25 - Topics on the fundamentals of the alcohol oxidation reactions in acid and alkaline electrolytes

Abstract

Oxidation of alcohols, especially electrochemical oxidation, is one of the most important reactions for studies on energy and fuel. Studies in this area have increased further with the advance of fuel cells, and it will remain important so long as the search for alternative energy sources for oil and other fossil fuels continues. The pH value of the environment in which the reaction takes place is as important as the alcohol and electrode types used in oxidation reactions of alcohols. Studies in this area are carried out in both acidic and basic environments. The alcohols most commonly used in studies are methanol and ethanol; however, isopropanol and butanol are also used. Among the various electrodes, platinum (Pt) has the best effectiveness. However, it also has disadvantages—namely, its high cost and the fact that its effectiveness gets reduced as a result of electrode poisoning by absorbing carbon monoxide (CO) on the surface. In recent years, studies have been made about the search for an alternative electrode to Pt. In these studies, catalysts formed by mixing similar metals with Pt in different proportions are made on Pt-free catalysts, carbon-supported catalysts, and catalysts created by combining different metals. Apart from the elements that make up the catalyst, compatibility with the reaction, working environment, and the species to be released are also very important in terms of catalyst selection and design. In this chapter, oxidation reactions in the acidic and alkaline electrolyte media of methanol, ethanol, and isopropanol (the most commonly used alcohols in alcohol oxidation reactions) are described. In addition, the advantages and disadvantages of acidic and alkaline environments are compared.