PdCu supported on dendritic mesoporous CexZr1-xO2 as superior catalysts to boost CO2 hydrogenation to methanol

Abstract

A dendritic PdCu/Ce_0.3Zr_0.7O₂ (PdCu/CZ-3) catalyst with uniform spherical morphology was prepared for boosting the catalytic performance of CO₂ hydrogenation to methanol (MeOH). The open dendritic pore channels and small particle sizes could reduce not only the diffuse resistance of reactants and products but also increase the accessibility between the active sites (PdCu and oxygen vacancy) and the reactants (H₂ and CO₂). More spillover hydrogen could be generated due to the highly dispersed PdCu active metals over the PdCu/CZ-3 catalyst. PdCu/CZ-3 can stimulate the generation of more Ce³⁺ cations, which is beneficial to produce more oxygen vacancies on the surface of the CZ-3 composite. Spillover hydrogen and oxygen vacancy could promote the formate and methoxy routes over PdCu/CZ-3, the primary intermediates producing MeOH. PdCu/CZ-3 displayed the highest CO₂ conversions (25.5 %), highest MeOH yield (6.4 %), highest PdCu-TOF_MeOH (7.7 h^-1) and superior 100 h long-term stability than those of other PdCu/Ce_xZr_1-xO₂ analogs and the reference PdCu/CeO₂ and PdCu/ZrO₂ catalysts. Density functional theory (DFT) calculations and in situ DRIFTS were performed to investigate the CO₂ - MeOH hydrogenation mechanism.

Keywords: CO(2) hydrogenation; Dendritic PdCu/Ce(0.3)Zr(0.7)O(2) catalyst; Hydrogen spillover; Methanol; Oxygen vacancy.