Researchers in Japan have mimicked the process of photosynthesis to produce methane from CO₂ water and sunlight. An open-access paper on their work is published in the journal ACS Engineering Au.

Previously, corresponding author Kazunari Domen from the University of Tokyo and colleagues developed a system that used sunlight to split water into hydrogen and oxygen gases. They wanted to evolve the process to more fully mimic photosynthesis, taking in CO₂ to store the sun’s energy in methane instead, while still using cost-effective and easily scalable materials.

The team created a set of reaction cells, similar to solar panels, that were each coated with an aluminum-doped strontium titanate (SrTiO₃) photocatalyst to help power the reaction. These coated cells were filled with water and placed in the sun. Under those conditions, the water split into hydrogen and oxygen gas, which were separated, and the purified hydrogen gas was fed into the second part of the system.

Block diagram of the artificial photosynthetic apparatus. Yamada et al.

In the second chamber, the hydrogen gas reacted with CO₂, forming methane and water, the latter being recycled back into the first step with the photoreactor.

Next, they created a 130-square-foot array of the cells that operated continuously for three days in a variety of weather conditions. Though promising, the team recognizes that the efficiency of artificial photosynthesis systems needs to improve before these devices can become viable options for large-scale power generation. The researchers say that this proof-of-concept system could be adapted to help produce precursors for plastics or other chemical feedstocks, as well as scaled up to produce larger amounts of sustainable biofuels.

The authors acknowledge funding from the Japan Technological Research Association of Artificial Photosynthetic Chemical Process and the European Innovation Council. Some authors are employees of INPEX Corporation, an oil and gas exploration and production company.

Resources

• Taro Yamada, Hiroshi Nishiyama, Hiroki Akatsuka, Shinji Nishimae, Yoshiro Ishii, Takashi Hisatomi, and Kazunari Domen (2023) “Production of Methane by Sunlight-Driven Photocatalytic Water Splitting and Carbon Dioxide Methanation as a Means of Artificial Photosynthesis” ACS Engineering Au 3 (5), 352-363 doi: 10.1021/acsengineeringau.3c00034