Self-supporting BiCu/carbon hybrid nanofiber membrane promotes efficient CO₂ electroreduction to formate

CO₂ electroreduction is an alluring technology for high-value CO₂ utilization and intermittent electrical energy storage. Self-supporting catalysts with high efficiency have clear advantages over powder ones in electrode construction but still lack effective synthesis methods. In this work, a self-supporting BiCu/carbon hybrid nanofiber membrane (BiCu/CHNM) was synthesized by electrospinning-calcination and employed directly as a working electrode in a flow cell for CO₂ electroreduction to formate with a high Faradaic efficiency of 87.67% at a partial current density of 142.9 mA cm⁻². In stability tests, the Faradaic efficiency of formate remained at 80% for 50 h at high partial current densities (>100 mA cm⁻²). In-situ Raman spectra and density functional theory calculations confirmed that copper doping lowers the energy barrier of HCOO⁻ formation on the Bi (012) plane and increases the conductivity of the carbon nanofiber network. Due to the well-designed conductive framework and the highly dispersed BiCu active sites, this hybrid membrane shows high activity, high selectivity, and long stability simultaneously.