Hydride-species-induced enhancement of CO2 hydrogenation selectivity on Ru-atom-modified CeO2 catalysts†

Abstract

Controlling product selectivity in heterogeneous catalytic reactions remains challenging, and elucidating the catalyst structure is essential for modulating the reaction selectivity. In this work, mono- and diatomic catalysts with various Ru geometries were tuned to achieve selective hydrogenation of CO₂ to CH₄ or CO. Experimental (such as in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and density functional theory (DFT)) results show that heterolytic H₂ dissociation occurs at the O–O_v sites on the Ru1/CeO₂ surface to produce hydride (H⁻) species; the resulting H⁻ species promote the selectivity of the CO₂ hydrogenation to form CH₄ at the Ru site via the formation of HCOO* intermediates. In contrast, homolytic H₂ dissociation to produce two Ru–H species on the Ru2/CeO₂ surface facilitates the selective hydrogenation of CO₂ to form COOH* intermediates, which generate CO. This work not only deepens understanding of the mechanism of CO₂ hydrogenation but also provides a novel strategy for developing Ce-based catalysts with high selectivity for CO₂ hydrogenation.