Insight into the effects of the oxygen species over Ni/ZrO2 catalyst surface on methane reforming with carbon dioxide

Carbon deposition on the catalyst surface has been considered as one of the main reasons to cause Ni catalyst deactivation during methane reforming with carbon dioxide (DRM). Generally, it is thought that the properties and levels of coke formation are significantly affected by the ability of CO2 adsorption and activation, which is closely related to the oxygen species over catalyst surface. In this study, the effects of oxygen species on the DRM over Ni/ZrO2 catalysts were investigated. Wherein, ZrO2 support was further treated under H-2, N-2, and O-2 atmospheres respectively to obtain different oxygen species distribution over the surface, and 3 wt.% Ni was introduced by the deposition-precipitation method. The representative samples were characterized using XRD, EPR, XPS, FTIR, TPR, TPD, TPSR, TG, Raman and TPH techniques, etc. It was found that the treatment to ZrO2 in the reducing gas such as H-2 was able to promote the formation of adsorbed oxygen species over the surface. CO2 DRIFTS and CH4-TPSR experiments further confirmed that adsorbed oxygen species were favorable for enhancing both CO2 adsorption and activation and CH4 dissociation. As a result, the catalyst with more adsorbed oxygen species exhibited relatively outstanding performance for the DRM and promotional ability in removal of the deposited carbon.