Oxygen Atom Migration in Ni2P/TiO2 Heterostructures Dynamically Regulates the Electrocatalytic CO2 Reduction Pathway

Abstract

Transition metal phosphides (TMPs) are widely applied in electrocatalytic reactions, such as the hydrogen evolution reaction (HER), due to their excellent physicochemical properties. However, when utilized in CO₂ reduction reactions, severe hydrogen evolution limits the activation of CO₂ molecules. In this study, oxygen atoms were successfully migrated from TiO₂ into Ni₂P nanoparticles through a simple impregnation and low-temperature phosphidation process, constructing an O–Ni₂P/TiO₂ nanowire array electrode that modulates the surface electronic structure, inhibits hydrogen evolution, and promotes CO₂ activation. At a potential of −0.4 V (vs RHE), the CH₄ production rate reached 1.46 μmol·h^–1·cm^–2, with a Faraday efficiency of 11.8%, and maintained long-term stability during the 36-h electrocatalytic process. In situ infrared spectroscopy revealed that CO* and CH₃* intermediates are easily formed on the surface of the material, which are key intermediates directly related to the CO₂ to CH₄. Further density functional theory (DFT) calculations indicated that the oxygen-doped Ni₂P surface has a lower barrier for the formation of CHO*, thereby facilitating the conversion of CO₂ to CH₄.