The Pd/ZrO2 catalyst inversely loaded with various metal oxides for methanol synthesis from carbon dioxide

Abstract

The selectivity and stability of catalysts for methanol synthesis from CO2 still remain to be enhanced. In this work, we synthesized a series of Pd/ZrO2 catalysts inversely loaded with various metal oxide promoters (ZnO, In2O3, and CeO2), those would partially cover Pd metal surface and form some new metal-promoter interface, to explore the nature in the performance of CO2 hydrogenation to methanol. The catalyst synthesized by this approach could limit the growth of Pd particles during the reduction and form new metal–metal oxide interfaces with different functions of CO2 hydrogenation, improving the reaction performance of Pd-ZrO2 catalysts. As a result, the ZnO-Pd/ZrO2 catalyst exhibited the highest CO2 conversion (12.0 %), methanol selectivity (95.6 %), and STY of methanol (472 gMeOHkgcat-1h−1), with excellent stability. The results of HRTEM, H2-TPR, XPS, and XAFS showed that the ZnO-Pd/ZrO2 catalyst had the typical Pd-ZnO interface with Pd2+ species after the H2 reduction, which could enhance the adsorption and activation of CO2. In addition, the in situ DRIFTS and NAP-XPS results implied that the Pd-ZnO interface significantly improved the formation of formate (HCOO*) and methoxy (H3CO*) species, which were considered to be the key intermediates of methanol generation, and thus greatly enhanced the selectivity of methanol.