Electrocatalytic Mechanisms for Water Oxidation in Nickel-Based Hydroxides

Water oxidation, or the oxygen evolution reaction (OER), underpins the efficiency of electrochemical energy conversion systems. Nickel-based hydroxides have emerged as leading candidates owing to their earth abundance, low cost and robust stability in alkaline environments. The active catalyst forms through in situ oxidation of nickel hydroxide phases (Ni(OH)2) to oxyhydroxide phases (NiOOH), which mediate the multi‐step proton–electron transfers required to convert water into molecular oxygen. Central mechanistic themes include adsorption of hydroxide anions and water molecules at oxidised nickel centres, the sequential breaking of O–H bonds, formation of surface-bound hydroperoxide intermediates and release of dioxygen. Doping with iron or other transition metals has been shown to tune electronic structure, lower the energy barriers of key steps and enhance charge‐transfer kinetics. Structural parameters such as phase composition, crystallite size, stacking disorder and surface morphology also govern active site density, mass transport and long‐term durability. Advances in operando spectroscopy and first‐principles modelling continue to reveal how the electronic spin state, local coordination environment and dynamic phase transformations converge to dictate catalytic performance. These insights drive the design of next‐generation electrodes for sustainable hydrogen production and grid‐scale energy storage technologies.

Research from Nature Portfolio

Recent studies have elucidated the role of iron dopants in NiOOH by showing that at low concentrations Fe adopts a low‐spin state, which aligns Fe–O bond lengths with those of Ni–O and yields substantially lower overpotentials for water oxidation. Thermodynamic modelling connects this spin‐state crossover to enhanced surface activity, explaining the observed solubility limit of Fe in NiOOH and its superior catalytic currents. Foundational work on carbon‐supported nickel phosphide nanoparticles has revealed that, under OER conditions, the nickel centres convert to β-NiOOH via structural deformation. This in situ activation leads to increased active area and a marked drop in overpotential during extended cycling, highlighting the importance of phase evolution and interfacial transformations in achieving high stability and activity.

Electrocatalytic Mechanisms for Water Oxidation in Nickel-Based Hydroxides publication trend

The graph below shows the total number of articles in electrocatalytic mechanisms for water oxidation in nickel-based hydroxides across all publications each year (not limited to Nature Index journals).

Technical terms

Overpotential: The extra electrical potential required above the thermodynamic threshold to drive the OER at a given current density.

NiOOH: The oxidised oxyhydroxide phase of nickel that serves as the active site for water oxidation.

Tafel slope: A kinetic parameter describing how current density changes with overpotential, indicative of rate‐limiting steps.

Turnover frequency (TOF): The number of catalytic reaction cycles per active site per unit time.

Spin state: The arrangement of unpaired electrons in a transition metal centre, affecting bond strengths and reaction barriers.

References

1. Ni-based compounds in multiwalled graphitic shell for electrocatalytic oxygen evolution reactions. Advanced Composites and Hybrid Materials (2024).
2. Low-spin state of Fe in Fe-doped NiOOH electrocatalysts. Nature Communications (2023).
3. Anomalous in situ Activation of Carbon-Supported Ni2P Nanoparticles for Oxygen Evolving Electrocatalysis in Alkaline Media. Scientific Reports (2017).
4. Deciphering the Exceptional Performance of NiFe Hydroxide for the Oxygen Evolution Reaction in an Anion Exchange Membrane Electrolyzer. ACS Applied Energy Materials (2022).
5. Determination of layered nickel hydroxide phases in materials disordered by stacking faults and interstratification. Journal of Materials Chemistry A (2023).
6. Practical Cluster Models for a Layered β-NiOOH Material. Materials (2017).
7. Synthesis and spectroscopic identification of nickel and cobalt layered hydroxides and hydroxynitrates. Dalton Transactions (2022).