Electrocatalytic Oxygen Evolution Mechanisms in Acidic Media

Electrocatalytic oxygen evolution in acidic aqueous environments underpins proton exchange membrane water electrolysis for sustainable hydrogen production. The sluggish kinetics of the oxygen evolution reaction (OER) at the anode, coupled with the corrosive nature of low-pH media, pose significant challenges. Iridium-based oxides remain the benchmark catalysts owing to their unique balance between activity and stability, yet the high cost and scarcity of Ir drive the search for alternatives and strategies to reduce noble-metal loading. Mechanistic studies reveal that the sequence of proton-coupled electron transfers depends on the binding energies of surface intermediates (M–OH, M–O and M–OOH), with pathways ranging from the classical adsorbate evolution mechanism to emerging lattice-oxygen or lattice-water-assisted routes. Advanced characterisation techniques—including in situ spectroscopy and synchrotron methods—combined with density functional theory are elucidating dynamic active sites, redox transitions and reconstruction processes. Catalyst design now exploits perovskite and double-perovskite architectures, nanocomposites and atomically dispersed sites to optimise electronic structure, surface coordination and mass activity. Achieving a durable, low-overpotential OER in acid will accelerate the deployment of high-current-density electrolyser systems for decarbonised energy storage and fuel generation on a global scale.

Research from Nature Portfolio

A low-loading catalyst comprising an IrO₂@TaB₂ nano-diboride support has demonstrated ultrastable oxygen evolution at 2 A cm⁻² in acidic media. The TaB₂ framework confines IrO₂ clusters, modulates charge distribution and suppresses agglomeration, delivering high activity and negligible degradation over hundreds of hours. Concurrently, a cost-effective Mn₇.₅O₁₀Br₃ oxybromide electrocatalyst exhibits an overpotential of just 295 mV at 10 mA cm⁻² and retains performance for over 500 h. In situ spectroscopic and theoretical analyses attribute its exceptional durability to the formation of a self-oxidised surface layer that enhances electronic transmission and resists dissolution.

Electrocatalytic Oxygen Evolution Mechanisms in Acidic Media publication trend

The graph below shows the total number of articles in electrocatalytic oxygen evolution mechanisms in acidic media across all publications each year (not limited to Nature Index journals).

Technical terms

Oxygen evolution reaction (OER): The anodic half-reaction in water splitting that generates O₂ via successive proton-coupled electron transfers.

Proton exchange membrane water electrolyser (PEMWE): A device that splits water into H₂ and O₂ using an acidic polymer electrolyte and applied voltage.

Overpotential: The extra voltage beyond the thermodynamic potential required to drive an electrochemical reaction at a given rate.

Turnover frequency (TOF): The number of reactant molecules converted per active site per unit time, reflecting intrinsic catalyst activity.

Adsorbate evolution mechanism (AEM): A pathway in OER where intermediates remain surface-bound, proceeding through discrete M–OH, M–O and M–OOH steps.

Lattice-water-assisted mechanism: A variant in which structurally incorporated water molecules facilitate O–O bond formation and rapid oxygen exchange.

References

1. Nano-metal diborides-supported anode catalyst with strongly coupled TaOx/IrO2 catalytic layer for low-iridium-loading proton exchange membrane electrolyzer. Nature Communications (2023).
2. Acidic oxygen evolution reaction: Mechanism, catalyst classification, and enhancement strategies. Interdisciplinary Materials (2023).
3. IrOx·nH2O with lattice water–assisted oxygen exchange for high-performance proton exchange membrane water electrolyzers. Science Advances (2023).
4. Iridium-based double perovskites for efficient water oxidation in acid media. Nature Communications (2016).
5. Efficient oxygen evolution electrocatalysis in acid by a perovskite with face-sharing IrO6 octahedral dimers. Nature Communications (2018).
6. In-situ spectroscopic observation of dynamic-coupling oxygen on atomically dispersed iridium electrocatalyst for acidic water oxidation. Nature Communications (2021).