Electrochemical and morphological characterization of poly(12-pyrrol-1′-yl dodecanoic acid)

12-Pyrrol-1′-yl dodecanoic acid was prepared and electrochemically polymerized on ITO electrodes by three different methods. The electrochemical and morphological properties of poly(12-pyrrol-1′-yl dodecanoic acid) films were investigated by cyclic voltammetry, galvanostatic charge–discharge curves and AFM, which characteristics varied as function of deposition method. Films deposited by potentiodynamic and galvanostatic methods showed capacitive properties and are promising for application in polymeric capacitors.     

A voltammetric study of α- and β-hydroxides over nickel alloys

The hydrogen evolution reaction (HER) is one of the most studied electrochemical process due to the alternative energy conversion and the importance in some chemical process. The search for new electrocatalytic materials lead to investigate metals and alloys with particular characteristics/properties. This paper describes aspects of hydrogen adsorption and Ni-hydroxide formation over nickel alloys (SAF2205, INCONEL625 and MONEL400) utilizing cyclic voltammetry. The SAF2205 (6.4% Ni) alloy present behavior analogue to pure Ni electrodes to hydroxide species, and can bring some advantages to HER compared with the carbon steel (SAE1020) electrode commonly utilized in industrial process.     

Synthesis and characterization of poly[(R)-(−) and (S)-(+)-3-(1′-pyrrolyl)propyl-N-(3″,5″-dinitrobenzoyl)-α-phenylglycinate]s as chiral oligomers of pyrrole

Chiral polypyrrole oligomers were prepared from (R)-(?) (1) and (S)-(+)-3-(1′-pyrrolyl)propyl-N-(3″,5″-dinitrobenzoyl)-α-phenylglycinate (2) by oxidative polymerization in the presence of FeCl₃ as an oxidant. The new polymers were characterized by ¹H NMR, FTIR and UV–vis (λ_máx = 251 nm). TGA analyses of the corresponding polymers, poly1 and poly2, demonstrate an excellent thermal stability up to 204 °C, followed by two consecutive weight losses at higher temperatures. Relative number-average molecular weights of about 1.4 × 10³ and 2.3 × 10³, for poly1 and poly2, respectively, were measured by SEC, corresponding to oligomeric chains. Specific optical rotation measurements (c 0.1, THF) for poly1 [α]_D²⁰ = ?44 and poly2 ([α]_D²⁰ = +44) suggest that chirality is retained during the polymerization. Transversal section analysis of SEM images indicates the materials isolated right after the synthesis is highly porous.     

Energy loss in electrochemical diaphragm process of chlorine and alkali industry – A collateral effect of the undesirable generation of chlorate

Contamination of NaOH with chlorate constitutes a major problem for the chlorine–alkali industry, particularly when electrolytic cells based on the diaphragm process are employed. In this paper, pilot and laboratory cell experiments revealed that chlorate contamination in diaphragm cells also inhibits hydrogen evolution and gives rise to a significant increase in electrical energy consumption. Electrolysis carried out under conditions that simulated the industrial process (current density 240 mA cm⁻²; temperature 90 °C; brine flux 23 L cm⁻² h⁻¹) revealed that chlorate formation depends on brine flux and NaOH production. The inhibitory effect of chlorate on the main cathodic reaction was demonstrated in bench cell experiments, with cathodic displacement of the hydrogen evolution reaction by more than 100 mV in the presence of 0.4% chlorate compared with ideal conditions in which chlorate formation was absent. This hydrogen generation overpotential can charge the total electric energy balance in more than 5% of the total value, consisting of a critical loss for this process.     

Dual-type electrochromic device based on polypyrrole and polythiophene derivatives

A dual-type electrochromic device was assembled using optically transparent electrodes modified with thin films of poly[(R)-(-)-3-(1-pyrrolyl)propyl-N-(3,5-dinitrobenzoyl)-α-phenylglycinate], poly(DNBP) and poly(3,4-ethylenedioxy-thiophene), PEDOT and a polymer electrolyte. After assembling, the device was characterized by spectroelectrochemical techniques. The best performance of this device could be obtained by adjusting the relative thickness of the active polymer films and the potential range of operation of the device. The device shows color variation during ca. 350 charge/discharge cycles and can be constructed under atmospheric conditions.     

The effect of the conditions of electrodeposition on the capacitive properties of dinitrobenzoyl-derivative polypyrrole films

Films of poly[(R)-(−)-3-(1-pyrrolyl)propyl-N-(3,5-dinitrobenzoyl)-α-phenylglycinate] (polyDNBP) were deposited, using the galvanostatic method, onto indium tin oxide electrodes in the presence of the electrolytes tetrabutylammonium tetrafluoro-borate [(C₄H₉)₄NBF₄] or LiClO₄. Atomic force microscopy revealed that polyDNBP/(C₄H₉)₄NBF₄ films exhibited a grainy morphology with higher roughness and greater superficial area than polyDNBP/LiClO₄ films. Moreover, polyDNBP/(C₄H₉)₄NBF₄ films exhibited a higher capacitive electrochemical response when characterised in LiClO₄ rather than in (C₄H₉)₄NBF₄. Since polyDNBP films exhibit both n- and p-doping, they may have considerable potential application as electrodes in type III capacitor assemblies.     

Electrochemical polymerisation of thiophene derivative induced by Lewis acid: Electrosynthesis of poly[(R)-(−)-2-(3′-thienyl)ethyl-(3′,5″-dinitrobenzoyl)-α-phenylglycinate]

Films of poly[(R)-(−)-2-(3′-thienyl)ethyl-(3′,5″-dinitrobenzoyl)-α-phenylglycinate] were deposited on ITO electrodes by potentiodynamic, potentiostatic and galvanostatic methods using a (C₄H₉)₄NBF₄/CH₃CN electrolyte system containing 20% boron trifluoride diethyl etherate. Polymerisation occurred as a charge dependent process at a potential of 1.4 V vs. Ag/Ag⁺(CH₃CN). The surface morphologies of the films so-formed were examined using atomic force microscopy. The film deposited by the galvanostatic method displayed more homogeneous grain geometry and a larger superficial area than those formed by the other methods. Cyclic voltammetry revealed a well defined redox couple at the anodic region, attributable to polymer p-doping, and a poorly defined redox pair at the cathodic region, attributable to the reduction of the nitro group. The polymeric films obtained were yellow in colour (λ_max 425 nm) in the reduced state and light blue (λ_max 745 nm) in the oxidised state.