including transport (fuels, e.g., green hydrogen), manufacturing (chemical feedstocks), and agriculture (sustainable fertilizers). These reactions depend on breaking chemical bonds and selectively reassembling molecules into desired products with high activity and selectivity. Their commercial viability, however, hinges on delivering strong performance across key metrics in scalable processes.

Conventionally, progress has been driven by innovation at the catalyst level—for example, designing materials with targeted physicochemical properties. This approach is challenging because catalysts can change substantially under operating conditions, which limits predictive catalyst design. Moreover, operating at high rates in industrially relevant settings shifts the chemical environment and reaction pathways, increasing the importance of the electrochemical environment.

In this highly dynamic context, I will present examples of how understanding and controlling reactants (e.g., water) and intermediates at catalyst interfaces can tune local physicochemical properties, and how this control can improve multiple performance metrics in high-current-density water electrolysis and CO2 electroreduction. I will conclude by presenting strategies to program catalyst reconstruction to address the full CO2R interface.

Achieving large-scale, cost-effective green ethylene production is a major challenge for the chemical industry.¹ The electrochemical reduction of carbon dioxide (CO₂) offers a promising pathway.² While significant efforts are currently focused on demonstrating long-term electrolyzer stability for industrial deployment, the impact of fluctuating renewable power inputs has received far less attention.^3,4 As future CO₂ electrolysis systems are expected to be directly coupled with intermittent electricity generation, understanding their response to dynamic operating conditions is essential. In this work, we assess the performance of a CO₂ zero-gap electrolyzer under repeated load variations representative of renewable-driven operation. We investigate the effect of reducing current density on key performance indicators, including product formation rate and cell voltage, and evaluate the extent to which performance is recovered once nominal operating conditions are restored. By distinguishing between reversible and irreversible effects, we identify which elements are most susceptible to degradation. Building on these insights, we are developing an adaptive operating protocol aimed at minimizing transient losses and facilitating stable operation under variable power conditions. Our results provide practical guidance for flexible operation of CO₂ electrolyzers and support their integration with renewable energy systems.

Electrochemical CO₂ reduction (eCO2RR) is a promising pathway for sustainable carbon utilization, but its industrial deployment depends on overcoming key challenges in long-term stability and reactor scale-up. This presentation focuses on bridging fundamental electrochemical degradation mechanisms with practical engineering solutions to enable efficient, durable formate production.

Investigations into carbon-free metal-based gas diffusion electrodes (GDEs), specifically those using tin (Sn) and bismuth (Bi), reveal that performance decline is largely driven by process-level phenomena such as localized pH shifts and conductivity loss, rather than intrinsic catalyst degradation. By addressing these root causes through electrolyte management and anodic pulsing, the operational lifespan of Bi-based GDEs can be successfully extended past 4,000 hours at a steady current density of 100 mA cm⁻² [1].

To tackle the secondary bottleneck of scalability, the performance of VITO CORE® GDEs was analyzed across a range of reactor sizes from 10 cm² up to 400 cm². Findings demonstrate that while numbering-up via reactor stacking presents significant mass-transport and fluid-dynamic complications, utilizing a single, large-area 400 cm² reactor yields a high coulombic efficiency of 73% while concurrently reducing energy demands [2]. Ultimately, merging these mechanistic insights with targeted reactor engineering clears a pathway toward highly durable, industrial-scale CO₂ electrolysis systems.

Copper-based catalysts are among the most promising materials for the electrochemical reduction of CO₂ to multicarbon products such as ethylene; however, their performance is often limited by instability, surface restructuring, and competing reaction pathways^1,2. In this work, we investigate the use of ultrathin silica (SiO₂) layers grown by atomic layer deposition (ALD) on copper oxide nanoparticles to tune the catalyst-electrolyte interface and improve performance in a membrane electrode assembly (MEA) configuration.

Silica layers were deposited in a fixed-bed ALD reactor using a controlled number of cycles from 5 to 30 cycles. The ALD process was further optimized to reduce residual chlorine species by adjusting purge conditions, leading to improved surface quality and more reliable interfacial properties. Silica and other oxide slayers have been testing for different electrochemical reactions showing a strong permeability and selectivity for specific species without affect the electrocatalytic activity^3–5

Initial results show that ultrathin coatings (5 ALD cycles) not only preserve catalytic activity but also enhance selectivity toward ethylene. At higher current densities 200 mA/cm² , silica-modified electrodes exhibit a comparable faradaic efficiency for C₂H₄ compared to bare copper, along with a decrease in CO formation, indicating a shift in reaction pathways driven by interfacial effects. These findings suggest that the SiO₂ layer acts as a proton-permeable, semi-transparent interface that tunes the local reaction environment without blocking active sites.

