92
5 Synthesis of Three-Dimensional Nanomaterials
at an overpotential of γ = 300 mV for electrochemical water oxidation, outperforming even expensive rare earth iridium oxide catalysts. The unique features of
these NiO nanocrystals provide great potential for the novel composite materials
which can be applied in the field of (photo) electrochemical water splitting. Such
as the preparation of uniform hole-conducting layers for organic solar cells, the
dispersed colloidal solutions may also show other applications. In addition, Mishra
et al. reported the synthesis of carnation flower-like SnS 2 (CF-SnS 2 ) by a onestep solvothermal method as supercapacitor electrodes for potential application in
energy storage devices (Mishra et al. 2017). In a typical procedure, 1.54 mmol of
SnCl 4 · 5H 2 O was added to an 80 mL isopropyl alcohol solution under vigorous
magnetic stirring. Then, 6 mmol of C 2 H 5 NS was added to the solution. After vigorous
stirring using a magnetic bar for 15 min, the solution was transferred to a 100 mL
Teflon-lined stainless steel autoclave, which was sealed tightly and held in a convection oven at 180 °C for 24 h. After cooling to room temperature, the obtained precipitate was collected and washed several times using deionized water and isopropyl
alcohol to remove impurities, followed by drying in an oven at 60 °C in air. Thereafter,
CF-SnS 2 was carefully collected as the final synthesized product.
In addition to the architecture, we should not ignore the importance of component or composite. Hybrid supercapacitors (HSCs) are attracting increasing scientific
attention as they hold the promise to realize battery-level energy density together
with a long calendar life and short charging time as supercapacitors. Complex mixed
metal oxides such as NiCo 2 O 4 have been considered as promising candidates to
be the battery-like (faradaic) electrode. The employment of complex non-spherical
hollow micro-/nanostructures is highly desirable to address the limitation of the redox
reaction at the near surface. However, the synthesis faces additional challenges. A
novel self-templated method had been developed by Ma et al. to fabricate ultrathin
mesoporous NiCo 2 O 4 nanosheet-assembled hierarchical tetragonal microtubes via
thermal transformation of a nickel–cobalt layered double hydroxide (NiCo-LDH)
precursor (Ma et al. 2016). Of note, the NiCo-LDH microtubes were prepared by
a one-pot solvent-heat method, involving the formation of metal acetate hydroxide
solid prisms and a subsequent hollowing process (demonstrated in Fig. 5.6B). Due to
their complex structures with ultrathin subunits, these hierarchical NiCo 2 O 4 microtubes deliver exquisite electrochemical performance, including high specific capacitance as well as a long lifespan as a battery-type electrode for HSCs. The research
finding will provide a possibility to eliminate the performance gap between batteries
and supercapacitors.
Similarly, Huang et al. devised a route synthesize NiMn LDH@rGO composite
with 3D flower-like architecture by a facile one-step solvothermal way (Huang
et al. 2018). By manipulating the composition of the precursors, shell structures
with different loadings of NiMn LDH on graphene nanosheet were obtained. The
whole process was shown in Fig. 5.7a. Electrochemical characterization showed that
LDH/rGO-4 with flower-like hierarchical architectures exhibited superior specific
capacitance and high rate performance owing to the large accessible specific surface
area and high capacitance. The assembled ASC constructed from LDH/rGO-4 and
5 Synthesis of Three-Dimensional Nanomaterials
at an overpotential of γ = 300 mV for electrochemical water oxidation, outperforming even expensive rare earth iridium oxide catalysts. The unique features of
these NiO nanocrystals provide great potential for the novel composite materials
which can be applied in the field of (photo) electrochemical water splitting. Such
as the preparation of uniform hole-conducting layers for organic solar cells, the
dispersed colloidal solutions may also show other applications. In addition, Mishra
et al. reported the synthesis of carnation flower-like SnS 2 (CF-SnS 2 ) by a onestep solvothermal method as supercapacitor electrodes for potential application in
energy storage devices (Mishra et al. 2017). In a typical procedure, 1.54 mmol of
SnCl 4 · 5H 2 O was added to an 80 mL isopropyl alcohol solution under vigorous
magnetic stirring. Then, 6 mmol of C 2 H 5 NS was added to the solution. After vigorous
stirring using a magnetic bar for 15 min, the solution was transferred to a 100 mL
Teflon-lined stainless steel autoclave, which was sealed tightly and held in a convection oven at 180 °C for 24 h. After cooling to room temperature, the obtained precipitate was collected and washed several times using deionized water and isopropyl
alcohol to remove impurities, followed by drying in an oven at 60 °C in air. Thereafter,
CF-SnS 2 was carefully collected as the final synthesized product.
In addition to the architecture, we should not ignore the importance of component or composite. Hybrid supercapacitors (HSCs) are attracting increasing scientific
attention as they hold the promise to realize battery-level energy density together
with a long calendar life and short charging time as supercapacitors. Complex mixed
metal oxides such as NiCo 2 O 4 have been considered as promising candidates to
be the battery-like (faradaic) electrode. The employment of complex non-spherical
hollow micro-/nanostructures is highly desirable to address the limitation of the redox
reaction at the near surface. However, the synthesis faces additional challenges. A
novel self-templated method had been developed by Ma et al. to fabricate ultrathin
mesoporous NiCo 2 O 4 nanosheet-assembled hierarchical tetragonal microtubes via
thermal transformation of a nickel–cobalt layered double hydroxide (NiCo-LDH)
precursor (Ma et al. 2016). Of note, the NiCo-LDH microtubes were prepared by
a one-pot solvent-heat method, involving the formation of metal acetate hydroxide
solid prisms and a subsequent hollowing process (demonstrated in Fig. 5.6B). Due to
their complex structures with ultrathin subunits, these hierarchical NiCo 2 O 4 microtubes deliver exquisite electrochemical performance, including high specific capacitance as well as a long lifespan as a battery-type electrode for HSCs. The research
finding will provide a possibility to eliminate the performance gap between batteries
and supercapacitors.
Similarly, Huang et al. devised a route synthesize NiMn LDH@rGO composite
with 3D flower-like architecture by a facile one-step solvothermal way (Huang
et al. 2018). By manipulating the composition of the precursors, shell structures
with different loadings of NiMn LDH on graphene nanosheet were obtained. The
whole process was shown in Fig. 5.7a. Electrochemical characterization showed that
LDH/rGO-4 with flower-like hierarchical architectures exhibited superior specific
capacitance and high rate performance owing to the large accessible specific surface
area and high capacitance. The assembled ASC constructed from LDH/rGO-4 and