Five-fold twinned copper nanowire gas diffusion electrodes for electrochemical CO2 reduction with enhanced C2 product selectivity and stability

Abstract

Copper nanowires with fivefold twinned structures (t-CuNWs) are shown to be effective as cathode catalysts for the electrochemical CO2 reduction reaction (CO2RR) in a zero-gap electrolyzer to produce ethylene. The t-CuNWs, with surfaces enclosed by (100) facets, were selected for their enhanced CO adsorption strength, which along with the presence of the twin boundary defects, are proposed to promote C-C coupling—a key pathway toward multi-carbon (C2) products. We also find that the entangled t-CuNWs exhibit enhanced hydrophobicity when compared to commercial Cu nanoparticles (CuNPs), which reduces electrode flooding and contributes to enhance the stability of the cathode. These characteristics distinguish t-CuNWs from CuNPs in terms of activity (overpotential, selectivity) and stability. The t-CuNWs exhibited ∼40% C2H4 Faradaic efficiency (FE) for more than 4 hours under a current density of 100 mA cm−2, while commercial CuNPs exhibited ∼20% C2H4 FE for less than 4 hours and the CuNPs devices consistently required increased operating voltages. These findings highlight the potential of (100) faceted t-CuNWs for C2 product formation in CO2RR with facet engineering and hydrophobicity control.