Tunable synthesis of carbon quantum dots from the biomass of spent tea leaves as supercapacitor electrode. (March 2023)

• Record Type: Journal Article
• Authors: Inayat, Abid; Albalawi, Karma; Rehman, Ata-ur; Adnan, ; Saad, Aiman Y.; Saleh, Ebraheem Abdu Musad; Alamri, Mubarak A.; El-Zahhar, Adel A.; Haider, Ali; Abbas, Syed Mustansar
• Is Part Of: Materials today communications. Volume 34(2023)
• Publication Date: 2023-03
• Subjects: Supercapacitor -- Carbon quantum dots -- Biomass -- Spent tea leaves -- Energy density; Materials science -- Periodicals; 620.11
• DOI: 10.1016/j.mtcomm.2023.105479
• Languages: English
• ISSNs: 2352-4928

Abstract

Abstract: A simple and cost-effective method has been used for obtaining highly conductive carbon quantum dots (CQDs) by hydrothermal oxidation of spent tea leaves. The obtained CQDs are characterized by various analytical techniques demonstrating a crystalline structure. CQDs proved to be exceptional working electrodes in the three-electrode cell in H2 SO4 aqueous electrolyte. Based on X-ray diffraction and microscopic analysis, the synthesized CQD is crystalline, with a diameter of 2–5 nm. Electrochemical impedance spectroscopy, cyclic voltammetry and charge-discharge measurements are used to evaluate the electrochemical performance of CQDs in an aqueous electrolyte. The CQD-based supercapacitor demonstrated a superior specific capacitance of 302.0 F g 1 at a current of 0.5 Ag 1, cyclability with 144.4 F g 1 at 20 A g 1 after 5000 cycles, and rate performance of 186.4 F g 1 at 20 A g 1 . The CQDs electrode also exhibited an enhanced energy density and power density of 41.9 Wh g 1 and 250 W g 1, respectively at a current rate of 0.5 A g 1 . In experiments, it is demonstrated that many thousands of cycles could be run consistently at near 100% efficiency and a stable capacity. This explains the possibility of using spent tea leaves as a bioresource, the ease of synthetically producing these materials, and the favourable redox reaction of CQDs for high-energy devices. Graphical Abstract: ga1 Highlights: CQDs are derived from biomass via a simple and economically viable approach. CQDs with significant electrochemical performance in supercapacitors. CQD SC shows 144.4 F g 1 at 20 A g 1 after 5000 cycles with high energy density.