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

• Published in: Applied catalysis. B, Environmental Environmental, 2022-10, Vol.314, p.121516, Article 121516
• Main Authors: Wu, Jinwei, Gao, Jie, Lian, Shuangshuang, Li, Jianpeng, Sun, Kaihang, Zhao, Shufang, Kim, Young Dok, Ren, Yujing, Zhang, Meng, Liu, Qiaoyun, Liu, Zhongyi, Peng, Zhikun
• Format: Article
• Language: English
• Subjects: C-H activation; Carbon; Carbon deposition; Carbon dioxide; Catalysts; Catalytic converters; Cations; Cerium oxides; Commercialization; Deactivation; Deposition; Hydrogen bonds; Methane; Oxygen; Oxygen vacancy; Reforming; Single atom catalysts; Vacancies
• ISSN: 0926-3373; 1873-3883
• DOI: 10.1016/j.apcatb.2022.121516

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/CeO2 SAC was synthesized and employed in dry reforming of methane (DRM) reaction. The oxygen vacancies (OV) with different concentrations were successfully regulated on CeO2 surface by the replacement of Ce4+ cation by a smaller-size cation M (M= Mg, Co, Zn). The catalyst with the highest OV 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 OV 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 CO2 activation function from OV were synergistically combined, leading to a high activity of methane conversion and an effective carbon removal process in the OV-SAC catalytic system. This work provides a novel strategy to obtain a robust OV-SAC catalytic system for efficient and stable C-H activation. Here, we successfully regulated the concentration of oxygen vacancies on Ni/CeO2 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 CH4 but suffer from carbon deposition. The oxygen vacancies activate CO2 and produce adsorbed oxygen species, which removed carbon deposition and recovered activity of Ni atoms. By constructing this OV-SAC model catalyst, the efficient and stable C-H activation was achieved. [Display omitted] •Various concentration of oxygen vacancies have been constructed on the Ni/CeO2 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.