The joint research project involving NEDO, ARPChem, The University of Tokyo, Fujifilm, TOTO, Mitsubishi Chemical, Meiji University and Shinshu University (who was responsible for the photocatalytic water-splitting technology) demonstrated that in a large-scale outdoor area of 100m2 it is possible to split water using a powder photo catalyst and solar rays to retrieve solar hydrogen from the generated hydrogen-oxygen gas. More rigorous safety tests are still needed, but if a properly designed system is used, the highly explosive hydrogen-oxygen gas can be safely handled for long periods. Therefore, a system for producing a large amount of solar hydrogen at low costs through the improvement of the visible light responsive photo catalyst, the photo catalyst panel, and the gas separation module is within reach,
The photo catalyst in this study uses ultraviolet light. A highly efficient visible light-responsive photo catalyst with a practicality level of 5% or higher solar energy conversion efficiency will need to be realized for real-world implementation. The group is also working to lower the cost and expand the scale of the photo catalyst panel. The current panel reactor is robust, but it is necessary to develop an inexpensive reactor that can be mass-produced while maintaining durability and safety. The separation performance and energy efficiency of the gas separation process needs improvement because the separation membrane used was ready-made and not designed for this gas separation module. The separation performance of hydrogen from hydrogen-oxygen mixed gas was not sufficient. The separation process has no precedent, so there is no comparative example which means there is still room for improvement.