Cobalt hydroxide film on Pt as co-catalyst for oxidation of polyhydric alcohols in alkaline medium

Electrochemical behavior of chemically prepared Co(OH)2 film on Pt has been studied in alkaline medium using cyclic voltammetry and chronoamperometry. Amount of Co(OH)2 deposited increases linearly with the number of times of deposition. The deposit is of fibrous structure, as shown by scanning electron microphotograph. There is evidence of CoII/CoIII and CoIII/CoIV redox transitions during the cyclic potential scan. The former oxidation proceeds under diffusion control. The Co(OH)2 deposit acts as an efficient co-catalyst for anodic oxidation of ethanediol, propanediol and glycerol on Pt in alkaline medium. This is demonstrated by appreciable enhancement of the alcohol oxidation currents upon deposition of Co(OH)2 on Pt. Among the alcohols studied, the highest oxidation currents are obtained for ethanediol, both on Co(OH)2/Pt and bare Pt. Co(OH)2 alone also acts as a redox mediator for alcohol oxidation at more positive potentials.