Abstract:

Bamboo char, with its distinctive porous structure, offers significant potential for applications in adsorption and energy storage. However, bamboo is a silicon-rich plant. The inorganic components in bamboo carbon, especially Si, can seriously affect its performances. Therefore, it is of significance to develop an effective and cost-efficient approach for impurity removal. In this paper, an innovative method was presented to remove Si and other inorganic components from bamboo char, in which bamboo was impregnated by KOH, followed by co-carbonization of KOH and bamboo, and acid washing. The effects of KOH concentration, impregnation duration, and carbonization temperature on the removal efficiency of silicon and other inorganic components were systematically investigated using EDS and ICP-MS, and the mechanism of alkali impregnation-carbonization-acid washing was explored. In addition, hard carbon samples were prepared from bamboo char and low ash bamboo char, respectively, and their electrochemical properties were characterized. The results show that KOH can be effectively loaded onto bamboo. After the bamboo is immersed in 3 mol·L^-1 KOH solution for 4 h and carbonized at 650℃ and then acid-washed, the ash content of bamboo charcoal can be reduced to 0.55%, the deashing rate reaches 84.76%, the Si content is reduced to 0.3%, and the desiliconization rate reaches 76.19%. During carbonization, KOH reacts with silicon in bamboo to form acid-soluble silicates, which are effectively removed by acid washing. The electrochemical performance of hard carbon prepared from bamboo char with low ash and silicon contents is significantly better than that from un-deashed bamboo char samples. The initial coulombic efficiency reaches 70.67% at a current density of 50 mA·g^-1. After charging and discharging at a current density of 50 mA·g^-1—5 A·g^-1, the reversible specific capacity of the hard carbon prepared from low ash bamboo charcoal is still as high as 365 mAh·g^-1 when the current density is restored to 50 mA·g^-1. Acid washing of char from carbonization of alkali-impregnated bamboo is an effective approach for deep deashing and desilication. Hard carbon derived from bamboo char with low ash and silicon contents has excellent electrochemical performance.

Key words: biomass, bamboo, alkali impregnation-carbonization-acid washing, deashing, silica, hard carbon, electrochemistry

摘要：

竹炭在储能等领域有巨大的应用潜力。然而，无机成分尤其是硅会严重影响其性能。采用KOH浸渍竹材、与竹材共炭化后酸洗脱除硅及其他无机组分，考察KOH浓度、浸渍时间、炭化温度对脱硅脱灰效果的影响；借助ICP-MS等方法表征脱灰效果、探究脱灰机理。此外，将竹炭制为硬炭，表征电化学性能。结果表明，KOH可有效负载到竹材上，竹材在3 mol·L^-1 KOH溶液中浸渍4 h，650℃下炭化后酸洗，竹炭灰分含量可降低至0.55%、脱灰率达84.76%，Si的含量降低至0.3%、脱硅率达76.19%；低灰竹炭制备硬炭的电化学性能显著优于未脱灰样品；50 mA·g^-1的电流密度下首次库仑效率达到70.67%；低灰竹基硬炭经过50 mA·g^-1~5 A·g^-1电流密度的循环后，在50 mA·g^-1下可逆比容量可恢复至365 mAh·g^-1。碱浸竹材炭化后酸洗是深度脱灰脱硅的有效途径，低灰竹基硬炭的电化学性能优异。

关键词: 生物质, 竹, 碱浸-炭化-酸洗, 脱灰, 二氧化硅, 硬炭, 电化学