Insight of an easy topochemical oxidative reaction in obtaining high performance electrochemical capacitor based on (CoCoIII)-Co-II monometallic cobalt Layered Double Hydroxide

摘要

A series of monometallic Layered Double Hydroxides (LDH) using electroactive cation, i.e. divalent or trivalent cobalt, was prepared by Topochemical Oxidation Reaction (TOR) under O-2 atmosphere at 40 degrees C from pristine beta-Co(OH)(2) platelets. The oxidation state of the ill-defined layered materials was evaluated by coupling thermal measurements and chemical titration (iodometry). Their characterization by ancillary techniques was completed by the study of their magnetic behavior. The obtained magnetic moments suggest the presence of structural local deformation around the Co-II ions, unhomogeneous charge distribution yielding to clustering effects cannot be discarded. Their pseudo-faradic properties as supercapacitor in KOH solution was thoroughly investigated by using Cyclic Voltammetry (CV), Galvanostatic Cycling with Potential Limitation (GCPL) and Electrochemical Impedance Spectroscopy (EIS) techniques. As a function of the oxygen treatment, the relative amount of Co-II/Co-III was found to range into 5.3 and 13.3, which is unusually high when compared to classical LDH charge distribution. Pseudocapacitance as high as 1540 F g(-1) was obtained underlining a high percentage of Co-II, approximate to 40%, involved in electrochemical process. This high percentage is tentatively explained by an extended outer-active electrochemical surface which demonstrates that TOR is a quick and easy process to get a high pseudocapacitive performance. (C) 2015 Elsevier B.V. All rights reserved.