Carbon-polymer electrochemical systems and methods of fabricating them using layer-by-layer technology
One aspect of the invention provides ion-exchange and gas-diffusion membranes, fabricated by a layer-by-layer approach, for use, e.g., in electrochemical cells; a process for making membrane electrode assemblies fabricated using porous frameworks, LBL composite membranes and LBL carbon-Polymer electrodes; and the application of the membrane and electrode assemblies to a variety of devices, both electrochemical and otherwise.
1. A method of forming an electrically conductive membrane comprising:
sequentially depositing, under pH controlled conditions, a mixture of a colloid and a charged polymer on a surface to form a plurality of layers comprising a first layer and a second layer; wherein
the surface is a porous surface;
said first layer is deposited from a mixture of a first colloid and a first polymer selected from the group consisting of polyallylamine hydrochloride, polydiallyldimethylammonium chloride, poly(dimethylamine-co-epichlorohydrin), linear poly(ethyleneimine), and poly(aniline);
said second layer is deposited from a mixture of a second colloid and a second polymer selected from the group consisting of polyacrylic acid, polymethacrylic acid, polystyrene sulfonate, poly(2-acrylamido-2-methyl-1-propane sulfonic acid), oligoethylene glycol dicarboxylic acid, poly(styrene sulfonic acid-maleic acid), and poly(acryl-co-acrylamide acid);
said first colloid consists essentially of a carbon powder, a metal or a combination thereof; and
said second colloid consists essentially of a carbon powder, a metal or a combination thereof.
2. The method of claim 1 , further comprising the step of removing said electrically conductive membrane from said porous surface.
3. The method of claim 1 , wherein said porous surface is organic, semi-metallic or metallic.
4. The method of claim 1 , wherein said first polymer is selected from the group consisting of polydiallyldimethylammonium chloride, linear poly(ethyleneimine), and poly(aniline).
5. The method of claim 1 , wherein said second polymer is selected from the group consisting of polyacrylic acid, polystyrene sulfonate, poly(2-acrylamido-2-methyl-1-propane sulfonic acid), and poly(acryl-co-acrylamide acid).
6. The method of claim 1 , wherein said second polymer is poly(2-acrylamido-2-methyl-1-propane sulfonic acid).
7. The method of claim 3 , wherein said porous surface is selected from the group consisting of metal, carbon cloth, porous stainless steel, porous silicon, porous titanium alloys and gold.
8. The method of claim 1 , wherein said first polymer is poly(aniline).
9. The method of claim 1 , wherein said plurality of layers comprises a plurality of first layers and a plurality of second layers; and said first layers are deposited in an alternating fashion with said second layers.
10. The method of claim 1 , wherein said first colloid is made charged by said first polymer.
11. The method of claim 1 , wherein said second colloid is made charged by said second polymer.
12. The method of claim 1 , wherein the porous surface is conductive.