Revealing the Regulation Mechanism of Ir–MoO2 Interfacial Chemical Bonding for Improving Hydrogen Oxidation Reaction

Different interfacial chemical bonds, Ir–O, Ir–Mo, and mixed Ir–Mo/O, are employed to explore the regulating mechanism of MoO2-supported Ir catalysts in optimizing hydrogen oxidation reaction (HOR) activity by using density functional theory calculations and an experimental study. We found that the interfacial electron distribution of the catalyst Ir/O–MoO2 via Ir–O bonds is localized, only concentrated on Ir–O bonds, which downshifts the d-band center of the surface Ir atoms and weakens H and OH adsorption. It accordingly enhances the HOR activity. Its HOR exchange current density is as high as 1.96 mA/cmECSA2. In contrast, the interfacial electron distribution of the catalyst Ir/Mo–MoO2 via Ir–Mo bonds is delocalized, dispersed on all interfacial Ir and Mo atoms, which upshifts the d-band center of surface Ir atoms and strengthens H and OH adsorption. Its HOR activity is not as good as Ir/O–MoO2. Its HOR exchange current density is only about 1.47 mA/cmECSA2. In the case of the mixed interfacial bonds Ir–Mo/O of Ir/MoO2, irregular H adsorption on the catalyst is responsible for the poor HOR activity with an exchange current density of 1.10 mA/cmECSA2. We conclude that regulating interfacial chemical bonding patterns can optimize the electronic configuration of the metal oxide-supported metal catalysts and thus improve their catalytic activity effectively.