Oxygen vacancy assisted hydrogen evolution reaction over CeO2-based solid solutions

Producing sustainable hydrogen through water electrolysis is a promising approach to meet the growing demand for renewable energy storage. Developing affordable and efficient electrocatalysts made from non-precious metals to replace platinum-based catalysts for hydrogen evolution reactions (HERs) continues to be a significant challenge. In the present study, pristine CeO₂ and doped solid solutions Ce_0.95Co_0.05O₂, Ce_0.95Ni_0.05O₂ and Ce_0.95Cu_0.05O₂ were evaluated for the HER, and the electrochemical studies in alkaline medium showed superior HER activity for the doped catalysts, with Ce_0.95Ni_0.05O₂ achieving the lowest overpotential and highest mass activity, comparable to Pt/C. Tafel slopes and EIS measurements suggested a Volmer–Heyrovsky mechanism facilitated by oxygen vacancies and hydrogen spill-over. Stability tests confirmed the durability of Ce_0.95Ni_0.05O₂ under prolonged HER conditions. This study highlights aliovalent doping as a viable strategy for engineering oxygen vacancies and enhancing CeO₂-based catalysts for alkaline water electrolysis.