Catalytic Hydrogenation Mechanisms in Metal Oxides

Metal oxides have emerged as versatile catalysts for hydrogenation reactions, leveraging their intrinsic acid–base sites, defect structures and metal–support interfaces to activate molecular hydrogen and transfer it to unsaturated substrates. Two principal pathways for H₂ activation are recognised: homolytic dissociation, which yields neutral hydrogen radicals, and heterolytic dissociation, which produces a proton–hydride pair at adjacent acidic and basic sites. The balance between these pathways is governed by surface coordination, electronic properties and the presence of vacancies or dopants. Advanced spectroscopic and kinetic analyses, alongside computational modelling, have unveiled the pivotal role of surface hydride formation, stabilised by under-coordinated metal cations, in driving efficient hydrogenation of carbonyls, olefins and carbon dioxide. Tailoring oxide composition, defect density and metal–oxide interfaces has enabled significant improvements in activity, selectivity and energy efficiency, holding promise for sustainable chemical processes and carbon-neutral fuel generation.

Research from Nature Portfolio

Recent studies have demonstrated that coordinatively unsaturated metal centres on oxide surfaces can facilitate homolytic H₂ cleavage under mild conditions, leading to high hydride coverage and enhanced catalytic performance. In gallium oxide, transient kinetic and spectroscopic investigations revealed that in situ formation of unsaturated Ga³⁺ sites triggers efficient homolytic dissociation, boosting hydrogenation rates of CO₂ to CO, methanol and light olefins by several-fold. Complementarily, surface engineering of ceria nanorods to introduce controlled oxygen vacancies has generated solid frustrated Lewis pairs, where adjacent Ce³⁺ and lattice oxygen sites synergistically cleave H–H bonds with minimal activation energy. This defect-driven strategy has enabled selective hydrogenation of alkenes and alkynes at reduced temperatures, underscoring the power of atomic-level design in oxide catalysis.

Catalytic Hydrogenation Mechanisms in Metal Oxides publication trend

The graph below shows the total number of articles in catalytic hydrogenation mechanisms in metal oxides across all publications each year (not limited to Nature Index journals).

Technical terms

Homolytic dissociation: Cleavage of the H–H bond into two neutral hydrogen radicals.

Heterolytic dissociation: Cleavage of the H–H bond into a proton (H⁺) and hydride (H⁻) at adjacent acid–base sites.

Frustrated Lewis pair: A proximate acid and base site that remain unquenched, enabling activation of small molecules such as H₂.

Hydride species: Surface-bound H⁻ intermediates essential for hydrogen transfer to substrates.

Oxygen vacancy: A missing lattice oxygen atom that alters the electronic environment and enhances catalytic activity.

References

1. Homolytic H2 dissociation for enhanced hydrogenation catalysis on oxides. Nature Communications (2024).
2. Solid frustrated-Lewis-pair catalysts constructed by regulations on surface defects of porous nanorods of CeO2. Nature Communications (2017).
3. Heterolytic Dissociation of H2 in Heterogeneous Catalysis. ACS Catalysis (2022).
4. Hydride Generation on the Cu-Doped CeO2(111) Surface and Its Role in CO2 Hydrogenation Reactions. Catalysts (2022).
5. Formation and Activity Enhancement of Surface Hydrides by the Metal–Oxide Interface. Advanced Materials Interfaces (2021).
6. Operando Monitoring of Homolytic Cleavage of H2 into Surface Hydrides on Defective Cerium Dioxide Nanoparticles. ChemCatChem (2024).