Structure modulation and properties of NiCo2O4 nanothorn electrode materials prepared by a self-sacrificial template method

Abstract

Herein, we report the preparation of an effective and novel NiCo2O4 dendritic structure with nanothorn arrays, using a stepwise, bottom-up hydrothermal and self-sacrificial template method. Rod-like ZnO is synthesized on Ni foam as self-sacrificing template, and Ni-Co-based precursor is grown on it through a hydrothermal method. NiCo2O4 dendritic crystals are obtained by alkali etching of the template and calcination, which significantly enhance its performance on electrochemical energy storage. Although the ZnO matrix is removed by alkali etching, it provides a basis for the growth of Ni-Co oxide. Using ZnO as template is simple to operate and can directly determine the shape and size of the hollow structure. Meanwhile, the ZnO template core can be well separated from the hollow structure, and the template can be used without surface functionalization, which is more simple and efficient. The obtained material can be directly used as electrode material without further processing, offering the benefit of unique structural advantages and low electron transmission resistance, as there is no need to use a binder. The as-obtained NiCo2O4 nanothorn electrode exhibits excellent electrochemical performance. It shows ultrahigh specific capacitance of 1534 C g−1 at 1 A g−1 current density, good rate discharge performance (75.8% retention from 0.5 A g−1 to 5 A g−1), values superior to those of nanothorn NiO, Co3O4 and bare Ni-Co 1-2 nanosheet structures and excellent cycling ability (83% retention after 5000 cycles). The as-assembled Ni-Co 1-2//AC hybrid supercapacitor device also exhibits high energy density of 64.1 Wh kg−1 at the power density of 450 W kg−1.