Regulating the Hydrogen Oxidation Reaction Pathway via Pd–Mn x O y Interactions

Abstract

PdxO species have long been identified as the dominant active phase responsible for catalytic activity, while the exact role of oxidation state is still controversial. Herein, we use MnxOy (MnO, Mn3O4, and MnO2) as supports to reveal the effect of PdxO species in the hydrogen oxidation reaction. At 150 °C, the Pd/Mn3O4 catalyst delivers an O2 conversion of 97.8%, representing a remarkable 2.6 times enhancement relative to Pd/MnO2 (37.7%). Density functional theory (DFT) calculations, together with in situ characterizations, reveal that the activated H* species by the Pd metal undergoes spillover to the Pd–O–Mn active sites, promoting the activation and conversion of O2. More strikingly, OOH* as the intermediate for reaction of O2* species hydrogenation was found on the Pd/MnO2 catalyst, while the more active Pd–O–Mn sites lower the energy barrier toward O–O bond cleavage, enhancing the formation of OH* species on the Pd/Mn3O4 catalyst. Benefiting from the different pathways, an extremely catalytic performance and reactivity is observed on the Pd/Mn3O4 catalyst than on the Pd/MnO2 catalyst. This study enriches the understanding of the hydrogen oxidation pathway and offers clear insights into designing efficient Pd-based catalysts.