Biotemplate derived three dimensional nitrogen doped graphene@MnO₂ as bifunctional material for supercapacitor and...

Natural diatomite with abundant pores was used as a biotemplate for the massive production of three-dimensional (3D) porous graphene by chemical vapor deposition method. Subsequent template removal and nitrogen doping treatment yield nitrogen doped 3D graphene with preserved shape and complex internal features of the diatomite. After further deposition with MnO₂ nanosheets, the N-doped 3D graphene@MnO₂ (N-G@MnO₂) hybrid exhibited excellent supercapacitor and good oxygen reduction reaction (ORR) performance. Accordingly, the porous N-G@MnO₂ electrode exhibited a high specific capacitance (411.5 F g^-1) and a good cycling performance (88.3% capacitance retention after 4000 charge/discharge cycling test). When tested in a two-electrode configuration, N-G@MnO₂ achieved a wide potential window up to 1.8 V with a high energy density of 46.1 Wh kg^-1. Furthermore, the as-prepared N-G@MnO₂ showed good performance in oxygen reduction reaction, which is comparable to those of commercially available Pt/C electrode. The enhanced capacitive and electrocatalytic properties and stability is due to the synergistic interactions between the porous 3D graphene and MnO₂ nanosheets. The results indicate that the 3D N-G@MnO₂ could be useful for supercapacitor and ORR catalyst.