Metal/CeO2_x with regulated heterointerface, interfacial oxygen vacancy and electronic structure for highly efficient hydrogen evolution reaction

The high activity of the metal/oxide heterostructures towards hydrogen evolution reaction (HER) is generally attributed to the metal-oxide synergy. A comprehensive study is thus needed to definitely unveil the origin of the catalytic activity of the metal/oxide heterostructures. Herein, Ni/CeO2_x, Co/CeO2_x and NiCo/CeO2_x heter-ostructures are in -situ synthesized by hydrogenation. Both experimental and computational results validate that the presence of Ni favors the formation of interfacial oxygen vacancies, which facilitate the adsorption of H2O molecules for HER. Theoretical calculations further show that the desorption of OH* is the rate-determining step, and that the desorption barrier of OH* on the NiCo/CeO2_x is the lowest because of the NiCo alloying induced regulation in electronic structure. Additionally, the NiCo-CeO2_x heterointerface greatly promotes the charge accumulation, leading to the low onset potential. Therefore, the NiCo/CeO2_x presents the highest intrinsic activity with a small overpotential of 30 mV at 10 mA cm_2 in 1.0 M KOH.