▎ 摘　　要

Graphene-based composites offer enhanced catalytic performance of metal and semiconductor nanoparticles, but their development is challenging because catalytic performance strongly depends on the structure and composition of the composite. Herein we show that the catalytic performance of a nanoparticlegraphene composite is very dependent on catalyst loading, which can be optimized for simultaneous enhancement of activity and selectivity. A glassy carbon working electrode has been modified with a gold nanoparticlegraphene (AuG) composite with a varied number of gold nanoparticles per graphene, so that the conducting property of graphene and the electrocatalytic property of the metal were effectively coupled to give the best catalytic activity and selectivity. The modified electrode was used for simultaneous electrochemical detection of a mixture of electroactive species with high sensitivity. This result shows that the catalytic performance of a graphene-based composite is sensitive to the catalyst loading and should be optimized for the best performance.