Electrochemical characterization of nanocrystalline RuO2 with aqueous multivalent (Be2+ and Al3+) sulfate electrolytes for asymmetric supercapacitors

Ruthenium oxide (RuO2) is one of the most investigated electrode materials due to its unique characteristics, such as high reversibility and high capacitance, etc. However, it has always been tested with univalent electrolyte systems for charge storage applications. In contrast, here, for the first time, we examined electrochemical characteristics of a nanocrystalline RuO2 using multivalent aqueous 0.5 M BeSO4 (pH-2.2) and 0.167 M Al2(SO4)3 (pH-2.8) electrolytes and then compared the performance with the data obtained using a commonly investigated univalent 0.5 M H2SO4 (pH-1.08) electrolyte. The asymmetric two electrode systems of RuO2 Vs. activated carbon (AC) showed maximum capacitances of 397 (at 3.12 Ag−1) and 189 Fg−1 (at 3.65 Ag−1) with Be2+ and Al3+ sulfate electrolytes, respectively, reflecting both the double layer and pseudo capacitance mechanisms for charge storage. These studies present an advantage of multivalent electrolytes for RuO2 based charge storage applications.