Electrochemical characterization of RuO2 and activated carbon (AC) electrodes using multivalent Ni(NO3)2 electrolyte for charge storage applications

Abstract

Among various transition metal oxides, Ruthenium oxide (RuO2) has been widely studied for its high ionic conductivity, excellent electrochemical reversibility and superior pseudocapacitive properties. However, it is significantly expensive from the practical applications point of view. On the other hand, activated carbon (AC) has been an attractive choice for electrochemical double layer supercapacitors due to its tailorable porosity and surface area, high electronic conductivity and low cost. In the current study, we examined the electrochemical behavior of nanocrystalline RuO2 against AC in an asymmetric configuration using a multivalent aqueous Ni(NO3)2 electrolyte with a purpose to understand the applicability of a multivalent and inexpensive Ni based electrolyte for charge storage in RuO2 electrodes. The electrochemical characterization of asymmetric RuO2/AC cells in 1M aqueous Ni(NO3)2 electrolyte revealed a maximum specific capacitance of 248 Fg−1 for RuO2 electrodes with a retention of 93.9% of its initial capacitance over one thousand cycles. These results demonstrated the viability of charge storage in RuO2 and AC electrodes using multivalent Ni2+ ion/electrolyte while shedding the light on possible changes in the crystallinity and surface chemistry of RuO2 electrode.