Architecture-Driven Porous Copper Nanofiber Networks for High-Rate CO₂ Electroreduction to Ethylene

Abstract

The electrochemical reduction of CO₂ to multi-carbon products offers a promising route for carbon-neutral energy conversion, yet achieving high selectivity toward ethylene (C₂H₄) remains challenging. While CuO-derived catalysts are widely studied, their performance is often limited by structural and interfacial factors. Here, we show that copper nanofiber (Cu NF) architecture, rather than Cu content alone, controls C–C coupling efficiency and CO₂ reduction reaction (CO₂RR) selectivity. Cu nanofibers are prepared via electrospinning and calcination with systematically varied Cu/PVP ratios, enabling precise control over porosity, interconnectivity, and electrochemically active surface area (ECSA). Structural analyses reveal that an intermediate Cu loading (Cu/PVP 7%) forms a highly interconnected nanoporous network with the highest roughness factor (23.48) and ECSA (25.45 mF cm⁻²). In a flow-cell configuration using 1 M KOH, this catalyst delivers a C₂H₄ Faradaic efficiency of 55 ± 4% at a partial current density of 330 ± 40 mA cm⁻², outperforming Cu-rich and Cu-deficient analogues. Electrochemical impedance and distribution of relaxation times analyses attribute the enhanced performance to faster charge transfer, improved *CO retention, and mitigated mass-transport limitations. Density functional theory calculations further show that surface roughness and low-coordinated Cu sites stabilize *CO, promote C–C coupling, and suppress hydrogen evolution. These results establish morphology-engineered Cu nanofibers as a scalable platform for selective CO₂-to-ethylene conversion.