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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 ...
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.
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 ...
The process of permeation involves the diffusion of molecules, called the permeant, through a membrane or interface. Permeation works through diffusion; the permeant will move from high concentration to low concentration across the interface. A material can be semipermeable, with the presence of a semipermeable membrane. Only molecules or ions ...
This is done in a configuration called an electrodialysis cell. The cell consists of a feed (dilute) compartment and a concentrate compartment formed by an anion exchange membrane and a cation exchange membrane placed between two electrodes. In almost all practical electrodialysis processes, multiple electrodialysis cells are arranged into a ...
where i T,∞ is the diffusion-limited current, n is the number of electrons transferred at the electrode tip (O + ne − → R), F is Faraday's constant, C is the concentration of the oxidized species in solution, D is the diffusion coefficient and a is the radius of the UME disc. In order to probe a surface of interest, the tip is moved ...
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 fuel cell (DEFC). Poly(fluorenyl-co-aryl piperidinium) (PFAP)-based anion exchange materials (electrolyte membrane and electrode binder) with high ion conductivity and durability under ...
In the cases of gas separations, pervaporation, membrane distillation, reverse osmosis, nanofiltration, ultrafiltration, and microfiltration separations, the concentration profile has a higher level of solute nearest to the upstream membrane surface compared with the more or less well mixed bulk fluid far from the membrane surface.