AsianScientist (Dec. 14, 2018) – A research group in Japan has developed a material that can efficiently produce hydrogen fuel from solar energy and water. Their findings are published in Applied Energy Materials.
In a process called photoelectrochemical water splitting, a semiconductor absorbs high-energy photons from sunlight, which drives the splitting of water molecules around the semiconductor into hydrogen and oxygen. Hydrogen can then be stored and used as energy.
The problem, however, is that conventional semiconductors can only absorb ultraviolet (UV) light, which accounts for about five percent of the solar spectrum. Made of titanium oxide, these photo anodes are highly efficient at converting the solar energy they capture, but they’re not a viable option for industrial use because they capture so little solar energy.
In the present study, a team of scientists led by Professor Katsuya Teshima at Shinshu University, Japan, instead used tantalum nitride, which absorbs light from a much wider range of the solar spectrum. The researchers placed the metal tantalum samples on top of powder sodium compounds and heated them with ammonia gas at high temperatures.
They were able to control how evenly the sodium compounds reacted with the tantalum, as well as how thick the crystal layer grew by altering the ratio of the sodium compounds, the temperature, and the time taken for the reaction. This resulted in a crystal layer that was uniform in thickness and coverage, therefore leading to efficient light capture and water splitting.
“Our ultimate goal is to efficiently produce hydrogen and oxygen gasses from natural water by use of our flux-grown photo anode,” Teshima said. “As environment and energy problems are global issues, we want to contribute to their solutions.”
Source: Shinshu University; Photo: Katsuya Teshima.
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