Photocatalytic Water Splitting in Two-Dimensional Materials

Photocatalytic water splitting harnesses solar energy in the presence of a semiconductor catalyst to decompose water into hydrogen and oxygen. Two-dimensional materials, characterised by atomic thickness and a large surface-to-volume ratio, have emerged as prime candidates for this process. Their reduced dimensionality endows them with quantum confinement effects, tunable electronic properties and strong light–matter interactions. By applying defect engineering, doping, strain or heterostructure design, researchers can optimise light absorption in the visible and ultraviolet ranges, facilitate efficient charge separation and transport, and align band edges with the redox potentials of water. Novel asymmetric ‘Janus’ structures further enhance internal dipoles to improve carrier separation. Despite substantial progress, challenges remain in suppressing charge recombination, ensuring chemical stability under operating conditions and scaling synthesis methods. Advances in computational screening, precision synthesis and interfacial engineering continue to drive the field towards efficient, durable and economically viable systems for sustainable hydrogen production.

Research from Nature Portfolio

Recent first-principles studies of gallium arsenide monolayers have highlighted their potential as efficient photocatalysts. Electronic structure calculations reveal a direct band gap that straddles the water redox potentials, enabling simultaneous hydrogen and oxygen evolution under solar illumination. Thermodynamic analysis of surface reaction pathways shows that water adsorption and dissociation can proceed with minimal overpotential, even without additional co-catalysts. High predicted carrier mobility—substantially exceeding that of many conventional two-dimensional semiconductors—suggests rapid transport of photogenerated charges to active sites, reducing recombination losses. These findings position GaAs monolayers as promising platforms for experimental validation and integration into photocatalytic devices.

Photocatalytic Water Splitting in Two-Dimensional Materials publication trend

The graph below shows the total number of articles in photocatalytic water splitting in two-dimensional materials across all publications each year (not limited to Nature Index journals).

Technical terms

Photocatalytic water splitting: A light-driven process in which a semiconductor catalyst absorbs photons to generate electron–hole pairs that drive the decomposition of water into hydrogen and oxygen.

Two-dimensional materials: Crystalline solids comprising one or a few atomic layers, exhibiting unique electronic, optical and mechanical properties due to quantum confinement.

Janus structure: An asymmetric two-dimensional configuration in which the two faces of the monolayer have different chemical compositions or terminations, inducing an internal dipole and enhancing charge separation.

Band gap: The energy difference between the valence band maximum and conduction band minimum of a semiconductor, determining the spectral range of absorbed light.

Redox potentials: The energies at which a catalyst’s conduction and valence band edges align with the hydrogen evolution and oxygen evolution reactions in water splitting.

Carrier mobility: A measure of how quickly photogenerated electrons or holes move through a semiconductor under an electric field, influencing charge-transport efficiency.

References

1. First Principles Calculation for Photocatalytic Activity of GaAs Monolayer. Scientific Reports (2020).
2. Engineering 2D Materials for Photocatalytic Water-Splitting from a Theoretical Perspective. Materials (2022).
3. Anisotropic Janus SiP2 Monolayer as a Photocatalyst for Water Splitting. The Journal of Physical Chemistry Letters (2021).
4. Janus Aluminum Oxysulfide Al2OS: A promising 2D direct semiconductor photocatalyst with strong visible light harvesting. Applied Surface Science (2022).
5. Janus transition metal dichalcogenides: a superior platform for photocatalytic water splitting. Journal of Physics Materials (2020).