Rational design of graphene oxide and its hollow CoO composite for superior oxygen reduction reaction

Graphene oxide (GO) is an important derivative of graphene, fascinating the entire world with its dazzling properties and versatile performance. However, the synthesis of GO via chemical routes often results in limited control of the density of functionalities and their distribution, presenting a barrier to the spread of GO applications. We modified Hummers' method and aimed at controlling the oxygen functionality of GO. The highest oxygen content of the modified synthetic GO (MdGO) occurs at edge regions, and the large proportion of carboxyl groups can be easily removed upon annealing. The excellent conductivity of intrinsic graphene can thus be recovered after the removal of the main functional groups. The resulting MdGO was reduced and doped with NH3, and the reduced MdGO (rMdGO) was determined to be an excellent support for oxygen reduction reaction (ORR) electrocatalysts. As a demonstration, a composite of CoO and N-rMdGO was fabricated, which exhibited highly comparable ORR performance in alkaline relative to 20 wt.% Pt/C.