Efficient oxidation of hydrazine using amine-functionalized cobalt and nickel porphyrin-modified electrodes

The meso-tetra(para-aminophenyl) porphyrinatocobalt(II) (Co(II)MTpAP) and meso-tetra(para-aminophenyl)porphyrinatonickel(II) (Ni(II)MTpAP) were self-assembled on a glassy carbon electrode (GCE) and were utilized for the oxidation of hydrazine. The oxidation of hydrazine at the self-assembled monolayers (SAMs) of Co(II)MTpAP and Ni(II)MTpAP occurred at ?0.20 and 0.42 V, respectively. When compared to the SAM of Ni(II)MTpAP, Co(II)MTpAP SAM not only decreased the overpotential of hydrazine oxidation but also enormously increased its current. The oxidation of hydrazine was influenced by pH. While increasing the pH, the oxidation potential of hydrazine was shifted towards a less positive potential. Further, an inverted shape cyclic voltammogram (CV) was observed for the oxidation of hydrazine at Co(II)MTpAP-modified GCE, whereas a normal CV curve was observed at Ni(II)MTpAP-modified GCE. The appearance of the inverted shape peak for hydrazine oxidation at the SAM of Co(II)MTpAP is due to the oxidation of axially ligated hydrazine molecules during the reverse potential scan. The hydrazine oxidation was also performed at amine-functionalized cobalt and nickel phthalocyanine-modified electrodes in order to study the influence of a macrocyclic ring. Irrespective of the macrocyclic ring, an inverted shape CV was observed at cobalt phthalocyanine-modified electrode.