Electrochemical impedance spectroscopy (EIS) was used to probe resistance changes within the MEA configuration as a function of coating thickness, providing insight into transport and interfacial phenomena. Furthermore, inductively coupled plasma (ICP) analysis revealed no detectable copper dissolution for silica-coated nanoparticles, highlighting the protective role of the ultrathin SiO₂ layer under electrolysis conditions. Complementary characterization by X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) supports the structural and chemical stability of the coated systems before and after electrolysis.

Overall, this work demonstrates that ultrathin ALD-grown silica layers provide an effective strategy to enhance ethylene selectivity while improving catalyst stability, emphasizing the importance of nanoscale interface engineering in CO₂ electroreduction systems.

The potential of low-temperature electrolysis for direct conversion of CO₂ into fuels and commodities (CO, formate, alcohols, C₂+) has been demonstrated at laboratory scale by various academic institutions. Despite a fast-growing research field and a wide industrial interest, most of CO₂ electrolysis is still limited to TRL~3-5, and several fundamental knowledge gaps still remain at the level of a single electrochemical cell, as well as a wide range of unknowns on reactor and process design. At TNO we aim to identify upscaling hurdles at an early stage by combining catalyst development, process parameter understanding and computational modelling to advance CO₂ electrolysis towards industrial implementation. Solutions developed include reactor conditioning, process control, parameter space mapping and regeneration strategies. Integrating R&D at all levels (electrodes>cell>reactor>process>system) is urgently needed to bring the technology towards industrial implementation. In particular, the electrochemical conversion of CO₂ to formic acid and ethylene in a low temperature and pressure environment over a gas diffusion electrode (GDE) can be challenging due to the complex interplay of various parameters.

During this presentation the following recent developments at TNO will be covered:
1.) Investigating the effects of process control and system parameters (P, dP, T, pH, V, A) to extend the lifetime of small scale CO2 electrolysers.
2.) Extending the lifetime of CO2-to-ethylene and CO2-to-formate at 5 and 25 cm2. Learnings and the implications of these findings for further scale-up to 100 cm2.
3.) An update on the development and first-testing of our metal-free testing station AGLAIA for CO2 electrolysis at 100 cm2.

The electrochemical CO₂ reduction reaction (CO₂RR) is a key enabling technology for transitioning from fossil-derived feedstocks toward sustainable manufacturing using CO₂. Among the most relevant application areas is the textile industry, where polyester production remains almost entirely dependent on petrochemical intermediates despite its significant environmental footprint. Achieving industrial production of polyester precursors from CO₂ requires efficient and scalable electrolysis of CO₂ to CO, placing electrolyzer and system-level scale-up at the core of technological development.

In this work, we investigate the scale-up of CO₂ electrolysis systems from laboratory scale to a TRL 6 pilot-scale platform, with a focus on electrolyzer design, long-term operation, and system integration. To address the issue of large hydraulic pressure, we developed robust in-house cathodes capable of withstanding flooding while maintaining electrochemical performance. Furthermore, the differential pressure was studied, to maintain electrolysis in flow-by operation window. High CO₂ flow rates improve throughput but lead to product dilution and increased downstream separation costs. In addition, ion crossover across the membrane was identified as a major driver of electrolyte imbalance and long-term performance degradation, highlighting critical constraints for durable operation at scale. Through optimization of operating conditions and cell design, stable operation for over 60 h was demonstrated at 150 mA/cm² in a flow-by electrolyzer configuration, maintaining CO selectivity above 90%. We further established preliminary operational recovery protocols following cell failure, enabling robust restart.

These findings were translated into pilot-scale system engineering through comprehensive process flow diagrams (PFDs) and piping and instrumentation diagrams (P&IDs). The balance-of-plant was designed for fully automated operation enabling real-time monitoring, and process control. A modular electrolyzer platform with a 0.36 m² unit cell area was designed and scaled to stacks of up to 80 cells. Parallel development of scalable cathode manufacturing, including ink formulation and batch processing, enabled translation to large-area electrodes. This work demonstrates a complete scale-up pathway for CO₂ electrolysis, towards high CO production.

