Oxford University has demonstrated an enzyme-based hydrogen fuel cell that operates without platinum or other costly catalysts.
“The technology is immensely developable,” said Professor Fraser Armstrong. “We are at the tip of a large iceberg, with important consequences for the future.”
The fuel cell uses enzymes from Ralstonia metallidurans, a hydrogen metabolizing bacteria that evolved 2.5 billion years ago when there was no oxygen in Earth’s atmosphere.
“Other scientists have been investigating enzymes as electrocatalysts for years,” said Armstrong. “Most hydrogenases have fragile active sites that are destroyed by even traces of oxygen, but oxygen tolerant hydrogenases have evolved to resist attack.”
The cell has two electrodes coated with the enzymes placed inside a container of air plus three per cent hydrogen - just below the four per cent explosion hazard level.
Armstrong admits that his is not the first team to use oxygen tolerant hydrogenases in a fuel cell, but “this research established for the first time that it is possible to generate electricity from such low levels of hydrogen in air”, he said, “there is still much to do before this generation of enzyme-based fuel cells becomes commercially viable.”
Since the hydrogenases are chemically selective and tolerant, they work in mixtures of hydrogen and oxygen without the need for fuel-separation membranes, and according to Armstrong these enzymes work at about the same rate as platinum-based catalysts.
Prototype versions have produced enough to power a watch. One focus of research is to adapt the chemistry in the enzyme’s active site to make bio fuel cells that are even more tolerant of oxygen.
In the current version of the cell, the enzyme is not attached tightly to the electrode and the cell runs for only about two days, said the University. The researchers also are investigating the use of enzymes from other organisms.