The Photoreaction Control Research Center of the National Institute of Advanced Industrial Science and Technology (AIST) has developed the world's first oxide semiconductor photocatalyst that enables water to be split into hydrogen and oxygen using visible light and that can produce clean fuels. The photocatalyst is an InTaO₄ compound doped with Ni. The research team worked with the AIST's National Institute for Materials Science (NIMS) to analyze the structure of this compound. The production of hydrogen fuel, a clean energy source, from the inexhaustible supplies of water and sunlight has long been a dream for many scientists. The ability to split water using visible light, which accounts for about half of incoming solar energy, is a major breakthrough in establishing a hydrogen-fuel production technology in the future. The results of this research were published in the December 6 issue of the natural sciences journal Nature.

• To date, the development of a photocatalyst that can split water into hydrogen and oxygen under visible light irradiation has proved difficult.
  Research has been conducted around the world into photocatalysts that can directly split water, since the oil crisis in the early 1970s. However, photocatalytic splitting of water using visible light is extremely difficult and such systems were previously not realized.
   
• The AIST has discovered and developed various oxide semiconductor photocatalysts with promise to realize this technological goal.
  The Photoreaction Control Research Center discovered and developed materials with optimal band gaps and control technologies for the band gaps, with an emphasis on oxide semiconductors that are stable in solution.
   
• The team successfully developed a semiconductor photocatalyst made up of an InTaO₄ compound doped with Ni.
  The AIST research showed that a semiconductor made up of an InTaO₄ compound (indium tantalum oxide) doped with Ni acted as a water-splitting catalyst that was responsive to visible light.
  Currently, the photocatalyst cannot produce hydrogen at a rate sufficient for application to the production of hydrogen fuel. The team plans to continue the research in order to improve the energy conversion efficiency.