Full charge for the future
The quest for better hydrogen fuel cells
If the ‘Hydrogen Roadmap’, part of the energy strategies for New Zealand, is on track, green hydrogen could account for around eight per cent of New Zealand’s total energy demand by 2050 and support key export markets in countries like Japan, Korea and Singapore to decarbonise.
Vehicles powered by hydrogen (H2) are already being trialled and, starting in 2023, Taranaki-based Hiringa Energy plans to assemble a nationwide green hydrogen refuelling network for the heavy transport sector. There’s talk of the South Island’s Manapouri hydro station being converted into the world’s largest hydrogen production facility – once the Tiwai Point smelter closes.
“New Zealand’s in quite an enviable position in that we can make lots of electricity in a green and sustainable manner which we can then use to produce hydrogen fuel,” says Chemical Sciences Professor Geoff Waterhouse, based at the Faculty of Science at Waipapa Taumata Rau, University of Auckland.
“Potentially, we can completely decarbonise New Zealand’s energy sector, and also have these exciting export opportunities in the Asia-Pacific region around hydrogen.”
However, the transition to a green hydrogen economy faces numerous obstacles including the need for more efficient water electrolysis technologies to produce H2. The fuel cells that convert hydrogen back into electricity are also quite expensive, and then there’s the challenge of developing more environmentally-friendly rechargeable batteries as a short-term electricity storage solution.
New Zealand’s in quite an enviable position in that we can make lots of electricity in a green and sustainable manner which we can then use to produce hydrogen fuel.”
In 2021, Waterhouse was awarded a James Cook Research Fellowship to develop catalysts for the oxygen evolution reaction (OER) and the oxygen reduction reaction (ORR) that are vital chemical processes in water electrolysis, fuel cells and rechargeable metal-air batteries.
Historically, precious metal nanoparticle catalysts containing platinum, ruthenium and iridium have been used to drive these reactions. But only metal atoms on the surface of the nanoparticles participate in OER and ORR so metal atoms in the interior of the nanoparticles do very little and are effectively wasted.
The focus is on the discovery and technology transfer of low-cost metal single atom catalysts based on earth- abundant metals like iron, nickel and cobalt. By making metal single atom catalysts, comprising isolated metal atoms immobilized on a conductive support, 100 per cent utilisation of the metals is possible.
Waterhouse says: “It’s about improving the utilisation efficiency of metal atoms when you’re making catalysts for these devices, whilst at the same time substituting precious metals for cheaper metals.”
It may sound complicated, but Waterhouse’s work takes inspiration from nature. In designing metal single atom catalysts for the oxygen reduction reaction, he noted that haemoglobin which transports oxygen around the body has an iron active site (oxygen binds to an iron atom surrounded by nitrogen atoms inside a globular protein).
“By immobilizing iron atoms on nitrogen-doped carbon supports, we have been able to accurately recreate the same type of active site, delivering electrocatalysts with remarkable activity for the oxygen reduction reaction that outperform commercial platinum-based catalysts.”
As for timeframes, the development of metal single atom catalysts for water electrolysis is at a relatively early stage due to the fact that low-cost nickel foam catalysts are already in use for this application even though they are much less energy efficient than precious metal- based catalysts.
Professor Geoff Waterhouse: Developing new catalysts for more environmentally-friendly batteries.
Professor Geoff Waterhouse: Developing new catalysts for more environmentally-friendly batteries.
It may sound complicated, but Waterhouse’s work takes inspiration from nature's invention haemoglobin
However the development of fuel cells and rechargeable batteries containing metal single atom catalysts is far more advanced with prototype devices already built and their excellent performance validated.
“We’re at a really good stage where we’ve produced state-of-the-art single atom catalysts for ORR, comparable to anything else that’s been produced in the world to date,” he says.
His team’s previous research on the development of a zinc-air battery to replace lithium-ion batteries has been funded by private donor philanthropists and their continued funding has enabled Waterhouse to bring on board three postdoctoral fellows and move closer to commercial devices.
Efficiency in electricity storage, and efficiency in getting electricity out of batteries of H2 are the key challenges to be addressed and Waterhouse sees recyclable rechargeable batteries as an important, yet often overlooked part of a future hydrogen economy.
“New Zealand has great capacity to create electricity. Rechargeable batteries represent a short-term electricity storage solution, and hydrogen production represents a longer-term electricity storage solution – especially for grid-scale electricity storage and transport sector."
While the New Zealand Government has set ambitious goals to reach 100 percent renewable energy by 2035 and become a carbon neutral economy by 2050, Waterhouse is not driven by political or commercial imperatives. “I do see potential for this stuff to head towards commercialisation but that’s not my personal driver. It's to discover really good catalysts for OER and ORR and then potentially license our catalysts out to the manufacturers of these energy-conversion devices so they can build them more cheaply.”
Building close relationships between countries and sharing ideas is key to global decarbonisation efforts in the energy sector, and Waterhouse collaborates nationally and internationally in his OER and ORR catalyst development work with researchers in the MacDiarmid Institute and leading research institutes in China. He is also part of a New Zealand team that was recently awarded $2 million to partner with German scientists in the development of anion exchange membrane electrolysers (AEMEL) which could drastically reduce hydrogen production costs. In a novel twist, the iron single atom catalysts that his group has developed for ORR also show promise in the electrochemical extraction of uranium from seawater. “There’s a thousand-fold more uranium in the earth’s oceans than in ore on land. So, if you can come up with a smart way of harvesting uranium from the seawater, this could support the whole decarbonisation initiative.”
It may be off the agenda in New Zealand, but Waterhouse says that other countries see nuclear power as a clean way of producing electricity. “We should not discount nuclear power as part of a global zero-carbon future.” But for New Zealand hydrogen is an important part of our energy future.
Built with Shorthand