The capacitive performance of activated carbon–ruthenium oxide composites for supercapacitors: effects of ultrasonic treatment in NaOH and annealing in air

The utilization of electrode materials could be greatly promoted by the employment of a mesh-type stainless steel (SS) current collector in comparison with a plate-type one. The capacitive behavior of activated carbon (AC) and AC–ruthenium (AC–Ru) composites fabricated by the wet impregnation were systematically investigated in 0.1 M H2SO4 by cyclic voltammetry (CV) and chronopotentiometry (CP). The specific capacitance of AC reached a maximum (ca. 117 F g−1) through a combination of the impregnation of ruthenium precursors and the chemical conversion of the chloride precursors into hydroxides in an ultrasonic bath of NaOH for 30 min (AC–Ru(OH)x). The stability of AC–Ru(OH)x composites was greatly promoted by annealing in air at 240 °C although a significant loss in total capacitance was found. The crystalline information and chemical environment of the impregnated oxy-hydroxyl-Ru species with annealing was, respectively, obtained from the X-ray diffraction (XRD) patterns and X-ray photoelectron spectra (XPS). The specific surface area and pore size distribution of these composites were analyzed by the Brunauer–Emmett–Teller (BET) method.