Decrease In Electroactivity Research Articles

Effect of CeO2 Presence on the Electronic Structure and the Activity for Ethanol Oxidation of Carbon Supported Pt

Pt/CeO2/C electrocatalysts in different compositions were prepared and their structural characteristics and activities for ethanol oxidation in alkaline media were evaluated. In the presence of CeO2, an increase in the platinum particle size was observed. XANES measurements indicated that the Pt d-band vacancies increased with increasing CeO2 amounts. For the first time, the decrease in electro activity was described to an electronic effect for high CeO2 contents. The dependence of the activity for ethanol oxidation on CeO2 content went to a maximum, due to the counteracting bifunctional and electronic effects of the metal oxide.

Phenothiazine Redox Active Conducting Polymer Films at Nanocomposite Surfaces

A redox active polymer based on phenothiazine (thionine) doped poly (3,4-ethylenedioxythiophene) PEDOT film was examined on a range of transducers (glassy carbon, Pt and screen printed electrodes). This was followed by investigations into the use of super activated carbon (SAC) and platinized super activated carbon (SAC-Pt) nanostructured electrode modifiers for enhanced polythionine/PEDOT film deposition. The Polythionine/PEDOT film was found to undergo a two-electron, two-proton (pH 1–4) or a two-electron, one-proton process (pH 4–8). Electrochemical investigations included scan rate studies confirming the surface confined behavior, with the most stable films (15% decrease in electroactivity) being evident at SPE modified with SAC-Pt—surface coverage (Γ) 1.16 × 10−10 mol cm−2. Surface morphology of the formed film was investigated via SEM/EDX and film hydrophobicity examined via contact angle measurements.

Enhanced electrochemical response of solution-deposited n-doping polymer via cocasting with ionic liquid

A novel cocasting approach is presented for improving electroactivity of solution-cast films of conducting polymers. Solutions of the n-doping polymer poly(benzimidazobenzophenanthroline) (BBL) were co-deposited with the ionic liquid electrolyte 1-ethyl-3-methyl-imidazolium bis(trifluoromethylsulfonyl)imide (EMIBTI). The resultant co-continuous mixture yielded highly porous polymer films (CC-BBL) upon removal of solvent and EMIBTI. Electrochemical quartz crystal microgravimetry revealed that the n-doping process in neat ionic liquid is anion-dominant, which is contrary to what is observed in dilute electrolyte solutions. The CC-BBL films exhibit a thirty-fold increase in initial current response and capacity relative to non-cocast BBL films. While current response and capacity of the non-cocast BBL improve with cycling, they level out after 800 cycles at 35% of those of the CC-BBL. CC-BBL shows high n-doping stability; no decrease in electroactivity is seen after 1000 cycles. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012

Impedance study of thiolated polyaniline

Covalent attachment of thiolated probes to conducting polymers such as polyaniline (PANI) is a promising approach towards the development of electrochemical sensors and biosensors. However, thiolation alters the conjugated polymer backbone and influences the electrochemical behavior of the conducting polymer. PANI studied in this work was electropolymerized on glassy carbon (GC) electrodes from a solution of 0.1 M aniline in 0.5 or 1.0 M H2SO4. The GC/PANI electrodes were then functionalized by covalent attachment of 2-mercaptoethanol to the PANI backbone. The progress of thiolation was studied by cyclic voltammetry and electrochemical impedance spectroscopy (EIS). Thiolation of PANI was found to cause an initial decrease in electroactivity at 0–0.25 V and an increase in electroactivity at 0.25–0.6 V. However, prolonged thiolation caused a loss of electroactivity of PANI, which could be seen from EIS measurements as a dramatic decrease in the bulk redox capacitance of PANI.

On the behaviour of doped SnO 2 anodes stabilized with platinum in the electrochemical degradation of reactive dyes

In this paper the electrochemical characterisation of Ti/SnO 2–Sb–Pt anodes prepared by thermal decomposition is researched using different techniques. These results were also compared to those obtained for the Ti/SnO 2, Ti/SnO 2–Sb and deactivated Ti/SnO 2–Sb–Pt anodes. SECM technique confirmed the increase of electroactivity observed with the antimony doping and a little amount of platinum. In contrast, deactivated Ti/SnO 2–Sb–Pt anodes showed a drastic decrease in electroactivity. SEM and EDX analyses were also employed to evaluate the differences observed among these anodes. These results corroborated the high service life of Ti/SnO 2–Sb–Pt anodes being very useful for wastewater treatment. COD, HPLC, UV–vis and potential control measurements were also used to verify the viability of these anodes to degrade and decolourise wastewater solutions containing a reactive dye: C.I. Reactive Orange 4. With this purpose, different oxido-reduction electrolyses were carried out in presence of either 0.1 M Na 2SO 4 or 0.1 M NaCl as electrolyte. Although the use of NaCl gave the best results in decolourisation rate, the oxidation efficiency was practically the same independently of what type of electrolyte was used. It was also found that treated solutions presented oxidation-resistant intermediates as final products in all cases.

Effect of thermal treatment on the electroactivity of polyaniline

A series of polyaniline films have been coated on electrodes by chemical and electrochemical means in order to investigate the thermal stability of the electroactivity in air and nitrogen atmospheres. Polyaniline was also synthesized chemically and cast as a membrane (thick film). It was found that the electroactivity and conductivity of the films was stable up to 150°C. Exposure to higher temperatures leads to a decrease in electroactivity and conductivity, although use of a nitrogen atmosphere had less effect on the properties. Thermogravimetric analysis profiles confirmed that the polymer was stable to above 350°C. The changes in the electroactivity may be attributed to morphological (annealing) effects in the polymer and to loss of moisture and dopant ions.