Study On Preparation And Supercapacitive Performance Of Biomass Based Carbon Composite Electrode Materials

Supercapacitors have been widely used in electronic vehicles, electronic devices and other fields due to their characteristics of long cycle life, fast charge-discharge rate capability and higher power density. Carbon materials with high electrical conductivity, high chemical stability and abundant raw materials have been as one kind of the uppermost electrode materials of supercapacitors. Currently, finding low-cost, eco-friendly and renewable raw materials to prepare activated carbon ?AC? has been as a hot spot. Using biomass as raw materials of carbon production can not only reduce cost but also ease the problem of environment caused by burning waste biomass.In this work, we use cheap biomass as raw materials to prepare AC electrode materials and AC-based composite electrode materials of supercapacitors. The major research results are listed as follows:?1? ACs with high specific surface areas were prepared by pyrolysing waste dragon fruit skin ?DF?, momordica grosvenori skin ?MG? and firmiana catkins ?FC? under argon atmosphere, subsequently activating with KOH and finally carbonization treatment under argon atmosphere. SEM images, XRD patterns and Raman spectra illustrated that as-prepared ACs with amorphous texture had low graphitization degree. FTIR spectra and XPS spectra profiled a large amount of containing-oxygen functional groups on the surface of as-prepared ACs, increasing pseudo-capacitance of as-prepared ACs and enhancing hydrophilic of electrolyte and electrode materials. N2 adsorption-desorption isotherms showed that as-prepared ACs had high specific surface areas and microporous-mesoporous structure, facilitating diffusion and transmission of electrolyte ions. Electrochemical tests suggested that specific capacitances of DF-AC MG-AC and FC-AC were 287 F g-1,239 F g-1 and 227 F g-1 at 0.5 A g-respectively. Furthermore, as-prepared ACs also showed excellent cycling performance with nearly 100% retention over 5000 cycles at 4 A g-1.?2? Pomelo peel ?pp? AC was obtained by pyrolysing waste pomelo peel under argon atmosphere, subsequently activating with KOH and finally carbonization treatment under argon atmosphere. We mainly discussed influences of structure and supercapacitive performance of as-prepared ACs under different molar concentration of KOH. SEM images illustrated that PP/KOH-3 presented inter-connective porous structure, providing paths for transmission of electrolyte ions and increasing the specific surface area of PP/KOH-3. XRD patterns illustrated that as-prepared ACs with amorphous texture had low graphitization degree. Electrochemical tests suggested that specific capacitances of PP/KOH-1, PP/KOH-2, PP/KOH-3 and PP/KOH-4 were 191 F g-1,247 F g-1,260 F g-1 and 225 F g-1 at 1 A g-1, respectively. As a result, specific capacitance of PP/KOH-3 was the highest. Furthermore, PP/KOH-3 also showed excellent cycling performance with nearly 100% retention over 1000 cycles at 2 A g-1.?3? a-Ni?OH?₂/PP-AC was prepared by hydrothermal method. We mainly discussed electrochemical performance of composites under different mass ratio of PP-AC and a-Ni?OH?2. XRD patterns illustrated that composite was consisted by a-Ni?OH?2 and C. Electrochemical tests suggested that specific capacitance of composite ?the mass ratio of PP-AC and a-Ni?OH?2 was 1:20? was 994 F g-1 while that of pure a-Ni?OH?2 was 832 F g-1 at 6 A g-1. Furthermore, cycling performance with 84% retention of composite ?the mass ratio of PP-AC and a-Ni?OH?2 was 1:20? had been obtained over 1000 cycles at 8 A g-1, which was higher than that of pure a-Ni?OH?2 ?cycling performance with 62% retention?. As a result, compared with pure a-Ni?OH?2 and PP-AC, specific capacitance and cycling stability of composite had been enhanced.?4? NiMoO₄ xH₂O/PP-AC was prepared by hydrothermal method. We mainly discussed electrochemical performance of composites under different molar ratio of PP-AC and NiMoO4 xH2O. XRD patterns illustrated that composite was consisted by NiMoO4 xH2O and C. SEM images illustrated that some granular NiMoO4 xH2O were adsorbed in pores of PP-AC, increasing specific surface areas ?SSAs? of materials. Electrochemical tests suggested that specific capacitance of composite ?the molar ratio of PP-AC and NiMoO4.xH2O was 25:24? was 1075 F g"1 while that of pure NiMoO4 xH2O was 667 F g-1 at 1 A g-1. Furthermore, cycling performance with 87% retention of composite ?the molar ratio of PP-AC and NiMoO4.xH2O was 25:24? had been obtained over 1000 cycles at 2 A g-1, which was higher than that of pure NiMoO4 xH2O ?cycling performance with 77% retention?. As a result, compared with pure PP-AC and NiMoO4 xH2O, specific capacitance and cycling stability of composite had been enhanced.According to the obtained experimental results, DF-AC, MG-AC and FC-AC with excellent electrochemical performance could be prepared as the electrodes of supercapacitor. Electrochemical performance of a-Ni?OH?2/PP-AC and NiMoO4 xH2O/PP-AC had been increased obviously.