Platinum is undoubtedly quite an expensive element to use as a catalyst in hydrogen fuel cells. For that reason, scientists at Brown University are trying to find a cheaper material that can act in this same way and be just as effective.
Shouheng Sun and a group of his students developed a catalyst for the oxygen reduction reaction that can almost do what platinum does. It is a graphene sheet covered by cobalt and cobalt-oxide nanoparticles. It was found to have the best reduction performance out of all nonplatinum catalysts, according to the lead author of the publication- Shaojun Guo.
The cathode side of a hydrogen fuel cell is where the oxygen reduction reaction occurs. Fuel cells are not very commonly used, exactly because this reaction requires a catalyst, which currently is the very expensive platinum.
The team is certain that graphene-cobalt is the best replacement. Tested under laboratory conditions, the material was found to perform slightly slower in initiating the reaction, however once it has started the element acted at even faster pace. The “new” catalyst was also more stable with slower degradation rate.
Because of the difficulty in controlling the size, shape and composition of the graphene nanoparticles, Sun’s team had to use a self-assembly method. They firstly dispersed cobalt nanoparticles and graphene in two separate solutions. Later on, these two were combined so that the nanoparticles could attach evenly to the graphene in a single layer. Using a centrifuge, the material was pulled out of the solution, forming a shell of cobalt-oxide when exposed to oxygen. In order to control the thickness of the shell and adjust the structure, the material had to be heated at 70 degrees Celsius. They established that the most optimal thickness of the shell is 1nm.
The team is very positive and convinced that although the material is now only comparable with platinum in an alkaline medium, one day it will be used as a cheaper source of power for cars and devices.
Via: Brown University