ZnO Promoted In Situ Carburization of MoO ₃ for Enhanced Low-Temperature Reverse Water–Gas Shift Reaction

Molybdenum carbide is highly active in reverse water–gas shift (RWGS) reaction, but its synthesis often needs a carburization temperature above 700 °C. In situ synthesis of molybdenum carbide under mild conditions is highly desirable in order to generate more exposed active sites, which however remains challenging. Here, molybdenum carbide with a MoC x phase has been prepared by ZnO-facilitated in situ carburization of MoO 3 at a low temperature of 350 °C in the RWGS reaction. The added ZnO boosts the removal of dissociated oxygen from CO 2 via reaction with spilled-over hydrogen, and the generated CO facilitates carburization of metallic Mo to form MoC x with the highest proportion at an optimized ZnO loading of 5 wt % during the reaction. The formed MoC x shows 22.0% CO 2 conversion under a space velocity of 24,000 mL·g cat. –1 ·h –1 and a stable CO formation rate of 316.1 mmol·g cat. –1 ·h –1 under 200,000 mL·g cat. –1 ·h –1 at 350 °C, which is higher than most noble metal and carbide catalysts. It further presents long-term stability with almost no deactivation within 200 h at 200,000 mL·g cat. –1 ·h –1 and only a 9.7% deactivation rate within 100 h under harsh reaction conditions of 600,000 mL·g cat. –1 ·h –1 .