Synergistic Effects of Oxygen Vacancies and Metal-Support Interactions in Rare Earth Modified Cu-ZnO-Al2O3 Catalysts for CO2 Hydrogenation to Methanol

Abstract

The hydrogenation of CO2 to methanol is pivotal for carbon valorization and sustainable carbon cycle. However, conventional Cu-based catalysts are plagued by limited CO2 conversion and suboptimal methanol selectivity, which severely hinder their industrial application. To address this critical challenge, a series of rare earth (RE) doped Cu-ZnO-Al2O3 catalysts were synthesized via a facile and scalable method. Experimental results demonstrate that Ce-modified Cu-ZnO-Al2O3 catalyst exhibits the most outstanding catalytic performance. Specifically, under the reaction conditions of 220 °C, 3 MPa, and a gas hourly space velocity (GHSV) of 6000 mL g-1 h-1, the CO2 conversion reaches 11.4%, the methanol selectivity is 63.5%, and the maximum space-time yield (STY) of methanol attains 155.3 gMeOH kgCat-1 h-1. Comprehensive characterization and in-depth mechanism analysis reveal a significant synergistic effect between oxygen vacancies and metal-support interactions (MSI). The introduction of cerium not only induces the formation of abundant surface oxygen vacancies, which enhances the adsorption and activation of CO2, but also remarkably strengthens MSI. This synergistic effect effectively reduces copper particle size, promotes the formation of Cu-ZnO interfaces, and stabilizes the key Cu+ species favorable for methanol synthesis. This coupling of oxygen vacancy assisted molecular activation and MSI-dominated active site stabilization fundamentally boosts the catalytic efficiency of the Cu-based catalyst. In-situ DRIFTs confirm that the reaction follows the HCOO* hydrogenation pathway. This study highlights the effectiveness of RE elements in enhancing the catalytic performance of Cu-based catalyst by regulating the synergistic interaction between oxygen vacancies and MSI, thereby providing new insights and a feasible strategy for the design and development of highly efficient CO2 hydrogenation catalysts.