Effect of alkaline electrolytes on the charge storage capacity and morphology of porous layered double cobalt hydroxide-coated graphene supercapacitor electrodes

Although alpha-cobalt hydroxide (alpha-Co(OH)(2)) with a layered double hydroxide (LDH) structure has been widely used as a supercapacitor electrode, the effect of an alkaline electrolyte on the charge storage performance of the alpha-Co(OH)(2) has not yet been investigated. In this work, alpha-Co(OH)(2) was electrodeposited on reduced graphene oxide-coated carbon fiber paper (rGO/CFP) using chronoamperometry at -0.5 V vs. Ag/AgCl. The effect of alkaline aqueous electrolytes on the performance of the alpha-Co(OH)(2)/rGO/CFP electrodes was then investigated by means of scanning and transmission electron microscopies, X-ray photoelectron and absorption spectroscopies, and electrochemical techniques. It was found that the concentrated alkaline electrolytes (i.e., 3-6 M [OH-]) can strip off and/or deform the porous structure of the alpha-Co(OH) 2 deposited on rGO/CFP leading to poor charge storage capacity. 1 M [OH-] was found to be a suitable electrolyte concentration providing high specific capacitance (1096 F g(-1) at 1.8 A g(-1)) without the deformation of the porous alpha-Co(OH)(2) structure after testing. Morphological and electrochemical analyses of the alpha-Co(OH)(2)/rGO/CFP electrodes suggest that the effect of the alkaline electrolyte concentration plays a major role on the charge storage performance of alpha-Co(OH)(2)-based supercapacitors.