Electrooxidation behavior of ethanol toward carbon microbead-encapsulated ZnO particles derived from coffee waste

Zafar Khan Ghouri,Mohammad Zahid Farhad,Ahmed Abdel-Wahab,Ahmed Abdala,Khaled Elsaid

doi:10.1007/s10854-020-03209-w

Zafar Khan Ghouri, Mohammad Zahid Farhad + Show 3 more

Open Access

https://doi.org/10.1007/s10854-020-03209-w

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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.

Highlights

The world is expected to face an undeniable energy shortage in future due to the depletion of fossil fuel resources, increased energy demands, and the harmful environmental impacts of current energy resources [1]
No diffraction peaks for the ZnCl2 precursor are detected, which means that carbon microbead-encapsulated ZnO particles (CM-ZnO) has high
The elemental composition of CM-ZnO as obtained by energy-dispersive spectroscopy (EDS) analysis is summarized in Table 1, showing 5.5 wt% Zn, 7.66 wt% O, and 86.84 wt% C

Summary

Introduction

The world is expected to face an undeniable energy shortage in future due to the depletion of fossil fuel resources, increased energy demands, and the harmful environmental impacts of current energy resources [1]. Spent coffee ground (SCG) is a suitable raw source for the synthesis of valuable carbonous materials, and it is one of the widely consumed beverages and most popular commodities all around the world. It is grown in more than 80 territories and more than 6 million tons of SCG are produced annually [30]. Carbon microbead-encapsulated ZnO particles (CM-ZnO) have been synthesized from SCG by simple approach, involving a chemical activation and subsequent calcination at 700 °C and used as an electrocatalyst for ethanol electrooxidation in the alkaline medium. The introduced CM-ZnO demonstrated distinct textural characteristics that resulted in an enhanced catalytic activity toward ethanol electrooxidation

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