Content of research

To realize highly efficient artificial photosynthesis, it is essential to convert the energy into chemical substances by constructing a system that utilizes solar energy of visible and near-infrared wavelengths, which are not used in conventional artificial photosynthesis. We have succeeded in designing and fabricating an optical nano-antenna that can effectively collect light of various wavelengths by changing the shape and arrangement of the metal nanostructures. We have also successfully photodisintegrated water to produce hydrogen and oxygen stoichiometrically using sunlight in a wide range of wavelengths from visible to near-infrared. This system has also enabled us to photosynthesize ammonia through photoreduction of nitrogen in the air. Ammonia is attracting attention as a next-generation energy carrier, but its synthesis requires high-temperature and -pressure conditions, which may cause a huge environmental burden. This system is expected to be used as a method for ammonia synthesis at normal temperature and pressure using sunlight.

Potential for social implementation

• ・As with solar cells, this system enables the synthesis of hydrogen and ammonia at home. Its combination with ENE FARM gives us a safe and secure system that can generate energy at home even if lifelines are cut due to disasters.

Appealing points to industry and local governments

This artificial photosynthesis system is also expected to be applied as a solar cell, and by designing an optical nano-antenna, it can be developed into a transparent solar cell that is sensitive only to ultraviolet and near-infrared light, but allows the transmission of visible light. In addition, plasmon sensors are currently being used to detect trace amounts of biological substances, and may also be used to electrically extract signals instead of using conventional optical detection.