Properties of composite membranes prepared from ion exchange membranes and conducting polymers. II. Electrical potential generation from cell composed of a cation exchange membrane-polypyrrole composite membrane and a ferric ion form cation exchange membrane

Abstract

When a ferric ion form cation exchange membrane was immersed in an aqueous pyrrole solution, polypyrrole was formed on the membrane surfaces and ferric ions in the membrane were reduced to ferrous ions. Polypyrrole layers penetrated into the membrane matrix with increasing immersion period in the pyrrole solution. An electrical potential was observed by clamping the obtained composite membrane and the ferric ion form cation exchange membrane between two platinum plates and immersing the assembly into pure water. The potential was measured in relation to polymerization period. Before homogeneous distribution of polypyrrole in the membrane (4 hr), which was confirmed by conductivity measurement, an initial potential in discharge decreased and durability of the potential increased with increasing polymerization period. Beyond 4 hr of polymerization in the synthesis of the composite membrane, the initial potential on discharge attained almost a constant value and its durability decreased with increasing polymerization period in spite of increase in electron conductivity and the amount of ferrous ions in the composite membrane. It is thought that migration of ferrous ions in the composite membrane would be restricted because of a development of a tight and rigid polypyrrole structure in the cation exchange membrane.