Highly dispersed Pd nanoparticles supported on dendritic mesoporous CeZrZnOx for efficient CO2 hydrogenation to methanol

Abstract

A Pd2.0/CZZ catalyst (CeZrZnOx supported Pd catalyst with 2.0 wt% Pd) with dendritic morphology and highly dispersed Pd was prepared for methanol (MeOH) synthesis from CO2 hydrogenation. The deposition–precipitation method, higher specific surface area, and pore volume of CZZ support improve the dispersion degree of Pd on the CZZ support. The ultra-dispersed and optimized amount of Pd plays a crucial role in H2 dissociation, generating more spillover hydrogen on the Pd active sites, thus improving the CO2 hydrogenation performance. Moreover, introducing the optimized Pd of the Pd2.0/CZZ catalyst increases Ce3+/Ce4+ ratios, which are critical in generating more oxygen vacancies of the CZZ support, thus promoting the adsorption and activation of CO2 molecules. Pd2.0/CZZ catalyst presents the highest CO2 conversions (29.1 %), superior MeOH selectivity (43.8 %), highest MeOH yield (12.7 %), highest turnover frequency (TOF) (87.3 h−1), highest STY (5.11 molMeOH kg-1h−1) and excellent 100 h long-term stability among a series of Pdx/CZZ catalysts and the reference PdZn/CZ-Co catalyst. The in situ DRIFTS and density functional theory (DFT) simulation suggests that Pd2.0/CZZ catalyst with adequate Pd particle size and relatively high Pd metal dispersion promotes the pathway to *HCOO and *CH3O as primary intermediates of CO2 hydrogenation to MeOH.