Engineering the oxygen vacancies enables Ni single-atom catalyst for stable and efficient C-H activation

Ni single-atom catalysts (SACs) can perform with the extremely high activity in the activation of the C-H bond, however, deactivation caused by carbon deposition became the main obstacle for commercialization. Herein, Ni/CeO 2 SAC was synthesized and employed in dry reforming of methane (DRM) reaction. The oxygen vacancies (O V ) with different concentrations were successfully regulated on CeO 2 surface by the replacement of Ce 4+ cation by a smaller-size cation M (M= Mg, Co, Zn). The catalyst with the highest O V concentration has performed with the highest activity retention and a high turnover frequency of methane (14.5 s −1 ). During the DRM process, along with the increase of the O V concentration from 21.9% to 30.8%, the amount of carbon deposition decreased by 50%. The effective C-H activation function from Ni SACs and CO 2 activation function from O V were synergistically combined, leading to a high activity of methane conversion and an effective carbon removal process in the O V -SAC catalytic system. This work provides a novel strategy to obtain a robust O V -SAC catalytic system for efficient and stable C-H activation. Here, we successfully regulated the concentration of oxygen vacancies on Ni/CeO 2 single-atom catalysts, and achieved both high activity ( TOF =14.5 s -1 ) and stability (150 h) in dry reforming of methane. The atomically dispersed Ni atoms efficiently dissociate CH 4 but suffer from carbon deposition. The oxygen vacancies activate CO 2 and produce adsorbed oxygen species, which removed carbon deposition and recovered activity of Ni atoms. By constructing this O V -SAC model catalyst, the efficient and stable C-H activation was achieved. • Various concentration of oxygen vacancies have been constructed on the Ni/CeO 2 single-atom catalysts. • The introduction of a smaller-size cation increases the concentration of oxygen vacancies. • The Ni single atoms performed high activity in the C-H activation. • The presence of oxygen vacancies greatly enhances the stability of Ni single atoms.