Effect of surface acidity modulation on Pt/Al2O3 single atom catalyst for carbon monoxide oxidation and methanol decomposition

Abstract

With ideal metal utilization efficiency and homogeneous active sites, single atom catalysts (SACs) have attracted extensive attention in heterogeneous catalysis field. The performance of SACs is highly dependent on the local coordination environment of metal single atoms. However, few works reported the effect of surface acidity modification on the performance of SACs such as Pt SACs which have been widely studied nowadays. In this work, a Pt/Al2O3 SAC has been successfully prepared using a bayerite Al(OH)3 as support through simple IWI method for Pt loading. Through post-modification of Pt/Al2O3 with acidic WO3 and basic MgO, the surface acidity of Pt/Al2O3 was tuned. Activity of CO oxidation and methanol decomposition on the modified catalysts has been evaluated. It was found that the catalytic performance was highly related to the surface acidity of Pt SACs. Basic MgO modified Pt/Al2O3 performed better in CO oxidation under the reaction condition with H2O. Acidic WO3 modified Pt/Al2O3 showed superior activity in methanol decomposition. Detailed characterization and in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) study suggested that the positive H2O effect on CO oxidation was due to the mitigated formation of bicarbonate species on Pt/Al2O3 and WO3/Pt/Al2O3 catalysts and the promoted desorption of carbonate species from MgO/Pt/Al2O3. The superior methanol decomposition performance on WO3/Pt/Al2O3 was owing to its abundant oxygen vacancies and high resistance to carbonate accumulation. This study highlights the importance of surface acidity modulation of Pt SACs in heterogeneous catalysis and suggests that fine-tuning the surface acidity can be an effective strategy in new SACs development.