Controllable Codoping of Nitrogen and Sulfur in Graphene for Highly Efficient Li-Oxygen Batteries and Direct Methanol Fuel Cells

Lithium-oxygen batteries (LOBs) and direct methanol fuel cells (DMFCs) are both attractive technologies for the development of future energy storage and conversion devices, while the lack of highly active electrocatalysts has largely hampered their large-scale commercial applications. In the present work, we have demonstrated the controllable synthesis of nitrogen and sulfur codoped graphene (NS-G) nanosheets via a simple and cost-effective approach. Owing to their distinctive structural advantages, such as large surface areas, good flexibility, coexistence of N and S atoms with tunable doping contents and positions, and high electrical conductivity, the obtained NS-G sheets exhibit low discharge-recharge voltage gaps and high round-trip efficiencies as well as exceptional rate capability when used as cathode materials for LOBs. Furthermore, the NS-G layers are also identified to be an ideal substrate for the decoration of ultrafine Pt nanoparticles. Benefiting from the synergetic effects, exceptional electrocatalytic properties including high activity, strong poison tolerance, and outstanding long-term stability are observed for the resulting Pt/NS-G hybrid toward methanol oxidation reaction, which are significantly superior to those for Pt/undoped graphene and commercial Pt/C catalysts.