Synergy of Oxygen Vacancies and Ni⁰ Species to Promote the Stability of a Ni/ZrO₂ Catalyst for Dry Reforming of Methane at Low Temperatures

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 CO2 and oxidization of Ni0 hamper the catalytic performance of Ni-based catalysts at low temperatures. Herein, a Ni/ZrO2 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 CH4 and CO2 turnover frequencies of 0.26 and 0.18 s–1 at 320 °C, respectively. The presence of Ni0 species and oxygen vacancies promotes the activation of CO2 at 300 °C, proved by CO2 temperature-programmed oxidation (CO2-TPO). Combined with O2 temperature-programmed decomposition (O2-TPD), C18O2-DRM, in situ X-ray photoelectron spectroscopy (XPS), and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) results, after CH4 decomposition on the Ni0 site, the resultant C would react with nearby surface oxygen species and lattice oxygen species of ZrO2, forming CO and an oxygen vacancy. The oxygen vacancy nearby Ni0 species with more electron transfer would promote the activation of CO2. This work highlights the importance of CO2 activation and emphasizes the key role of the synergistic effect between Ni0 species and the oxygen vacancy in enhancing the stability of catalysts over low-temperature DRM reactions.