Interfacial Modification of Pd/ZrO2 Catalyst by Atomic-Layer In2O3 for Enhanced CO2 Hydrogenation to Methanol

Abstract

Although Pd/ZrO2 represents a highly promising catalyst for CO2 hydrogenation, it still faces challenges such as low methanol selectivity and intense competing side reactions. In this study, we precisely constructed an In2O3 interfacial layer between Pd and ZrO2 by atomic layer deposition (denoted as Pd/xIn2O3/ZrO2, where x represents the number of atomic layer deposition cycles) and systematically investigated the role of this interlayer in modulating the catalyst microstructure, reaction pathways, and methanol selectivity. Catalytic performance evaluation results reveal that under reaction conditions of 320 °C and 3 MPa, the Pd/10In2O3/ZrO2 catalyst exhibits the best performance for CO2 hydrogenation to methanol, whereby the methanol selectivity was significantly enhanced from 6.6% to 76.6%, and the methanol space-time yield increased by approximately 6 times (2.40 vs. 13.37 gMeOH·gPd–1·h–1) when compared to pristine Pd/ZrO2 catalyst. Multifaceted characterization and in situ diffuse reflectance infrared Fourier transform spectroscopy demonstrate that the introduction of In2O3 substantially strengthens CO2 adsorption and activation, promotes further hydrogenation of the key CO* intermediate, and establishes a dual-path synergistic mechanism involving both formate and CO-hydrogenation routes, thereby effectively suppressing the formation of the byproduct CO. Collectively, this work demonstrates that catalyst interface engineering via atomic layer deposition provides an effective strategy for tuning the reaction network and optimizing methanol selectivity in catalytic CO2 hydrogenation systems.