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US RESEARCHERS say they may have developed a new contender in the race to find a cheap replacement for platinum in fuel cells, made from cobalt and graphene nanoparticles.

The team, from Brown University, claims that its cobalt-graphene creation can catalyse the oxygen reduction reaction almost as well as platinum, while at the same time being “substantially” more durable. According to researcher Shaojun Guo, the new material “has the best reduction performance of any non-platinum catalyst.”

The oxygen reduction reaction occurs on the cathode side of a hydrogen fuel cell. Oxygen functions as an electron sink, stripping electrons from hydrogen fuel at the anode and creating the electrical pull that keeps the current running through electrical devices powered by the cell.

“The reaction requires a catalyst, and platinum is currently the best one,” says Brown chemist Shouheng Sun, who led the research team. “But it’s very expensive and has a very limited supply, and that’s why you don’t see a lot of fuel cell use aside from a few special purposes.”

So far, scientists have been unable to develop a viable alternative. A few researchers – the Brown team included – have developed new catalysts that reduce the amount of platinum required, but an effective catalyst that uses no platinum at all has remained elusive.

According to Sun, this new graphene-cobalt material “is the most promising candidate yet.”

“It is the first catalyst not made from a precious metal that comes close to matching platinum’s properties,” he says.

Lab tests performed by Sun and his team showed that the new graphene-cobalt material was slower than platinum in getting the reaction started. Once it got going, however, the new catalyst actually reduced oxygen at a faster pace than platinum. The new catalyst also proved to be more stable, degrading much more slowly than platinum over time.

“After about 17 hours of testing, the graphene-cobalt catalyst was performing at around 70% of its initial capacity,” says Sun. “A platinum catalyst the team tested performed at less than 60% after the same amount of time.”

The researchers are continuing to test the new catalyst, but admit that “it’s not ready for use yet.” They are optimistic that with more study, it could one day be a suitable replacement for platinum catalysts.

Ultimately, Sun says, finding a suitable non-platinum catalyst is the key to getting fuel cells out of the laboratory phase and into production as power sources for cars and other devices.