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

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 g_MeOHkg_cat^-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.