Scientists at RMIT have made a breakthrough by developing a cheaper and more energy-efficient way to make hydrogen directly from seawater, without having to desalinate the water.

Hydrogen has long been touted as a sustainable alternative fuel and a potential solution to critical energy challenges, particularly for industries that find it more difficult to transition to low-carbon sources such as manufacturing, aviation and shipping.

Almost all hydrogen in the world currently comes from fossil fuels. Production accounts for approx 830 million tons of carbon dioxide per year, equivalent to the annual emissions of the United Kingdom and Indonesia combined.

But emission-free ‘green’ hydrogen, made by splitting water, is so expensive that it is not commercially viable and accounts for only 1% of total global hydrogen production.

A new approach, invented by a multidisciplinary Clean Energy and Environmental Materials (MC2E) research group at RMIT, uses a unique catalyst specifically designed to work with seawater.

Lead researcher Dr Nasir Mahmood, Senior Research Fellow of the Vice Chancellor at RMIT, said the existing water splitting process has these problems:

• Expensive catalyst and has a huge water and energy consumption.
• You can only use fresh or desalinated water (without the impurities found in seawater).
• It generates toxic by-products such as chlorine, which far exceeds the amount of hydrogen produced and used.
• It is not sustainable because it consumes a lot of energy and essentially means using fossil fuel to make that energy

So a new method from RMIT University researchers is a crucial step towards a truly viable green hydrogen industry. It uses an electrolyser to split the seawater directly into hydrogen and oxygen – eliminating the need for desalination and its associated costs, energy consumption and carbon emissions.

But it also solves one of the biggest challenges yet of using seawater to make hydrogen – excess chlorine production.

“Not only does our process leave out carbon dioxide, it also produces no chlorine,” said Dr Mahmood.

“The biggest hurdle in 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 problem first, we would be producing 240 million tons of chlorine every year – three to four times the world’s needs.

“It makes no sense to replace hydrogen made by fossil fuels with hydrogen production that could otherwise harm our environment. Our method of producing hydrogen directly from seawater is simple, scalable and much more cost effective than any green hydrogen approach currently on the market.”

The RMIT electrolysis experiments

A provisional patent application has been filed for the RMIT process.

Doctoral student Suraj Loomba said their focus was on producing highly efficient, stable catalysts that can be manufactured cost-effectively.

“Our approach focused on changing the internal chemistry of the catalysts through a simple method, making them relatively easy to produce on a large scale, so that they can be easily synthesized on an industrial scale,” he said.

Mahmood said the technology could reduce the cost of electrolysers – to meet the Australian government’s green hydrogen production target of $2 per kilogram, to make it competitive with fossil fuel hydrogen.

RMIT researchers are working with industrial partners to develop aspects of this technology.

The next phase of the research is the development of a prototype electrolyser that combines a series of catalysts to produce large amounts of hydrogen.