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• Cost-effective 3D porous diatomite biomass is used to fabricate conductive networks. • The CNTs/graphene hybrid can enhance the electric conductivity and surface area. • The MnO 2 @CNTs/G/diatomite shows high specific capacitance and good cyclic stability. • The ASC exhibits high energy density (64.4 W h kg−1) and power density (19.8 kW kg−1). Natural abundant and industrial available biomass diatomite is act as the porous template to in-situ grown graphene layer (G), while the carbon nanotubes (CNTs) arrays are subsequently grown on the graphene surface. The seamless anchored 1D CNTs arrays together with 3D interconnected graphene networks can construct conductive hierarchical framework to enhance the electric conductivity. Furthermore, the enlarged effective surface area of the CNTs/G/diatomite can increase the active material loading amount and facilitate the electrolyte infiltration. Therefore, the MnO 2 @CNTs/G/diatomite hybrid exhibits a highest specific capacitance of 264.0 F g−1 (based on the MnO 2 , the value is ~880.0 F g−1), good rate capability and excellent cyclic stability. Moreover, the asymmetric supercapacitor assembled by MnO 2 @CNTs/G/diatomite and microwave exfoliated graphite oxide reveals a highest energy density of 64.3 W h kg−1 and maximum power density of 19.8 kW kg−1, respectively. [ABSTRACT FROM AUTHOR]

Rational construction of three-dimensional (3D) porous carbon nanotubes (CNTs) hierarchical architectures can provide diverse frameworks for fabrication of functionalized electrodes to effectively enhance their electrochemical performance. In this paper, a modified electroless deposition (ELD) process for uniformly anchoring of Ni@Pd seeds on substrates is reported. The tightly immobilized bi-metal seeds without aggregation during annealing leads to in-situ growth of uniform intertwined CNTs arrays. The ELD seeding and CNTs growth method was successfully applied on different 3D carbon- and metal- based substrates. The 3D interconnected CNTs/carbon composites offer a hierarchical micro-/nano- network to facilitate electrolyte infiltration, while the CNTs arrays can effectively improve the electrical conductivity and enlarge the active surface area of the hybrids substrate. The hierarchical hybrid electrodes exhibit enhanced electrochemical performance in electrocatalysis and as a supercapacitor. The ELD process can be a general and scalable strategy for industrialized fabrication of any 3D carbon-based substrate and will be much promising in the applications of energy storage and conversion. Unlabelled Image • Modified electroless deposition process is fabricated to uniformly anchoring the Ni@Pd seeds on substrates. • The tightly immobilized bi-metal seeds without aggregation lead to in-situ growth of uniform intertwined CNTs arrays. • The ELD seeding and CNTs growth method can be applied on different 3D carbon- and metal- based substrates. • The electrical conductivity and the active surface area of the CNTs/carbon cloth hybrid substrate can be highly improved. [ABSTRACT FROM AUTHOR]