Low-cost coin-cell supercapacitors based on waste graphite from spent dry-cell batteries

In this study, graphite rods were extracted from dry-cell batteries and processed for chemical activation using potassium hydroxide. Prior to activation, the filtered graphite powder displayed a surface morphology of highly graphitic small stratified particles with a diameter of around 5 µm to 30 µm. While the surface morphology of the activated carbon surprisingly had no visible pore formation, it appears to have developed into thin flakes. The elemental composition and chemical composition of the activated carbon have been observed to be similar to graphene oxide, in agreement with its surface morphology. Partial oxidation and alkali metal intercalation in the interplanar spacings with exfoliation into thin layers have resulted in the chemical activation of graphite into exfoliated oxidized graphite layers. The chemically activated carbon was then utilized for the fabrication of supercapacitor electrodes and coin-cell supercapacitors modified with nickel oxide and reduced graphene oxide composite. Increased potential window and higher overall current readings were observed on a 2:1 ratio due to the redox reaction capability of nickel oxide and fast ion transport of reduced graphene oxide. The electrochemical performance of both the supercapacitor electrode and the coin-cell supercapacitor displayed excellent electric-double layer capacitance behavior and fast ion transfer kinetics between the electrode and electrolyte surface. The specific capacitance for both the supercapacitor electrode and the coin-cell supercapacitor was calculated to be 27.8 F g-1 and 20.10 F g-1 at a current density of 0.1 A g-1, respectively. The highest energy density was calculated to be 40.20 Wh/kg at a power density of 1,440 W/kg

Determination of heavy metals in herbal food supplements using bismuth/multi-walled carbon nanotubes/Nafion modified graphite electrodes sourced from waste batteries

An electrochemical sensor based on graphite electrode extracted from waste zinc-carbon battery is developed. The graphite electrode was modified with bismuth nanoparticles (BiNP), multi-walled carbon nanotubes (MWCNT) and Nafion via the drop coating method. The bare and modified graphite electrodes were used as the working electrode in anodic stripping voltammetry for the determination of trace amounts of cadmium (Cd2+) and lead (Pb2+). The modified electrode exhibited excellent electroanalytical performance for heavy metal detection in comparison with the bare graphite electrode. The linear concentration range from 5 parts per billion (ppb) to 1000 ppb (R2 = 0.996), as well as detection limits of 1.06 ppb for Cd2+ and 0.72 ppb for Pb2+ were obtained at optimized experimental conditions and parameters. The sensor was successfully utilized for the quantification of Cd2+ and Pb2+ in herbal food supplement samples with good agreement to the results obtained by atomic absorption spectroscopy. Thus, the BiNP/MWCNT/Nafion modified graphite electrode is a cost-effective and environment-friendly sensor for monitoring heavy metal contamination. © 2019, The Author(s)