Visualization of CO formation at the triple-phase boundary in gas diffusion electrodes for ecCO2RR

<h2>Summary</h2> Electrochemical CO₂ reduction represents a promising technology for mitigating the impact of greenhouse gas emissions, particularly CO₂. Gas diffusion electrodes (GDEs) are widely utilized in this process. Although CO₂ reduction has been successfully demonstrated on small scales with various catalysts, the role of the wetting state of the catalyst layer in GDEs remains poorly understood. This factor significantly influences current density and faradaic efficiency. However, two fundamental questions persist: where within the electrode does the desired reaction occur, and what operating state should be targeted for optimizing performance? In this study, we employ a microfluidic electrolyzer to visualize and selectively identify reaction zones producing CO, the desired product. This approach enables the characterization of reactivity across different states of the electrode, revealing the impact of catalyst-layer wetting on product selectivity. Together with our previous research on GDEs, these findings provide a comprehensive understanding of electrochemical CO₂ reduction.