Effect of H2O and CO2 on CO oxidation over Pt/SSZ-13 with active sites regulated by Lewis acidity

Strategies for controlling the size of metal species using zeolites and their catalytic behavior in industrially relevant processes have attracted widespread attention, but the effect of H2O and CO2 on the catalytic performance of zeolite-based metal catalysts remains obscure. This study investigated the influence of H2O and CO2 on CO oxidation over zeolite-based metal catalysts, along with the precise control of active sites through the regulation of Lewis acidity. It was found that the presence of H2O enhanced CO oxidation and alleviated the inhibitory effect of CO2. Abundant Lewis acid sites of low SiO2/Al2O3 ratios in the Pt/SSZ-13 catalyst facilitate Pt dispersion (61.07%), a high Ptn+/Pt ratio (4.43), and small Pt particles (2.31 nm) formation. In situ DRIFTS revealed that CO2 inhibits CO adsorption and the decomposition of carbon intermediates. Water alters the CO adsorption configuration of Pt-0, thereby weakening the Pt-CO bond to promote the CO oxidation reaction. Meanwhile, water dissociated into hydroxyl groups on the surface adsorbs oxygen species, participating in reactions and promoting CO2 production from carbon intermediates. (H2O)-O-18 isotope labeling experiments validated the water involvement in the reaction and emphasized the importance of the presence of oxygen species during the water dissociation process. Regulation of Lewis acid sites promotes the Ptn+ species formation, enhancing the CO oxidation activity, while Pt-0 species enhance the water-promotion effect.