Catalytic electro-oxidation of hydrazine on phthalocyanines deposited on graphite electrodes

The catalytic properties phthalocyanines of Fe, Co, Ni and Cu for the electro-oxidation of hydrazine have been examined. The metal chelates were deposited on ordinary pyrolytic graphite electrodes and their redox properties were studied by cyclic voltammetry. The catalytic activity was found to decrease as follows: FePc > CoPc > CuPc ～ NiPc > graphite.The kinetics of the process with Fe-Pc and Co-Pc were examined. Tafel slopes of 40 mV for Fe-Pc, and of 60 m V for Co-Pc were obtained. The chemical order in N₂H₄ is 1 both complexes. The order in OH^? is 2 for Fe-Pc and 1 for Co-Pc. With Fe-Pc, the transfer of a second electron seems to be rate determining. With Co-Pc, a slow chemical step preceded by a fast one-electron transfer seems to operate.