Electrocatalytic Water Oxidation with Manganese Oxides

Electrocatalytic water oxidation, the anodic half-reaction of water splitting, is fundamental to sustainable hydrogen production and artificial photosynthesis. Manganese oxides have attracted particular interest owing to their earth abundance, low toxicity and the precedent of a manganese–calcium cluster in natural photosystem II. The oxygen evolution reaction (OER) on manganese oxides proceeds through multiple proton-coupled electron-transfer steps, often involving MnIII, MnIV and high-valent species such as MnV=O or MnVII=O. The performance of these catalysts is critically influenced by crystal structure, particle size, coordination environment and electronic structure. Amorphous or low-crystallinity MnOx phases typically exhibit high intrinsic activity due to abundant defect sites and favourable proton-transport pathways, whereas crystalline polymorphs can offer improved stability. Recent research has explored a wide range of morphologies, including sub-10 nm nanocrystals, ultrathin films and intermetallic-derived mixed-phase materials, as well as strategies such as heteroatom doping and support modification to optimise catalytic activity and durability under neutral or alkaline conditions. Despite inherent challenges arising from manganese dissolution and structural reorganisation during OER, advances in operando spectroscopy and synthetic control have begun to reveal mechanistic pathways and design principles for next-generation manganese-based water-oxidation catalysts.

Research from Nature Portfolio

Recent studies have employed manganese phosphates as model systems to elucidate the role of coordination geometry and oxidation states in OER. By comparing tetra- and octa-coordinated Mn centres within isostructural phosphate frameworks, researchers have identified MnV=O intermediates as key species for O–O bond formation and demonstrated that dynamic shifts between MnIII–OH and MnV=O govern intrinsic activity. Another investigation into Ni-doped Mn3O4 nanoparticles has spectroscopically captured low-spin MnIV-oxo moieties stabilised by ligand-field engineering, revealing that spin-state control enhances catalytic turnover. These findings provide direct evidence of reactive intermediates and structure–activity correlations, guiding the rational design of manganese-oxide catalysts with improved efficiency and stability.

Electrocatalytic Water Oxidation with Manganese Oxides publication trend

The graph below shows the total number of articles in electrocatalytic water oxidation with manganese oxides across all publications each year (not limited to Nature Index journals).

Technical terms

Oxygen evolution reaction (OER): The four-electron oxidation of water to molecular oxygen at the anode of an electrolyser.

Overpotential: The extra potential applied beyond the thermodynamic requirement for a given electrochemical reaction.

Coordination environment: The arrangement of ligands or anions around a central metal ion affecting its electronic properties.

Operando spectroscopy: Techniques that probe the catalyst structure and intermediates during actual catalytic operation.

Birnessite: A layered manganese-oxide mineral with mixed MnIII/MnIV valence, often highly active for water oxidation.

References

1. Electrocatalytic water oxidation with manganese phosphates. Nature Communications (2024).
2. Partially Oxidized Sub-10 nm MnO Nanocrystals with High Activity for Water Oxidation Catalysis. Scientific Reports (2015).
3. Boosting Water Oxidation through In Situ Electroconversion of Manganese Gallide: An Intermetallic Precursor Approach. Angewandte Chemie International Edition (2019).
4. Water-Oxidation Electrocatalysis by Manganese Oxides: Syntheses, Electrode Preparations, Electrolytes and Two Fundamental Questions. Zeitschrift für Physikalische Chemie (2020).
5. On the Origin of the OER Activity of Ultrathin Manganese Oxide Films. ACS Applied Materials & Interfaces (2021).
6. Alkaline manganese electrochemistry studied by in situ and operando spectroscopic methods – metal dissolution, oxide formation and oxygen evolution. Physical Chemistry Chemical Physics (2019).
7. Identifying MnVII-oxo Species during Electrochemical Water Oxidation by Manganese Oxide. iScience (2018).
8. Spectroscopic capture of a low-spin Mn(IV)-oxo species in Ni–Mn3O4 nanoparticles during water oxidation catalysis. Nature Communications (2020).