Microstructure Optimization of Nickel–Nitrogen-Doped Porous Nanofibers for Enhanced Electrochemical CO₂ Reduction

The utilization of renewable energy for electrocatalytic CO₂ reduction (CO₂RR) represents a significant advancement in green carbon conversion technologies. Single atom catalysts (SACs) featuring a transition metal-nitride-carbon (M-N_x-C) architecture exhibit catalytic activity for the reduction of CO₂ to CO. However, the impact of the morphology of carbon supports, particularly their pore structure, on the electrocatalytic performance of CO₂RR warrants further investigation. In this study, we fabricated a series of Ni-based SACs supported by porous carbon nanofibers through electrospinning and sacrificial template method. We examined variations in microstructure of these porous carbon nanofiber carriers at different pyrolysis temperatures and elucidated their effects on CO₂RR catalytic performance. The catalyst obtained at 1000 °C demonstrated efficient electrocatalysis for converting CO₂ to CO due to its large specific surface area, abundant hierarchical pore structure, and high content of Ni-N_x species resulting from both the sacrificial template method and high-temperature pyrolysis. A Faradaic efficiency exceeding 90% was sustained across potentials ranging from −0.7 V to −1.3 V (versus RHE), with a peak efficiency reaching 96.1% at −1.0 V (versus RHE). Kinetic analysis indicated that this sample exhibited the highest reaction kinetics alongside minimal charge transfer resistance.