New catalyst combines an outer shell of platinum atoms (gray spheres) with ordered layers of platinum and cobalt atoms (blue spheres) in its core
Researchers from Brown University developed a new catalyst to make hydrogen fuel cell-powered vehicles more economical. The new catalyst is efficient, long lasting, and cost-effective as compared to pure platinum, as it is based on nanoparticles made of an alloy of platinum and cobalt. Fuel cells contain a proton exchange membrane (PEM) with hydrogen on one side and air containing oxygen on the other. Electrons are stripped from the hydrogen atoms and taken up by the oxygen atoms in what is called the oxygen reduction reaction to generate electricity. Catalyst is required for accelerating the reaction.
Platinum as catalyst is prone to poisoning where impurities latch onto the platinum molecules, preventing reactions. According to researchers, alloying platinum with metals such as cobalt is cost-effective and increases efficiency of the catalyst. However, the base metal oxidizes inside the harsh conditions of the fuel cell and leeches away. To overcome this problem, the developed nanoparticles comprising an outer layer of pure platinum and an interior built up of alternating layers of platinum and cobalt atoms.
Tests of the new catalytic nanoparticles reported that they already out-perform platinum and remained active after 30,000 voltage cycles – a point at which platinum drops off radically. However, the team explains that stresses that what happens on a lab bench is different from what happens inside a fuel cell with its greater temperature and acidity. The new catalyst was therefore sent to the Los Alamos National Lab for further testing inside an actual cell.
The tests indicate that the new catalyst exceeds the targets set by the US Department of Energy (DOE) for both initial activity and longer-term durability, with an initial activity of 0.56 amps per milligram and an activity after 30,000 cycles (roughly equivalent of five-years inside a fuel cell) of 0.45 amps. The research was published in Joule in October 2018.