Electrocatalytic and Photocatalytic Mechanisms in Water Splitting Systems

Water splitting combines electrochemical and photochemical pathways to convert water into hydrogen and oxygen gases, offering a sustainable route to clean energy storage. In electrocatalysis, an external voltage drives the hydrogen evolution reaction (HER) at the cathode and the oxygen evolution reaction (OER) at the anode. Efficient catalysts lower the overpotential, accelerate charge transfer and steer reaction intermediates along favourable pathways. Photocatalysis harnesses light to generate electron–hole pairs in semiconductors; photogenerated electrons reduce protons to hydrogen, while holes oxidise water to oxygen. Key design principles include maximising light absorption, ensuring rapid separation and migration of charge carriers, and providing active surface sites for molecular adsorption and bond cleavage. Coupling photoactive materials with co-catalysts can further enhance kinetics by localising reaction sites and reducing recombination losses. Integration of electrocatalytic and photocatalytic components into hybrid or tandem systems has emerged as a frontier, exploiting synergistic interactions to approach solar-to-hydrogen efficiencies beyond those of individual processes. Advances in nanoscale structuring, surface engineering, and computational screening underpin the rapid evolution of water splitting technologies, bridging fundamental understanding and scalable applications in renewable hydrogen production.

Research from Nature Portfolio

Recent studies have demonstrated a robust single-crystal oxide nanocube catalyst with an adaptive surface layer that reversibly transforms between oxide and oxyhydroxide phases during oxygen evolution, yielding ultrastable performance over extended operation. A data-driven approach employing symbolic regression has identified a simple descriptor based on perovskite structural factors, guiding the discovery of new oxide materials with markedly enhanced oxygen evolution activities and accelerating the design of high-performance electrocatalysts. In addition, the development of highly crystalline iridium-based nanoparticles has revealed uniquely reversible catalytic behaviour: under anodic conditions a thin oxide shell forms to drive oxygen evolution, while cathodic potentials restore the metallic core for hydrogen evolution and oxidation, offering a multifunctional solution for reversible electrolyser and fuel-cell interfaces.

Electrocatalytic and Photocatalytic Mechanisms in Water Splitting Systems publication trend

The graph below shows the total number of articles in electrocatalytic and photocatalytic mechanisms in water splitting systems across all publications each year (not limited to Nature Index journals).

Technical terms

Electrocatalyst: A material that facilitates electrochemical reactions by lowering activation energies and improving charge transfer at electrode–electrolyte interfaces.

Photocatalyst: A light-absorbing semiconductor or composite that generates electron–hole pairs under illumination to drive redox reactions without external bias.

Hydrogen evolution reaction (HER): The cathodic half-reaction in water splitting, in which protons gain electrons to form molecular hydrogen.

Oxygen evolution reaction (OER): The anodic half-reaction in water splitting, involving the oxidation of water molecules to release molecular oxygen and protons.

Turnover frequency (TOF): A kinetic metric denoting the number of reactant molecules converted to product per active site per unit time under specified conditions.

References

1. Reversible adapting layer produces robust single-crystal electrocatalyst for oxygen evolution. Nature Communications (2015).
2. Simple descriptor derived from symbolic regression accelerating the discovery of new perovskite catalysts. Nature Communications (2020).
3. High crystallinity design of Ir-based catalysts drives catalytic reversibility for water electrolysis and fuel cells. Nature Communications (2021).
4. Machine Learning-Assisted Low-Dimensional Electrocatalysts Design for Hydrogen Evolution Reaction. Nano-Micro Letters (2023).
5. Determining materials for energy conversion across scales: The alkaline oxygen evolution reaction. Carbon Energy (2024).
6. Catalytic reactivity descriptors of metal‐nitrogen‐doped carbon catalysts for electrocatalysis. EcoEnergy (2023).