Photoelectrochemical Water Splitting Technologies

Photoelectrochemical water splitting harnesses sunlight to drive the separation of water into hydrogen and oxygen using semiconductor electrodes immersed in an aqueous electrolyte. Progress in this field centres on five interlinked challenges: maximising light absorption across the solar spectrum, promoting efficient charge separation and transport, suppressing electron–hole recombination, enabling rapid surface redox kinetics and ensuring electrode stability under operation. A diverse palette of materials—from metal oxides such as bismuth vanadate and haematite to more exotic III–V semiconductors and copper(I) oxide—has been explored in single-absorber cells, tandem assemblies and hybrid photovoltaic–electrolyser configurations. Nanostructuring, orientation control and heterojunction engineering have emerged as powerful strategies to tune bandgaps, extend carrier lifetimes and facilitate directional charge flow. These advances underpin efforts to deliver scalable, cost-effective systems for sustainable hydrogen production and broader solar-fuel synthesis, addressing global imperatives of decarbonisation and energy security.

Research from Nature Portfolio

Recent studies have demonstrated that single-crystal copper(I) oxide photoelectrodes grown with a dominant [111] orientation exhibit an order-of-magnitude increase in carrier mobility compared with other facets, yielding photocurrent densities of up to 7 mA cm⁻² and stable operation for over 120 hours. Another innovative approach couples the photoelectrochemical oxidation of glycerol with dark hydrogen evolution or carbon dioxide reduction in a continuous-flow cell under concentrated sunlight, achieving photocurrent densities exceeding 110 mA cm⁻² with suppressed parasitic oxygen evolution and altered product selectivity. Complementary work on bismuth vanadate photoanodes has shown that tuning the work function via molybdenum doping and constructing a heterojunction with boron-doped carbon nitride greatly improves charge separation, culminating in a record applied-bias photon-to-current efficiency of 2.67 % at a bias of 0.54 V versus a reversible hydrogen electrode.

Photoelectrochemical Water Splitting Technologies publication trend

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

Technical terms

Photoanode: Semiconductor electrode at which photo-induced holes drive oxidation reactions, typically the oxygen evolution reaction during water splitting.

Photocathode: Semiconductor electrode at which photo-induced electrons drive reduction reactions, typically hydrogen evolution from water.

Heterojunction: Interface between two dissimilar semiconductors engineered to promote directional charge separation and reduce recombination losses.

Bandgap: Energy difference between the valence band and conduction band of a semiconductor, determining the range of photon energies that can be absorbed.

Charge carrier recombination: Process by which photogenerated electrons and holes recombine without contributing to chemical reactions, reducing device efficiency.

Solar-to-hydrogen conversion efficiency: Ratio of the chemical energy stored in produced hydrogen to the incident solar energy on the photoelectrode.

References

1. High carrier mobility along the [111] orientation in Cu2O photoelectrodes. Nature (2024).
2. Paired photoelectrochemical conversion of CO2/H2O and glycerol at high rate. Nature Catalysis (2024).
3. Solar-Driven Sustainability: III–V Semiconductor for Green Energy Production Technologies. Nano-Micro Letters (2024).
4. Photoelectrochemical devices for solar water splitting – materials and challenges. Chemical Society Reviews (2017).
5. A comparative technoeconomic analysis of renewable hydrogen production using solar energy. Energy & Environmental Science (2016).
6. Enhancing photoelectrochemical water splitting by combining work function tuning and heterojunction engineering. Nature Communications (2019).