▎ 摘　　要

A highly effective way to produce an oxygen reduction electrocatalyst was developed through the self-assembly of exfoliated single layers of cobalt hydroxide (Co(OH)(2)) and graphene oxide (GO). These 2D materials have complete contact with one another because of their physical flexibility and the electrostatic attraction between negatively charged GO and positively charged Co(OH)(2)layers. The strong coupling induces transformation of the Co(OH)(2)single layer into a discrete nanocrystal of spinel Co(3)O(4)with an average size of 8 nm on reduced GO (RGO) during calcination, which could not be obtained with bulk-layered cobalt hydroxide because of its rapid layer collapse. The ultrafine Co3O4/RGO hybrid exhibited not only comparable performance in the oxygen reduction reaction but also higher durability compared with the commercial 20 wt % Pt/C catalyst.