The nanostructure preservation of 3D porous graphene: New insights into the graphitization and surface chemistry of non-stacked double-layer templated graphene after high-temperature treatment

Three-dimensional (3D) porous graphene materials with few layer nature and non-stacked structural feature afford significant advantages in high electrical conductivity, large surface area, and interconnected porous nanostructures. However, the structure evolution of porous graphene under high temperature is poorly understood. In this contribution, 3D double-layer templated graphene (DTG) composed of two non-stacked graphene layers with interlayer spacing around 15 nm and separated by a large quantity of protuberances, was employed as a special case to track the structure evolution of 3D porous graphene at high temperature. Compared with thermally reduced graphene oxide with easy graphitized nature, the unique non-stacked DTG structure was well preserved after a high-temperature annealing at 1600 °C. With limited self-healing of defects for graphene layers, and with preservation of mesosized protuberances that prevent graphene layers stacking during annealing, DTG is regarded as 'hard carbon' ('non-graphitizable carbon'). The electron microscopy, Raman spectroscopy, X-ray diffraction spectroscopy, X-ray photoelectron spectroscopy, thermogravimetric analysis, gravimetric elemental analysis, nitrogen/water physisorption, and probe reactions of electrochemical oxygen reduction reaction were employed to reveal the graphitization degree and surface chemistry of non-stacked DTG after high-temperature treatment.