Battery-free artificial photosynthesis device turns sunlight into formic acid fuel

Researchers at Osaka Metropolitan University have developed a battery-free artificial photosynthesis system that continuously converts sunlight, water, and carbon dioxide into formic acid, a liquid fuel and energy-storage chemical. The device eliminates the need for batteries and complex electronic controls by using a self-regulating electrolyser that adapts to changing sunlight conditions. This approach could lower the cost and complexity of solar fuel production. The system produces formic acid, which can store hydrogen in a stable liquid form and is made directly from captured CO2. The design was tested in Osaka, Japan, in May 2024 and was used to power a display at Expo 2025 Osaka.