Tracking Dynamics of Supported Indium Oxide Catalysts in CO2 Hydrogenation to Methanol by In Situ TEM.

Supported reducible oxides, such as indium oxide on monoclinic zirconia (In2O3/m-ZrO2), are promising catalysts for green methanol synthesis via CO2 hydrogenation. Growing evidence suggests that dynamic restructuring under reaction conditions plays a crucial but poorly understood role in catalytic performance. To address this, the direct visualization of the state-of-the-art In2O3/m-ZrO2 catalyst under CO2 hydrogenation conditions (T  =  553 K, P  =  1.9 bar, CO2:H2  =  1:4) is pioneered using in situ scanning transmission electron microscopy (STEM), comparing its behavior to In2O3 on supports with similar (tetragonal, t-ZrO2 or anatase TiO2) or lower (LSm-ZrO2) surface areas. Complementary in situ infrared spectroscopy and catalytic tests confirm methanol formation under equivalent conditions. A machine-learning-based difference imaging approach differentiates and ranks restructuring patterns, revealing that partially reduced InOx species on m-ZrO2 undergo cyclic aggregation-redispersion via atomic surface migration, maintaining high active phase dispersion. High-resolution ex situ STEM analysis further shows the epitaxial formation of In2O3 mono- and bilayers on (100) m-ZrO2 facets, highlighting strong oxide-support interactions. In contrast, sintering prevails on t-ZrO2, a-TiO2, and low-surface m-ZrO2, correlating with lower methanol productivity. This work underscores the pivotal role of oxide-support interfacial interactions in the reaction-induced restructuring of InOx species and establishes a framework for tracking nanoscale catalyst dynamics.