The Photoreaction Control Research Center of the National Institute of Advanced Industrial Science and Technology (AIST) has used an artificial photosynthesis system that emulates the photosynthesis mechanism in plants and, for the first time ever, splits water completely split into hydrogen and oxygen using visible light. The system is extremely simple, using two types of oxide semiconductor powder that are reactive to visible light these powers are suspended in an aqueous solution containing iodine. Simply by irradiating with visible light, the light energy is converted and hydrogen is produced from the water. The system is expected to have applications in low-cost technologies to convert solar energy or in hydrogen-production technologies using renewable energy sources. The research results are published in the latest (November) edition of the UK Royal Society of Chemistry rapid-publication journal Chemical Communications.

• To date, development of a photocatalytic system responsive to visible light that splits water by a mechanism similar to photosynthesis has proved difficult.
  The plant photosynthesis process that splits water using visible light is an energy-storing reaction. Much work has been done to simulate this mechanism as a way to use solar energy, but this research has not been successful to date.
   
• The AIST took several approaches in the development of a photocatalytic process responsive to visible light.
  At the Photoreaction Control Research Center, studies were performed on the relationship between the natural photosynthetic systems PSI and PSII. Dedicated research then focused on a two-step photocatalytic process to split water.
   
• The research used an artificial photosynthesis system that, for the first time ever, split water completely using visible light.
  This first-ever reaction used iodine oxidation-reduction to link chromium-doped, platinum-carried strontium titanate (SrTiO₃) (the PSII system) with platinum-carried tungstic oxide (WO₃) (the PSI system).
  The researchers plan to increase the reaction activity in the future.