University of Calgary researchers have developed a new family of amorphous catalysts based on iron oxide — rust — that turns water into hydrogen fuel. The innovation could improve systems for storing energy from intermittent, renewable sources like solar and wind.
Currently, expensive materials like iridium or ruthenium oxide are used to overcome the activation energy barrier for the electrolytic splitting of H2O into O2 and H2, the latter of which can be reacted in a fuel cell to release this stored energy. But electrolyzers are only affordable on an industrial scale, and many groups are searching for better catalysts. Chemist Simon Trudel says the key may lie not in the composition of the material, but its structure. “Until now, the common approach was to use crystalline materials,” says Trudel. “But when you think about what makes something reactive, you realize that a disordered, amorphous material has all kinds of defects where a water molecule could easily come in.”
In a recent paper in Science, Trudel and his team describe an improved method for fabricating amorphous metal oxides. First, a metalcontaining organic precursor molecule — for example, iron (III) 2-ethylhexanoate — is spin-coated on a surface. Next, UV light destroys the organic carrier molecule leaving behind the amorphous metal, which quickly oxidizes in air. The process works with any combination of metals in any proportion. “We have access to about 80 per cent of the periodic table,” says Trudel. “The combinations are infinite.”
The team has fabricated a combination of iron, nickel and cobalt oxide that performs on par with catalysts thousands of times more expensive. The ultimate goal is to find even more efficient metal oxide combinations for beer fridge-sized electrolyzers suitable for use in a home. “When we talk to people in industry, that’s where they get really excited,” says Trudel.