Advancing CO ₂ RR to Highly Selective C ₂ Products in Flow Cells Using Bimetallic CuM (M = Ag, Ni) Catalysts on Porosity-Controlled Carbon

The electrochemical CO2 reduction reaction (CO2RR) to multicarbon (C2+) products offers a promising route for carbon utilization. In this study, CuAg and CuNi alloy catalysts supported on nitrogen-doped porous carbons are systematically engineered to couple alloying effects with controlled pore structures. Chemically, steam-activated carbon supports enable precise control over micropore/mesopore ratios and metal dispersion. Structural characterizations reveal that the CuAg alloy forms relatively larger nanoparticles with enhanced CO generation capability. In flow cell tests, the Cu9Ag1/N–P1K3 (N-doped porous carbon support in this study) catalyst shows faradaic efficiencies of 36.2 and 32.2% for ethylene and ethanol, respectively, at −0.60 V vs RHE, with production rates of 5.0 mg·cm–2·h–1 and sustained stability over repeated operations. The synergy between Ag-induced CO generation, Cu-facilitated C–C coupling, the high surface area of N–P1K3, and superior mass transport of the flow cell enhances C2 products selectivity. Comparisons with steam-activated carbon supports show that although smaller, more uniformly dispersed nanoparticles increase active site density, they also promote the hydrogen evolution reaction, decreasing the C2 product formation. This study establishes a catalyst–reactor codesign framework, demonstrating that integrating alloy, porous carbon engineering, and flow cell operation can deliver high C2 selectivity, current densities, and scalable economic potential for sustainable CO2 utilization.