Year: 2026
Type: article
Abstract: High Resolution Image Download MS PowerPoint Slide The concentration and reactivity of H atoms on oxide surfaces govern the rate and selectivity of many hydrogenation reactions, such as CO 2 conversion to methanol. On some oxides, H 2 molecules may dissociate in a heterolytic fashion and populate the surface with chemically distinct proton H + and hydride H − species. In this study, we demonstrate through systematic density functional theory (DFT) simulations that H 2 dissociates heterolytically on MgO(110), CaO(110), SrO(110), anatase TiO 2 (101), ZrO 2 (101), HfO 2 (001), ZnO (101̅0), α-Al 2 O 3 (110), γ-Al 2 O 3 (110), and β-Ga 2 O 3 (100) surfaces. These oxides do not form two H + species upon H 2 dissociation because their high band gaps are found to hinder the injection of released electrons into the conduction band. In contrast, reduced oxide surfaces such as Ti 2 O 3 (012), Ce 2 O 3 (011̅1), and FeO(100) preferentially stabilize H − over H + upon adsorption of a single H atom. The oxygen vacancy formation energy was found to serve as a general descriptor of the preference for H + + H − over H + + H + as the H 2 dissociation product across all considered oxides. Moreover, we show that the surface H + species preferentially react with O during CO 2 hydrogenation to form COOH intermediates, whereas surface H − species preferentially attack C atoms, forming HCOO intermediates. Thus, tuning the band gap of oxide surfaces is suggested as a strategy to control the charge of surface H atoms, which is shown to direct the hydrogenation pathway and the selectivity of oxide catalysts.
Source: ACS Catalysis
Language: English
Subfield: Catalysis
Field: Chemical Engineering
Domain: Physical Sciences
Open Access status: hybrid
Estimated APC paid: $4,500
Award: G1634667181
OpenAlex ID: W7162129629