Kinetics and Mechanism of Anodic Oxidation of n-Butanol by Nickel Peroxide

Abstract

A detailed mechanism of indirect oxidation of n-butanol by using NiO(OH) as the mediator has been proposed. After NiO(OH), a kind of nickel peroxide, abstracts a hydrogen atom from n-butanol to form RC•HOH free radical, indirect and direct oxidation paths may occur, and the indirect oxidation path is preferred to the direct electrooxidation path. From the theoretical analysis, when the applied potential is lower than 0.550 V (vs Ag/AgCl), the apparent current shows first-order dependence on both the hydroxide ion and n-butanol concentrations, i.e., i = where β is the roughness factor of the working electrode, k 2 is the rate constant in the rate determining step, (S) is the total active site, i.e., the summation of Ni(OH)2 and NiO(OH), is the forward standard rate constant, and is where is the backward standard rate constant for the electrochemical step; f equals F/RT. Combining the electrochemical kinetic analysis and BET result, is about 0.696 cm3/mol s. The theoretical analysis correlates the experimental results well. At higher potential, the magnitudes of hydroxide and n-butanol in the rate equation reduce because oxygen evolution increases.

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