Cathodic plasma–induced syntheses of graphene nanosheet/MnO2/WO3 architectures and their use in supercapacitors. (10th May 2020)

• Record Type: Journal Article
• Authors: Huang, Shih-Yu; Le, Phuoc-Anh; Yen, Po-Jen; Lu, Yi-Chun; Sahoo, Sumanta Kumar; Cheng, Hao-Wen; Chiu, Po-Wen; Tseng, Tseung-Yuen; Wei, Kung-Hwa
• Is Part Of: Electrochimica acta. Volume 342(2020)
• Publication Date: 2020-05-10
• Subjects: Cathodic plasma process -- Sequential syntheses -- G/MnO2/WO3 architectures -- Supercapacitor; Electrochemistry -- Periodicals; Electrochemistry, Industrial -- Periodicals; 541.37
• DOI: 10.1016/j.electacta.2020.136043
• Languages: English
• ISSNs: 0013-4686

Abstract

Abstract: In this study, we synthesized new 0.01–2 μm graphene nanosheet/MnO2 /WO3 (G/MnO2 /WO3 ) architectures through an electrochemically induced cathodic plasma process in a single batch at a lower temperature (70 °C) and for a shorter time (2 h) than those required for the syntheses of similar structures when using a hydrothermal method. We first obtained 0.01–1 μm leaf-like graphene (G) nanosheets, then 0.1–0.3 μm long and approximately 10 nm diameter petiole-like MnO2 nanowires on the G nanosheets, and finally 0.20–2.0 μm petal-like WO3 on MnO2 /G — thereby forming the G/MnO2 /WO3 architectures — as evidenced using scanning electron microscopy and transmission electron microscopy. We deciphered the step-wise reaction mechanism behind the formation of the G/MnO2 /WO3 architectures during the plasma process. The high surface area of 291 m 2 g −1 in the G/MnO2 /WO3 architecture was contributed mainly by the G nanosheets, providing a suitable surface area for diffusion of the charge carriers during the charging and discharging process. As a result, an electrode incorporating the G/MnO2 /WO3 architectures exhibited an excellent specific capacitance of 620 F g −1 — 45 and 200% higher than those of G/MnO2 (421 F g −1 ) and G (189 F g −1 ) electrodes, respectively — at a current density of 0.5 A g −1 . Moreover, the G/MnO2 /WO3 –incorporated electrode exhibited good electrochemical cycling stability, with 90% capacitance retention over 5000 cycles at 1 A g −1 . Such new G/MnO2 /WO3 heterojunction structures, not only provide high-performance electrode applications, but also suggest a potential approach toward fabricating other heterojunction structures having high surface areas for energy storage applications. Highlights: Cathodic plasma–induced syntheses of G/MnO2 /WO3 architectures in a single batch. Proposed reaction mechanism for the cathodic plasma process. G/MnO2 /WO3 structure displaying a high specific capacitance of 620 F g −1 at 0.5 A g −1 . G/MnO2 /WO3 architectures exhibiting good stability during electrochemical cycling.