Unraveling the Electrocatalytic Performance and Structural Stability of Ag Nanowire Gas Diffusion Electrodes for CO₂...

The electrocatalytic reduction of CO₂ is a promising technology for a versatile conversion of CO₂ emissions into a reactive feedstock, in a process compatible with intermittent renewable power supply. It requires first efficient catalysts with low over potential and high selectivity. Second, the setup must allow for an efficient use of the CO₂ feed, toward a complete conversion. Third, catalyst and electrolytic parameters have to be optimized for long-term stability. Here, we implement Ag as a selective catalyst for CO₂ reduction into CO, shaped into silver nanowires to ensure both a large electrochemical surface area and a high conductivity. The sprayed silver nanowire electrodes are tested i) in a flow cell for electrochemical characterization in three-electrode configuration, and ii) in a zero-gap electrolyzer offering high throughput and tightness for accurate Faradaic efficiency FE_CO measurements and relevant current density. They demonstrate state-of-the-art catalytic efficiency from -1.0 V_RHE, and a stable FE_CO exceeding 90% over 8 h. Surprisingly, this long-term stable electrocatalytic performance contrasted with the morphological changes in the silver nanowire electrode observed early in CO₂RR, even at low current density. We show that these structural changes correlate with the partial removal of the polymer capping layer around the silver nanowires.