Template-engaged synthesis of uniform mesoporous hollow NiCo2O4 sub-microspheres towards high-performance electrochemical capacitors

Abstract

An efficient template-engaged synthetic strategy, where silica spheres were applied as hard templates, was developed to synthesize hierarchical mesoporous hollow NiCo 2 O 4 sub-microspheres assembled entirely from ultrathin nanosheets with a thickness of a few nanometers. The as-prepared mesoporous hollow NiCo 2 O 4 sub-microspheres are very uniform in size, mesoporous in textual property, and structurally robust benefiting from the in situ template removal. The morphologies of the hollow submicrospherical architecture can be tuned easily by varying the concentrations of Ni 2+ , Co 2+ , and the precipitant. When evaluated as an appealing electroactive material for electrochemical capacitors (ECs), the as-fabricated hierarchical hollow NiCo 2 O 4 sub-microspheres delivered a specific capacitance (SC) of 678 F g 21 at a current density of 1 A g 21 , and even kept it as high as 540 F g 21 at 10 A g 21 . Additionally, a desirable cycling stability of 13% SC degradation over 3500 continuous cycles at a current density of 10 A g 21 is observed, suggesting their promising application in advanced ECs.

Integrating large specific surface area and high conductivity in hydrogenated NiCo2O4 double-shell hollow spheres to improve supercapacitors

“…The adsorption isotherms are shown in Figure 3. All the isotherm profiles can be classified as type IV 12 and hysteresis loops are observed in the range of 0.7-1.0 P/P 0 (Figure 3a) and 0.5-1.0 P/P 0 (Figure 3b), suggesting that the as-prepared samples have a typical mesoporous structure, which can be further supported by the Barrett-Joyner-Halenda pore size distribution (Supplementary Figure S2). Results demonstrate that most of the , respectively.…”

“…On the one hand, large specific surface area will provide more electroactive sites for the Faradaic reactions, and load more doublelayer charges. Along such idea, many kinds of nanomaterials, [9][10][11] especially hollow spheres, 12 have been developed to improve pseudocapacitors, but the increased contact resistance often emerges in these porous materials. On the other hand, increasing conductivity will greatly favor the Faradaic reactions, which has been demonstrated typically in the integration of oxides with metal foam, 13 carbon cloth, 9 graphene and carbon nanotubes.…”

Mesoporous NiCo2O4 nanoneedles grown on three dimensional graphene networks as binder-free electrode for high-performance lithium-ion batteries and supercapacitors

“…As showed inFig. 4d, the NiCo 2 O 4 /3DGN demonstrates superior cycling stability at high charge/discharge current density with the capacitance retention of ~96.5% after 3 000 cycles, which is also superior to many reported results[30,48,[82][83][84]. Specially, the charge/discharge curves remain undistorted and essentially symmetric after 3000 cycles (InsetFig.…”

“…As one of the most promising metal oxides for LIBs and SCs, spinel nickel cobaltite (NiCo 2 O 4 ), possessing the advantages of high theoretical capacitance/capacity, intriguing electronic conductivity, easy-preparation, abundant resources and environmental friendliness, has been mostly investigated [23][24][25][26]. Considerable efforts have been made to improve the electrochemical performances of NiCo 2 O 4 for LIBs and SCs by adjusting the morphologies, such as nanowires [27,28], nanosheets [29], nanotubes [25], and microspheres [30,31], etc. However, they still suffer from the low power densities and unstable cycling performance to meet the new and high requirements for future applications.…”

Nickel Cobaltite Nanostructures for Photoelectric and Catalytic Applications

“…Therefore, morphologically controllable synthetic methods aiming for well-defi ned nanocrystals are the primary step. So far, the main synthesis strategies include liquid-phase co-precipitation, [ 43,70 ] hydro-and solvothermal routes, [ 1,41,71 ] microwave-assisted methods, [ 72 ] electrodeposition methods, [ 32 ] electrospinning methods, [ 73 ] high-temperture [ 23,24,69 ] [ 30 ] mesoporous hollow sub-microspheres, [ 70 ] and hollow crossed nanocubes. [ 74 ] Microspheres ( Figure 2 a) and hollow sub-microspheres (Figure 2 b) (Figure 2d,e), [ 25,45 ] nanowires (Figure 2 f,g), [ 43 ] and nanotubes (Figure 2 h), [ 46 ] whose lateral dimensions are in the range of several hundred nanometers to several 2 Ti foil electrocatalytic oxygen evolution [11] nanowire arrays co-precipitation route Ni(NO 3 ) 2 , Co(NO 3 ) 2 − oxygen reduction reaction, electrocatalytic oxygen evolution [56] www.small-journal.com micrometers.…”