Roles of oxygen vacancies and the Ni–support interface in CO2 hydrogenation over Ni/Y-doped BaZrO3 revealed by experimental and computational studies

Understanding the roles of oxygen vacancies, proton-conducting supports, and metal–support interfaces is essential for the rational design of efficient CO2 hydrogenation catalysts. Herein, we investigate CO2 hydrogenation over Ni-supported Ydoped BaZrO3 (Ni/BZY) by combining powder X-ray diffraction (XRD), surface area measurements, CO2 temperatureprogrammed desorption (CO2-TPD), X-ray photoelectron spectroscopy (XPS), catalytic measurements, and density functional theory (DFT) calculations. CO2-TPD and DFT calculations consistently show that oxygen vacancies on BZY strongly stabilize CO2 adsorption. Oxygen vacancy enables facile CO2 dissociation and preferential CO formation via the reverse water–gas shift reaction. In contrast, the Ni–BZY interface provides moderate CO2 adsorption together with efficient H2 dissociation, creating favorable sites for the hydrogenation of CO-derived intermediates to CH4. DFT calculations further reveal that proton migration in BZY is energetically favorable, allowing protonic species to accumulate near the catalyst surface and participate in surface reactions. The reaction pathway through CO is identified as the most favorable route for methane formation at the Ni–BZY interface, whereas the carbide and carboxylic pathways are kinetically unfavorable. These results demonstrate the complementary functions of oxygen vacancies, proton conduction, and the Ni–support interface in governing CO2 activation and product selectivity, providing mechanistic insights and design principles for proton-conducting oxide-supported catalysts for thermochemical CO2 conversion.