Promotion of electrolytic ethylene production in acidic media through a single-atom cocatalyst: The dual role in inhibiting hydrogen evolution and boosting C–C coupling

Electrocatalytic CO2 reduction (eCO2R) in acidic electrolytes is propitious to enhance CO2 utilization, yet suffering from low current efficiency due to the rapid kinetics of the competing hydrogen evolution reaction (HER), especially under high current densities. This study proposes the implementation of a single-atom NiNC cocatalyst concurrently generating CO and releasing OH− to neutralize H+ in the electrolyte, thereby simultaneously suppressing HER and promoting C–C coupling. By homogeneously mixing the NiNC cocatalyst with Cu nanoparticles (NPs), as opposed to a stratified configuration, a high ethylene Faradaic efficiency (FE) of 57 % was achieved at 600 mA cm−2 in acidic media, along with a remarkable single-pass CO2 conversion efficiency of 52.4 %. While rotating disk electrode tests and operando Raman spectroscopy attest to the restricted H+ diffusion and elevated local pH near the catalyst surface, in situ Infrared and differential electrochemical mass spectrometries corroborate the spillover of CO from the cocatalyst to neighboring Cu NPs for enhanced C–C coupling. This work offers new insights into the design and application principles of compositional eCO2R catalysts for promoting multicarbon synthesis in acidic media at high current density.