Alcohol Crossover Behavior in Direct Alcohol Fuel Cells (DAFCs) System

Abstract

The alcohols (methanol, ethanol, and 1‐propanol) crossover behavior of through fuel cell membrane electrode assembly (MEA) in direct alcohol fuel cell (DAFC) system was studied. We divided five different factors which affect alcohol crossover behavior through MEA to analyze alcohol crossover behavior. Those are membrane effect, physical blocking effect of anode, alcohol oxidation effect of anode electrocatalysts, physical blocking effect of cathode, and alcohol oxidation effect of cathode. Among these five factors, the four factors caused by two different electrodes (anode and cathode) were evaluated by fabricating various types of MEA. In the case of alcohols through membrane without any electrode was increased when the cell temperature was raised from room temperature to 100 °C, but it was decreased above the cell temperature of 100 °C. Among the electrode effects on alcohol crossover rate, physical blocking effect of electrodes played dominant role below 100 °C. However alcohol oxidation effects of electrodes was predominant above the 100 °C.

The correlation of electrochemical and fuel cell results for alcohol oxidation in acidic and alkaline media

“…Organic alcohols are polar particles with a small size and can therefore be transported through these same channels, called as alcohol crossover. This phenomenon is strongly influenced by the cell temperature and a clear increase in values is observed with elevated temperatures for both acidic and alkaline membranes [225,226]. This is unfortunate because also the electrode reactions are enhanced at higher temperatures and therefore the cells are often operated at as high temperature as possible.…”

“…One method to hinder the alcohol crossover is to select larger alcohols as fuel components because their permeability is decreased especially at the low temperatures as observed for both PEMs [5,200,225] and AEMs [67,68]. Another method is to select thicker membrane materials for DAFCs (for instance Nafion 115 or 117) in comparison to PEFC with gaseous fuels (Nafion 112).…”

Polypyrrole‐Derived Fe−Co−N−C Catalyst for the Oxygen Reduction Reaction: Performance in Alkaline Hydrogen and Ethanol Fuel Cells

“…Thus, their application is primarily focused to portable and off‐grid power applications up to about 3 kW . These lower performances are mainly due to the slower kinetics of alcohol oxidation reactions compared to H 2 oxidation especially in acidic medium, and to the so‐called “crossover” problem, which is represented by the diffusion of the alcohol through the membrane from the anode to the cathode, where it is quickly oxidized . This causes a decrease of the cell performance due to the presence of mixed potentials, and to the poisoning of the Pt‐based cathode catalysts with CO intermediates…”

Hydrogen from electrochemical reforming of C1–C3 alcohols using proton conducting membranes

“…It is well-known in literature that Nafion membranes are permeable to alcohols[53,55,56]. For this reason DAFCs which operate at high current densities suffer from large cathodic overpotentials, caused by the blocking of the cathodic active sites by the alcohol molecules.…”