Electrochemistry in Direct Methanol Fuel Cells

Abstract Direct methanol fuel cells (DMFCs) are being considered as one of the highly valued renewable energy sources, as evident from enormous work being carried out on the development of these devices over the past three decades. DMFCs are devices that directly transform the stored chemical energy of methanol into usable electrical energy. For this purpose, the fuel methanol gets oxidized at the anode of a DMFC, and oxygen gets reduced at the cathode in the presence of suitable electrocatalysts. Both the electrooxidation and electroreduction processes require involvement of protons and electrons. These electrode reactions, along with the transport of protons through the membrane electrolyte separator, are the backbone of DMFC operation, and the efficiencies of these phenomena are critical in the ultimate performance of the DMFC device. Keeping this in mind, this article has been completely dedicated to discussion and analysis of in‐depth fundamental electrochemistry involved within the membrane electrode assembly of DMFCs. In this regard, the involved electrochemical reactions in both acidic and alkaline media have been systematically described, with precise emphasis on the methanol oxidation reaction and the oxygen reduction reaction. In addition, the membrane characteristics and the mixed potential arising due to methanol crossover through the membrane have also been explained. Finally, the fundamental electrochemical aspects of DMFCs have been discussed systematically for easy understanding of the readers.