Experts outline potential for hydrogen fuel production using sunlight

Tokyo, Japan (SPX) Dec 04, 2024
Japanese scientists are pioneering advancements in hydrogen fuel production by leveraging sunlight and water, aiming to reduce reliance on fossil fuels. While hydrogen is predominantly sourced from natural gas, researchers at Shinshu University have demonstrated the potential for using photocatalytic sheets and reactors to refine hydrogen directly from water.

"Sunlight-driven water splitting using photocatalysts is an ideal technology for solar-to-chemical energy conversion and storage, and recent developments in photocatalytic materials and systems raise hopes for its realization," said Prof. Kazunari Domen, senior author of the study published in Frontiers in Science. "However, many challenges remain."

Harnessing sunlight to split water

Photocatalysts play a key role in splitting water into hydrogen and oxygen. In one-step systems, a single photocatalyst handles the entire process but operates with low efficiency. More effective are two-step systems where separate photocatalysts manage hydrogen and oxygen evolution, enhancing solar-to-hydrogen conversion rates.

"Obviously, solar energy conversion technology cannot operate at night or in bad weather," explained Dr. Takashi Hisatomi, first author of the study. "But by storing the energy of sunlight as the chemical energy of fuel materials, it is possible to use the energy anytime and anywhere."

Despite these improvements, challenges persist, including identifying durable photocatalysts that withstand daily operation cycles and achieving cost-effective conversion efficiencies. Current methods of refining hydrogen using natural gas remain cheaper, making efficiency improvements critical for wider adoption.

Addressing safety and scalability

Producing hydrogen and oxygen separately can mitigate the risks associated with oxyhydrogen, which is highly explosive. The team has identified design strategies to manage these risks, such as using narrow compartments to prevent destructive explosions and selecting materials like soft PVC plastic to reduce impact if ignition occurs.

The researchers also ran a proof-of-concept reactor spanning 100 square meters over three years, achieving higher performance under real-world sunlight compared to lab conditions. However, efficiency remains capped at approximately 1% under simulated standard sunlight and slightly higher in natural sunlight.

"To achieve practical implementation, we must improve solar energy conversion efficiency," said Hisatomi. "Reaching even 5% efficiency under natural sunlight would mark a significant milestone."

Paving the way for solar-powered hydrogen

The researchers stress the importance of safety standards and efficiency benchmarks to advance the technology. Introducing accreditation and licensing systems, alongside standardized efficiency metrics, could accelerate progress.

"The most important aspect to develop is the efficiency of solar-to-chemical energy conversion by photocatalysts," Domen added. "If it is improved to a practical level, many researchers will work seriously on the development of mass production technology and gas separation processes, as well as large-scale plant construction. This will also change the way many people, including policymakers, think about solar energy conversion, and accelerate the development of infrastructure, laws, and regulations related to solar fuels."

Research Report:Photocatalytic water splitting for large-scale solar-to-chemical energy conversion and storage