Discussion on operational voltage and efficiencies of ionic-liquid-based electrochemical capacitors

In this article, we explore electrical double-layer capacitors (EDLCs) based on ionic liquids (IL), focusing on their stability and efficiencies (Coulombic and energetic). We analyze the conventional voltammetric methods to determine the electrochemical stability window, pointing out that a simple analysis of Coulombic efficiency, under different current and voltage conditions in galvanostatic experiments, has the advantage of being more representative for real cells, especially when studied together with energy efficiency. In addition, we study how IL-based EDLCs differ from aqueous and organic ones in terms of energy efficiency correlating with the physicochemical properties of electrolytes. Finally, we discuss the high resistance of this type of EDLC that has a detrimental effect on energy efficiency and cycling performance, even when the Coulombic efficiency is close to 100%.The authors would like to thank the Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq)/Brazil for ́ the financial support (Process No. 458487/2014-7). The authors would like to acknowledge the Instituto Nacional de Ciencia e Tecnologia em Nanomateriais de Carbono (INCT ̂ Nanocarbono)/CNPq. R.L.L. is recipient of fellowship from CNPq (Grant No. 313304/2017 - 3). M.C.G.S. thankfully acknowledge the scholarship received from the Coordenaca̧ õ de Aperfeicoamento de Pessoal de Nivel Superior (CAPES) - Brazil

Direct electrodeposition of hydrogenated reduced graphene oxide from unsonicated solution and its electrochemical response

Reduced graphene oxide (rGO) is successfully electrodeposited from a graphene oxide-containing suspension under stirring and no sonication onto Ni foam by applying -1.5 V/SCE. The electrodeposited material is characterized by X-Ray Diffraction (XRD), Scanning electron microscopy (SEM), Raman spectroscopy, Fourier Transform Infra-Red spectroscopy (FTIR) and Thermogravimetric analysis (TGA). FTIR and TGA results indicate the formation of hydrogenated rGO after electrodeposition. In addition, the electrochemical response of the rGO/Ni electrode is evaluated by cyclic voltammetry in 1 M potassium hydroxide solution. The results reveal that the electrode possesses higher conductivity and lower polarization loss compared to bare Ni foam, opening wider perspectives to design composites with improved electrochemical performance.info:eu-repo/semantics/publishedVersio