Japanese scientists simplify clean fuel production with new invention

Artificial photosynthesis uses sunlight to convert water and carbon dioxide into usable fuels or means for generating electricity. One of the key products of this process is formic acid, which serves as an efficient energy storage medium in fuel cells. The centerpiece of this system is an electrolyzer, a device that converts electricity from solar cells into chemical energy, thus enabling the creation and storage of "fuel".

The biggest challenge with this type of technology is, of course, the fluctuation of sunlight throughout the day. To ensure the system works efficiently, classic devices are equipped with MPPT (maximum power point tracking) technology, which constantly adjusts voltage and current. These problems usually require additional electronics and batteries to stabilize the energy flow, which significantly increases the final cost.

A research team led by Associate Professor Yasuo Matsubara and Professor Yutaka Amao from the Artificial Photosynthesis Research Center, in collaboration with Iida Group Holdings Co., Ltd., has found an elegant solution. They have completely redesigned the electrolyzer using a special solid electrolyte. This new design allows the device to perform the MPPT function itself, making external controllers, inverters, and batteries completely redundant.

The system works by automatically adjusting its electrical properties by changing its thermal characteristics and resistance. As the intensity of sunlight increases, the electrolyzer naturally heats up. This heating causes a drop in electrical resistance, allowing the free flow of electricity. Due to this self-regulating phenomenon, fuel production remains stable throughout the day, and the system is fully automated and independent of expensive external components.

The scientists confirmed the prototype's efficiency in outdoor tests, where the device successfully and reliably produced formic acid despite changing lighting conditions. The technology was previously successfully demonstrated at the Osaka Kansai Expo 2025 exhibition in the joint pavilion of the Iida Group and the university. There, the system produced enough formic acid to power a miniature model, demonstrating its practical potential for future use and powering various devices in our homes. The results of this research were published in the professional journal EES Solar.