Hydrophobic porous catalytic membrane

Volkov et describe the use of porous polypropylene hollow fibre membranes loaded with palladium particles on the external surface, as dis-tributer/contactor membrane reactors for the catalytic removal of dissolved oxygen (DO) from water. Hydrophobic porous catalytic membrane serves three key functions ... 

An active, catalytic layer, comprising a three-dimensional porous structure composed of a mixture of hydrophilic carbon particles (Vulcan XC-72) supporting a finely dispersed catalyst, and a hydrophobic binder (PTFE). This layer faces the liquid side and can be visualised as being formed from many hydro-phobic channels (the route of the oxygen supply) and hydrophilic channels, required for the rapid removal of caustic released into the gap between the membrane and GDE. 

In polymer electrolyte membrane fuel cells, like in many other kinds of fuel cells, gas-diffusion electrodes are used. They consist of a porous, hydrophobic gas-diffusion layer (GDL) and of a catalytically active layer. The diffusion layers (often called backing layers) usually consist of a mixture of carbon black and about 35% by mass of polytetrafluoroethylene (PTFE) applied to a conducting base (most often a thin graphitized cloth). The GDLs yield a uniform supply of reactant gas... 

Considerable changes are needed in the anodic part of the membrane-electrode assemblies in order to accommodate the first two of the above-mentioned points. Instead of the porous gas diffusion layer that in polymer electrolyte membrane fuel cells ensures a uniform distribution of hydrogen across the surface, a gas-liquid diffusion layer that contains a set of hydrophilic as well as a set of hydrophobic pores is needed here. Through the hydrophilic pores, this layer must secure the unobstructed access of the aqueous methanol solution to the reaction zone and its uniform distribution. Through the hydrophobic pores, this layer must secure the unobstructed elimination of carbon dioxide, as the gaseous reaction product, from the reaction zone. Analogous changes must be made in the catalytically active anode layer of the membrane-electrode assemblies, where the gas is actually formed, and must be removed toward the gas-liquid diffusion layer. 

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