Gd‐Induced Oxygen Vacancy Creation Activates Lattice Oxygen Oxidation for Water Electrolysis

Abstract As a key reaction in water electrolysis and fuel cells, the oxygen evolution reaction (OER) involves a sluggish four‐electron proton transfer process. Understanding the OER pathways and kinetics is critical for designing efficient electrocatalysts. In this study, through density functional theory (DFT) calculations, it is demonstrated that the incorporation of Gd into Fe‐doped NiO elevates the O 2 p band center and generates more unoccupied oxygen states. Furthermore, Gd promotes the formation of oxygen vacancies, which, together, enhance the lattice oxygen oxidation mechanism (LOM) pathway for the OER. The adsorption‐free energy diagrams confirm that Gd doping significantly lowers the theoretical overpotentials at both the Fe and Ni sites in Fe‐doped NiO, thereby improving OER activity. Based on these findings, Gd and Fe co‐doped NiO ultrathin nanosheets are synthesized via spray combustion. As an OER catalyst, the material exhibited a low overpotential of 227 mV, which is 40 mV lower than that of Fe‐doped NiO, and demonstrated long‐term catalytic stability for over 150 h. In an anion exchange membrane water electrolysis system, Gd and Fe co‐doped NiO exhibited stable performance for more than 120 h at a current density of 20 mA cm −2 .