Pore Engineering in Gas Diffusion Layer of Phthalocyanine Cobalt Cathode to Promote Electrochemical CO2-to-CO Reduction

While substantial electrocatalysts have been proposed and efficiently catalyze CO2 to multiple products, mass transport is becoming a major constraint to further improve the performance of CO2 electrochemical reduction reaction (CO2ERR). Gas diffusion electrode (GDE) technique has been identified as an effective way to overcome the confined mass transfer of CO2. While many research efforts have focused on the catalyst layer (CL), considerably fewer efforts have focused on the gas diffusion layer (GDL), the support and substrate of GDE. Herein, we studied the effect of the GDL on the performance of phthalocyanine cobalt (CoPc)-based GDE to catalyze CO2 to CO with a special emphasis on the hydrophilicity, porosity, and wettability. We demonstrate a facile and reproducible method of PTFE impregnation to tune the hydrophobicity and pore characteristics of GDL, to enhance CO2ERR. Using a proper designed GDL as the substrate, the CoPc-based GDE achieves a high current density of 321.7 mA cm(-2) and Faradaic efficiency for CO of 98.4% at a cathode potential of -1.2 V (vs RHE), representing the highest performance of CoPc-based GDEs reported in the literature.