Polyaniline/12-phosphotungstic acid/V2O5 nanocomposite and its platinum analog as oxygen reduction electrocatalysts

Abstract

A guest-host nanocomposite based on electroconducting polyaniline doped with 12-phosphotungstic acid and V 2 O 5 as well as its bifunctional analog containing not more than 5 mass % nanosized platinum were obtained. A study was carried out on the structure of these nanocomposites, their redox characteristics, and electrocatalytic activity in the reduction of oxygen. These nanocomposites were found to display catalytic properties in the electrochemical reduction of oxygen, while the presence of even a slight amount of nanosized platinum in the bifunctional composite leads to a significant increase in its electrocatalytic activity.A major precondition for conversion to hydrogen power is the development of reliable and inexpensive fuel cells (FC). Present FC are technically on the threshold of commercialization although their common use is being hindered by the high cost of the required equipment, primarily due to the use of platinum or other noble metal catalysts. In addition to the high cost of platinum, we should also note the limited supply of this metal and the high sensitivity of platinum catalysts toward traces of CO and sulfur compounds, which reduces the lifetime of FC. The commercialization of FC is closely related to the search and development of new methods to generate efficient and available electrocatalysts, whose cost would be reduced by minimizing or even eliminating the noble metals and which would function for long periods in aqueous electrolytes in a broad pH range. The development of efficient catalysts for the reduction of oxygen is important not only for FC but also for advancing many other fields such as metal-air chemical power sources and electrosynthesis.Organic electroconducting polymers (ECP) and composites derived from these materials, which possess a broad range of unique properties, are among the new generation of functional materials attracting recent attention [1][2][3][4][5][6][7]. The redox activity and high electrical conductivity characteristic for ECP account for the special interest in the electrochemical aspects of using such materials, in particular, for the development of chemical power sources, energy transformation systems, supercondensers, electrochemical sensors, and electrocatalysts [2][3][4]7]. Podlovchenko [4] and Barsukov [8] have discovered that polyaniline (PAN), polypyrrole, and other ECP may display electrocatalytic properties in the reduction of oxygen (RO), which is a precondition for the use of these materials in the development of electrocatalysts for this reaction. The use of specific dopants for PAN or polypyrrole, namely, Keggin heteropolyacids (HPA), has been proposed to raise the efficiency of polymer electrocatalysts for RO [9,10]. The molecular dispersion of catalytically active particles known as Keggin units in the ECP matrix, which is formed in this case, tends to enhance the catalytic activity of these materials in RO in comparison with ECP with the traditional dopants. 3340040-5760/07/4305-0334

Electrocatalytic properties of polyaniline–TiO2 nanocomposites

“…It was found earlier [6,7] that three-component nanocomposites are based on CPs (PAni or PPy), HPA and V 2 O 5 -CP HPA/V 2 O 5 , and their bifunctional analogues. Nanosize platinum containing CP HPA/V 2 O 5 /Pt single material and the properties of both CP HPA/V 2 O 5 and CP/ Pt composites show high electrocatalytic activity in ORR which is due to nanostructuring and interaction between the components.…”