Electrolyzers Polymer Electrolyte Membrane

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. 

In the 1960s, the use of solid-state polymer electrolytes instead of the liquid electrolytes normally used in alkaline electrolysis led to the development of novel concepts for water electrolysis. The US company General Electric was the first to realize solid polymer electrolyte water electrolysis (SPE) with the aid of the solid polymer electrolyte membrane (Nafion ) developed by DuPont [16]. At the same time, ABB [17, 18] in Switzerland and Fuji Electric [19] in Japan also developed PEM electrolyzers with single electrode areas of up to 2500 cm. These... 

Different technologies can be used for RFC systems. Electrolyzers can be classified by the electrolyte they use alkaline, polymer electrolyte membrane (PEM) and solid oxide electrolyte (SOE) [5]. Alkaline, PEM, and SOE electrolyzers can also be used for FCs. The electrolytes differ according to the ion that is conducted and their operating temperatures (Table 8.1). 

In a fuel cell, the membrane is sandwiched between two bipolar plates. This structure puts it under compressive stress, which can change the membrane resistance. It has been found that the resistance of Nafion membranes increased when they were compressed, and the increase was consistent with the elastic compression of the membrane (Satterfield et al, 2006). Casciola et al. (2006) also found that membrane conductivity decay occurs only when the membrane is forced to swell anisotropically along the plane parallel to the membrane surface. In addition to the effect of compression on conductivity decay, polymer membranes in fuel cells undergo creep, which can cause membrane thinning, pinhole formation, and other failure. Stuck et al. (1998) proposed that local stress most likely triggered and/or enhanced the nonuniform thinning of the Nafion membranes in a polymer electrolyte membrane electrolyzer. 

Laconti, A., Liu, H., Mittelsteadt, C., and McDonald, R. 2006. Polymer electrolyte membrane degradation mechanisms in fuel cells—Findings over the past 30 years and comparison with electrolyzers. ECS Transactions 1 199-219. 

Generally, lead dioxide (Pb02) and platinum (Pt) electrodes are used as electrocatalysts for ozone generation [2-4]. The electrolytic cell consists of a porous anode, a porous cathode and a solid-state polymer electrolyte membrane instead of an electrolyte solution these are stacked, as shown schematically in Fig. 24.1(a). Pure water, or tap water without additives as an electrolyte, is directly supplied to the anode compartment, the electrolysis of water occurs, and the electrolyzed water containing dissolved ozone is directly drained. Electrolytic ozonizers based on this system have already become available on the market. 

Later, Hinatsu et al. studied the uptake of water, from the liquid and vapor states at various temperatures, in acid form Nafion 117 and 125, and Aciplex and Flemion membranes, although the latter two similar products will not be discussed here. These studies were motivated by a concern over the deleterious effects, involving either overly dry or overly wet membranes, on electrical conductivity within the context of polymer electrolyte fuel cells and polymer electrolyte water electrolyzers. 

H. Takenaka, Technology of water electrolysis using solid polymer electrolyte and its application, Soda Enso (Soda Chlorine) 1986, 37, 323-337 S. Stucki, G.G. Scherer, S. Schlagowski and E. Fischer, PEM water electrolyzers evidence for membrane failure in 100 kW demonstration plants, J. Appl. Electrochem., 1998, 28, 1041-1049. 

Solid polymer acid electrolytes were first developed for fuel cell applications in the late 1950 s by the General Electric Company (GE), which initiated a program to develop membrane cells and electrolyzers. The first membranes developed by GE for fuel cell applications were made by the condensation of phenolsulfonic acid and formaldehyde. These membranes were found to be brittle, prone to cracking when dried, and rapidly hydrolyzed... 

A particular approach adopted by General Electric In U.S.A. is the solid polymer electrolyte (SPE) cell in which the porous cloth-type separator is replaced by a polymeric ion exchange membrane which is conductive to cations (Figure 5). The particular membrane employed, NAFION, is a perfluorsulphonlc acid pol3nner which is extremely stable in both acid alkaline solution. Appropriate electrocatalysts are coated on each face of the polymer sheet and these are contacted by a metal mesh current collector. Further research is aimed at reducing the cost and improving the electrical efficiency of the system to make it competitive with conventional electrolyzers. 

During these programs, PME fuel cells and electrolyzers were developed. These first solid membranes were made of sodium polystyrene sulfonate, and would be replaced by Nafion, which was discovered by DuPont in the same decade. Thus, it was in 1966 that the very first solid-polymer electrolyte (SPE) electrolyzer was built by General Electric (GE) for Project GEMINI to produce oxygen on board the spacecraft. 

Production of hydrogen via water electrolysis using an alkaline medium is a mature technology. At the same time, solid polymer electrolyte (SPE)-based systems, for water electrolysis, have a much weaker market share globally. The main reasons for the limited implementation of SPE-based electrolyzers includes the expensive PGM catalyst and proton conducting membrane, lower durability, and lower hydrogen output. However, the advantages of SPE... 

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