Carbon-neutral sustainable energy technology: Direct ethanol fuel cells

Ethanol is a sustainable, carbon-neutral transportation fuel. It is an ideal fuel source for direct oxidation fuel cells for portable and mobile applications, as it offers multiple advantages over hydrogen and methanol, including ease of transportation, storage and handling as well as higher energy density. Tremendous efforts have been made to improve direct ethanol fuel cells (DEFC) that use proton exchange membranes. This type of acid DEFC still exhibits low performance (the state-of-the-art peak power density is 96 mW cm^-2 at 90°C), despite employing expensive platinum-based catalysts. However, it has been recently demonstrated that the use of anion exchange membranes and non-platinum catalysts in DEFCs enables a dramatic boost in performance (the state-of-the-art peak power density can be as high as 185 mW cm^-2 at 60°C). This article provides an overview of both acid and alkaline DEFC technologies by describing their working principles, cell performance, system efficiency, products of the ethanol oxidation reaction, and cost. Recent innovations and future perspectives of alkaline DEFCs are particularly emphasized.