Catalytic Mechanisms in Water-Gas Shift Reactions

The water-gas shift (WGS) reaction—CO + H₂O → CO₂ + H₂—serves as a cornerstone of industrial hydrogen production and plays a vital role in syngas conditioning for fuel cells and ammonia synthesis. Catalytic mechanisms for WGS generally fall into two broad classes: associative pathways, in which adsorbed CO and H₂O form surface intermediates such as formates or carboxyls, and redox pathways, in which lattice oxygen from the support oxidises CO followed by re-oxidation of the vacant site by H₂O. The precise activity and selectivity of a WGS catalyst depend critically on the nature of metal-support interfaces, the availability of oxygen vacancies, and dynamic surface transformations under reaction conditions. Recent advances in in situ spectroscopy and microscopy have revealed how engineered interfacial sites, dual-functional architectures and oxygen mobility synergise to lower activation barriers, mitigate CO poisoning and steer the reaction towards efficient H₂ release. A combination of theoretical modelling and operando characterisation now underpins rational design strategies that balance dissociative H₂O activation, CO oxidation and product desorption, thereby aligning catalyst composition and structure with the thermodynamic and kinetic demands of both low- and high-temperature WGS processes.

Research from Nature Portfolio

A novel catalyst comprising CeO₂-x/CoO₁-x/Co dual interfaces has been shown to deliver exceptional low-temperature WGS activity. In this system, reduced ceria modulates the oxidation state of cobalt to generate two distinct active boundaries: one that alleviates CO-induced surface poisoning, and another that promotes H₂ formation. Synergistic redox cycles at these dual sites result in a marked enhancement of both turnover frequency and stability under industrially relevant conditions. Another recent advance centres on Ni–NiOx–Y₂O₃ composites that exploit the electrophilic character of yttria to facilitate H₂O dissociation at metal–oxide junctions. Abundant Ni–NiOx–Y₂O₃ interfaces accelerate the rate-limiting step of water activation, achieving record activity for Ni-based catalysts in the medium-temperature regime and illustrating the power of rare-earth oxide promotion in WGS catalysis.

Catalytic Mechanisms in Water-Gas Shift Reactions publication trend

The graph below shows the total number of articles in catalytic mechanisms in water-gas shift reactions across all publications each year (not limited to Nature Index journals).

Technical terms

Associative mechanism: A pathway in which adsorbed CO and H₂O form surface-bound intermediates (formate or carboxyl) before decomposition to products.

Redox mechanism: A pathway involving lattice oxygen from the support to oxidise CO, followed by H₂O replenishment of the oxygen vacancy.

Metal-support interface: The boundary region where metal nanoparticles contact oxide supports, providing unique active sites for reactant activation.

Oxygen vacancy: A defect in the oxide lattice that enhances oxygen mobility and can participate directly in redox reactions.

Spillover: The migration of adsorbed species (for example, oxygen atoms or hydrogen atoms) from one catalyst component (support) to another (metal particle).

References

1. Boosting reactivity of water-gas shift reaction by synergistic function over CeO2-x/CoO1-x/Co dual interfacial structures. Nature Communications (2023).
2. Catalytically efficient Ni-NiOx-Y2O3 interface for medium temperature water-gas shift reaction. Nature Communications (2022).
3. Promoting Molecular Exchange on Rare-Earth Oxycarbonate Surfaces to Catalyze the Water–Gas Shift Reaction. Journal of the American Chemical Society (2023).
4. Lattice oxygen self-spillover on reducible oxide supported metal cluster: the water–gas shift reaction on Cu/CeO 2 catalyst. Chemical Science (2021).
5. The role of chromium in iron-based high-temperature water-gas shift catalysts under industrial conditions. Applied Catalysis B Environment and Energy (2021).