A catalytic sites contiguity study on atomically-dispersed ZnO-Cu/SiO2 catalysts to improve methanol formation from CO2 hydrogenation

Cu-ZnO-based catalysts are commonly used in research on catalytic carbon dioxide (CO2) hydrogenation for methanol (MeOH) synthesis. This work studied the catalytic sites contiguity, for example, the surface orientation or arrangement of the CO2 and H-2 activating sites and their capability to facilitate the interaction between the adsorbed species, and its effects on the catalytic performance of MeOH formation. Cu/SiO2 precursor was prepared by impregnating copper nitrate solution on a commercial SiO2 gel. Controlling the exposure time and cycle numbers in atomic layer deposition (ALD), atomic-level dispersion of ZnO (ADZn) was formed on the uncalcined and calcined Cu/SiO2 precursors as well as on the SiO2 gel. Characterizations allowed for identification of Cu+-Cu-0 and ADZn(2+)-Cu+/Cu-0 sites contiguity on the reduced catalyst surface. Catalytic performance tests showed that the ALD ZnO-Cu/SiO2-C catalyst facilitated the MeOH space-time yield to 33.1 g/(kg(catal) center dot h) at 240 degrees C, three times the yield of its Cu-only counterpart. The property-performance correlation indicated that two types of ZnO-Cu sites contiguity were responsible for MeOH and CO formation from CO2 hydrogenation with the ADZn(2+)-Cu+/Cu-0 favouring more MeOH formation. The various contiguity of ADZn(2+)-Cu+/Cu-0 sites also influence the MeOH formation from CO2 hydrogenation.