Water-Gas-Shift Reaction on Au/TiO_2–x Catalysts with Various TiO₂ Crystalline Phases: A Theoretical and Experimental Study

Au supported on TiO 2 (Au/TiO 2 ) 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 (O v ) 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 Au 8 cluster supported on TiO 2 with three crystalline phases (Au/ana-O v, Au/rut-O v, and Au/bro-O v ) is systematically performed. Notably, Au/ana-O v gives the lowest energy barrier at each step of the WGS reaction, indicating a superior catalytic activity, and a redox pathway is confirmed: H 2 O undergoes the dissociation adsorption on O v while interface Au serves as an active site for CO activation. The microkinetic modeling results confirm the favorable operating condition ( p H 2 O / p CO ≤ 4) for this reaction. Furthermore, experimental researches verify that the Au/ana-O v 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/TiO 2– x system, which would pave a way for the development of heterogeneous catalysts toward interface sensitive reactions.