ZrO2 Morphology-Dependent Cu–ZrO2 Interfacial Catalysis in CO2 Hydrogenation to Methanol Reaction

In this study, we utilize monoclinic ZrO 2 with different morphologies, including nanoparticulate ZrO 2, rod-like ZrO 2, and star-like ZrO 2, to investigate the ZrO 2 morphology effect on Cu–ZrO 2 interfacial catalysis in the CO 2 hydrogenation to methanol reaction. ZrO 2 morphology strongly affects the structures, adsorption behaviors, and catalytic performance of Cu/ZrO 2 catalysts. Various Cu/ZrO 2 catalysts show very different catalytic selectivities, although their catalytic activities are rather poor. Bridged (bri-HCOO*) and monodentate (m-HCOO*) formate species form on Cu/ZrO 2 catalysts during the CO 2 hydrogenation to methanol reaction. Elementary surface reaction kinetics analysis using temporal in situ DRIFTS in combination with online mass spectrometry reveals elementary reaction activation energies of 61.3 ± 5 kJ/mol for bri-HCOO* hydrogenation mainly to methanol and 85.0 ± 14 kJ/mol for m-HCOO* hydrogenation mainly to CO. Meanwhile, the apparent activation energy for CH 3 OH and CO formations from the CO 2 hydrogenation reaction catalyzed by Cu/nanoparticulate ZrO 2 is 65.7 ± 4 and 118.6 ± 14 kJ/mol, respectively. These results suggest that bri-HCOO* should be the formate intermediate for methanol production by CO 2 hydrogenation, and its hydrogenation reaction should be the rate-limiting step. Our findings clearly differentiate the reaction pathways of bri-HCOO* and m-HCOO* intermediates on Cu/ZrO 2 during the CO 2 hydrogenation to methanol reaction and demonstrate catalyst structural engineering in combination with elementary surface reaction kinetics analysis as a powerful strategy for fundamental studies of complex heterogeneous catalytic reactions.