Cheaper hydrogen energy created from water

A team of researchers has demonstrated a sustainable, more cost-effective way of creating hydrogen, publishing results in Nature Communications.

Scientists from UNSW Sydney, Griffith University and Swinburne University of Technology are using low-cost metals — iron and nickel — as catalysts to capture hydrogen by splitting it from oxygen in water. The nickel–iron catalyst speeds up the chemical reaction but requires less energy than other catalysts such as platinum.

Precious metals ruthenium, platinum and iridium — regarded as benchmark catalysts in the water-splitting process — could be replaced by the abundant metals iron and nickel. Current metal prices indicate how this discovery could speed the transition towards the hydrogen economy and the future market for hydrogen-powered cars. Iron and nickel are priced at $0.13 and $19.65 per kilogram compared with ruthenium, platinum and iridium, which cost $11.77, $42.13 and $69.58 per gram, respectively. The significant price differential brings the hydrogen economy one step closer.

UNSW School of Chemistry Professor Chuan Zhao said, in water splitting, two electrodes apply an electric charge to water which enables hydrogen to be split from oxygen and used as energy in a fuel cell.

“What we do is coat the electrodes with our catalyst to reduce energy consumption,” he said.

“On this catalyst there is a tiny nanoscale interface where the iron and nickel meet at the atomic level, which becomes an active site for splitting water. This is where hydrogen can be split from oxygen and captured as fuel, and the oxygen can be released as an environmentally friendly waste.”

In 2015, Prof Zhao’s team developed a nickel–iron electrode for oxygen generation, reported to demonstrate record-high efficiency. Prof Zhao explained that, on their own, iron and nickel are not good catalysts for hydrogen generation, but where they join at the nanoscale is “where the magic happens”.

“The nanoscale interface fundamentally changes the property of these materials,” he said.

“Our results show the nickel–iron catalyst can be as active as the platinum one for hydrogen generation.

“An additional benefit is that our nickel–iron electrode can catalyse both the hydrogen and oxygen generation, so not only could we slash the production costs by using Earth-abundant elements, but also the costs of manufacturing one catalyst instead of two.

“At the moment in our fossil fuel economy, we have this huge incentive to move to a hydrogen economy so that we can be using hydrogen as a clean energy carrier which is abundant on Earth,” Prof Zhao said.

“We’ve been talking about the hydrogen economy for ages, but this time it looks as though it’s really coming.”

Prof Zhao said that if the water-splitting technology is developed further, there could one day be hydrogen refuelling stations similar to the petrol stations we have today. Hydrogen fuel-cell cars could be refilled with hydrogen gas produced by this water-splitting reaction, which could occur in a matter of minutes compared with the hours it takes to charge a lithium-battery-powered electric car.

“We’re hoping our research can be used by stations like these to make their own hydrogen using sustainable sources such as water, solar and these low-cost, yet efficient, catalysts,” Prof Zhao said.

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