72
4 Synthesis of Two-Dimensional (2D) Nanomaterials
which is useful in confining C−C coupling reaction in two dimensions during the
endogenous solid-state polymerization. The synthesized 2D polymer shows distinct
lamellar structure with highly regular pore size in the range of 0.7–1.0 nm, which is
advantageous for supercapacitive energy storage. When employed as positive electrode in an asymmetric supercapacitor, it provides a specific capacitance of 233 F g
−1
at a current density of 1.0 A g
−1 in 2 M KCl aqueous electrolyte. It shows an excellent cycle life with ∼80% capacity retention over 10,000 cycles (Fig. 4.4i). These
results show that endogenous polymerization is a facile access to 2-D polymer with
well-defined pores and conjugated aromatic structure, which can be used as green
organic electrodes in supercapacitor applications.
Yao et al. (2018) reported a strategy of growth of conductive polymer (PPy) on 2D
coordination polymers (CPs) nanosheets to enhance their capacitive performances
(Fig. 4.4j). On one hand, the PPy coating layer can form conductive pathways on the
surfaces of 2D CPs; on the other hand, the tight encapsulation of PPy can buffer the
interfacial stress resulted from the volume variation during charging and discharging,
making the hybrid a potential candidate for high-performance capacitive material.
Moreover, the thickness of PPy can also influence the electrochemical performance
by affecting the electrical conductivity, ion diffusion resistance, and synergistic cooperation of the composites (Ji et al. 2015). Besides, this strategy is considered to be
applicable for growth of other conductive polymers (Such as Polyaniline and Polythiophene) on other 2D CPs (or coordination supramolecular networks). As proof of
concept, they choose a typical 2D CP (Cu-TCPP, TCPP = 5, 10, 15, 20-tetrakis(4carboxyphenyl)porphyrin) as the 2D platform, onto which PPy is grown by a simple
in situ chemical oxidation method. In this kind of 2D CPs nanosheets, one TCPP
ligand is linked by four Cu paddlewheel metal nodes, i.e., Cu 2 (COO) 4 , to form a
2D layered sheet (Zhao et al. 2015b). The strong π-stacked conjugation and the
heteroatom of the TCPP may enhance both the electron transport and the interaction
with conductive polymers.
Huang et al. (2018) proposed a synthetic strategy to grow a large area and transferable Zn-coordination 2D polymer, where OH functional groups and the amphoterism
of zinc hydroxides play an active role in the separation/selection using the charge
exclusion principle. Figure 4.4k depicts the method of synthesizing large-area and
free-standing 2D polymeric layers based on zinc(II) benzimidazolate complex on the
water surface of a Langmuir trough. The charge barrier feature has been integrated
into the Li-S battery to mitigate the polysulfide shuttle effects by the electrostatic
shield, largely promoting the Li-S capacity and cycle performance. The synthesis is
simple, scalable, and cost-saving, and it is anticipated that this type of functional 2D
coordination polymer can soon be adopted for practical use.
4 Synthesis of Two-Dimensional (2D) Nanomaterials
which is useful in confining C−C coupling reaction in two dimensions during the
endogenous solid-state polymerization. The synthesized 2D polymer shows distinct
lamellar structure with highly regular pore size in the range of 0.7–1.0 nm, which is
advantageous for supercapacitive energy storage. When employed as positive electrode in an asymmetric supercapacitor, it provides a specific capacitance of 233 F g
−1
at a current density of 1.0 A g
−1 in 2 M KCl aqueous electrolyte. It shows an excellent cycle life with ∼80% capacity retention over 10,000 cycles (Fig. 4.4i). These
results show that endogenous polymerization is a facile access to 2-D polymer with
well-defined pores and conjugated aromatic structure, which can be used as green
organic electrodes in supercapacitor applications.
Yao et al. (2018) reported a strategy of growth of conductive polymer (PPy) on 2D
coordination polymers (CPs) nanosheets to enhance their capacitive performances
(Fig. 4.4j). On one hand, the PPy coating layer can form conductive pathways on the
surfaces of 2D CPs; on the other hand, the tight encapsulation of PPy can buffer the
interfacial stress resulted from the volume variation during charging and discharging,
making the hybrid a potential candidate for high-performance capacitive material.
Moreover, the thickness of PPy can also influence the electrochemical performance
by affecting the electrical conductivity, ion diffusion resistance, and synergistic cooperation of the composites (Ji et al. 2015). Besides, this strategy is considered to be
applicable for growth of other conductive polymers (Such as Polyaniline and Polythiophene) on other 2D CPs (or coordination supramolecular networks). As proof of
concept, they choose a typical 2D CP (Cu-TCPP, TCPP = 5, 10, 15, 20-tetrakis(4carboxyphenyl)porphyrin) as the 2D platform, onto which PPy is grown by a simple
in situ chemical oxidation method. In this kind of 2D CPs nanosheets, one TCPP
ligand is linked by four Cu paddlewheel metal nodes, i.e., Cu 2 (COO) 4 , to form a
2D layered sheet (Zhao et al. 2015b). The strong π-stacked conjugation and the
heteroatom of the TCPP may enhance both the electron transport and the interaction
with conductive polymers.
Huang et al. (2018) proposed a synthetic strategy to grow a large area and transferable Zn-coordination 2D polymer, where OH functional groups and the amphoterism
of zinc hydroxides play an active role in the separation/selection using the charge
exclusion principle. Figure 4.4k depicts the method of synthesizing large-area and
free-standing 2D polymeric layers based on zinc(II) benzimidazolate complex on the
water surface of a Langmuir trough. The charge barrier feature has been integrated
into the Li-S battery to mitigate the polysulfide shuttle effects by the electrostatic
shield, largely promoting the Li-S capacity and cycle performance. The synthesis is
simple, scalable, and cost-saving, and it is anticipated that this type of functional 2D
coordination polymer can soon be adopted for practical use.