茶渣衍生多级孔炭的电化学和吸附性能研究

Electrochemicaland Adsorption Performance of Tea Waste Derived Carbon with Hierarchical Pores

为探索废弃生物质材料的高值化利用在储能和环境修复中的应用潜力,本文以武夷岩茶茶渣(简称为茶渣)为原料,利用一种简便的KOH活化法制备了多级孔炭材料(TWBC_(750)),并系统研究了其作为超级电容器电极与环境吸附剂的性能。研究结果显示TWBC_(750)高度石墨化,具有分级多孔结构,且比表面积高达1014.54 m^(2)·g^(−1),孔体积为0.50 cm^(3)·g^(−1)。TWBC_(750)电极在1.0 A·g^(−1)时的最大比电容可达150 F·g^(−1),在10 A·g^(−1)电流密度下充放电循环10000圈后容量保持率高达94%;基于该材料所组装的对称超级电容器在功率密度为700 W·kg^(−1)时,最大能量密度为9.73 Wh·kg^(−1),并展现出优异的长期循环稳定性能(10000圈后容量保持率为91.75%)。准二级动力学模型可以更好描述TWBC_(750)吸附水中阿莫西林的过程,吸附等温线均符合Langmuir和Freundlich等温吸附方程,在45℃时其Langmuir的理论吸附容量最大(129.249 mg·g^(−1));吸附热力学数据表明这是一个非自发的熵减吸热的吸附过程。本研究合成的高效TWBC_(750)为茶叶废弃物同时在能源储存和环境修复领域的可循环利用提供了一定的理论依据。

With the continuous development of urbanization and industrialization,the model of"high energy consumption,high pollution,and high waste"has triggered increasing environmental concerns.It is necessary to explore novel green alternatives to eliminate these negative risks.Recently,the strong demand of supercapacitors is sharply increasing due to their excellent energy storage performance,which would be efficient to solve kind of renewable sources depletion problem.Meanwhile,the aquatic environment is seriously threatened by the occurrence of emerging water contaminants.For example,antibiotics in water,even at very low concentrations,can result in a long-term adverse effect on ecological sustainability.As the only phenolic penicillin based onβ-lactam ring structure,amoxicillin(AMX)is identified as one of the top ten most frequently consumed drugs used for the treatment of bacterial infections.Referred to the report,an oral intake of 500 mg of AMX results in the excretion of 86%±8%through urine after two hours of consumption.Thus,the widespread application of AMX and their subsequent release in natural water bodies have attracted the attention of the scientific community.Fortunately,biomass-derived porous carbon materials have demonstrated advantages in dealing with these challenges.Over the years,the valorization of waste biomass is attractive in energy storage and environmental restoration.As an abundant,ecofriendly material with high-oxygen content(favorable for improving pseudocapacitance),biomass is a global leading topic in green chemistry,especially as a promising carbon source forthe porous carbons.Owing to the poor performance of pristine porous carbons,engineered porous carbonshave emerged,which are derived from physical,chemical,and biological modifications to improve their surface properties and thus adsorption capacity.The physico-chemical characteristics(e.g.low cost,high surface area and volume,excellent conductivity and physicochemical stability)of porous carbon strongly impact their applications such as energy storage and wastewater treatment.Teawaste biomass is one of such sources that has shown significant prospective forbiochar fabrication.Tea is the most popular and widely consumed beverage that is consumed around the world.China is a leading tea producer and consumer,with anannual tea production of more than 2 million tons.It is quite evident that large amounts of tea waste being generated brings about solid wasteproblems associated with their improper disposal.Tea waste contains a large number of usefulcomponents,including cellulose,hemicellulose,lignin,poly-phenols,proteins,amino acids,vitamins,major elements,andtrace elements,which contribute to its potential as a proper precursor material for the production of activated carbon.Hierarchically porous carbon materials have great potential in both capacitive energy storage and contaminant sorption applications.In this work,the Wuyi rock tea waste(rock tea waste)-derived hierarchically porous carbon(TWBC_(750))had been prepared via the convenient KOH-activation method at 750℃.Their electrochemical performance as a symmetric supercapacitor electrode and the removal of AMX as an adsorbent were systematically studied,respectively.The physio-chemical properties of TWBC_(750) were characterized by scanning electron microscopy(SEM),transmission electron microscope(TEM),Brunauer Emmett Teller(BET)with pore size distribution,X-ray diffraction(XRD),Raman spectroscopy,Fourier transform infrared spectroscopy(FTIR)and X-ray photoelectron spectroscopy(XPS)techniques.TWBC_(750) possessed a high degree of graphitization and an abundant porous structure with a pore volume of 0.50 cm^(3)·g^(−1) and a high specific surface area of 1014.54 m^(2)·g^(−1).As an electrode,TWBC_(750) exhibited a maximum specific capacitance of up to 150 F·g^(−1) at 1 A·g^(−1) and excellent cycling stability with 94%retention over 10000 cycles at 10 A·g^(−1).Notably,TWBC_(750) based on symmetric supercapacitor achieved a maximum energy density of 9.73 Wh·kg^(−1) at the power density of 700 W·kg^(−1),with a long-term cycle lifespan(91.75%capacitance retention at 5 A·g^(−1) after 10000 cycles).The excellent electrochemical performance of the TWBC_(750) electrode would be mainly attributed to three factors:(1)The large surface area and large pore volume with hierarchical pores were beneficial for rapid ion penetration and transportation,boosting its high capacitance and rate capability.(2)The abundant functional groups provided extra faradaic pseudo capacitance.(3)The hollow-hole structure alleviated the volume expansion of the electrode in the charging and discharging process,and its high graphitization degree increased the conductivity of the material and jointly improved the cyclic stability of the electrode.As adsorbents,the adsorption equilibrium and adsorption kinetics results evidenced the fitted Langmuir and pseudo-second order models.Langmuir isotherm suggested a high adsorption capacity of 129.249 mg·g^(−1) at 45℃.Thermodynamic parameters indicated that the removal of AMX by TWBC_(750) was a nonspontaneous,entropy-decreasing and endothermic process.Furthermore,TWBC_(750) was used to remove AMX from wastewaters and the results showed 98.68%and 90.23%removal of AMX at 1.06 and 7.68 mg·L^(−1),respectively.This work showcased recyclable utilization of tea waste as a cost-effective and efficient porous carbon for energy storage and environmental remediation.