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Principle of the gas diffusion electrode. The principle of gas diffusion is illustrated in this diagram. The so-called gas distribution layer is located in the middle of the electrode. With only a small gas pressure, the electrolyte is displaced from this pore system. A small flow resistance ensures that the gas can freely flow inside the ...
Transport of Gases, p+ and e- in PEMFC. The PEM is sandwiched between two electrodes which have the catalyst embedded in them. The electrodes are electrically insulated from each other by the PEM. These two electrodes make up the anode and cathode respectively. The PEM is typically a fluoropolymer (PFSA) proton permeable electrical insulator ...
PEMFCs are built out of membrane electrode assemblies (MEA) which include the electrodes, electrolyte, catalyst, and gas diffusion layers. An ink of catalyst, carbon, and electrode are sprayed or painted onto the solid electrolyte and carbon paper is hot pressed on either side to protect the inside of the cell and also act as electrodes.
Methanol cross-over and/or its effects can be alleviated by (a) developing alternative membranes (e.g. [6] [7]), (b) improving the electro-oxidation process in the catalyst layer and improving the structure of the catalyst and gas diffusion layers (e.g. [8]), and (c) optimizing the design of the flow field and the membrane electrode assembly ...
A proton-exchange membrane, or polymer-electrolyte membrane (PEM), is a semipermeable membrane generally made from ionomers and designed to conduct protons while acting as an electronic insulator and reactant barrier, e.g. to oxygen and hydrogen gas. [1]
The oxidizing gas (e.g., pure O 2, O 2 in air, CO 2, etc.) percolates through a hydrophobic layer on the gas diffusion electrode, acting as a cathode. After the gas diffuses to the electrically conducting layer acting as an electrocatalyst (e.g., hydrophilic activated carbon), the gas is electrochemically reduced.
The two electrodes are separated by a porous matrix saturated with an aqueous alkaline solution, such as potassium hydroxide (KOH). Aqueous alkaline solutions do not reject carbon dioxide (CO 2) so the fuel cell can become "poisoned" through the conversion of KOH to potassium carbonate (K 2 CO 3). [2]
Anion exchange membranes are used in electrolytic cells and fuel cells to separate reactants present around the two electrodes while transporting the anions essential for the cell operation. An important example is the hydroxide anion exchange membrane used to separate the electrodes of a direct methanol fuel cell (DMFC) [ 1 ] or direct-ethanol ...