To be a completely green source of energy, hydrogen must be produced by electrolysis, which requires the use of catalysts. Researchers all over the world are working on better non-metal catalysts, and a group of Japanese researchers has recently discovered one that is particularly effective.
Catalysts are required for the electrolysis process to work, and the best current industrial electrodes are made of precious metals such as iridium, ruthenium, and platinum. None of these metals are common, but iridium is one of the most rare elements on the planet, with only ten tonnes produced each year. Asteroids are thought to be responsible for much of the iridium in the Earth’s crust, which is found in ‘iridium anomalies.’
The researchers describe a method of splitting water with the more abundant cobalt and manganese in a paper published in Nature Catalysis. Manganese is the fifth most common metal in the Earth’s crust, and cobalt is several hundred thousand times more abundant than platinum.
Their catalyst lasts over two months and produces nearly as much hydrogen per energy input as current iridium catalysts. There’s still work to be done – iridium catalysts can last for at least a decade – but this breakthrough is a significant step forward from non-iridium catalysts, which corrode after a few hours or days.
Cobalt oxides are very active catalysts, but they corrode quickly during electrolysis, which was a problem for the researchers. Manganese oxides, on the other hand, are less active but are more stable. Through trial and error, the team combined and tested cobalt and manganese oxides. They eventually discovered a single compound – Co2MnO4 – that combined the best properties of both metals.
The researchers are now looking for ways to improve the catalyst’s activity and lifespan.
