Science Foundation Ireland: Creating a clean energy source for the future

Tyndall researchers aim to unlock the energy potential of water in €1m research project

Prof Martyn Pemble of the Tyndall National Institute in Cork. Photograph: Daragh Mc Sweeney/Provision

Prof Martyn Pemble of the Tyndall National Institute in Cork. Photograph: Daragh Mc Sweeney/Provision

Mon, Jun 9, 2014, 01:00

Researchers at Tyndall National Institute, Cork, are collaborating with scientists from the US and Northern Ireland in a Science Foundation Ireland-supported project which aims to unlock the energy potential in water.

The researchers are bringing skills and knowledge acquired in advanced microelectronics to bear on this issue and are exploring how semiconductor materials and sunlight can be used to isolate energy-laden hydrogen in water by replicating processes found in nature.

Hydrogen is highly inflammable and, after being burned, water is its emission. As such it could make an ideal environmentally-friendly alternative to hydrocarbon fuels if a cheap and energy-efficient means were found to extract it from water.

The €1 million Research into Emerging Nanostructured Electrodes for the Splitting of Water (Renew) project, is led by Prof Martyn Pemble and Dr Paul Hurley at Tyndall, Prof Paul McIntyre at Stanford University and Prof Andrew Mills at Queen’s University Belfast.

The researchers’ first task is to create what is effectively an artificial leaf using layers of semiconducting materials such as silicon. This would duplicate the photosynthesis process which occurs naturally in plants to split the molecules of water into hydrogen and oxygen under natural conditions without any additional energy.

“The main focus for the project is a tiny, stacked arrangement of materials that is used for some transistors in the electronic industry,” explains Prof Pemble.

“Previous work has shown that these structures can act as basic artificial leaves for splitting water and the aim now is to make them more efficient. Our primary focus is on creating an efficient structure that will work when sunlight falls on it without us having to give it an extra kick.”

The Renew project had its genesis in work being carried out at Stanford University. “People have been looking at various ways of splitting water for a long time,” says Pemble.

“The issue with using semiconductors is that they usually require ultra-violet light to do it. We thought that it would be better to if they would work with visible light and other more available parts of the light spectrum such as near infra-red.

Corrosive effects

“Our colleagues at Stanford had been doing some very interesting experiments with silicon and they had built a device which showed very promising water splitting qualities. When we got together, we realised that other forms of semiconductor could do a better job.”

The Stanford team showed that if you put the right metal on the surface of a silicon stack and provide light, then you can get it to oxidise water to give oxygen. Then, on another electrode connected to it – perhaps a platinum wire – the electrons produced can be used to reduce water, and this produces hydrogen.

“So it only requires the sunlight to fall on this stack of layers where the water oxidation takes place. Andrew Mills from Queen’s University Belfast is an acknowledged expert on photocatalysis and has shown that the rest of the process is driven by the electrochemistry.”

Pemble points out that silicon is not particularly efficient when it comes to absorbing visible light and that his team at Tyndall is looking at other materials including cadmium sulphide which are more efficient in this respect.