Abstract

Carbon microbead-encapsulated ZnO (CM-ZnO) particles have been synthesized from the spent coffee ground (SCG) by chemical activation with ZnCl₂ followed by calcination at 700 ℃ in N₂ environment. Interestingly, ZnCl₂ can act as an activating agent as well as a precursor for ZnO particles. The structure of the core and shell of the CM-ZnO was investigated by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) techniques. Moreover, X-ray diffraction (XRD) and energy-dispersive spectroscopy (EDS) studies confirmed the presence of the encapsulated ZnO particles. The Brunauer–Emmett–Teller (BET) and Barrett–Joyner–Halenda (BJH) plots showed a well-developed porous structure with a specific surface area of 210 m²/g, average pore volume of 1.12 cm³/g, and an average pore radius of 31.7 Å. The electrooxidation behavior of ethanol toward the synthesized CM-ZnO was then studied using cyclic voltammetry (CV) technique. For comparison, two types of modified electrodes were prepared: the first one with the non-activated SCG and the second one with the CM-ZnO. The electrochemical measurements of the prepared CM-ZnO demonstrated higher electrocatalytic activity with a current density of ~ 35 mA/cm² at 0.4 V vs. Ag/AgCl for ethanol electrooxidation in an alkaline medium. The electrochemical measurements specified that the presence of ZnO particles and the high surface area of the activated sample have a significant influence on electrooxidation activity. Therefore, the introduced CM-ZnO particles could be an alternative and effective non-precious electrocatalyst for ethanol electrooxidation.

中文翻译：

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乙醇对咖啡渣中碳微珠包裹的ZnO颗粒的电氧化行为

摘要

碳微珠包裹的ZnO（CM-ZnO）颗粒是通过用ZnCl ₂化学活化，然后在N ₂环境中在700℃下煅烧，由废咖啡渣（SCG）合成的。有趣的是，ZnCl ₂既可以充当活化剂，又可以充当ZnO颗粒的前体。通过扫描电子显微镜（SEM）和透射电子显微镜（TEM）技术研究了CM-ZnO核和壳的结构。此外，X射线衍射（XRD）和能量色散光谱（EDS）研究证实了封装的ZnO颗粒的存在。Brunauer-Emmett-Teller（BET）和Barrett-Joyner-Halenda（BJH）图显示了发达的多孔结构，比表面积为210 m ²/ g，平均孔体积为1.12 cm ³ / g，平均孔半径为31.7Å。然后使用循环伏安法（CV）研究了乙醇对合成的CM-ZnO的电氧化行为。为了进行比较，制备了两种类型的修饰电极：第一种具有未活化的SCG，第二种具有CM-ZnO。制备的CM-ZnO的电化学测量显示出更高的电催化活性，电流密度为〜35 mA / cm ²在0.4 V vs. Ag / AgCl的条件下，在碱性介质中进行乙醇电氧化。电化学测量表明，ZnO颗粒的存在和活化样品的高表面积对电氧化活性有重大影响。因此，引入的CM-ZnO颗粒可以作为乙醇电氧化的替代且有效的非贵金属电催化剂。