Researchers at Osaka Metropolitan University have developed an artificial photosynthesis system that continuously produces solar fuel without requiring battery‑based control equipment. By embedding a self‑regulating chemical component directly into the electrolyzer, the team simplified the setup and reduced costs.
Artificial photosynthesis mimics natural plant processes, using sunlight to convert water and carbon dioxide into energy‑dense chemicals. One such product, formic acid, can serve both as a fuel and as an energy‑storage medium.
How Artificial Photosynthesis Produces Solar Fuel
The core of these systems is an electrolyzer that transforms electricity from solar cells into chemical energy, storing it as fuels like formic acid.
A key challenge is maintaining efficiency as sunlight intensity varies throughout the day. Many existing systems employ Maximum Power Point Tracking (MPPT) to continuously adjust voltage and current, ensuring optimal power output from the solar cells.
Conventional MPPT solutions rely on batteries and additional electronics to smooth energy flow, which adds expense and complexity.
Self‑Regulating Electrolyzer Eliminates Batteries
To address this, Associate Professor Yasuo Matsubara, Professor Yutaka Amao, and their team at Osaka Metropolitan University’s Research Center for Artificial Photosynthesis, in collaboration with Iida Group Holdings, redesigned the electrolyzer itself.
The new design incorporates a specially engineered solid electrolyte directly into the device, enabling the electrolyzer to perform MPPT autonomously and removing the need for battery‑based control systems.
Instead of external electronics or converters, the electrolyzer adjusts its electrical characteristics through its intrinsic thermal and impedance properties.
“As sunlight intensifies, the electrolyzer warms up, reducing its electrical resistance and allowing more current to flow,” Professor Amao explained. “This intrinsic response automatically adapts the system’s electrical behavior.”
“The self‑regulating action stabilizes fuel production throughout the day and eliminates reliance on batteries and costly external components,” he added.
Stable Formic Acid Production Under Real Sunlight
Field tests demonstrated that the system consistently generated formic acid from water and CO₂ despite fluctuating sunlight levels.
Professor Matsubara noted, “We were confident of success after showcasing this technology at the Joint Pavilion Iida Group × Osaka Metropolitan University exhibition during the Osaka Kansai Expo 2025. The device produced enough formic acid to power a small diorama, highlighting its potential for efficient artificial photosynthesis applications in residential settings.”
The research was published in EES Solar.