Production of Methane by Sunlight-Driven Photocatalytic Water Splitting and Carbon Dioxide Methanation as a Means of Artificial Photosynthesis

This article describes an experimental apparatus of artificial photosynthesis, which generates methane gas from water and carbon dioxide with the aid of sunlight energy. This apparatus was designed on the basis of our previous 100 m2-scale photocatalytic solar hydrogen production mini-plant, which continuously produced filtered hydrogen gas for more than several months. A catalytic CO2 methanator was attached, converting photogenerated H2 into CH4. The overall setup was successfully operated, and photosynthetic CH4 was accumulated. Several versions were examined by changing the sizes of the composing assemblies and choosing specific purposes for experiments. The performances of the water-splitting photocatalytic panels, the hydrogen filtration subsystem, and the methanator are illustrated. One of the versions was implemented in the competition of the European Innovation Council (EIC) Horizon Prize on Artificial Photosynthesis “Fuel from the Sun” in 2022. For future expansion as artificial photosynthetic plants, the technical issues related to scaling up the plant size are extracted and discussed from these results.