Efficient ways of liberating hydrogen from water are a key part of the so-called hydrogen economy – the long-hyped, but still elusive vision of a society where hydrogen is the key fuel for making energy, rather than hydrocarbons. Electrolysis is the most common process, but water being a very stable molecule, some catalyst is invariably needed to reduce the energy needed to force the separation of hydrogen and oxygen. However, up to now the most effective catalysts available have been based on precious metals like platinum and ruthenium, making the process very expensive.
The breakthrough from the stream at Washington State, in Pullman, Washington, is a method for making large amounts of as high-quality catalyst, based on nickel and iron – much cheaper and more abundant materials than precious metals. The catalyst is in the form of a metal foam with nanometre-scale pores; a highly effective structure, as its ratio of surface area to mass is huge, providing many active sites for the dissociation reaction to take place.
In a paper in the journal Nano Energy, the team claims that the nanofoam works better than other currently available catalysts, including those based on precious metals. The method to make the material, explained in detail in the paper, works by in-situ reduction of metal precursor compounds; according to graduate student Shaofang Hu, who synthesised the catalyst and did most of the activity testing, this is a simple process. "We took a very simple approach that could be used easily in large-scale production," he said.
The nanofoam showed very little loss in activity after 12 hours of constant testing, unlike other catalyst candidates which have proven to have stability problems. Lin now hopes to work on large-scale testing of the production process and the use of the catalyst in industrial-scale electrolysers