The solar splitting of water into hydrogen fuel, using only sunlight and water, has been considered a very promising sustainable approach to producing clean energy. The photoelectrode materials are the dominant factor in this solar-to-fuel conversion process. Among different semiconductors, Cu2O is of particular interest due to its unique properties such as a bandgap of 2 eV for visible light absorption, favourable band positions for water splitting, good carrier mobility, earth abundance and being environmentally benign. Developing a facile, cost-effective and scalable method to fabricate efficient Cu2O photoelectrodes is the key for practical solar hydrogen generation.

Improved properties

The research team reports a simple and large-scale solution method to synthesize the Cu2O photoelectrodes with different 3D structures including nanowires, nanorods and networks. Their studies showed that Cu2O networks provide a large photocathodic current and a high spectral photoresponse, compared to those of Cu2O nanowires or nanorods.

Importance of neutrality

The high photocathodic current of Cu2O networks in a neutral solution is a promising feature for practical solar hydrogen production; a neutral medium is more desirable as the natural water resources such as seawater are usually in a neutral condition. The issue of Cu2O instability is also investigated by the team and, using a metal oxide multi-layer protection strategy, they exhibited a significant stability improvement.

The ongoing research in the group involves further improvement of the photocathode energy-conversion efficiency and stability. It also involves coupling the photocathode to an efficient photoanode for accomplishing spontaneous overall solar water splitting in a full solar water splitting system.

More information about the research can be found in the journal Nanotechnology 25 205401.

Further reading

Nanotrees harvest the sun's energy to turn water into hydrogen fuel (Mar 2012)
Bent substrate enhances water splitting (Jul 2012)
'Champion' nanostructures could improve solar water-splitting cells (July 2013)