The Structure And Electrochemical Properties Of Bean Pulp Activated Carbon

Supercapacitor, because it has the advantages of short charging time, long working life, wide working temperature, friendly to environment, make it outstanding in the field of energy storage. At the present, the main research of supercapacitor is focused on the electrode materials, in order to obtain good properties. Now, carbon materials is the most widely reserached by the masses of scientific research workers, just because its high specific surface area, excellent electrochemical performance and zero pollution. Here, in order to get high specific capacitance of carbon electrode material, we mainly make the following works.In this thesis, we take bean pulp as carbon source:(1) the first step is to estimate carbonation of bean pulp under the condition of 400 oC, and then with KOH as activator, using KOH/C ratio of 1, 2, 3, 4 at800 oC obtain activated carbon powders DP-X-Y(X:the proportion of activation; Y:activation temperature);Also, when the ratio of KOH/C is 3, we explored the effect of temperature on the properties of activated carbon structure respectively in 600, 700, 800, 900 oC(2) with ZnCl2 as activating agent to get activated carbon ZDP-X-Y(X:the proportion of activation; Y:activation temperature), under 550 oC with ZnCl2 / bean pulp ratio respectively0.5, 1, 2to activate the bean pulp; When the ZnCl2 / bean pulp is 1, we also activate the bean pulp under 450 oC and 600 oC to explore the optimal process conditions. At the same time, we respectively use Raman spectroscopy, X-ray diffraction(XRD), Scanning electron microscope(SEM), Transmission electron microscopy(TEM) and Infrared spectrum etc. to characterize the microstructure of activated carbon. We also study the electrochemical properties of bean pulp active carbon with two electrode system, using KOH solution as electrolyte.The results show that, when using KOH as activator, with the increase of activation rate the graphite layers gradually open; As the activation temperature increasing, the graphitization degree of active carbon increase with the decreases of the first, and carbon structure corrosion intensifies. Comprehensive two factors, the sample of DP-3-800 has high specific surface area and superior hierarchical pore structure. The electrochemical test results show that DP-3-800 has the largest specific capacitance values, up to 250 F g-1. Also with good cycle life, under the current density of 5A g-1, after 10000 cycles, the specific capacitance value remains at a rate of 97%; While when using ZnCl2 as activating agent, with the increase of activation rate, the degree of graphitization of active carbon increase with the decrease of the first. Tested by element analysis, it is found that activated carbon obtained under low temperature also contains nitrogen element, we can clearly see the presence of redox peaks in the cyclic voltammograms test curve, which identify the generation of pseudo-capacitance with the increasing of capacitance. Test results show that the sample ZDP-1-550 has the highest specific capacitance value, can achieve 121 F g-1.