Electropolymerization of pyrrole on a tantalum electrode

Electrically conducting samples of polyaniline (PANI) were prepared by doping with dodecylbenzene sulfonic acid (DBSA) using a thermal doping method without the application of shear. Besides characterizing the samples using optical microscopy, SEM, UV-vis-NIR, the degree of doping and the electrical conductivity were also measured. The pure PANI powder consisted of aggregates of PANI particles and was non-conducting. In the shear-free thermal doping of the PANI/DBSA mixture, the original aggregates were progressively broken up into smaller pieces with increasing temperature while maintaining the original primary particle shape and size and which were dispersed rather uniformly in the DBSA matrix. The electrical conductivity of doped PANI increased with increasing doping temperature. This increase strongly mirrored the increase in the levels of DBSA directly associated with PANI and suggested that the increasing levels of PANI doping were directly responsible for the increase in electrical conductivity as a function of the doping temperature. Despite the absence of the absorption peak at around 800 nm, the sample absorbed strongly in the near-infrared. Moreover, PANI/DBSA samples possessing a higher ratio of absorbance at 2600 nm to that at 800 nm showed higher electrical conductivity. These results suggest that shear-free thermal doping provides a simple route to controlling the morphology of the mixture by enabling the disintegration of the micron scale aggregates present in the as-purchased PANI. This in turn can be used to control the degree of doping of the PANI and consequently the conductivity of the sample.

Section: Introductionmentioning

confidence: 99%

Effect of processing temperature on thermal doping of polyaniline without shear

Goto

Asanuma

Takahashi

et al. 2011

Formation of PPy/Ta₂O₅/Ta structure by electropolymerization

Park¹,

Takeoka²,

Yamamoto³

et al. 1992

Electropolymerization of pyrrole on tantalum (Ta) electrodes was carried out in buffer solutions (0.04 M phosphoric acid, 0.04 M acetic acid, 0.04 M boric acid and 0.2 M sodium hydroxide) containing 0.1 M sodium ptoluenesulfonate (TsONa) under galvanostatic conditions and it was found that a polypyrrole (PPy) and a tantalum oxide (Ta2O5) layer are formed on a Ta electrode by an electrochemical oxidation process. The conditions of this simultaneous formation were studied in respect to current density (id), pyrrole concentration ([Py]), pH and the amount of electricity. Under certain conditions ([Py] = 0.25 M, pH = 1.8, id = 10–20 mA cm−2, the amount of electricity = 1 C), 6–8 μm thick PPy films were efficiently formed on homogeneous 30–50 nm thick Ta2O5 layers. The PPy film showed a high electrical conductivity (110 s cm−1), adhered well and covered the Ta2O5 layer. The resulting PPy/Ta2O5/Ta system is therefore proved to have excellent properties as a capacitor.

Oxidation of a PPy‐modified tantalum electrode

Park

Yamamoto

Takeoka

et al. 1993

A tantalum electrode on which polypyrrole (PPy) had been previously formed by electropolymerization was galvanostatically electrolyzed in an aqueous solution of 0.02 wt% phosphoric acid. This process contains the irreversible oxidation of a PPy film, the decomposition of solvent, and the formation of Ta,O, by the reaction of O H -coming through the PPy film, with Ta electrodes. A three layer-structure (PPy/Ta,O,/Ta) was confirmed by electron spectroscopy for chemical analysis (ESCA). A PPy film confaining CIO; as dopant [PPy(ClO;)l was significantly deteriorated in comparison with PPy(Ts0 -) at the electrolysis. Therefore, the (PPy(Ts0 -)/Ta,O,/Ta) system showed better electrical characteristics as a capacitor than the (PPy(CIO;)/Ta,O,/Ta) system.