Could seawater unlock a clean energy future?

Dr Xunyu Lu explains why producing hydrogen from seawater could be the solution to the renewable energy intermittency problem.

In a ground-breaking development that could help solve the intermittency problem in solar power generation, researchers at UNSW Chemical Engineering have found a way to generate hydrogen from one of the most abundant materials on the planet: seawater.Dr Xunyu Lu

“In the daytime, solar power often creates an excess of electricity, but we have not yet found a convenient method of storing this excess for use when the sun isn’t shining,” says Dr Xunyu Lu from UNSW Chemical Engineering.

“This is where seawater and hydrogen come in. Hydrogen is an attractive energy carrier to store solar energy because it has the highest energy density based on mass in the world, and it is also clean. Because hydrogen combustion generates only water, it is strictly zero emission and there is no harm to the environment,” he continues.

Xunyu, who is a DECRA Fellow (Discovery Early Career Researcher Award), explains that he and his colleagues have discovered a way to split seawater into hydrogen using the energy from solar panels. This hydrogen can then be stored and used in a hydrogen fuel cell when needed to re-generate electricity.

Their method involves creating a catalyst using a manganese-based metal organic framework on the surface of a nickel foam and Xunyu says their results have exceeded expectations.

“We found that our catalyst worked better than the platinum-carbon-based benchmark in terms of onset potential, as well as current density at a given potential. Our catalyst also had very good stability in hydrogen evolution reactions,” he says.

This discovery is like the holy grail of hydrogen evolution reactions because seawater is so abundant and can be found almost everywhere.

Dr Xunyu Lu, DECRA Fellow, UNSW Chemical Engineering

“Interestingly, we found that besides acting as a substrate for the catalyst, we can use the nickel to create a series of advanced novel nano-catalysts, which are comparable with, or in some cases can even beat, the precious metal-based catalysts for energy conversion reactions.”

These results are very promising, but one of the best (and most surprising) outcomes, says Xunyu, is their ability to do all this using natural seawater. “Based on the literature, most hydrogen evolution reaction to date has been carried out using buffered or simulated seawater,” he says. “Not real seawater.”

“The seawater we used was completely natural. In fact, it came from Maroubra, a beach very close to UNSW. This discovery is like the holy grail of hydrogen evolution reactions because seawater is so abundant and can be found almost everywhere.”

Xunyu says it is hard to say when their technology might be commercially available, but they have discovered that their lab-scale electrolyser is comparable to the commercially-available water electrolysers which are based on precious metals, which is good news.

“So far, we have only achieved small-scale water electrolysis, but our next step is to scale up, and hopefully in the next two years we can see something bigger and more practical for large-scale applications,” Xunyu continues.

“We are hoping our research will revolutionise the energy industry and help protect the environment, which are my twin passions. I think the advances we’re making in hydrogen technology are very exciting and will go some way to providing solutions to both of these issues in the near future.”

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