(July 15, 2015) In
the quest for better, less expensive ways to store and use energy, platinum and
other precious metals play an important role. They serve as catalysts to propel
the most efficient fuel cells, but they are costly and rare.
Now, a metal-free alternative catalyst for fuel cells may be
at hand. In a study published July 15 in ACS Central Science, a team of
chemists from the University of Wisconsin-Madison introduces a new approach
that uses a molecular catalyst system instead of solid catalysts. Although
molecular catalysts have been explored before, earlier examples were much less
efficient than the traditional platinum catalyst.
A fuel cell converts chemical energy into electricity by
reacting hydrogen and oxygen at two different electrodes. A catalyst makes the
reaction more efficient.
UW-Madison chemistry Professor Shannon Stahl and lab
scientist James Gerken took inspiration from their group's previous work with
catalysts that use oxygen in applications for the chemical industry. They
noticed a striking similarity between these aerobic oxidation reactions and the
oxygen reaction in fuel cells and decided to see if they could apply a similar
approach to a fuel cell.
The new catalyst is composed of a mixture of molecules
called nitroxyls and nitrogen oxides. These molecular partners play well
together; one reacts well with the electrode while the other reacts efficiently
with the oxygen.