Oxygen vacancy-regulated atomic dispersed Au on CeFeO_x for preferential oxidation of CO in H₂-rich stream

CO preferential oxidation in H₂-rich stream (CO-PROX) is a critical reaction for H₂ purification in emerging hydrogen economy including advanced fuel cell technology. Au-based catalysts are viewed as some of the most promising catalysts but achieving high catalytic efficiency and selectivity is still challenging. Defect engineering is deemed as a powerful strategy to improve the intrinsic catalytic activity. Herein, CeFeO_x-supported Au catalysts with controllable oxygen vacancy (O_v) concentrations were obtained and applied to CO-PROX. The results of characterizations showed that the O_vs were preferentially generated in conjunction with Au single atoms (SAs) rather than nanoparticles (NPs), which further modulated the surface electronic properties via surplus electrons in O_vs and enhanced the interfical interaction between O_vs and Au SAs. The CO-PROX results indicated that the reduced Au SA catalyst (Au₁/CeFeO_x-R) with the highest O_v concentration completely converted CO at temperature of 80 °C with relatively low reactivity towards H₂ oxidation. The remarkable catalytic activity and selectivity were attributed to the modified electronic properties by O_vs that played a bridging role in electron transfer and accelerated reaction process, as well as the coupling effect of O_vs and Au SAs that enhanced the dissociative adsorption of O₂ and the adsorption-oxidation of CO, resulting in a reduced reaction energy barrier and making CO oxidation more favorable than H₂ oxidation. This research opens up an alternative strategy to simultaneously stabilize and activate single-atom catalysts.