Reaction-induced unsaturated Mo oxycarbides afford highly active CO₂ conversion catalysts

Sustainable CO₂ conversion is crucial in curbing excess emissions. Molybdenum carbide catalysts have demonstrated excellent performances for catalytic CO₂ conversion, but harsh carburization syntheses and poor stabilities make studies challenging. Here an unsaturated Mo oxide (Mo₁₇O₄₇) shows a high activity for the reverse water-gas shift reaction, without carburization pretreatments, and remains stable for 2,000 h at 600 °C. Flame spray pyrolysis synthesis and Ir promoter facilitate the formation of Mo₁₇O₄₇ and its in situ carburization during reaction. The reaction-induced cubic α-MoC with unsaturated Mo oxycarbide (MoO_xC_y) on the surface serves as the active sites that are crucial for catalysis. Mechanistic studies indicate that the C atom in CO₂ inserts itself in the vacancy between two Mo atoms, and releases CO by taking another C atom from the oxycarbide to regenerate the vacancy, following a carbon cycle pathway. The design of Mo catalysts with unsaturated oxycarbide active sites affords new territory for high-temperature applications and provides alternative pathways for CO₂ conversion.