Carbon nanotube branch-grown nickel nanoparticles/graphene composites for a high-capacitance electrode

Despite the high capacitance and low cost, transition metal oxides have the limitation of low electrical conductivities and structural instability. In order to resolve these problems, herein, we propose a one-pot facile synthesis approach to construct a hierarchically structured nanohybrid material, where carbon nanotube (CNT) branches encapsulate NiO nanoparticles inside the tubes and interconnect them with steam-activated reduced graphene oxide. This unique hierarchical structure is attributed to large accessible surface areas, rapid electronic conduction, fast ion diffusion, and buffering effects. Moreover, the mixed Ni and NiO particles acts as catalysts to grow CNT branches and high capacitance redox active materials. In particular, the resulting composite electrode deliver a high specific capacitance of up to 1605.81 F g⁻¹ at a current density of 1 A g⁻¹ as well as, an excellent cycle stability with 71.56% capacitance retention after more than 10 000 cycles. Consequently, this research provides a rational material design chemistry to construct hierarchical architectures and multiple compositions of CNT/graphene/metal oxide nanoparticle hybrids for high-capacitance electrodes of composite capacitors.