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 MoOx (2 <x < 3), respectively, while it is not reduced on MoO3/Mo2C-C during the catalysis process. The metastable MoOx 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 molCO gcat‒1 s‒1, and 99 % CO selectivity under 500 °C. The function and formation conditions of metastable MoOx sites are comprehensively investigated in this work.