Synergy of Oxygen Vacancies and Ni<sup>0</sup> Species to Promote the Stability of a Ni/ZrO<sub>2</sub> Catalyst for Dry Reforming of Methane at Low Temperatures
Ye Wang, Li Li, Guiying Li, Qing Zhao, Xue shuang Wu, Yannan Wang, Yifei Sun, Changwei Hu
Abstract
Low-temperature dry reforming of methane (DRM) can avoid the sintering of nickel and reduce the cost of the process. However, inefficient activation of CO 2 and oxidization of Ni 0 hamper the catalytic performance of Ni-based catalysts at low temperatures. Herein, a Ni/ZrO 2 catalyst was prepared and used in the DRM reaction, which exhibited stable activity at low temperatures (400, 320 and 300 °C) for 10 h, with CH 4 and CO 2 turnover frequencies of 0.26 and 0.18 s –1 at 320 °C, respectively. The presence of Ni 0 species and oxygen vacancies promotes the activation of CO 2 at 300 °C, proved by CO 2 temperature-programmed oxidation (CO 2 -TPO). Combined with O 2 temperature-programmed decomposition (O 2 -TPD), C 18 O 2 -DRM, in situ X-ray photoelectron spectroscopy (XPS), and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) results, after CH 4 decomposition on the Ni 0 site, the resultant C would react with nearby surface oxygen species and lattice oxygen species of ZrO 2, forming CO and an oxygen vacancy. The oxygen vacancy nearby Ni 0 species with more electron transfer would promote the activation of CO 2 . This work highlights the importance of CO 2 activation and emphasizes the key role of the synergistic effect between Ni 0 species and the oxygen vacancy in enhancing the stability of catalysts over low-temperature DRM reactions.