Microwave-assisted solvothermal preparation of nitrogen and sulfur co-doped reduced graphene oxide and graphene quantum dots hybrids for highly efficient oxygen reduction

A facile solvothermal method assisted by microwave irradiation was developed for preparing nitrogen and sulfur co-doped reduced graphene oxide functionalized with fluorescent graphene quantum dots (N,S-RGO/GQDs). Graphene quantum dots (GQDs) show high fluorescence and excitation-dependent fluorescent properties. The resultant N,S-RGO/GQDs hybrids as a kind of metal-free electrocatalyst were demonstrated to have good catalytic properties with long-term operational stability and tolerance to the crossover effects of methanol for oxygen reduction via a four-electron pathway in alkaline solution. This research not only develops a low-cost, economic and scalable approach for preparing a metal-free electrocatalyst for the oxygen reduction reaction (ORR), but also produces nitrogen and sulfur co-doped graphene quantum dots (N,S-GQDs) with high fluorescent characteristics.