Japanese researchers have developed an innovative method that utilizes sunlight to split water into green hydrogen fuel, effectively leveraging two of humankind’s oldest energy sources while helping combat climate change.
With an ever-increasing need to develop cleaner energy sources, hydrogen fuel is an attractive option. The new work out of Shinshu University in Japan is essential in that it may lead the way in removing natural gas, a fossil fuel, from hydrogen production.
A New Reactor
Scientists involved with the new method developed photocatalytic sheets for a proof-of-concept reactor, demonstrating the process’s practicality in real-world applications. Simple to manufacture, the sheets enable large-scale hydrogen fuel production from water. So far, the reactor has successfully been running for three years in laboratory and direct sunlight conditions.
“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 co-author Prof Kazunari Domen of Shinshu University. “However, many challenges remain.”
Photocatalysts
Photocatalysts are essential in splitting water into hydrogen and oxygen components. When light hits the catalysts, chemical reactions separate the hydrogen and oxygen. Two principal varieties of these machines exist, comprising single-step systems, which work to break down the water entirely, and two-step systems, which have separate processes to remove hydrogen and oxygen from the water most efficiently.
While the two-step solution is still in the testing phase and not yet ready for practical implementation, researchers have made significant progress. Scientists are working to determine the most efficient photocatalysts that balance task efficiency with sustainability concerns. They are also exploring ways to manage the strain of solar energy’s start-stop nature. However, achieving efficiency and cost-effectiveness surpassing natural gas refinement processes remains challenging.
“Obviously, solar energy conversion technology cannot operate at night or in bad weather,” said lead author Dr Takashi Hisatomi of Shinshu University. “But by storing the energy of sunlight as the chemical energy of fuel materials, it is possible to use the energy anytime and anywhere.”
Considering Hydrogen Safety
Storing hydrogen fuel and even the water-splitting process pose significant safety challenges due to hydrogen’s flammability and the potential for explosive byproducts like oxyhydrogen. The two-step process avoids creating oxyhydrogen. However, the Japanese research team has developed a single-step method to mitigate the danger of this byproduct, minimizing the safety risk by burning off the oxyhydrogen in a narrow, controlled environment.
Making Hydrogen From Water A Commerical Reality
“In our system, using an ultraviolet-responsive photocatalyst, the solar energy conversion efficiency was about one and a half times higher under natural sunlight,” said Hisatomi. “Simulated standard sunlight uses a spectrum from a slightly high latitude region.
The solar energy conversion efficiency could be higher in an area where natural sunlight has more short-wavelength components than simulated reference sunlight. However, currently the efficiency under simulated standard sunlight is 1% at best, and it will not reach 5% efficiency under natural sunlight.”
Increasing the efficiency of photocatalysis and building larger reactors are the primary barriers to moving beyond 5% efficiency. Future researchers will need to conduct more real-world experiments to solve those problems. The team cautions that standardizing safety and efficiency standards will be necessary moving forward due to the potential hazards of implementing hydrogen as a fuel source. They recommend developing an accreditation body and licensing controls to maximize safety and move the field forward.
“The most important aspect to develop is the efficiency of solar-to-chemical energy conversion by photocatalysts,” Domen explained. “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,” Domen added.
The paper “Photocatalytic Water Splitting for Large-Scale Solar-to-Chemical Energy Conversion and Storage” appeared on December 02, 2024 in Frontiers in Science.
Ryan Whalen covers science and technology for The Debrief. He holds a BA in History and a Master of Library and Information Science with a certificate in Data Science. He can be contacted at ryan@thedebrief.org, and follow him on Twitter @mdntwvlf.