The Pore Characteristics Of Various Derived Activated Carbon And The Electrochemical Performance Of Pb Modified Activated Carbon

The negative plate of traditional lead acid battery can occur irreversible sulfate under high-rate partial-state-of-charge operation and cause the battery failure.The negative plate of superbattery is made by connecting the capacitor electrode and the lead-acid negative plate in parallel or mixing the carbon materials into the lead-acid negative plate so the superbattery have a good high rate performance and long cycle performance.Superbattery shows a promising future in electric vehicles.However,the operation potential of the carbon material doesn't match that of the negative of lead acid battery.This can cause a heavy evolution of hydrogen at the end of charge and the electrolyte dry-out of the battery,and futher makes the battery failure.So the development of the negative material of superbattery with a high over potential of hydrogen evolution is the key of the superbattery.In this work,various derived activated carbon were modified by PbSO₄.The microstructure,capacitance performance and the behavior of hydrogen evolution were studied.This work also extends the direction of the development of lead-carbon composites and offers some basic date support for the evaluation of the negative material of the superbattery.The bamboo carbon was modified with PbSO₄ by impregnation-precipitation method.The effects of the mesh of bamboo on the composite were studied.200 nm PbSO₄ particles were randomly distributed on the surface of the bamboo carbon.The modified bamboos have an obvious suppress effect on the hydrogen evolution.The rank of the suppress effect is AC₃₀₀₀/PbSO₄>AC₅₀₀₀/PbSO₄>AC₂₀₀/PbSO₄.The coconut-shell activated carbon was modified by PbSO₄.500 nm PbSO₄ particles were randomly distributed on the surface of the carbon.As the increase of the concentration of Pb?NO₃?₂,the contents of Pb on the carbon increase from16.68%to 23.79%,but the specific capacitances drop from 209.2 F/g?AC?to102.8 F/g?AC/PbSO₄-1.0?.The modified carbon can effectively decrease the current density of hydrogen evolution and the most extent can drop to 28.3%.The reason is that the carbon modified by PbSO₄ increase the charge transfer resistance,which makes the charge transfer of hydrogen evolution more difficult.The coconut-shell activated carbon was fist modified by HNO₃ or H₂O₂,and then modified by PbSO₄.When compared with AC/PbSO₄-0.5,no matter the activated carbon was treated by HNO₃ or H₂O₂,the microstructure,capacitance performance and the behavior of hydrogen evolution make no difference.The coal-based activated carbon was fist treated with H₂O₂ and then was modified by PbSO₄.C-H₂O₂/PbSO₄-0.5 was obtained.The surface of the carbon is occupied by large amount of 50 nm PbSO₄ particles which are implanted in the carbon not adsorb on the carbon.The content of Pb in C-H₂O₂/PbSO₄-0.5 is 15.36%,higher than that of C/PbSO₄-0.510.33%?The specific capacitance of the activated carbon drops from106.6 F/g to 35.0 F/g after modifications.However,the current density of hydrogen evolution of C-H₂O₂/PbSO₄-0.5 is only 2.8 A/g,about 68.3%of the C/PbSO₄-0.5.This means C-H₂O₂/PbSO₄-0.5 have a better effect on the suppress of hydrogen evolution.It can be inferred that this activated carbon treated by H₂O₂ could absorb more Pb²⁺and also change the mode of combination between lead and carbon.