Hydrogen power generation is often touted as a vital component of our green economy of the future, along with the likes of solar and wind energy. But while it’s true that burning hydrogen to generate electricity is as ‘green’ as it gets, producing only water as a byproduct, how we source said hydrogen is an entirely different matter.

Over 99% of all the hydrogen produced by mankind is actually made from and using fossil fuels. The most common method for producing hydrogen is natural gas reforming, a process in which methane from natural gas is heated, with steam, usually with a catalyst, to produce a mixture of carbon monoxide and hydrogen. Overall, fossil fuel-derived hydrogen accounts for 830 million tons of carbon dioxide a year, which is more than the annual emissions of the United Kingdom and Indonesia combined.

Emissions-free hydrogen, made by splitting water using renewable energy, accounts for just 1% of the total hydrogen production globally. But a groundbreaking new method could help even the score.

Researchers at the Royal Melbourne Institute of Technology (RMIT) University in Australia have developed a new method for producing hydrogen directly from seawater that is cheaper, more energy-efficient, and environmentally friendly. The process uses a special type of catalyst developed specifically for the task at hand that splits seawater into hydrogen and oxygen without the need for desalination.

“We know hydrogen has immense potential as a clean energy source, particularly for the many industries that can’t easily switch over to be powered by renewables,” said lead researcher Dr. Nasir Mahmood, a Vice-Chancellor’s Senior Research Fellow at RMIT.

“But to be truly sustainable, the hydrogen we use must be 100% carbon-free across the entire production life cycle and must not cut into the world’s precious freshwater reserves.

Splitting seawater

Although seawater is abundant, splitting it into hydrogen and oxygen is a cumbersome process that does more harm than good, causing corrosion and side reactions in the electrochemical cell. What’s more, sodium chloride (table salt) forms chlorine gas and sodium hydroxide under electrolysis, both of which are highly corrosive and potentially dangerous substances.

Just as salty ocean water cannot quench the thirst of sailors, it also could not satisfy the needs of the green hydrogen economy — or so we thought.

The new approach demonstrated at RMIT uses a special type of catalyst composed of porous sheets of nitrogen-doped NiMo₃P (N-NiMo₃P) developed to work specifically with seawater, which is also cost-effective and can be used at room temperature to boot.

“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.

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

The researchers hope that the new method will pave the way for a thriving green hydrogen industry. The process is simple, scalable, and far more cost-effective than any other green hydrogen approach currently on the market. It has the potential to bring down the cost of electrolyzers, enough to meet the Australian Government’s goal for green hydrogen production of $2/kilogram, making it competitive with fossil fuel-sourced hydrogen.

The researchers are working with industry partners to develop aspects of this technology. The next stage in the research is the development of a prototype electrolyzer that combines a series of catalysts to produce large quantities of hydrogen.

The findings appeared in the journal Small.