Scalable synthesis of nano-sandwich N-doped carbon materials with hierarchical-structure for energy conversion and storage

Increasing energy demands led us to explore cheap, sustainable and efficient materials for energy conversion and storage, but limited strategies have been established to prepare nanoscale carbon materials with tunable nanostructures. In this work, a large-scale nano-sandwich (porous carbon/graphene/porous carbon) N-doped carbon material was synthesized by in situ carbonization of glucose with small amounts of graphene oxide (GO), followed by activation with NH3. The resulting nano-sandwich N-doped carbon materials (NNCMs) possess variable nano-pores (0.8–5 nm) and high surface area (808–1959 m2 g−1), as well as nitrogen moieties (1.87–4.63 at%), which can be well tuned by the route conditions. The optimum NNCM-1050-70 exhibited excellent ORR performance with a high onset potential (0.26 V vs. Ag/AgCl) and a large limiting current density (4.1 mA cm−2 at 0.6 V vs. Ag/AgCl); in neutral conditions the obtained maximum power density (985.3 mW m−2) was higher than that of commercial Pt/C catalysts (874.3 mW m−2). When used as electrode materials for supercapacitors, the optimum NNCM-900-70 demonstrated remarkable performance with a specific capacitance of 178 F g−1 at a current density of 1 A g−1 in 6 mol L−1 KOH solution. Moreover, the NNCM-1050-70 also shows excellent performance of H2 and C2H2 adsorption compared to the best carbon materials. The excellent performance coupled with a scalable, facile and green method lead us to synthesize multifunctional carbon nanomaterials for energy conversion and storage.