Currently it is thought that the nanoparticles are formed by the reduction of diffusing Pt ions by H2 crossing over from the anode
Due to the crossover of both hydrogen and oxygen, a potential profile for an MEA in a running fuel cell is present, which has been modeled as a function of partial gas concentrations
Deposition mainly occurs at the point where the potential rapidly decreases to 0 V, resulting in the formation of the intense band, though particles do form further in the membrane, due to inhomogeneities in the gas crossover and the presence of seeding points