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

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.