Turning seawater into hydrogen fuel

RMIT University researchers have developed a method to split seawater directly into hydrogen and oxygen, skipping the need for desalination and its associated cost, energy consumption and carbon emissions.

Hydrogen has often been touted as a clean fuel of the future with potential to solve critical energy challenges, especially for industries that are difficult to decarbonise. However, emissions-free ‘green’ hydrogen, made by splitting water, is so expensive that it is largely commercially unviable and accounts for just 1% of total hydrogen production globally.

Nasir Mahmood, lead researcher and Senior Research Fellow at RMIT, said the method he and the researchers developed is simple, scalable “and far more cost-effective than any green hydrogen approach currently in the market”.

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

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 release chlorine, which is toxic to the environment.

“The biggest hurdle with using seawater is the chlorine, which can be produced as a by-product. 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,” Mahmood said.

The researchers’ process omits carbon dioxide and produces no chlorine by using a special type of catalyst developed to work specifically with sea water.

The study, with PhD candidate Suraj Loomba, focused on producing highly efficient, stable catalysts that can be manufactured cost-effectively. The new catalysts use little energy to run and could be used at room temperature, Mahmood said.

“Our approach focused 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,” Loomba said.

According to Mahmood, the technology has promise to bring down the cost of electrolysers enough to meet the Australian Government’s goal for green hydrogen production of $2/kg, making it competitive with fossil fuel-sourced hydrogen.

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.

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