SYNTHESIS AND ELECTROCHEMISTRY OF CONDUCTIVE COPOLYMERIC PORPHYRINS

This work focuses on electrochemical synthesis and characterization of conductive porphyrinic polymeric and copolymeric materials and their application for electrocatalytic oxidation of methanol and hydrazine and reduction of oxygen directly to water. Conductive polymeric and copolymeric film have been obtained by oxidative electropolymerization of several free-base and metalated porphyrins (N,N'-bis[5-p-phenylene-10,15,20-tris(3-methoxy-4-hydroxyphenyl)porphyrin]-1,10-phenanthroline-4,7-diamide, H-2-(1,10-phen)(TMHPP)2; 5-P-(pyrrol-1-yl)phenylene-10,15,20-tris(3-methoxy-4-hydroxyphenyl)porphyrin, H-2(p-pyr)TMHPP; meso-tris(3-methoxy-4-hydroxyphenyl)(p-aminophenyl)porphyrin, H-2(p-NH2)TMHPP) and their respective analogues that contain p-tolyl substituents (TTPP) instead of 3-methoxy-4-hydroxyphenyl. Metaloporphyrins with zinc(II) and cobalt(II) have been studied. Studies present evidence to show that the copolymeric new materials can have significantly altered electrocatalytic properties. Copolymers of Zn(1,10-phen) (TMHPP)2 and Zn(p-NH2)TTPP show significant enhancement of catalytic process over their constituents. This was especially true for electrocatalytic oxidation of hydrazine and reduction of oxygen directly to water. Electrocatalytic reduction of oxygen directly to water was enhanced for all copolymers studied. The current density (0.8-1.1 mA/cm2) for methanol (5%) oxidation on polymeric and copolymeric porphyrins is 5-7 times higher than that observed on a platinum electrode.