Solid polymer electrolysis

Solid Polymer E,kctroljte. The electrolyte in soHd polymer electrolyte (SPE) units is Nafion, a soHd polymer developed by Du Pont, which has sulfonic acid groups attached to the polymer backbone. Electrodes are deposited on each side of the polymer sheet. H" ions produced at the anode move across the polymer to the cathode, and produce hydrogen. The OH ions at the anode produce oxygen. These units have relatively low internal resistances and can operate at higher temperatures than conventional alkaline electrolysis units. SPE units are now offered commercially. 

Fuel cells (hydrogen-oxygen, hydrogen-air, methanol-air) and industrial electrolysis (water, chlor-alkali) using ion-exchange membranes are the most demanding applications for the membranes. In these apphcations, the membranes have often been designated as SPE, which can be read as solid polymer electrolyte or solid... 

Nuttall L.J., Conceptual design of large scale water electrolysis plant using solid polymer electrolyte technology, Int.. Hydrogen Energ., 2,395-403,1977. 

Han SD, Park KB, Rana R, Singh KC (2002) Developments of water electrolysis technology by solid polymer electrolyte. IndJChem 41 A 245-253... 

Paddison SJ (2003) Proton conduction mechanism at low degrees of hydration in sulfonic acid-based polymer electrolyte membranes. Ann Rev Mater Res 33 289-319 Rasten E, Hagen G, Tunold R (2003) Electrocatalysts in water electrolysis with solid polymer electrolyte. Electrochimica acta 48 3945-3952... 

Water electrolysis using solid polymer electrolytes. 

In the case of a-methylstyrene with a high ceiling temperature of the polymerization, trimer or tetramer were produced in the solution at room temperature, and after electrolysis for a desired time the cell was brought into a dry ice-methanol bath in order to complete polymerization. Yields of polymer of high molecular weight were almost quantitative. The colored solution at the cathode did not distribute to the anode side through the sintered glass disk over a few hours. In the anodic solution no solid polymer was observed. 

Notably, advances in the direct, safe and continuous synthesis of neutral H202 solutions with concentrations of up to 8 wt% from 02 and water have been reported recently [64] using an improved electrolysis method involving a solid-polymer electrolyte (SPE). The formation and accumulation of neutral H202 were strongly... 

See color insert following page 140.) The process of electrolysis can use liquid or solid electrolyte. (a) Liquid electrolyte, (b) Solid polymer membrane electrolyte (SPE). 

In proton exchange membrane (PEM) or solid polymer electrolyte (SPE) electrolysis, the electrolyte is replaced by an ion-exchange resin. These units are compact, provide high current densities, but are more expensive, and because of the corrosive nature of the electrolyte, require special construction materials. 

Two cases were examined for the production of water electrolysis. Data were taken from Reference (1) and adjusted to mid-1979 levels in accordance with Table 1. The costs of "current technology" electrolysis were averaged in Reference (1) from information provided by Lurgi, Electrolyser Corp., General Electric, and Teledyne Isotopes. An advanced electrolyzer design, based upon the General Electric Solid Polymer Electrolyte (SPE) design, was also addressed as the second case. 

Nuttall, L. J., "Water Electrolysis Using Solid Polymer Electrolytes", General Electric Co., Presented at the Institute of Gas Technology s "Hydrogen for Energy Distribution Symposium", July 24-28, 1978. 

The solid polymer electrolyte is a solid plastic material which has ion exchange characteristics that make it highly conductive to hydrogen ions. The particular material that is used for the current electrolysis cells is an analogue of TFE teflon to which sulfonic acid groups have been linked. This plastic sheet is the only electrolyte required, there are no free acidic or caustic liquids, and the only liquid used in the system is distilled water. 

Alternative solid polymer electrolytes are also being evaluated to assess advantages in cost and performance. The Nafion 120 is an extremely stable (and thus long-lived) material under water electrolysis operating conditions. Any alternative SPE considered viable must have equivalent life stability. A radiation-grafted tri-fluorostyrene was extensively evaluated, but demonstrated insufficient operational stability to be considered as a viable alternative. The search for other alternatives is continuing. 

Russell, J.H., Sedlak, Dr. J.M., General Electric Company, Direct Energy Conversion Programs, Economic Comparison of Hydrogen Production Using Solid Polymer Electrolyte Technology for Sulfur Cycle Water Decomposition and Water Electrolysis, EPRI Research Project 1086-3, Final Report, December 1978. 

