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

Abstract

Abstract The reverse water-gas shift (RWGS) reaction is crucial for sustainable CO 2 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 MoO 3 surface layers under RWGS conditions. In-situ characterization techniques and theoretical analyses reveal that the MoO 3 layer on MoO 3 /MoO 2 -C and MoO 3 /Mo 2 N-C is in-situ reduced to MoO 2 and metastable MoO x (2 <x < 3), respectively, while it is not reduced on MoO 3 /Mo 2 C-C during the catalysis process. The metastable MoO x species on MoO 3 /Mo 2 N-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.