Hokkaido University Research Profiles

Nanotechnology / Materials

Artificial Photosynthesis System Using Localized Plasmons

Ammonia photosynthesis system involving hydrogen produced from water by visible and near-infrared light using an optical nano-antenna

To realize highly efficient artificial photosynthesis, we have used an optical nano-antenna made of metal nanostructures to convert solar energy to a wide range of wavelengths from visible to near-infrared, succeeding in hydrogen generation based on the photolysis of water and the photosynthesis of ammonia, which has recently attracted attention as an energy carrier.

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.

  • From left to right: Resonance spectra of the optical antenna structure and action spectra of the photoelectric conversion efficiency, artificial photosynthesis system for water-splitting of light using the optical antenna structure, and the dependence of hydrogen and oxygen production on the light irradiation time.

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.

Intellectual property related to this research

特許第6230039号 「水素発生装置及び水素発生方法」