A team of researchers at the Osaka Metropolitan University has developed a more practical approach to artificial photosynthesis by creating a device that can regulate itself without relying on a battery-powered control system. By removing the need for this additional component, the design reduces both the cost and complexity of producing solar fuels.

Like the natural process used by plants, artificial photosynthesis harnesses sunlight to convert water and carbon dioxide into energy-rich compounds. In this system, the end product is formic acid, a chemical that can be stored and later used as a clean fuel or industrial feedstock.

The key element is the electrolyzer, which converts the electricity generated by solar cells into chemical energy, making it possible to capture and store solar power in the form of formic acid for future use.

Breakthrough reduces reliance on complex electronics

Maintaining efficient solar fuel production becomes challenging when sunlight intensity changes throughout the day. To address this, many artificial photosynthesis systems rely on a technique known as Maximum Power Point Tracking (MPPT), which continuously adjusts voltage and current to ensure solar cells operate at their highest possible efficiency. 

However, conventional MPPT setups usually require batteries or extra electronic control hardware to smooth out fluctuations in energy flow. These additional components add both cost and engineering complexity, making large-scale deployment of artificial photosynthesis systems more difficult.

To deal with this challenge, a research team at Osaka Metropolitan University developed a simpler artificial photosynthesis system by building the control function directly into the electrolyzer. Led by Associate Professor Yasuo Matsubara and Professor Yutaka Amao, and working with Iida Group Holdings Co., Ltd, the researchers integrated a special solid electrolyte into the device.

Instead of depending on batteries and additional electronic controls to keep the solar cells running efficiently, the new electrolyzer can adjust itself automatically. It uses the properties of the solid electrolyte to regulate its electrical behavior, allowing it to perform the Maximum Power Point Tracking (MPPT) function without extra hardware.

Heat-responsive electrolyzer keeps solar fuel production running efficiently 

According to Professor Amao, the system automatically responds to changes in sunlight without the need for external controls. As solar intensity rises, the electrolyzer warms up, which lowers its electrical resistance and allows electricity to flow more easily. This built-in response enables the device to adjust its own electrical behavior and maintain efficient operation.

Amao added that the built-in self-regulating mechanism helps maintain more consistent fuel production throughout the day while reducing the need for batteries and other expensive external hardware. By automatically adjusting to changing conditions, the system also simplifies the overall design.

To demonstrate the concept, the researchers tested a prototype equipped with the new technology under real outdoor sunlight. The device was able to continuously convert water and carbon dioxide into formic acid, maintaining stable performance even as sunlight intensity changed.

The researchers further noted that the technology has already demonstrated its practical potential in a real-world setting. According to the team, the system generated enough formic acid to power a miniature diorama displayed at the pavilion, illustrating how an efficient artificial photosynthesis system could one day produce and store clean energy for use in household applications.

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