Introduction
Significant efforts in recent decades have been focused on the direct electrochemical oxidation of alcohol and hydrocarbon fuels. Organic liquid fuels are characterized by high energy density, whereas the electromotive force associated with their electrochemical combustion to CO2 is comparable to that of hydrogen combustion to water [1–3]. Among the liquid organic fuels, methanol has promising characteristics in terms of reactivity at low temperatures, storage and handling. Accordingly, a methanol-feed proton exchange membrane fuel cell (PEMFC) would help to alleviate some of the issues surrounding fuel storage and processing for fuel cells. Technological improvements in DMFCs are, thus, fuelled by their perspectives on applications in portable, transportation and stationary systems especially with regard to the remote and distributed generation of electrical energy [4, 5]. Methanol is cheap and can be distributed by using the present infrastructure for liquid fuels. It can be obtained from fossil fuels, such as natural gas or coal, as well as from sustainable sources through fermentation of agricultural products and from biomasses. Compared with ethanol, methanol has the significant advantage of high selectivity to CO2 formation in the electrochemical oxidation process [1–3]. However, despite these practical system benefits, DMFCs are characterized by a significantly lower power density and lower efficiency than a PEMFC operating with hydrogen because of the slow oxidation kinetics of methanol and methanol crossover from the anode to the cathode.