In polyelectrolyte gels the variation of pH or salt concentration (cs) causes a swelling or shrinkage. Therefore, in this case chemical energy is transformed to mechanical work (artificial muscles). An increase of cs (or a decrease of temperature) makes the gel shrink. Usually, the shrinking process occurs smoothly, but under certain conditions a tiny addition of salt leads to the collapse of the gel [iii, iv]. Hydration of macroions also plays an important role, e.g., in the case of proton-conductive polymers, such as -> Nafion, which are applied in -rfuel cells, -> chlor-alkali electrolysis, effluent treatment, etc. [v]. Polyelectrolytes have to be distinguished from the solid polymer electrolytes [vi] (- polymer electrolytes) inasmuch as the latter usually contain an undissociable polymer and dissolved small electrolytes. 

Current electrolysis technologies fall into two basic categories (1) solid polymer (which provides for a solid electrolyte) and (2) liquid electrolyte, most commonly potassium hydroxide (KOH). In both technologies, water is introduced into the reaction environment and subjected to an electrical current that causes dissociation the resulting hydrogen and oxygen atoms are then put through an ionic transfer mecha-... 

A second commercially available electrolyzer technology is the solid polymer electrolyte membrane (PEM). PEM electrolysis (PEME) is also referred to as solid polymer electrolyte (SPE) or polymer electrolyte membrane (also, PEM), but all represent a system that incorporates a solid proton-conducting membrane which is not electrically conductive. The membrane serves a dual purpose, as the gas separation device and ion (proton) conductor. High-purity deionized (DI) water is required in PEM-based electrolysis, and PEM electrolyzer manufacturer regularly recommend a minimum of 1 MQ-cm resistive water to extend stack life. 

P. Choi, D. G. Bessarabov, and R. Datta, A simple model for solid polymer electrolyte (SPE) water electrolysis, Solid State Ionics, 175 535 (2004). 

Rasten, E., Hagen, G., Tunold, R. (2003). Electrocatalysis in water electrolysis with solid polymer electrolyte. Electronica Acta 48,3945-3952. 

When cells with solid polymer electrolytes (SPE) are used, no electrolytes need to be dissolved in the medium, and solvents, which usually cannot be employed in electrolysis, may be used [74—79]. 

Industrial cells are mainly bipolar consisting of a large number of individual plate cells connected back to back and coupled in blocks according to the filter press principle. If the electrolysis is carried out under pressure, the energy consumption can be reduced by 20%. Further recent developments are the use of porous electrodes, high temperature steam electrolysis and the SPE-process (solid polymer electrolyte). Heavy water, D2O, can be produced as a byproduct in water electrolysis through enrichment in the electrolyte. 

Another design that is used in chlo-ralkali electrolysis, water electrolysis, and electro-organic synthesis [95-97] is the solid polymer electrolyte (SPE) cell, where an ion exchanger membrane, for example, Nafion , serves as the electrolyte, Fig. 9. The microporous catalytic reaction layers are pressed directly onto the membrane with porous current collectors allowing transport of dissolved reactants and gaseous products into and out of the reaction layer. 

But membrane electrolysis suffers a severe drawback the high costs for the solid polymer electrolyte. If membranes being... 

Solid Polymer Electrolysis (SPE) and Proton-exchange Membrane Fuel Cell (PEMFC)... 

Equation (3) and (4) mean that the supply of the energetic e is needed to split water. This is the basic principle of water-electrolysis. The PEMFC is just the reverse operation of the SPE. Hydrogen fuel is decomposed into 2e and 2H+ by the catalytic cathode. The protons pass through the solid polymer (electrolyte) and arrive at the anode (A) to react with the electrons and the supplied oxygen. Then, water is produced. The electrons come to A via the external resistance. This fuel cell generates, ideally, about 1 V-direct current power. A stack of the cells is constructed to give the output power with, for example, 25 kW, which is set together to drive the vehicles. 

Takenaka, H., R D on solid polymer electrolyte water electrolysis in Japan , Proceedings of International Hydrogen and Clean Energy Symposium 95, pi65. 

Ion-exchange membrane coated with porous catalyst metal (Solid Polymer Electrolyte, SPE) as well as GDE can provide gas phase electrolysis of CO2. The first attempt was published by Ito et al., communicating thin porous Au layer electrode coated on a cation exchange membrane. The SPE could not enhance the cathodic current of CO2 reduction.2" DeWulf et al. applied an SPE with Cu as the catalyst layer on a cation exchange membrane (CEM) Na-fion 115. The SPE reduced CO2 to CH4 and C2H4 for a while, but the current density for CO2 reduction dropped below 1 mA cm after 70 min electrolysis. " ... 

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