New Artificial Photosynthesis Technology That Increases Oxygen-Producing Efficiency by More Than 100-fold

New Artificial Photosynthesis in the Spotlight

Some plants absorb sunlight and utilize it to produce oxygen and their nutrients from carbon dioxide (CO2) and water. This process is called photosynthesis.

If this mechanism of photosynthesis can be artificially reproduced and practically applied, it will be possible to generate storable clean energy. Since artificial photosynthesis could contribute to solving energy and environmental issues without a need to rely on fossil fuels like oil, it is garnering much attention.

The study of artificial photosynthesis is conducted by imitating photosynthesis processes in plants. Photosynthesis consists of two major processes: a “light reaction” and “dark reaction.” In a light reaction, plants use sunlight energy to split water and make oxygen. The light reaction in artificial photosynthesis uses sunlight energy to extract electrons from a photocatalyst material * on electrodes. At the same time, this process generates oxygen by oxidizing water in the solution.

Artificial photosynthesis technology

*: A material that has a high energy internally when it absorbs light energy, causing electricity to flow (electrons to move). For artificial photosynthesis, many oxide and nitride ceramics such as GaN-xZnO are being studied.

Improving Electroceramics Technology

Reflectivity of sunlight with the new material

Fujitsu Laboratories has developed a new technology for forming photocatalyst material on the electrode by improving the thin-film process of electroceramics. This technology increases the efficiency of producing photocurrent and oxygen by more than 100-fold when compared to using photocatalyst material, as is.

Nanoparticle deposition (NPD) is a technology for forming films of a structure in which a particle state is maintained (nanoparticle structure) by spraying a gas including ceramic nanoparticles. Since this technology enables to control a crystalline structure inside the film, a composition with broader wavelength for absorbing the spectrum of sunlight can be investigated.

The conventional electrodes used for light reaction can only use a narrow range of wavelength of sunlight (visible light wavelength). With the electrode consisting of NPD thin films, the spectrum of sunlight that can be absorbed is broadened from a maximum wavelength of 490 nm using existing technology to 630 nm. As a result, this technology more than doubles the usable amount of light that can be gathered from sunlight. The analysis of the film’s surface structure found that it increases the surface area that can react with water. It also found that the ordered crystal planes with high electron-density are arranged on the film surface. This effectively increases by more than a factor of 50 the surface area of the material that can react with water. Taken together, these advances have been verified to increase the efficiency in producing electricity and oxygen by more than a factor of 100.

Structure of light-reacting electrodes for artificial photosynthesis [High electron density crystal layer is highly arranged near film surface] (Image courtesy Crystal Interface Laboratory at the University of Tokyo)

Contributing to Solving Environmental Problems by Making Further Improvements

The artificial photosynthesis technology could enable storable fuels, such as methanol and methane, to be generated solely from natural resources (water, CO2, and sunlight). If it becomes a reality, self-sufficient energy supply can be achieved simply by installing an artificial photosynthesis unit in each house. The technology would not only be implemented for generating storable clean energy. By collecting a volume of factory and automobile-emitted CO2 and using it as raw material for energy fuel, it could also contribute greatly to solving the problem of global warming.

Fujitsu Laboratories is continuing to work on further advances in photocatalyst materials and process technology to improve the characteristics of photoreactive electrodes, and is working on developing technologies for the dark-reaction part (CO2-reducing reactions) and the overall system, with the goal of implementing artificial photosynthesis technology.

Fujitsu Laboratories seeks to contribute to a more sustainable society through renewable energies, and to develop the foundation for sustainable energies and the environment.