Unraveling the chemical nature of hydrides on doped ceria catalysts

Abstract

Surface hydrogen, especially hydrides (H−), can serve as key active species in heterogeneous catalysis, yet the fundamental understanding of their nature and reactivity remains elusive. In this study, we systematically investigate the physico-chemical properties and hydrogenation reactivities of different hydrogen species at metal-doped CeO2(111) surfaces through density functional theory calculations. The results reveal that the properties of the hydride directly interacting with the doped metal (HM) are strongly correlated with the metal’s valence orbitals and exhibit periodic trends regarding the structures, stabilities, and ionicities, which in turn govern their catalytic behaviors. In particular, the HM species generated by s/p-valence dopants are strongly ionic and possess high-energy and weakly metal-coupled frontier orbitals that readily involve in C2H2 hydrogenation. In contrast, the HM species formed by d-valence dopants are generally less ionic, with the reactivity dominated by low-energy and strongly metal-coupled σ-bonding orbitals and thus exhibiting substantially reduced hydrogenation activity. By clarifying how the electronic character of dopants can dictate the frontier orbitals of active hydrides, our work provides effective strategies for controlling hydrogenation kinetics and selectivity through dopant engineering, thereby helping the design of advanced hydrogenation catalysts.