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.