Vegetarians and animal lovers might baulk at the idea, but Japanese scientists have invented a cheap alternative to the expensive platinum-group catalysts required by PEM electrolysers — by combining iron-rich pig-blood waste with discarded sea-pineapple shells.
A team of academics from three Japanese universities took dried blood left over from pig meat processing, and combined it with cellulose nanofibres from the shells of sea pineapples — strange marine animals that eat their own brains after attaching themselves to the seabed, which are eaten as a delicacy in Japan and South Korea (despite apparently tasting like rubber dipped in ammonia).
Both pig blood and sea pineapple shells are usually thrown away, while the platinum and iridium or ruthenium used in PEM electrolysers to help split water molecules into hydrogen and oxygen are among the most expensive metals on the planet.
In the journal Science and Technology of Advanced Materials, the Japanese scientists explain that they mixed blood meal (a dry powder made from blood) and the sea-pineapple nanofibres together in water, then dried the mixture at room temperature, before heating it in an electric oven to 700-900°C. This created a powder-like carbon alloy that was then turned into a “catalyst ink” that was cast onto “a glassy carbon insert of a rotating ring-disk electrode and dried”.
They found that the biomass catalyst exhibited “similar” values to platinum catalysts typically used in polymer-electrolyte-membrane (PEM) electrolysers, and point out that the material would also work in advanced batteries and PEM fuel cells.
“Both the methodology developed for preparing the electrocatalysts and the electrocatalysts themselves will contribute to realizing a sustainable society by reducing CO2 emissions associated with battery production and will contribute to the high[-scoring] LCA [environmental life-cycle assessment] of energy devices such as PEFCs [polymer electrolyte fuel cells], metal–air batteries, and water electrolyzers.”
While only a few milligrams of platinum and iridium/ruthenium are needed per PEM electrolyser, platinum-group metals are very rare in nature and an increase in demand would inevitably push up their prices. Iridium, in particular, was cited as a potentially expensive bottleneck for the electrolyser industry by the International Renewable Energy Agency in January.
And any technology that would reduce the cost of PEM electrolysers would also reduce the levelised cost of hydrogen.
PEM electrolysers are currently more expensive to produce than standard alkaline electrolysers, with BloombergNEF recently putting their average prices at $1,400/kW versus $1,200/kW. But PEM machines are able to ramp up and down a lot faster, so are considered to be more suitable for green hydrogen projects that rely on variable wind and solar power.
So, while the initial cost of a PEM system might be higher than an alkaline one, the levelised cost of green hydrogen produced over the 20-30-year lifetime of a project might well be lower.
