Water-Gas-Shift Reaction on Au/TiO<sub>2–<i>x</i></sub> Catalysts with Various TiO<sub>2</sub> Crystalline Phases: A Theoretical and Experimental Study
Pan Yin, Jun Yu, Lei Wang, Jian Zhang, Yao Jie, Lifang Chen, Xiaojie Zhao, Haisong Feng, Yusen Yang, Ming Xu, Xin Zhang, Jingbin Han, Hong Yan, Min Wei
Abstract
Au supported on TiO2 (Au/TiO2) catalysts have shown excellent activity in low-temperature water-gas-shift (LT-WGS) reaction; however, the effects of different crystalline phases of the support, the oxygen vacancies (Ov) on the support, and the metal-support synergy on the catalytic performance still remain indistinct. In this work, a combination of density functional theory (DFT) calculation, microkinetic modeling, and experimental investigation for the LT-WGS reaction mechanism over the Au8 cluster supported on TiO2 with three crystalline phases (Au/ana-Ov, Au/rut-Ov, and Au/bro-Ov) is systematically performed. Notably, Au/ana-Ov gives the lowest energy barrier at each step of the WGS reaction, indicating a superior catalytic activity, and a redox pathway is confirmed: H2O undergoes the dissociation adsorption on Ov while interface Au serves as an active site for CO activation. The microkinetic modeling results confirm the favorable operating condition (pH2O/pCO ≤ 4) for this reaction. Furthermore, experimental researches verify that the Au/ana-Ov sample exhibits the optimum catalytic activity, which accords well with the prediction conclusions of theoretical calculation. This work provides the detailed information on the metal-support synergistic catalysis as well as the in-depth understanding of the reaction mechanism of LT-WGS over the Au/TiO2–x system, which would pave a way for the development of heterogeneous catalysts toward interface sensitive reactions.