Water electrolyzers are promising devices that use electricity to split water into hydrogen and oxygen. If powered by solar cells or other renewable energy technologies, they could contribute to the sustainable production of hydrogen used to make ammonia, which in turn is used to produce fertilizers and other valuable compounds.
Most water electrolyzers require purified water, even though seawater is far more abundant on Earth. This is because the salts in seawater can damage the devices and interfere with electrolysis, the process by which water is split into hydrogen and oxygen.
Researchers at the Chinese Academy of Sciences recently developed a system that could produce hydrogen from seawater while also desalinating it to produce fresh water. A 20-kilowatt pilot system, introduced in a paper published in Nature Energy, operated stably for 100 days, reliably producing both hydrogen and fresh water.
"Hydrogen production from seawater is attractive given its abundance, but direct seawater electrolysis is challenging due to the poor stability and low energy efficiency," wrote Shang Jiang, Peixin Zhu and their colleagues in their paper. "We report the co-production of hydrogen and fresh water from seawater by coupling alkaline water electrolysis with low-temperature desalination, wherein low-grade waste heat from the electrolyzer drives seawater distillation to generate fresh water for both electrolysis and external use."
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