Electropolymerization of iron phenanthrolines and voltammetric response for pH and application on electrocatalytic sulfite oxidation

Polymerization from the complexes of iron(II) tris(1,10-phenanthroline) can be initiated by electrochemical reduction between pH 2 and 7 in aqueous solution to produce stable and electrochemically active films on both glassy carbon electrodes and transparent semiconductor indium oxide electrodes. Some of the other complexes of iron(II) tris(5-chloro-1,10-phenanthroline) and iron(II) tris(5-methyl-1,10-phenanthroline) can also produce polymer films in aqueous solution. Iron(II) tris(5-NH2-1,10-phenanthroline) in a non-aqueous solution can produce a polymer film which is stable in acidic and basic aqueous solution when transfered to a weak acidic aqueous solution and electrochemically oxidized and shows similar properties to the former films. Electroreduction and then electrooxidation of the monomer of iron(II) phenanthrolines in aqueous solution leads to the adherence of a polymeric film on a glassy carbon electrode or an indium oxide electrode. There are higher electrode surface coverage and polymerization rates at pH 4.0 and 3.0 than at the more acidic or basic buffer solutions of pH 1.7 and 6.0. The density of the surface coverage on the glassy carbon electrode surface is approximately 1 x 10(-9) to 3 x 10(-9) mol cm(-2). The electrode surface coverage Gamma increases quickly over the first 10 scans, then the coverage rate slows and becomes a constant after about 50 scans. The polymeric films were obtained with a formal potential and responded between pH 1 and 14 with a slope of -60 mV (pH)(-1). The polymer film from iron(II) tris(5-NH2-1-10-phenanthroline) can perform the electrocatalytic oxidation of sulfite to sulfate in pH 2.0 aqueous solution.