Stabilizing Polarized Ni Sites via CeO2 Incorporation for Enhanced Electrochemical CO Reduction to C1–C6 Hydrocarbons

The electrochemical CO2 or CO reduction reactions (CO2RR or CORR) to hydrocarbons offers a promising sustainable route for carbon utilization, yet efficient hydrocarbon formation beyond C1–C3 products on Cu-based catalysts remains challenging. In this study, NiO/CeO2 composite catalysts were synthesized and evaluated for CO reduction to hydrocarbons in a membrane electrode assembly (MEA) electrolyzer. At an optimal CeO2 loading of 20 wt %, the Faradaic efficiency (FE) for C1–C6 hydrocarbon formation reached 16.8%, which is tripled that of the 4.9% on pristine NiO. A volcano-shaped dependence on CeO2 loading was further observed, with excess CeO2 reducing the number of active Ni sites and promoting the competing hydrogen evolution reaction. Cyclic voltammetry and in situ Raman spectroscopy reveal that the oxidized Ni species are stabilized by CeO2, which may be due to the formation of Ni–O–Ce bonds in NiO/CeO2 composite catalysts. Operating conditions further influence CORR performance, with higher CO partial pressure and moderate applied current densities favouring hydrocarbon formation. These findings establish CeO2 incorporation as a viable strategy for stabilizing polarized Ni species and provide practical guidance for optimizing Ni-based catalysts toward long-chain hydrocarbon synthesis under mild electrochemical conditions.