Hydrogen is one of the sustainable energy solutions being used to shift some parts of the international energy market away from fossil fuels. It’s quite a brilliant energy source, as it can be created and stored as a gas and as water (which is in abundance on Earth), but why is it so hard to use seawater in hydrogen?
So up until now, the biggest hurdle with creating hydrogen from seawater has been the chlorine, which is abundantly present in the ocean (in a dissolved, diluted form throughout the water). When creating hydrogen from seawater, chlorine is present as a byproduct.
The byproduct chlorine content that’s generated is potentially harmful to the environment and the ozone layer.
“The biggest hurdle with using seawater is the chlorine, which can be produced as a byproduct. If we were to meet the world’s hydrogen needs without solving this issue first, we’d produce 240 million tons per year of chlorine each year – which is three to four times what the world needs in chlorine,” the vice-chancellor’s senior research fellow at RMIT Doctor Nasir Mahmood said. Mahmood’s team has been working on a solution (more on that below).
“There’s no point replacing hydrogen made by fossil fuels with hydrogen production that could be damaging our environment in a different way.”
Additionally, saltwater can actively corrode parts of the electrolysis machine that’s converting the seawater to water, limiting the machine’s lifespan. Adding to all of this, desalination treatment of the water has been posited as a solution, but it’s often expensive.
So, up until now, it’s been an efficiency, cost and harm reduction issue. The seawater damages the electrolysis machine, and we’re left with a toxic compound as a byproduct, which actively goes against the entire point of the process.
But there’s no need for hopelessness, as researchers are working on solutions.
We may be able to use seawater as a source for hydrogen
Mahmood’s team at RMIT has been working on a method of creating hydrogen from seawater without the need for desalination and without the creation of chlorine as a byproduct.
“Our method to produce hydrogen straight from seawater is simple, scaleable and far more cost-effective than any green hydrogen approach currently in the market,” Mahmood said.
“To be truly sustainable, the hydrogen we use must be 100 per cent carbon-free across the entire production life cycle and must not cut into the world’s precious freshwater reserves.”
The team has developed a system in which an electrolyser sends a current through the water to split it into both hydrogen and oxygen. It uses a newly developed catalyst, that has been created specifically for seawater.
The end result is a highly efficient and stable catalyst that can be manufactured cost-effectively.
The hope is that this method can be used widely in Australia to meet the federal government’s green hydrogen goals, making it competitive against fossil fuel-generated alternatives.
The next stage of the research is to develop a prototype to develop large quantities of hydrogen. The team is actively working with industry partners to develop aspects of the technology.
Let’s hope that this research leads to a huge uptake of clean, green hydrogen. The team at RMIT isn’t the only one that’s working on seawater hydrogen solutions, but with chlorine as a major consideration, it is one of the more exciting ones.
You can read more on the RMIT website, or read the research paper in Nano-Micro Small.