Unraveling surface sensitivity for generating metastable active sites in molybdenum-based catalysts for CO2 hydrogenation

The reverse water-gas shift (RWGS) reaction is crucial for sustainable CO₂ conversion, yet catalyst surface remodeling at high temperatures remains a complex and pivotal phenomenon. This study investigates the complex relationship between surface reconstruction and catalytic performance using a series of molybdenum-based catalysts, which can generate different catalytic MoO₃ surface layers under RWGS conditions. In-situ characterization techniques and theoretical analyses reveal that the MoO₃ layer on MoO₃/MoO₂-C and MoO₃/Mo₂N-C is in-situ reduced to MoO₂ and metastable MoO_x (2 <x < 3), respectively, while it is not reduced on MoO₃/Mo₂C-C during the catalysis process. The metastable MoO_x species on MoO₃/Mo₂N-C shows an unprecedented CO yield (up to 48.3 %) nearing the equilibrium conversion limit, a CO formation rate of 8.26 × 10^-5 mol_CO g_cat^‒1 s^‒1, and 99 % CO selectivity under 500 °C. The function and formation conditions of metastable MoO_x sites are comprehensively investigated in this work.