Reverse water-gas shift reaction over Pt/MoOx/TiO2: reverse Mars–van Krevelen mechanism via redox of supported MoOx

Abstract

The reverse water-gas shift (RWGS) reaction is a promising catalytic route for reducing CO₂ emissions because its product, CO, is a key intermediate in various industrialized catalytic processes that produce fuels and chemicals. We describe herein a MoO_x/TiO₂-supported Pt catalyst (Pt(3)/MoO_x(15)/TiO₂; Pt loading = 3 wt%, MoO₃ loading = 15 wt%) that promotes the RWGS reaction at low temperature (200–300 °C) with high activity and selectivity. The catalytic performance for both CO₂ conversion and selectivity of Pt(3)/MoO_x(15)/TiO₂ is better than those of Pt catalysts on other supports and other metal catalysts supported on MoO_x(15)/TiO₂, as well as Cu– and Fe–Cr-based industrial catalysts. Moreover, results of operando X-ray absorption spectroscopy studies show that the reaction takes place via the reverse Mars–van Krevelen mechanism where H₂ acts as a reducing agent to create oxygen vacancies on the supported Mo oxide species that are filled by CO₂ as an oxidizing agent.