The application of CO₂ electrolysis holds immense promise for decarbonization, yet significant challenges remain to bridge the gap from proof-of-concept to industrial application. While upscaling to megawatt-level stacks is the ultimate objective for commercialization, mastering lab-scale devices is a critical prerequisite. This presentation argues that rigorous lab-scale investigation is essential to identify and resolve fundamental failure modes that would otherwise cripple industrial systems.

 The lab scale allows to investigate critical system choices, including material choice, cell architecture and operating conditions before committing to a system for scale-up. This presentation shows examples for each of these, demonstrating, how challenges can be identified and mitigation strategies can be developed with scale-up in mind. 

Regarding material choice, we investigate cost-effective alternatives to noble metal catalysts. By substituting IrOx with stainless steel as an anode catalyst, we identify a critical stability bottleneck: the dissolution of chromium from the steel, which subsequently crosses over to the cathode and poisons the reaction. This highlights the risk that aggressive cost-reduction in materials can compromise long-term system viability.

In terms of cell architecture, we examine the implementation of bipolar membranes (BPMs) to suppress carbon crossover and enable pure water operation. We address the resulting challenge of interfacial blistering caused by CO₂​ formation by perforating the AEM side of the membrane. Furthermore, we identify self-humidification processes within the BPMs as the next primary bottleneck for achieving the high current densities required for industrial application.

Finally, we explore how operating conditions affect the internal state and longevity of the cell. Through operando neutron imaging, we demonstrate that a pulsed operation mode stabilizes the cell and extends its lifetime by inducing short periods of high humidification at the cathode, which effectively removes salt precipitates. Adding multiphysics simulations further allows us to map gradients in CO₂​ availability and cation concentration along the channel, providing key insights for the optimization of flow field designs in larger cells.

By systematically addressing these failures in materials, architecture, and operation at the lab scale, we provide a roadmap to mitigate risks before upscaling. This approach ensures that the transition to stack-scale electrolysis is built upon a foundation of understood phenomena, directly resolving the primary bottlenecks to industrial application.

CO₂ electrolysis (CO₂E) powered by renewable electricity offers a sustainable route for fuel and chemical production while reducing CO₂ emissions. Traditionally, CO₂E is coupled with the oxygen evolution reaction (OER) at the anode, but OER suffers from high overpotentials, slow kinetics, and low-value oxygen production, reducing overall efficiency. To address this, alternative anodic reactions, such as the hydrogen oxidation reaction (HOR), have been explored.¹ HOR has been widely studied in fuel cell applications and for electrochemical hydrogen pumps (EHP) to produce high purity hydrogen streams from an impure hydrogen input at the anode.²

In this work, we leverage the EHP concept and integrate it with CO₂ electrolysis to reduce overall cell voltage and simplify electrolyzer operation. Owing to the fast kinetics and low overpotential of HOR, we demonstrate a substantial decrease in cell voltage, enabling industrially relevant current densities of up to 500 mAcm^-2 at < 2 V without the need for a circulating aqueous electrolyte.

We systematically investigate HOR-coupled CO₂ electrolysis and evaluate key factors affecting its efficiency and scalability. Using a membrane electrode assembly (MEA) configuration, we first establish the feasibility of electrochemical hydrogen pumping, coupling HOR at the anode with the hydrogen evolution reaction (HER) at the cathode. In this configuration, current densities of 500 mA cm⁻² were sustained at cell voltages below 0.5 V. We then replace HER with CO₂ electroreduction at the cathode, employing silver and platinum as the cathode and anode catalysts, respectively. The performance of both proton exchange membranes (PEMs) and anion exchange membranes (AEMs) is systematically compared, followed by an investigation of the role of alkali metal cations in this architecture.

Furthermore, operando wide-angle X-ray scattering (WAXS) and X-ray fluorescence (XRF) measurements reveal important insights into cation transport, local cation accumulation, and water management within the cell. These observations provide a deeper understanding of systems involving gaseous reactants at both electrodes and highlight critical transport phenomena governing device performance. Overall, our findings demonstrate that HOR-coupled CO₂ electrolysis can significantly improve energy efficiency and offer a promising route toward scalable and economically viable carbon utilization technologies.

An important bottleneck to commercializing CO₂ electrolysis is the high cell voltage under operating conditions (often U_cell ≥ 3V), partly due to the oxygen evolution reaction (OER), which is typically employed as the anode process. Replacing the OER with alternative anode processes, such as the oxidation of small organic molecules, could decrease the cell voltage while enabling the formation of valuable products. Glycerol is an attractive candidate for this purpose, since it is widely available in a relatively pure form as the byproduct of biodiesel production.

