Poly-porphyrin electrocatalytic films obtained via new superoxide-assisted electrochemical deposition method

Abstract

We present electrocatalytic films of ClFe(III)5,10,15,20-tetrakis(p-aminophenyl) porphyrin (FeClT(p-NH2Ph)P) formed by new electrochemical deposition method using oxygen saturated dimethyl sulfoxide solutions (DMSO) as a medium. Superoxide promotes the poly-porphyrin film formation on the working electrode surface due to it high affinity both to hydrogen atom and to proton. The most favorable pathway of the superoxide-assisted electrochemical polymerization is proposed. The resulting poly-FeClT(p-NH2Ph)P films are smooth, golden colored, well adhesed with substrate and quite insoluble in water, ethanol and dichloromethane. The film formation accompanied with broadening and red-shifting of the Soret band. Atomic force microscopy (AFM) investigation shows homogeneity, low roughness and nanoscale globular structure of the poly-FeClT(p-NH2Ph)P films. Electrocatalytic activity of obtained films was tested for electroreduction of oxygen in alkaline media. The current of oxygen electroreduction is increased and oxygen electroreduction onset is shifted to the positive about 0.14V in the presence of poly-FeClT(p-NH2Ph)P film. The stability of the poly-FeClT(p-NH2Ph)P film was tested under oxygen electroreduction conditions. It was found that for >20cycles the oxygen electroreduction parameters were unchanged. The modified electrodes removed from the electrochemical cell had the same view as before testing.