Photocatalytic Water Splitting Using Solid Solutions

Photocatalytic water splitting using solid solutions involves the design of mixed semiconductor compounds in which two or more parent materials are combined at the atomic level to tune optical and electronic properties for solar-driven hydrogen and oxygen production. By forming homogeneous lattices, solid solutions such as gallium nitride–zinc oxide (GaN:ZnO) and gallium oxynitride (GaON) achieve adjustable band gaps that extend light absorption into the visible region. Morphological control—ranging from nanosheets and nanorods to nanoparticulate films—enhances surface area and exposes specific crystalline facets to promote charge separation. Incorporation of proton-reduction and oxygen-evolution cocatalysts further accelerates hydrogen- and oxygen-evolution reactions by facilitating interfacial charge transfer. Advanced architectures, including Z-scheme heterojunctions and photocatalyst sheets, enable complementary light harvesting across different wavelength ranges. Together, these strategies aim to deliver efficient, robust, scalable pathways to convert abundant solar energy into green hydrogen fuel.

Research from Nature Portfolio

Recent studies have demonstrated the solvothermal synthesis of GaON nanosheets with uniform morphology and a narrowed band gap of approximately 1.9 eV, leading to enhanced photoelectrochemical performance under simulated solar irradiation. These nanosheets exhibit stable photocurrent densities and prolonged charge-carrier lifetimes in standard three-electrode cells, owing to effective p–d repulsion at the Ga–N interface and surface-directed hole accumulation. Another investigation has focused on aerosol-type nanoparticle deposition of GaN:ZnO films onto conductive glass substrates, achieving band-gap reduction through controlled electronic structuring. Optimised films delivered photocurrents nearly two orders of magnitude higher than conventionally processed electrodes, highlighting the impact of deposition conditions on electrode efficiency and offering a route to high-performance artificial photosynthesis anodes.

Research from all publishers

A long-wavelength photoresponsive GaN:ZnO solid solution containing 66 mol % ZnO has been shown to absorb light up to 600 nm and deliver an apparent quantum yield of 11.9 % at 420 nm for oxygen evolution when coupled with an iridium oxide cocatalyst. Integration of this material into a Z-scheme system with a complementary hydrogen-evolution photocatalyst extended overall water-splitting activity to wavelengths near 700 nm. A comprehensive review of semiconductor nanomaterial photocatalysts has underscored band-gap engineering via solid solutions, the design of multiphase heterojunctions and Z- and S-scheme architectures, and the crucial role of co-catalyst functionalisation in achieving high solar-to-hydrogen conversion efficiencies. Foundational spectroscopic studies on GaN:ZnO solid solutions have further clarified that deep trap-state filling and efficient electron extraction by proton-reduction cocatalysts prolong hole lifetimes on the order of tens of seconds, thereby sustaining overall water splitting without sacrificial agents.

Photocatalytic Water Splitting Using Solid Solutions publication trend

The graph below shows the total number of articles in photocatalytic water splitting using solid solutions across all publications each year (not limited to Nature Index journals).

Technical terms

Photocatalysis: A process by which a semiconductor absorbs light and drives chemical reactions at its surface.

Solid solution: A homogeneous crystalline phase in which two or more materials share a common lattice to yield tailored properties.

Band gap: The energy difference between the valence band and conduction band that determines a semiconductor’s light-absorption threshold.

Z-scheme: A dual-photocatalyst configuration that mimics natural photosynthesis by sequentially driving oxidation and reduction steps.

Cocatalyst: A secondary catalyst deposited on a photocatalyst surface to enhance charge separation and lower reaction overpotentials.

Charge carrier: An electron or hole generated in a semiconductor that participates in redox reactions upon light absorption.

References

1. Long-wavelength photoresponsive gallium zinc oxynitride for efficient oxygen evolution and Z-scheme water splitting reactions. Journal of Materials Chemistry A (2024).
2. Semiconductor Nanomaterial Photocatalysts for Water-Splitting Hydrogen Production: The Holy Grail of Converting Solar Energy to Fuel. Nanomaterials (2023).
3. Sonochemical Assisted Solvothermal Synthesis of Gallium Oxynitride Nanosheets and their Solar-Driven Photoelectrochemical Water-Splitting Applications. Scientific Reports (2016).
4. Understanding the visible-light photocatalytic activity of GaN:ZnO solid solution: the role of Rh 2−y Cr y O 3 cocatalyst and charge carrier lifetimes over tens of seconds. Chemical Science (2018).
5. An artificial photosynthesis anode electrode composed of a nanoparticulate photocatalyst film in a visible light responsive GaN-ZnO solid solution system. Scientific Reports (2016).