Preparation And Electrochemical Properties Of Polypyrrole And Its Composites

Polypyrrole?PPy?as a kind of conductive polymers possesses many advantages,such as easily prepared,low cost,good stability,high conductivity and high specific capacitance,but it is prone to volume shrinkage and expansion during multiple constant current charge and discharge processes,which results in long cycle stability,solubility and processing performance are relatively poor,thus limitting its widespread application.When polypyrrole is combined with graphene and metal phosphide,it can not only exert its own advantages of high specific capacitance,but also to weaken the shrinkage and expansion of volume during charging and discharging by good synergistic effect,so as to improve the electrochemical performance of supercapacitor.In this paper,the preparation methods of different polypyrrole composites were studied,and the phase characterization and electrochemical performance tests were carried out.The following are the research works of this thesis:?1?The polypyrrole/graphene oxide?PPy/GO?composites were successfully synthesized by one-step in-situ polymerization.According to the test results,the composite material is composed of cauliflower-like PPy nanoparticles and pleated GO.PPy is more evenly dispersed on the surface of the GO and between the layers.The surface area of the composite was measured by specific surface area analysis?BET?,the surface area of the composite is greatly improved compared with PPy monomer,and the electrochemical performance of the PPy/GO composite as a supercapacitor electrode material is tested and analyzed.The results show that the electrochemical properties such as the specific capacitance,charge and discharge performance and long-cycle stability have been significantly improved compared with PPy monomer.Even at a current density of 1 A·g^-1,with a higher specific capacitance of 369.8 F·g^-1,the charge transfer resistance is 4.6?,and even after a long cycle of 3000 cycles,the capacity retention rate is 87%.?2?Polypyrrole/nickel phosphide?PPy/Ni₂P?composite was successfully prepared using a two-step method,the first step is to use NiCl₂·6H₂O as the nickelsource,deionizedwaterasthesolvent,andCTAB?cetyltrimethylammonium bromide?as the surfactant,Ni₂P monomer was successfully prepared by hydrothermal method at 180°C,reaction for 16 h.The second step is to dissolve Ni₂P in deionized water and stirred until uniform,the same amount of Py?pyrrole monomer?was added,and the PPy/Ni₂P composite was successfully prepared by polymerization under ice bath condition.By changing the mass fraction of Ni₂P,the PPy/Ni₂P products with different Ni₂P mass fractions were obtained.The results of structural characterization show that the composite consists of cauliflower-like PPy and spherical Ni₂P nanoparticles.The electrochemical properties were tested and analyzed.It was found that when the mass fraction of Ni₂P was 30%,the prepared PPy/Ni₂P composite has a higher specific capacitance of 476.5 F·g^-11 at a current density of1 A·g^-1,and a smaller charge transfer resistance for 1.8?,its capacity retention rate is up to 89%after a long cycle of 3000 cycles.?3?Polypyrrole/nickel phosphide/graphene oxide?PPy/Ni₂P/GO?ternary composites were successfully prepared by one-step ball milling.Using PPy/Ni₂P composite and GO monomer as reactants,absolute ethanol as solvent.The characterization and electrochemical performance of PPy/Ni₂P/GO ternary composites were tested.The results show that the PPy/Ni₂P composites are dispersed on the surface of the GO and between the layers,and there is no significant change for the morphology and size before and after compounding,the electrochemical performance of the obtained ternary composite are significantly improved compared with PPy/GO and PPy/Ni₂P binary composites,and at the optimum composition(m_PPy/Ni2P:m_GO=1:6)of the ternary composite,it has a higher specific capacitance of 563.1 F·g^-11 at the current density of 1 A·g^-1and a smaller charge transfer resistance for 1.1?,its capacity retention rate reaches 91%after a long cycle of 3000 cycles.