Self-sacrifice-template epitaxial growth of hierarchical MnO2@NiCo2O4 heterojunction electrode for high-performance asymmetric supercapacitor

Constructing three-dimensional (3D) hierarchical bimetallic pseudocapacitive materials with abundant opening channel and heterojunction structures is rather promising but still challenging for high-performance supercapacitors. Herein, a self-sacrifice-template epitaxial growth strategy was proposed for the first time to construct 3D hierarchical bimetallic pseudocapacitive material. By using this strategy, NiCo 2 O 4 nanowires (NiCo 2 O 4 NW) arrayed randomly to form a porous shell via in-situ epitaxial growth fully enclosing a MnO 2 tube core, forming multiple transport channels and nano-heterojunctions between MnO 2 and NiCo 2 O 4 NW, which facilitates electron transfer, i.e. exhibiting high electronic conductivity than any single component. As a result of the self-sacrifice-template epitaxial growth method, special hollow tectorum-like 3D hierarchical structure with considerable inter-nanowire space and hollow interior space enables easy access of electrolyte to NiCo 2 O 4 NW surface and MnO 2 core, thereby resulting in highly exposed redox active sites of MnO 2 core and NiCo 2 O 4 NW shell for energy storage. Comprehensive evaluations confirmed MnO 2 @NiCo 2 O 4 NW was a supercapacitor electrode candidate, delivering a superior energy density of 106.37 Wh kg −1 . Such performance can be ascribed to the synergistic coupling effect of 3D hierarchical tube and nano-heterojunction structures. The proposed self-sacrifice-template epitaxial growth strategy provides important guidance for designing high-performance energy storage materials.