RuO2/Cysteine Nanocomposites for High-Performance Supercapacitors

RuO2/Cysteine (RuO2/Cys) nanocomposites were synthesized using a facile high-temperature hydrothermal method, with improved specific capacitance and good electrochemical durability. The advantage of using cysteine is that its molecule is rich in ligands such as carboxyl, sulfhydryl, and amino groups, which can be easily bound to hydrated RuO2, thus facilitating its effective dispersion. Analyses of its morphology, structure, and chemical composition showed that the incorporation of L-cysteine greatly inhibited the agglomeration of RuO2 and improved its dispersion, and the scale of RuO2 was reduced from the original micrometer scale to the nanometer scale. Such structures facilitated proton transfer and electron transfer, so RuO2/Cys nanocomposites showed significantly improved specific capacitance, up to 1221.7 F g(-1), and the energy density was up to 108.6 Wh kg(-1) with a power density of 400.2 W kg(-1) at 1 A g(-1) in a 0.5 M H2SO4 electrolyte. The combination of L-cysteine with RuO2 also effectively prevented the deformation of RuO2 in the redox process, and the capacitance retention rate was increased to 87.7% compared to 48.8% of pristine RuO2 after 10,000 charging-discharging cycles. High capacitance performance and improved cyclic stability enable RuO2/Cys nanocomposite to be a favorable electrode material for wide applications in energy storage.