Regulating crystal phase of TiO2 to enhance catalytic activity of Ni/TiO2 for solar-driven dry reforming of methane

Abstract

Ni/TiO₂ catalyst is widely employed for photo-driven DRM reaction while the influence of crystal structure of TiO₂ remains unclear. In this work, the rutile/anatase ratio in supports was successfully controlled by varying the calcination temperature of anatase-TiO₂. Structural characterizations revealed that a distinct TiO_x coating on the Ni nanoparticles (NPs) was evident for Ni/TiO₂-700 catalyst due to strong metal-support interaction. It is observed that the TiO_x overlayer gradually disappeared as the ratio of rutile/anatase increased, thereby enhancing the exposure of Ni active sites. The exposed Ni sites enhanced visible light absorption and boosted the dissociation capability of CH₄, which led to the much elevated catalytic activity for Ni/ TiO₂-950 in which rutile dominated. Therefore, the catalytic activity of solar-driven DRM reaction was significantly influenced by the rutile/anatase ratio. Ni/TiO₂-950, characterized by a predominant rutile phase, exhibited the highest DRM reactivity, with remarkable H₂ and CO production rates reaching as high as 87.4 and 220.2 mmol/(g·h), respectively. These rates were approximately 257 and 130 times higher, respectively, compared to those obtained on Ni/TiO₂-700 with anatase. This study suggests that the optimization of crystal structure of TiO₂ support can effectively enhance the performance of photothermal DRM reaction.