If commercializable, this technology is expected to lead to the development of fuel cells that run on water and can be used in a wide range of products, from automobiles to computers.

GaN crystals are being studied for such uses as light sources for next-generation DVD devices. This is part of a research project of the Japan Science and Technology Agency -- a program overseen by Shuji Nakamura, who created the blue LED and works as professor of materials at the University of California, Santa Barbara.

The researchers connected GaN crystals with platinum using wire, then immersed these in water. When light is applied to the GaN, electricity flows through the water and causes it to decompose into oxygen and hydrogen through electrolysis.

The rate of conversion efficiency, which is the ratio of hydrogen produced to the energy used to shine the light, is still a low 0.5 per cent to 0.7 per cent.

"Theoretically, this can be raised to more than 20 per cent," said Kazuhiro Ohkawa, a professor in the physics department at the Tokyo University of Science, who played a leading role in the research. The minimum conversion efficiency needed for commercialization is said to be 20 per cent.

The team plans to continue work on the project to make improvements.