Mo2C-Mo3N2 Heterojunction Encapsulated Within N-Doped Carbon Cage for Enhanced Selective Hydrogenation of CO2 to CO.

Abstract

The reverse water gas shift reaction (RWGS) can convert CO₂ into CO, but the low activity and the inexpensive catalysts inhibit the industrialization process. As a potential material for the RWGS reaction, Mo₂C faces the challenges of high dispersibility and synthesis efficiency. Here, the Mo₃N₂-Mo₂C heterojunction encaged in N-doped carbon matrix is synthesized using in situ carbonization method, which exhibits high activity under mild temperature. The CO₂ conversion is 38.3%, the selectivity of CO is 99.1% upon 410 °C. The Space Time Yield is 17333.6 mgCO g_cat ^-1h^-1 (619.06 mmol g_cat ^-1 h^-1) under 450 °C, and WHSV = 240 000 mL g_cat ^-1 h^-1, which is superior than traditional catalysts such as Cu-Zn-Al and noble metal catalysts. The catalyst shows 99.9% selectivity of CO, and maintaining equilibrium conversion for 200 h under 500 °C. The structure-performance relationship studies indicate the synergistic effect of Mo₂C-Mo₃N₂ heterojunction active sites enhances H₂ adsorption and dissociation significantly, which boosting the H assisted CO₂ reduction reaction. Moreover, the N-doped carbon cage confined environment greatly boosts the catalyst stability. This work provides a simple and feasible strategy for the synthesis of highly dispersed Mo₂C-Mo₃N₂ heterojunction active site for CO₂ hydrogenation reaction, and a way to boost the H₂ activation capacity of Mo₂C catalyst.