▎ 摘　　要

Graphene-based electrocatalysts have been widely investigated for their excellent performance in electrocatalytic oxygen reduction. The surface chemistry of graphene-based electrocatalysts is important for developing more efficient fuel cells and metal-air batteries. In addition, the nanostructured gas-diffusion electrode (GDE) on which the electrocatalysts are loaded needs to be carefully tailored to facilitate mass transport (reactants and products). A polymer binder is often used to fabricate the GDE which means there is a need to optimize the ratio of binder to electrocatalyst. Herein we demonstrate the impacts of graphene-based GDE nanostructures on the efficiency of oxygen electroreduction by comparing a series of graphene/chitosan composites with varying compositions. In these nanostructured GDEs graphene acts as the electrocatalyst and chitosan as the binder. Our results illustrate a critical ratio of graphene to chitosan for enhanced electrocatalytic surface area and facilitated mass transport, while'a continuous network for electron conduction is effectively established. We believe this work is an important piece of the puzzle to better understanding the electrode behavior of electrocatalysts consisting of graphene-like two-dimensional materials in oxygen reduction reaction. (C) 2014 Elsevier Ltd. All rights reserved.