Enzymes could replace expensive platinum catalysts in hydrogen fuel cells, say scientists.
Fraser Armstrong at the University of Oxford, UK, and colleagues used an enzyme to catalyse the oxidation of hydrogen to water in a safe, non-flammable atmosphere of only three percent hydrogen.
Hydrogen fuel cells can generate electricity through the reaction of hydrogen and oxygen. This is a green source of energy, if the hydrogen is made without using fossil fuels. The cells traditionally require high temperatures or expensive precious metal catalysts. Enzymes that can oxidise hydrogen, called hydrogenases, can work at rates similar to some platinum catalysts, but they are often inactive in the presence of oxygen.
Three of the fuel cells can power a wrist-watch for at least 24 hours
The team investigated enzymes from hydrogen-oxidising bacteria, called knallgas bacteria, which are tolerant to oxygen and other gases that might poison traditional platinum catalysts. ‘Finding a hydrogenase so selective for hydrogen that it will oxidise dilute hydrogen in air inspired us to test the concept of a fuel cell operating on safe, dilute, mixtures of hydrogen and air,’ said Armstrong.
Anthony Wedd, an expert in bioinorganic chemistry from University of Melbourne, Australia, said the work is a significant development. ‘It marries a naturally-occurring system with practical experimental conditions for the first time, making a hydrogen economy that much more feasible,’ he said.
Electricity from low-level H2 in still air – an ultimate test for an oxygen tolerant hydrogenase
K A Vincent, J A Cracknell, J R Clark, M Ludwig, O Lenz, B Friedrich and F A Armstrong, Chem. Commun., 2006