Search

Rational construction of unique hierarchical nanostructured electrodes with excellent electrochemical performance is a promising solution to satisfy the increasing demand of supercapacitors with high energy density. In this work, a novel nanostructure of bowl-like MnO 2 nanosheets with ultra-thin thickness (about 4 nm) has been successfully designed by a simple template-assisted hydrothermal method. The composition and morphology of the obtained bowl-like nanostructures have been characterized by FESEM, TEM, XRD, XPS and N 2 adsorption-desorption. Such novel nanostructures present several advantages, such as large surface area, compact contacts, reduced interior space, additional electroactive sites for reversible redox reactions and short/unimpeded diffusion channels for ions/electron transport. When evaluated as electrode materials, bowl-like MnO 2 nanosheets exhibit a specific capacitance of 379 F g −1 at a current density of 0.5 A g −1 , a capacitance retained ratio of 60.5% from 0.5 to 10 A g −1 and 87.3% capacitance retention after 5000 cycles. Moreover, a possible mechanism for the excellent electrochemical performance of the novel bowl-like nanostructures compared with hollow particles has been systematically studied. We believe that this strategy can open up an avenue and appropriate idea for the rational construction of other transition metal oxides with high performance for the practical supercapacitor applications. [ABSTRACT FROM AUTHOR]

Reasonable design of multi-component metal oxides hierarchical nanostructures is an effective and promising way to improve electrochemical performances of electrode materials. In this work, novel hydrangea-like ZnCo 2 O 4 /Ni 3 V 2 O 8 hierarchical nanostructures are constructed by adjusting the ratio of ZnCo 2 O 4 and Ni 3 V 2 O 8. The perfect architecture maximizes the synergistic effect between different components and provides abundant electrochemical reactive sites, promoting the diffusion and transfer of electrolyte ions in electrochemical reaction process. As a result, ZnCo 2 O 4 /Ni 3 V 2 O 8 electrodes deliver an enhanced specific capacitance of 1734 F g−1 at 1 A g−1 and cyclic stability (96% of initial capacitance is retained after 8000 cycles). Furthermore, the assembled ZnCo 2 O 4 /Ni 3 V 2 O 8 //AC device e achieves excellent energy density of 90 Wh kg−1 at power density of 812 W kg−1, proving the optimized hydrangea-like ZnCo 2 O 4 /Ni 3 V 2 O 8 hierarchical nanostructures are promising electrode material for supercapacitor. In addition, this work supplies helpful insights into rational design of structure and composition of multi-component metal oxides for enhanced electrochemical performance. [ABSTRACT FROM AUTHOR]

Highlights • Porous NiCo 2 O 4 /NiO/Co 3 O 4 nanoflowers (NCNs) are prepared by adding oxalic acid. • NCNs-0.1 possess optimal distribution of micro-mesopores. • NCNs-0.1 electrodes deliver an enhanced specific capacitance of 1693F g−1. • 88% capacitance can be retained after 6000 cycles. • Excellent energy densities of 43.02 Wh kg−1 and power densities of 820.29 W kg−1. Abstract The rational design of micro-mesopores is a hugely challenging for porous metal-based nanomaterials. Here oxalic acid (H 2 C 2 O 4) as control agent is proposed for the first time to prepare 3D optimal micro-mesoporous NiCo 2 O 4 /NiO/Co 3 O 4 nanoflowers (NCNs). Theoretical and experimental analyses demonstrate NCNs-0.1 which are prepared by adding 0.1 g H 2 C 2 O 4 possess optimal distribution of micro-mesopores. The optimal structure creates abundant active sites and fluent ionic channels. Beneficially, NCNs-0.1 electrodes deliver an enhanced specific capacitance of 1693F g−1 at 1 A g−1 and outstanding cyclic stability (88% capacitance retention after 6000 cycles). Further, the assembled NCNs-0.1//AC capacitor achieves excellent energy densities of 43.02 Wh kg−1 at power densities of 820.29 W kg−1. The current NCNs-0.1 confirms a practicable method to optimize the electrochemical performances of supercapacitors by utilizing H 2 C 2 O 4 to construct 3D optimal micro-mesoporous nanoflower architectures. [ABSTRACT FROM AUTHOR]

Reasonable design for structure and composition of multi-component metal oxides is an effective and promising way to improve electrochemical performance of electrode materials. In this work, novel carnations-like Mn 3 O 4 @NiCo 2 O 4 @NiO hierarchical nanostructures are constructed by introducing CATB as structure-directing agents and adjusting hydrothermal reaction time. The perfect architecture maximizes the synergistic effect between components, providing more electrochemical reactive sites and promoting the diffusion and transfer of electrolyte ions. As a result, Mn 3 O 4 @NiCo 2 O 4 @NiO electrodes deliver an enhanced specific capacitance of 1905 F g−1 at 1 A g−1 and outstanding cyclic stability (92% of its initial capacitance is retained after 10000 cycles). Furthermore, ASC device which is assembled by the Mn 3 O 4 @NiCo 2 O 4 @NiO and activated carbon achieve excellent energy densities of 76.8 W h kg−1 at power densities of 800 W kg−1, proving the optimized Mn 3 O 4 @NiCo 2 O 4 @NiO is promising electrode material for supercapacitor. In addition, this work supplies helpful insights into rational design for structure and composition of multi-component metal oxides for enhancing electrochemical performance. [ABSTRACT FROM AUTHOR]