Oxidation of propenol on nanostructured Ni and NiZn electrodes in alkaline solution

Oxidation of propenol on nanostructured pulse plated Ni and NiZn alloys in alkaline solution gives the corresponding aldehyde, propenal, as the major product. The process is redox mediated by the NiOOH/Ni(OH)2 couple and starts as soon as NiOOH is formed on the surface. Depending on the applied potential, propenol oxidation takes place in parallel with water oxidation. The latter requires a higher surface concentration of NiOOH compared to propenol oxidation, indicating that a binuclear mechanism for oxygen evolution prevails at low overpotentials. The redox reaction of nickel oxide is markedly slower at the NiZn alloy than for solid Ni or pulse plated Ni, which also is reflected in the oxidation of water and propenol. Separation of all three oxidation currents (Ni(OH)2, water and propenol) shows that pulse plated Ni is more efficient as catalyst than NiZn per NiOOH site, for both water and propenol oxidation. The role of Zn ions in the mixed NiZn hydroxide is discussed and a mechanism for propenol oxidation is suggested.