Australian researchers are making hydrogen fuel directly from seawater, in a huge advance for the technology. 

A new method from RMIT University researchers splits seawater directly into hydrogen and oxygen - skipping the need for desalination and its associated cost, energy consumption and carbon emissions.

Hydrogen could be the next big future fuel, especially for industries that are harder to decarbonise like manufacturing, aviation and shipping.

But almost all the world’s hydrogen currently comes from fossil fuels and its production is responsible for around 830 million tonnes of carbon dioxide a year.

Currently, emissions-free ‘green’ hydrogen, made by splitting water, is so expensive that it is largely commercially unviable and accounts for just 1 per cent of total hydrogen production globally. Green hydrogen production processes are also costly and rely on fresh or desalinated water.

To be truly sustainable, hydrogen fuel production must be 100 per cent carbon-free across the entire production life cycle and must not cut into the world’s precious freshwater reserves.

To make green hydrogen, an electrolyser is used to send an electric current through water to split it into its component elements of hydrogen and oxygen.

These electrolysers currently use expensive catalysts and consume a lot of energy and water - it can take about nine litres to make one kilogram of hydrogen. They also have a toxic output: not carbon dioxide, but chlorine.

“The biggest hurdle with using seawater is the chlorine, which can be produced as a by-product,” says RMIT lead researcher Dr Nasir Mahmood.

“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. 

“There’s no point replacing hydrogen made by fossil fuels with hydrogen production that could be damaging our environment in a different way.

“Our process not only omits carbon dioxide, but also has no chlorine production.”

“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.”

The new approach uses a special type of catalyst developed to work specifically with seawater.

“These new catalysts take very little energy to run and could be used at room temperature,” Dr Mahmood says.

“While other experimental catalysts have been developed for seawater splitting, they are complex and hard to scale.”

The approach focuses on changing the internal chemistry of the catalysts through a simple method, which makes them relatively easy to produce at large-scale so they can be readily synthesised at industrial scales

Dr Mahmood says the technology could significantly bring down the cost of electrolysers - enough to meet the Australian Government's goal for green hydrogen production of $2/kilogram, to make it competitive with fossil fuel-sourced hydrogen.

A provisional patent application has been filed for the new method, detailed in a lab-scale study published in Wiley journal, Small.

The next stage in the research is the development of a prototype electrolyser that combines a series of catalysts to produce large quantities of hydrogen.