甘蔗渣基磷掺杂活性炭的制备及其电化学性能

Preparation and electrochemical performance of bagasse-based phosphorus-doped activated carbon

以甘蔗渣为生物质碳源,植酸为磷源和活化剂,制备磷掺杂活性炭,并将其应用于超级电容器领域。本文分析了活化温度和浸渍比对活性炭碘吸附值、亚甲基蓝吸附值以及电化学性能的影响,并通过孔隙结构、含磷官能团中P结合形态以及亲水性等探究磷掺杂提高活性炭电化学性能的机理。结果表明,植酸的活化作用促进了活性炭吸附能力和比表面积的提高,形成微孔/介孔复合的结构;植酸作为磷源,实现了活性炭的磷掺杂,其结合类型为C—P、C—P==O、C—P—O和C—O—P;含磷官能团的引入改善了活性炭的亲水性,为赝电容反应提供了活性位点,从而提升了电化学性能。电容贡献理论分析表明,扩散行为不是限制其电容行为的主要因素,电容行为主要受电极表面的双电层和赝电容反应的影响。在较佳工艺条件下,活化温度为900℃,浸渍比为1.5时,磷掺杂活性炭的碘吸附值、亚甲基蓝吸附值和比电容分别为1321mg/g、255mg/g和222F/g(电流密度为1A/g)。循环9000次后,其电容保持率仍为高达98.77%,说明磷掺杂活性炭具有作为超级电容器电极的潜力。

Bagasse-based phosphorus-doped activated carbon was prepared with bagasse as carbon source and phytic acid as phosphorus source and activator,and applied to the field of supercapacitors.The effects of activation temperature and impregnation ratio on the iodine adsorption value,methylene blue adsorption value and electrochemical performance of activated carbon were analyzed.The mechanism of phosphorus doping to improve the electrochemical performance of activated carbon was explored through the combination of pore structure,phosphorus-containing functional groups and hydrophilic characterization.The results showed that the activation of phytic acid promoted the adsorption capacity and specific surface area of activated carbon,forming a microporous/mesoporous composite structure.Phytic acid was used as a phosphorus source to achieve phosphorus doping of activated carbon,and the binding types were C—P and C—P==O,C—P—O and C—O—P.The introduction of phosphorus-containing functional groups improved the hydrophilicity of activated carbon,and provided active sites for pseudocapacitance reactions,and thus improving electrochemical performance.Theoretical analysis of capacitance contribution indicated that diffusion behavior was not the main factor limiting its capacitance behavior,which was mainly affected by the electric double layer on the electrode surface and the pseudocapacitance reaction.Under the optimum conditions,when the activation temperature was 900℃and the impregnation ratio was 1.5,the iodine adsorption value,methylene blue adsorption value and specific capacitance of phosphorus-doped activated carbon were 1321mg/g,255mg/g and 222F/g(current density was 1A/g),respectively.After 9000 cycles,its capacitance retention rate was still as high as 98.77%,showing that phosphorus doping had the potential as a supercapacitor.