Ordered Assembly of NiCo₂O₄Multiple Hierarchical Structures for High-Performance Pseudocapacitors

Abstract

The design and development of nanomaterials has become central to the advancement of pseudocapacitive performance. Many one-dimensional nanostructures (1D NSs), two-dimensional nanostructures (2D NSs), and three-dimensional hierarchical structures (3D HSs) composed of these building blocks have been synthesized as pseudocapacitive materials via different methods. However, due to the unclear assembly mechanism of these NSs, reports of HSs simultaneously assembled from two or more types of NSs are rare. In this article, NiCo2O4 multiple hierarchical structures (MHSs) composed of 1D nanowires and 2D nanosheets are simply grown on Ni foam using an ordered two-step hydrothermal synthesis followed by annealing processing. The low-dimensional nanowire is found to hold priority in the growth order, rather than the high-dimensional nanosheet, thus effectively promoting the integration of these different NSs in the assembly of the NiCo2O4 MHSs. With vast electroactive surface area and favorable mesoporous architecture, the NiCo2O4 MHSs exhibit a high specific capacitance of up to 2623.3 F g(-1), scaled to the active mass of the NiCo2O4 sample at a current density of 1 A g(-1). A nearly constant rate performance of 68% is achieved at a current density ranging from 1 to 40 A g(-1), and the sample retains approximately 94% of its maximum capacitance even after 3000 continuous charge-discharge cycles at a consistently high current density of 10 A g(-1).

Nickel Cobaltite Nanostructures for Photoelectric and Catalytic Applications

“…Reproduced with permission. [ 75 ] Copyright 2014, American Chemical Society. [ 70 ] Copyright 2013, Royal Society of Chemistry.…”

“…[ 1,17,52,53,75 ] By a simple hydrothermal route without templates, Shen and co-workers fabricated NiCo 2 O 4 urchins with a large surface area of 99.3 m 2 g −1 .…”

“…By employing a twostep hydrothermal preparation and subsequent annealing procedures, Li and co-workers fabricated 3D NiCo 2 O 4 multi ple hierarchical structures (Figure 3 f), urchin-like structures, and fl ower-like structrues. [ 75 ] The multiple hierarchical structures are composed of 1D nanowires and 2D nanosheets, with nanosheets serving as backbones and nanowires enclose them. During the hydrothermal process, the nanowires grow directly on the Ni foam and interconnect in the fi rst step, and the nanosheets are formed among the interspaces between the nanowires and impel the growth of multiple hierarchical structures in the second step.…”

Hierarchically nanostructured transition metal oxides for supercapacitors

“…Li et al [125] reported that the NiCo 2 O 4 multiple hierarchical structures (MHSs) composed of two-dimensional (2D) nanosheets and onedimensional (1D) nanowires were directly anchored on Ni foam (Fig. 6a).…”

Mixed Nickel Cobalt Manganese Oxide Nanorods for supercapacitor application

“…People are also trying to combine a battery and a supercapacitor to make a hybrid device which will provide both high power density as well as high energy density. Depending on the working procedure supercapacitor is mainly two types-(a) Electric Double Layer Capacitor (EDLC) (Wang and Zhang, 2012;Sharma and Bhatti, 2010) and (b) Pseudocapacitor (Augustyn et al, 2014;Simon and Gogotsi, 2008;Huang et al, 2013;Zhou et al, 2014). EDLC is a non-faradic electrochemical capacitor i.e., no transfer of charge occurs between electrode and electrolyte.…”