Cation rearrangement at tetrahedral sites in the Cu/ZnAl2O4 spinel enhancing CO2 hydrogenation to methanol

Cu/ZnAl 2 O 4 spinel is a promising catalyst for CO 2 -to-methanol due to its dual-site H 2 activation. However, controlling surface properties and metal-support interactions (MSI) through the coordination environment of spinel cations remains underexplored. Herein, the occupancy of Zn 2+ and Al 3+ cations in Cu/ZnAl 2 O 4 spinel is fine-tuned by manipulating the calcination atmosphere. More disordered structures (AlO 4 and ZnO 6 ) observed on the CZA-Ar catalyst benefit the creation of oxygen vacancies and surface hydroxyl groups, which facilitate the formation of highly dispersed small-sized Cu species. This enhances MSI and hydrogen spillover effects, thereby boosting CO 2 conversion and the space-time yield (STY) of methanol. High-pressure in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) results reveal that the crucial formate intermediates form at tetrahedral sites in ZnAl 2 O 4 spinel, with more Al-HCOO - species observed on the CZA-Ar catalyst due to the formation of AlO 4 . This work advances the understanding of spinel catalysts in CO 2 hydrogenation to methanol.