Pseudocapacitive behaviour of FeSx grown on stainless steel up to 1.8 V in aqueous electrolyte. (December 2019)

• Record Type: Journal Article
• Authors: Upadhyay, Kush K.; Nguyen, Tuyen; Silva, Teresa M.; Carmezim, Maria J.; Montemor, M.F.
• Is Part Of: Journal of energy storage. Volume 26(2019)
• Publication Date: 2019-12
• Subjects: Iron sulfide -- Cuboidal morphology -- Negative electrode -- Hydrothermal synthesis -- Pseudocapacitor -- Energy storage; Energy storage -- Periodicals; Energy storage -- Research -- Periodicals; 621.3126
• DOI: 10.1016/j.est.2019.100949
• Languages: English
• ISSNs: 2352-152X

Abstract

Highlights: FeSx having different morphologies have been directly grown on stainless steel substrate by hydrothermal synthesis process. Various synthesis periods have been explored to optimize the reaction conditions and corresponding reaction mechanism was proposed. Specific capacitance of 730 mF cm −2 at current density of 1 mA cm −2 was achieved. Interfacial redox kinetics responsible for charge storage is explored. Asymmetric setup showed supercapacitive behaviour up to 1.8 V in aqueous electrolyte and delivered 236 mF cm −2 at 0.5 mA cm −2 . Abstract: Iron sulfide was synthesized for 4 h, 7 h and 12 h by a hydrothermal process directly on stainless steel current collectors. The synthesis time determined the material morphology and electrochemical response. The shortest synthesis time promoted the formation of randomly oriented nanowires that evolved to nanosheets decorated with nanoflakes, organized in a cuboidal-like morphology upon longer synthesis times. XRD, Raman, FTIR and XPS investigations confirmed the formation of FeSx . The electrochemical activity was studied in a potential window ranging from −0.95 to 0 V and the material obtained after 7 h of synthesis stored the maximum specific capacitance of 730 mF cm −2 at the current density of 1 mA cm −2 . This material also retained approximately 34% of its initial capacitance at 10 mA cm −2 and showed very good cycling stability, keeping around 95% of the specific capacitance after 2000 galvanostatic charge-discharge (GCD) cycles. The kinetic analysis of the electrochemical results revealed the predominance of diffusional controlled processes. An asymmetric cell was assembled using FeSx as negative electrode and carbon nanofoam (CNF) as positive electrode. The FeSx ||CNF cell showed enhanced capacitive response in a potential window of 1.8 V in 1 M Na2 SO4 electrolyte and delivered specific capacitance of 236 mF cm −2 at 0.5 mA cm −2 with good rate capability. The FeSx ||CNF cell stored maximum energy density of 0.11 mW h cm −2 at the power density of 0.45 mW cm −2 . The cell showed very good stability by retaining 83% of the initial capacitance after 2000 cycles of consecutive charge discharge. Graphical abstract: Image, graphical abstract