Pseudocapacitance of chemically stable MnO2-NiO mixture layer on highly conductive Sb doped SnO2 nanowire arrays

We report the electrochemical properties of MnO2–NiO mixture layer that is coated on highly conductive SnO2 nanowires. In this study, the effect of the nanowire conductivity and coating composition on the pseudocapacitic performance was systematically examined. To control the electric conductivity of the nanowire, Sb was doped into SnO2 during vapor–liquid-solid (VLS) process. Subsequently, pure or NiO added MnO2 layer was electrochemically deposited on SnO2 nanowire arrays. Structural studies show that the electrodeposition layer uniformly and conformally covered the nanowires. Low concentration Sb doping (up to 5 at%) increases the electric conductivity of the nanowires which work as an electron transport layer of the pseudocapacitor. Electrochemical studies indicate that the addition of NiO to MnO2 promotes a charging/discharging process through Faraday reaction by changing the oxidation mechanism of MnO2. These results guide a design of the metal oxide mixture for the pseudocapacitor application.