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This work describes a two-step procedure for the electrochemical coating of reduced graphene oxide (RGO) and polypyrrole anthraquinone sulfonate (PPyAQS) onto an activated carbon cloth (ACC) by cyclic voltammetry (CV). The textile samples were characterized by CV, electrochemical impedance spectroscopy (EIS) and galvanostatic charge-discharge measurements using a sandwich-type (electrode/separator/electrode) cell designed to operate in three or two-electrode configurations. The presence of RGO onto the ACC surface optimized the electrosynthesis of PPyAQS and reinforced the stability of the polymer with the number of charge/discharge cycles. A retention capacity of 90% after 100 charge-discharge cycles together with an energy density of 7.8 × 10 −4  W h cm −2 at a power density of 1.8 × 10 −3  W cm −2 were obtained for the ACC/RGO/PPyAQS sample. The analyses by field emission scanning electron microscopy (FESEM) showed the RGO veils-like and PPyAQS glomerular structures covering the ACC-fibers. The Fourier transform infrared spectroscopy (FTIR) analyses not only detected the presence of PPy and AQS, but also, the changes in the molecular structure of PPyAQS, depending on its oxidation state, as consequence of the redox reactions occurred in the charge/discharge processes in the two-electrode cell. [ABSTRACT FROM AUTHOR]

A facile electrochemical route was applied to prepare polypyrrole (PPy)/anthraquinone sulfonate (AQS)/reduced graphene oxide (r-GO) composite. The as-synthesized composite showed an interconnected porous structure, which is related to the competitive relationship between two dopants. The cyclic voltammograms and electrochemical impedance spectra confirmed that the presence of highly conductive r-GO in PPy matrix ensured an efficient redox reaction obtained for redox-active AQS. As a result, the PPy/AQS/r-GO composite exhibited an enhanced specific capacity of 127.2 mAh g-1 with ca. 100% coulombic efficiency at 0.1 A g-1. Furthermore, the superior rate capability and cycling stability were also observed for PPy/AQS/r-GO, compared to AQS doped PPy. It is possible to adopt this co-dopants system for creating electro-active polymer materials with high capacities that are comparable to that of conventional inorganic intercalation electrode materials. [ABSTRACT FROM AUTHOR]

Abstract: We report the role of anthraquinone sulfonate dopants in promoting performance of electro-synthesized polypyrrole (PPy) composites for use in electrochemical supercapacitors. The incorporation of anthraquinone sulfonate species into the polymer matrix can significantly improve the surface area of PPy composites that are composed of submicron-/nano-sized particles, as evidenced from scanning electron microscopy (SEM) results. Cyclic voltammetry and galvanostatic charge–discharge measurements in 1M KCl solution reveal that these dopants result in an improved specific capacitance, a wide working potential range and enhanced long-cycle stability as compared to ClO4 − dopant. Among the samples investigated, the resulting PPy/AQS (9,10-anthraquinone-2-sulfonic acid sodium salt) composite exhibits the highest specific capacitance of 608Fg−1 at a scan rate of 5mVs−1 within a potential range between −0.9 and 0.5V (vs. saturated calomel electrode, SCE). [ABSTRACT FROM AUTHOR]

Abstract: A biosensor for amperometric determination of nitrite was developed using cytochrome c nitrite reductase (ccNiR) from Desulfovibrio desulfuricans immobilized and electrically connected on a glassy carbon electrode by entrapment into redox active [ZnCr-AQS] layered double hydroxide containing anthraquinone-2-sulfonate (AQS). The transduction step corresponded to the electro-enzymatic reduction of nitrite by immobilized AQS molecules at −0.6V. The biosensor showed a fast response to nitrite (5s) with a linear range between 0.015 and 2.35μM, a sensitivity of 1.8AM−1 cm−2 and a detection limit of 4nM. The apparent Michaelis–Menten constant () was 7.5μM. [Copyright &y& Elsevier]

• Electrocatalysis of O 2 reduction in solution often requires special electrode materials. • Our subtraction method allows electrochemical analysis with conventional GC/Pt RRDE. • Information about excess current and excess efficiency can be provided. • Upon rotation the excess current and electrocatalytic potentials are affected. The state-of-the-art procedure for investigating homogenous and heterogeneous electrocatalysts is cyclic voltammetry (CV). However, this technique usually requires an inactive electrode material. One common problem arising e. g. in studying the oxygen reduction reaction (ORR) is the significant background contribution to the overall ORR current provided by many carbon-based and metal-based electrode materials. Furthermore, rotating ring-disc electrodes (RRDEs) made of common materials like glassy carbon/platinum (GC/Pt) can be affected by overlapping reduction potentials on the disc. Interference from overlapping reactions on the ring might also occur, particularly in connection with oxygen reduction and hydrogen peroxide oxidation in ORR studies. We present herein a novel subtraction method which allows a semi-quantitative description of homogeneous electrocatalysts and helps to overcome the overlapping problems described above using anthraquinone-2-sulfonate (AQS) as a "case study material" for the ORR. [ABSTRACT FROM AUTHOR]