In this presentation, I will discuss our results on several glycerol oxidation (GOR) catalysts from the perspective of electrocatalytic GOR activity, selectivity, and (long-term) stability. Two sets of catalysts were investigated in continuous-flow electrolyzer cells: first, mono-, and bimetallic noble metal catalysts such as Au, Pt, Pd, PdAu, and PdPt. Secondly, non-noble metal-containing systems were also scrutinized, including Ni, Fe, and FeNi as single-atom catalysts anchored on an N-doped carbon support. In all cases, CO2RR was driven at the cathode (Ag nanoparticles) of the electrolyzer cell. While a considerable decrease in cell voltage was achieved in the case of noble metals, always a mixture of C1-C3 GOR products formed along with a considerable amount of CO₂ (20-40 % of the passed charge). As opposed to noble metals, formate was the primary GOR product in the case of the non-noble alternatives; however, the measured cell voltages remained only a bit lower than those measured if OER was the anode process. An additional advantage of the non-noble electrocatalysts is the marginal influence of glycerol on their long-term stability, in opposition to what was observed with noble metals.

The majority of published studies on paired CO2RR/GOR electrolysis have been conducted at the laboratory scale (e.g., cell and electrode sizes, duration of the experiment, etc.). In the second half of my talk, I will discuss the main obstacles hampering the scale-up of paired CO2RR/GOR electrolysis. These will be showcased by presenting results demonstrating how cell design, electrode support selection, and various operating conditions (temperature, glycerol concentration, flow rates, transmission of electrolyte, etc.) influence the performance of the paired CO2RR/GOR electrolyzer cell.

Electrochemical CO₂ reduction systems operating under industrially relevant conditions inherently experience significant self-heating due to ohmic losses and activation overpotentials, driving operation toward elevated temperatures. While beneficial for reducing cell voltages, this thermal increase directly impacts the local reaction environment within membrane electrode assemblies (MEAs), particularly through water transport phenomena that alter the microenvironment of Cu gas diffusion electrodes (GDEs) [1].

Here, we investigate the influence of temperature (ambient to 80 °C) on copper-based CO₂ electrolyzers across catholyte-fed and zero-gap configurations at industrially relevant current densities (100–300 mA cm^-2). Increasing temperature significantly lowers the cell voltage (3.94 → 3.37 V at 100 mA cm^-2) due to improved ionic conductivity and faster charge-transfer kinetics [2]. However, this energetic benefit is accompanied by a severe loss in selectivity, with ethylene (C₂H₄) Faradaic efficiency (FE) dropping from 19 to 3.5 %, while hydrogen evolution becomes dominant due to reduced CO₂ solubility and accelerated competing reactions [3].

At intermediate conditions (40–50 °C, 150 mA cm^-2), a favorable regime emerges, where C₂H₄ selectivity improves by ~15 percentage points, indicating a balance between kinetics and transport. At higher temperatures (>60 °C), catholyte-fed systems exhibit rapid instability (<20 min), driven by bubble accumulation, flooding, and three-phase boundary degradation [4].

Zero-gap electrolyzers mitigate these limitations by reducing liquid accumulation and stabilizing interfacial transport. At 300 mA cm^-2, a 7.2 h stability test shows a decline in C₂H₄ FE from 22.03 to 14.7% (FE_C2+ ~29 %), corresponding to a 33.2 % decrease while maintaining energy efficiency toward C₂₊ products above 10 %. This decay correlates with significant water transport (9.5 mL; 1.32 mL h^-1), indicating strong electro-osmotic drag affecting the cathode microenvironment.

Reducing the current density to 200 mA cm^-2 enables a 26 h test, where C₂H₄ FE decreases from ~20 to ~13% (≈ 35 %), while maintaining FE_C2+ > 30% and EE_C2+ > 11%. The cell voltage increases moderately (2.92 → 3.05 V; 3.46 mV h^-1), alongside a significantly lower water transport rate (0.37 mL h^-1), highlighting improved stability through controlled water management.

Overall, temperature emerges as a system-level design parameter, while water transport within MEAs plays a central role in governing stability and selectivity. Achieving efficient and durable CO₂ electrolysis requires integrated thermal–architectural co-design to control the catalyst microenvironment under industrial conditions [5].