Interface engineering integrates fractal-tree structured nitrogen-doped graphene/carbon nanotubes for supercapacitors

Abstract

To construct atomic-scale and seamless interface between various dimensional carbon nanostructures is essential for maximizing the componental attributes and benefiting the transport of masses, electrons, ions and energies involved in reactions and energies storages. Inspired by the structure of ‘Catalpa bungei’ tree which arranges its thorns regularly as nodes to bridge leaves and branches for nutrient transport, herein, NiMgAl layered double hydroxides (LDHs) are used to grow the graphene/carbon nanotubes (CNTs) host matrix, and then CO2 etching is employed to create defective sites within the matrix for anchoring the metal nanoparticles and grafting the tiny graphene oxide (GO) sheets. Based on such strategy, CNTs as the ‘branches’ can be grown over the metal nanoparticles and GO as the ‘leaves’ can be covalently bonding with the matrix with chemical vapor deposition (CVD), so that an all-in-one and omnidirectional fractal-tree structure of N-G/CNTs composite can be prepared deliberately. The results demonstrate that the N-G/CNTs composite has a high specific surface area of 190.66 m2 g−1, a narrow pore size distribution of 4–6 nm, uniform microstructural and compositional distribution, and excellent electron and ion conductivity. As a net consequence, the N-G@CNTs electrode exhibits excellent capacitor performance. In addition, three quasi-solid-state symmetrical supercapacitors assembled from the optimized N-G@CNTs composite can illuminate LED lamps. Our strategy can build solid ladder for manupulating structural units and integrating interfaces in a deliberate way to synergize the materials performance.