Membrane electrode assemblies electrochemical oxidation

The concept of the reversed fuel cell, as shown schematically, consists of two parts. One is the already discussed direct oxidation fuel cell. The other consists of an electrochemical cell consisting of a membrane electrode assembly where the anode comprises Pt/C (or related) catalysts and the cathode, various metal catalysts on carbon. The membrane used is the new proton-conducting PEM-type membrane we developed, which minimizes crossover. 

Fig. 1.6 Illustration of a planar-stack, solid-oxide fuel cell (SOFC), where an membrane-electrode assembly (MEA) is sandwiched between an interconnect structure that forms fuel and air channels. There is homogeneous chemical reaction within the flow channels, as well as heterogeneous cehmistry at the channel walls. There are also electrochemical reactions at the electrode interfaces of the channels. A counter-flow situation is illustrated here, but co-flow and cross-flow configurations are also common. Channel cross section dimensions are typically on the order of a millimeter.

The Membrane Electrode Assembly (MEA) is the core component of a PEFC, in which electric current is generated by anodic oxidation of the fuel which typically is hydrogen or methanol and cathodic reduction of the oxidant which typically is oxygen from the air. The MEA contains all electrochemically relevant interfaces at the anode and the cathode side. The central part of the MEA is formed by the... 

Palladium is more abundant in nature and sells at half the current market price of platinum. Unlike Pt, the Pd-based electrocatalysts are more active towards the oxidation of a plethora of substrates in alkaline media. The high activity of Pd in alkaline media is advantageous considering that non-noble metals are sufficiently stable in alkaline for electrochemical applications. Importantly, it is believed that the integration of Pd with non-noble metals (as bimetallic or ternary catalysts) can remarkably reduce the cost of the membrane electrode assemblies (MEAs) and boost the widespread application or commercialization of DAFCs [1]. Palladium has proved to be a better catalyst for alcohol electrooxidation in alkaline electrolytes than Pt [2]. Palladium activity towards the electrooxidation of low-molecular weight alcohols can be enhanced by the presence of a second or third metal, either alloyed or in the oxide form [3]. 

Rao V, Hariyanto H, Cremers C, Stimming U (2007) Investigation of the ethanol electro-oxidation in alkaline membrane electrode assembly by differential electrochemical mass spectrometry. Fuel Cells 7 417... 

Fuel cells are electrochemical cells where the chemical energy of the fuel was converted into electricity for power generation with high efficiency [1,2]. Industrial purified hydrogen and air are often used in fuel cells to eliminate any pollution or emission, which is known as proton exchange membrane fuel cells (PEMFCs). In a typical PEMFC, a steam of hydrogen is deUvered to the anode side of the membrane electrode assembly (MEA) [3,4], At the anode, it is catalyzed by platinum (Pt) and split into protons and electrons. This oxidation half-cell reaction is represented as follows ... 

Conventional fuel cell stack mainly comprises of (a) membrane electrode assemblies (MEAs) for achieving the electrochemical energy conversion process, (b) bipolar plates for the supply of reactant (fuel and oxidant) gases to MEAs in addition to providing cell to cell electronic conduction path and removal of heat and (c) auxiliary components for the reactant supply and product removal. Table 1 provides some of the essential differences between DMFC and micro fuel cell. 

Ciureanu M, Wang H (1999) Electrochemical impedance study of electrode membrane assemblies in PEM fuel cells I. Electro-oxidation of H2 and H2/CO mixtures on Pt based gas diffusion electrodes. J Electrochem Soc 146 4031—40... 

In planar fuel eells, the membrane is part of a layered sandwich structure (the membrane-eleetrode assembly) eonsisting of a thin eatalyst layer and a porous eleetrode (gas dilfusion layer) on either side of the membrane. The oxygen reduction and hydrogen oxidation reaetions take plaee at the eathode and anode catalyst layers, and the reaetants and produets are transported through the porous electrodes. A fuel eell model thus requires appropriate coupling of the membrane sub-model to the adjacent transport and electrochemical reactions. Detailed strategies for implementing complete fuel cell models have been discussed elsewhere [11-15]. 

---