Interface-EngineeredCo₄N–CeF₃ Heterostructure Induces ElectronicRedistribution and SignificantlyEnhances Oxygen Evolution at Large Current Density

The process of water electrolysis is an effective approach to generate extremely pure hydrogen. Nevertheless, the anodic oxygen evolution reaction (OER) is often slow and requires a high overpotential, resulting in excessive electricity consumption during water electrolysis. Hence, the utilization of exceptionally effective OER electrocatalysts with minimal overpotential, particularly under high current density, will undeniably accelerate the development of water electrolysis in industrial situations. Herein, we fabricated a heterostructure using CeF₃ and Co₄N phases, where electrocatalytically, nonactive CeF₃ is used to alter the electronic structure of Co₄N through the interface. This electronic modulation resulted in the generation of high-valent Co atoms on the catalyst surface, which are effective for the adsorption of the intermediates that are responsible for carrying out the OER. At a very low overpotential of 400 mV, the Co₄N–CeF₃ heterostructure yields a large current density of 1000 mA cm^–2. We also measured the ultralong durability of the catalyst for 500 h at a very large current density of 500 mA cm^–2. Remarkably, the water electrolyzer consisting of Pt/C||Co₄N–CeF₃ needs only a cell voltage of 1.61 and 1.68 V, respectively, to achieve a current density of 100 and 500 mA cm^–2. The electronic reallocation was well investigated by using X-ray photoelectron spectroscopy (XPS) and X-ray absorption near-edge spectra (XANES) analysis.