Electrocatalytic Oxygen Evolution in High-Entropy Oxides

The oxygen evolution reaction (OER) is a pivotal process in electrochemical water splitting, yet its inherent sluggish kinetics and high energy requirement pose significant challenges for sustainable hydrogen production. High-entropy oxides (HEOs) have emerged as a versatile class of electrocatalysts, characterised by five or more metal cations distributed in near-equimolar ratios. This multicomponent approach stabilises single-phase structures through high configurational entropy and introduces lattice distortions that can modulate the adsorption energies of reaction intermediates. Spinel and perovskite frameworks are particularly attractive, offering diverse coordination environments and electronic structures. By tailoring composition, strain and defect landscapes—such as oxygen vacancies—researchers can break conventional scaling relationships and achieve lower overpotentials, enhanced durability and superior current densities under alkaline or neutral conditions. Developments in rapid synthesis methods, including sol-flame, microwave-assisted and vacuum-controlled atmospheres, have enabled the scalable production of phase-pure HEOs. Together, these advances point to the global significance of HEOs as earth-abundant, noble-metal-free electrocatalysts poised to accelerate the deployment of green hydrogen technologies.

Research from Nature Portfolio

Recent studies have demonstrated that spinel-type HEOs synthesised by rapid sol-flame techniques exhibit remarkable OER activity and stability in alkaline media. The simultaneous mixing of five 3d transition metals induces equatorial strain at active metal–oxygen sites, creating a broad distribution of adsorption energies that lowers the kinetic barriers for intermediate formation. Theoretical investigations employing density functional theory confirm that the random distribution of cations is thermodynamically favoured and that the strain effects enhance both activity and durability. Experimentally, these HEOs outperform their lower-entropy counterparts, maintaining high current densities at reduced overpotentials even after prolonged operation, thereby underscoring the entropic stabilisation and synergistic electronic interactions as key drivers of electrocatalytic performance.

Electrocatalytic Oxygen Evolution in High-Entropy Oxides publication trend

The graph below shows the total number of articles in electrocatalytic oxygen evolution in high-entropy oxides across all publications each year (not limited to Nature Index journals).

Technical terms

Oxygen evolution reaction (OER): The electrochemical process by which water molecules are oxidised to oxygen gas, involving a four-electron transfer at the anode of an electrolyser.

High-entropy oxide (HEO): A crystalline material containing five or more metal cations in near-equimolar ratios, stabilised by high configurational entropy to form a single-phase structure.

Spinel structure: A cubic oxide lattice with general formula AB₂O₄, where A occupies tetrahedral sites and B occupies octahedral sites, enabling diverse electronic and catalytic properties.

Perovskite structure: An oxide lattice with general formula ABO₃, offering flexible cation substitution at A and B sites to tune electronic conductivity and surface binding characteristics.

Overpotential: The additional voltage required above the thermodynamic potential to drive an electrochemical reaction at a specified current density, indicative of kinetic barriers.

References

1. Synergistic effects of mixing and strain in high entropy spinel oxides for oxygen evolution reaction. Nature Communications (2023).
2. Engineering Oxygen Vacancies in (FeCrCoMnZn)3O4‐δ High Entropy Spinel Oxides Through Altering Fabrication Atmosphere for High‐Performance Rechargeable Zinc‐Air Batteries. Global Challenges (2023).