Exfoliated single layer of layered cobalt hydroxide for ultrafine Co3O4 nanoparticles on a graphene nanosheet as an efficient oxygen reduction electrocatalyst.

A highly effective way to produce an oxygen reduction electrocatalyst is developed through the self-assembly of exfoliated single layers of cobalt hydroxide (Co(OH) 2 ) and graphene oxide (GO). These two-dimensional materials have complete contact with one another because of the physical flexibility and electrostatic attraction between negative GO and positive Co(OH) 2 layers. The strong coupling induces the change of the Co(OH) 2 single layer into a discrete nanocrystal of spinel Co 3 O 4 with an average 8 nm on reduced GO during calcination, which could not be obtained with bulk-layered cobalt hydroxide because of its rapid layer collapse. The ultrafine Co 3 O 4 /RGO hybrid exhibited not only a comparable oxygen reduction reaction performance but also higher durability compared with the commercial Pt/C catalyst (20 wt% of Pt).