Turning free-standing three-dimensional graphene into electrochemically active by nitrogen doping during chemical vapor deposition process

By chemical vapor deposition on nanometer-size copper nanopowder sinter template with ammonia as nitrogen source, a free-standing N-doped three-dimensional graphene (N3DG) with macro–meso–micro-hierarchical porous structure was prepared. The existence of nitrogen-containing groups in N3DG turned inert graphene into electrochemically active. The flow ratio between methane and ammonia significantly influences the chemical environment of as-doped nitrogen atoms, the structure of defects in graphene, as well as the electrochemical performance. With the flow ratio between methane and ammonia of 1:4, the specific capacitance of N3DG could be as high as 558.9 F g^{− 1}. The areal capacitance is 4.26 F m^{− 2}.