4.1 2D Transition Metal Dichalcogenides
59
suggesting its outstanding cycling stability. The Coulombic efficiency for the entire
measurement is also measured, which is close to 100%. Taking all these results into
consideration, the combination of carbon materials and 2D metal sulfide is confirmed
to have great potential as storage material, contributing to the relief for the energy
issue and development of sustainable society.
4.2 2D Transition Metal Oxides
2D metal oxide nanomaterials have recently received tremendous attention owing to
their apparent advantages including high surface to volume ratio and unique chemical
and physical properties, which is capable to offer abundant active sites to enhance the
adsorption of molecules or ions and improve the transport of ionic species (Zhang
2015). Therefore, these nanomaterials have been applied in multitudinous fields such
as energy conversion and storage (Peng et al. 2017; Bao et al. 2015), gas sensors
(Kaneti et al. 2013; Kannan et al. 2015), catalysis (Deng et al. 2016; Cheng et al.
2014), and so on. However, it remains challenging to construct 2D transition metal
oxide materials nanomaterials with well-defined geometry and functional nanoarchitecture that are tailored for specific applications. Synthetic protocols are needed to
create various nanostructures and which can be generalized to many kinds of material
types. Additionally, it is urgent to demonstrate the ability to modulate material properties. Recently, many novel methods have been proposed to synthesize 2D TMOs
nanomaterials (Xu et al. 2016).
4.2.1 Co 3 O 4
Li et al. (2017a) used a self-sacrificing template preparation to synthesize 2D
porous Co 3 O 4 nanosheets for reversible electrochemical lithium storage. During
the calcination process, the Co-precursors are self-linked with each other to form
2D porous Co 3 O 4 nanosheets. Figure 4.2a illustrates the formation process of 2D
porous Co 3 O 4 nanosheets and the advantages for lithium-ion transport. During the
calcinations processes, the Co-precursors self-linked with each other to form the 2D
porous nanosheets. Interestingly, the 2D nanosheet structure was perfectly inherited in the calcined products (Fig. 4.2b, c), but with porous architectures and rough
surfaces in comparison with the Co-precursor. The magnified observations (Fig. 4.2c)
further testify that the 2D porous nanosheets structures are constructed by numerous
nanoparticles with a narrow size distribution, i.e., most of them are 15–30 nm in
diameter. Due to the abundant active surface and the improved charge transport
characteristics, 2D porous Co 3 O 4 nanosheets exhibit enhanced overall lithium-ion
storage properties. Electrochemical measurements display that the 2D porous Co 3 O 4
demonstrates an ultrahigh reversible discharge specific capacity of 1000 mA h g
−1 at
59
suggesting its outstanding cycling stability. The Coulombic efficiency for the entire
measurement is also measured, which is close to 100%. Taking all these results into
consideration, the combination of carbon materials and 2D metal sulfide is confirmed
to have great potential as storage material, contributing to the relief for the energy
issue and development of sustainable society.
4.2 2D Transition Metal Oxides
2D metal oxide nanomaterials have recently received tremendous attention owing to
their apparent advantages including high surface to volume ratio and unique chemical
and physical properties, which is capable to offer abundant active sites to enhance the
adsorption of molecules or ions and improve the transport of ionic species (Zhang
2015). Therefore, these nanomaterials have been applied in multitudinous fields such
as energy conversion and storage (Peng et al. 2017; Bao et al. 2015), gas sensors
(Kaneti et al. 2013; Kannan et al. 2015), catalysis (Deng et al. 2016; Cheng et al.
2014), and so on. However, it remains challenging to construct 2D transition metal
oxide materials nanomaterials with well-defined geometry and functional nanoarchitecture that are tailored for specific applications. Synthetic protocols are needed to
create various nanostructures and which can be generalized to many kinds of material
types. Additionally, it is urgent to demonstrate the ability to modulate material properties. Recently, many novel methods have been proposed to synthesize 2D TMOs
nanomaterials (Xu et al. 2016).
4.2.1 Co 3 O 4
Li et al. (2017a) used a self-sacrificing template preparation to synthesize 2D
porous Co 3 O 4 nanosheets for reversible electrochemical lithium storage. During
the calcination process, the Co-precursors are self-linked with each other to form
2D porous Co 3 O 4 nanosheets. Figure 4.2a illustrates the formation process of 2D
porous Co 3 O 4 nanosheets and the advantages for lithium-ion transport. During the
calcinations processes, the Co-precursors self-linked with each other to form the 2D
porous nanosheets. Interestingly, the 2D nanosheet structure was perfectly inherited in the calcined products (Fig. 4.2b, c), but with porous architectures and rough
surfaces in comparison with the Co-precursor. The magnified observations (Fig. 4.2c)
further testify that the 2D porous nanosheets structures are constructed by numerous
nanoparticles with a narrow size distribution, i.e., most of them are 15–30 nm in
diameter. Due to the abundant active surface and the improved charge transport
characteristics, 2D porous Co 3 O 4 nanosheets exhibit enhanced overall lithium-ion
storage properties. Electrochemical measurements display that the 2D porous Co 3 O 4
demonstrates an ultrahigh reversible discharge specific capacity of 1000 mA h g
−1 at