Steering CO Selectivity in CO2 Electroreduction over Silver Microtubular Gas-Diffusion Electrodes via Surface Reconstruction

An efficient gas diffusion electrode (GDE) is crucial for enhancing mass transport involving gas-phase CO2 conversion in the electrochemical CO2 reduction reaction (CO2RR). Microtubular hollow fiber GDE (HFGDE) with a porous hierarchical wall has garnered significant attention, which can modulate the triple-phase reaction zone and improve the performance of CO2RR. Simultaneously, engineering nano/microstructure surfaces of electrocatalysts have been demonstrated to effectively enhance the selectivity and activity in CO2RR. Here, we developed a porous microparticle Ag-based HFGDE via an in situ electrochemical oxidation–reduction method. Both the activity and selectivity of CO2 to CO conversion in the porous microparticle Ag-based HFGDE showed significant enhancement over the pristine and thermal reduced Ag HFGDE without surface reconstruction. At −1.2 V vs RHE, the faradaic efficiency for CO is 94%, with a partial current density of 83.4 mA cm–2, surpassing that of thermal treatment electrodes, which is only 26% with a partial current density of 12.3 mA cm–2. The distinctive reconstruction nano/microstructure on the electrocatalyst surface could be attributed to decreasing the activation energy barrier in the rate-limiting step of initial electron/proton transfer. This work represents a facile strategy for surface reconstruction of electrocatalysts in HFGDE as advanced electrode materials to enhance the efficiency of the CO2 conversion.