Green hydrogen is an excellent resource for weening humanity off of fossil fuels, but making it currently uses too much renewable energy.
A new method being explored by Japanese researchers would primarily use sunlight and a photocatalyst to separate hydrogen and oxygen in water.
This could help lower the cost of green hydrogen, making it a key player in the green energy transition.
Hydrogen fuels come in many colors—each one an indicator of how the fuel was initially created. Blue hydrogen refers to fuel created from steam (and capturing the resulting carbon underground), pink hydrogen means that nuclear energy powers the electrolysis process, and black and brown hydrogen (as their name denotes) splits H20 using fossil fuels, which isn’t exactly helpful with the whole cutting emissions thing. The industry’s holy grail is what’s known as “green hydrogen,” which is a climate-neutral process that uses renewable energy sources to create hydrogen.
However, according to the World Economic Forum, only 0.1 percent of all hydrogen production can be described as “green.” That’s because it requires so much renewable energy to create, making the process cost prohibitive. For green hydrogen to really take off, the industry needs a material breakthrough to lower the cost of this energy-dense alternative. Luckily, scientists at Shinshu University, located in Matsumoto, Japan, think they may be nearing a solution.
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Detailed in a new paper published in the journal Frontiers in Science, the researchers describe a proof-of-concept panel reactor built with a photocatalytic sheets that can split water using the power of sunlight.
“Sunlight-driven water splitting using photocatalysts is an ideal technology for solar-to-chemical energy conversion and storage,” Kazunari Domen, a senior author of the study from Shinshu University, said in a press statement, “and recent developments in photocatalytic materials and systems raise hopes for its realization.”
Photocatalysts are materials that promote chemical reactions—in this case, splitting hydrogen and oxygen. A one-step excitation system breaks apart the two elements, but the researchers say that this process is inefficient and delivers a low solar-to-hydrogen energy conversion rate. A two-step excitation process on the other hand, where one photocatalyst is dedicated to the evolution of each element, is much more efficient.
“Obviously, solar energy conversion technology cannot operate at night or in bad weather, but by storing the energy of sunlight as the chemical energy of fuel materials, it is possible to use the energy anytime and anywhere,” Takashi Hisatomi from University of Shinshu said in the press release.
Sounds great, right? Well, Domen readily admits that some challenges still remain. While the two-step excitation process is more efficient, the team still needs to find materials robust enough to withstand daily start-up and shut-down operations when the Sun is and isn’t shining while also increasing conversion efficiency so that these reactors can be as small as is physically possible. Designs also need to incorporate the safe handling of oxyhydrogen, which can be highly explosive.
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But there is also some good news. Domen and his team operated their proof-of-concept reactor for three years, and the machine actually performed better under natural sunlight than it did in laboratory conditions.
“The most important aspect to develop is the efficiency of solar-to-chemical energy conversion by photocatalysts,” Domen said in a press statement. “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.”
Japan is the world’s leader in hydrogen fuel, but some experts—including the Renewable Energy Institute—have worried that the country’s extreme focus on the technology has caused it to lag behind on implementing other green energy technologies. If scientists could somehow make the production of green hydrogen economically feasible, Japan’s dream of a “hydrogen society” could one day become a reality.
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Darren lives in Portland, has a cat, and writes/edits about sci-fi and how our world works. You can find his previous stuff at Gizmodo and Paste if you look hard enough.