| Recent years,supercapacitors have attracted ectensive research interest due to their intrinsic characteristics such as high power density,fast charge-discharge rate,longlife and low maintenance cost.These outstanding advantages make supercapacitors very promising candidate for energy.Now,scientists make their attention on the electrodes with higher power density and higher specific capacitance.Transition metal oxides were considered as the outstanding electrode due to its fleetly reversible Faraday redox reaction between electrode and electrolyte.Precious metal oxide(such as RuO2)is an excellent pseudocapacitance electrode,but limited by its high cost.We prepared series of Bi-based transition metal oxysalt(such as bismuth molybdate(Bi3.63Mo0.3606.55,Bi2MoO6)?bismuth tungstate(Bi3.84W0.16O6.24,Bi2WO6)and bismuth oxychloride(BiOCl))nanocomposites via hydrothermal method or solvothermal method.The structure,morphology and components of samples were characterized by XRD,SEM,TEM,XPS and Raman.Futuremore,we employed cyclic voltanmmetry(CV),galvanostatic charge-discharge(GCD)and electrochemical impedance spectra(EIS)to measure their electrochemical performance.The main work is the following:(1)The inner structure of electrode can influence its electrochemical performance.In this chapter,we synthesis uniform ?-Bi2MoO6 nanoroll via adjusting of the ratio of ethylene glycol and ethyl alcohol.The obtained ?-Bi2MoO6 nanoroll own better conductivity than nanosheets fabricated by other ratios.Higher conductivity can enhance electrochemical performance on account of its ability to effectively improve the electron transfer between electrode and electrolyte.?-Bi2MoO6 nanoroll possess high specific capacitance(317 F g-1 at 1 A g-1)and good cycling stability(retain 80%after 3000 cycles).(2)MoO3 belongs to environmental transition metal oxides with low cost,recently some papers regarding of MoO3 applied to pseudocapacitance electrodes were reported.Bismuth molybdate(Bi3.63Mo0.36O6.55,Bi2MoO6)can be expressed as Bi2O3·nMoO3 consisting of MoO3 and Bi2O3.In this chapter,we obtained Bi3.64Mo0.36O6.55,Bi2MoO6 and Bi3.64Mo0.36O6.55/Bi2MoO6 nanomaterials by adjusting the pH value via hydrothermal reaction.The electrochemical experiments indicated that Bi3,64Mo0.36O6.55 process the optimal electrochemical performance.The excellent specific capacitance(998 F g-1 at 1 A g-1)and good cycling stability(retain 80%after 5000 cycles)were obtained.The electrochemical performance of Bi3.63Mo0.36O6.55 is better than Bi2MoO6 due to its higher Bi contents.(3)Nanocomposites attract our interests due to dissatisfying of the limit application of simplex nanomaterials with the development of nanotechnology.In this chapter,we obtained Bi3.64Mo0.36O6.55/Bi3.84W0.16O6.24(pH=11-13)and Bi2MoO6/BiWO6(pH=3-5)nanocomposites by adding sodium tungstate as W source via the same condition as chapter 2.The electrochemical experiments indicated Bi3.64Mo0.36O6.55/Bi3.84W0.16O6.24 and Bi2MoO6/BiWO6 have better performance than simplex Bi3.64Mo0.36O6.55 or Bi2MoO6,respectively.Bi3.64Mo0.36O6.55/Bi3.84W0.16O6.24 possess specific capacitance(1056 F g-1 at 1 A g-1)and good cycling stability(retain 80%after 3000 cycles).Bi2MoO6/BiWO6 has the similar conclusion(699 F g-1 at 1A g-1,80%after 3000 cycles)(4)Bismuth molybdate nanocomposites can obtained under the condition of alcohol phase as well as aqueous phase.Regarding BiOCl,photogenerated electron-hole pairs can be separated effectively due to its unique layered structure and the presence of strong internal static electric field perpendicular,is an outstanding electron carrier.In this chapter,we presented a one-pot hydrothermal approach to produce Bi2MoO6/BiOCl heterojunction in the presence of dichloromethane(CH2Cl2)as the source of chloridion(Cl-)through alcoholysis.Bi2MoO6/BiOCl nanocomposite process twice electrochemical performance(651 F g-1 at 1 A g-1,80%after 5000 cycles)than Bi2MoO6 and prominent cycle stability due to its unique synthesis mechanism. |
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