Cell components Introduction

Sorensen is usually considered to be the first to have realized the importance of hydrogen ion concentration in cells and in the solutions in which the properties of cell components were to be studied. He is also credited with the introduction of the pH scale. Electrochemistry started at the end of the nineteenth century. By 1909, Sorensen had introduced a series of dyes whose color changes were related to the pH of the solution, which was determined by the H+ electrode. The dyes were salts of weak acids or weak bases. He also devised simple methods for preparing phosphate buffer solutions covering the pH range 6-8. Eventually buffers and indicators were provided covering virtually the whole pH range. 

The following reasoning shows also how inconvenient is the introduction of the temperature coefficient at constant volume if we warm a cell at constant volume, the pressure increase, and thus also the E.M.F., is definitely fixed only if we know, in addition to the coefficients of thermal expansion of the cell components, the proportions also in which they are present the E.M.F. measured at constant pressure is, however, independent of the proportions of the separate phases. This fact again shows that equation (157) is of a form which cannot usually be employed in practice. 

A reasonable approach to a gradual introduction of hydrogen is small-scale residential energy system modules comprising electrolyzer, metal hydride (or pressure vessel) as a buffer system, and CHP fuel cell components, ideal for applications far away from the grid. Roundtrip efficiencies of 30 % have already been demonstrated, 40 % are expected to be possible in the near fumre [20]. 

The alkaline cell has an open-circuit voltage of 1.5 V that can deliver 150 Wh/kg and 460 Wh/1. The reactions have fast kinetics and can deliver full capacity, even at high-rate discharges. Since its introduction in 1959, there has been a steady increase in performance of the alkaline cell as new materials and cell components were incorporated into the structure. The present alkaline cell designs are based on the use of nanostructured electrolytic manganese dioxide, a thinner polymer gasket seal with sealant to increase internal volume and improve shelf Ufe. Mercury has been eliminated by using new zinc alloy compositions. These improvements have resulted in about a 40 % improvement in performance over the same-size cells produced in 1959. 

Contamination of PEM fuel cells is an important durability and operational issue. Introduction of contaminants in the fuel or oxidant streams, or through fuel cell component materials composition, can result in negative performance effects and increase degradation modes. This book will cover the issues and understanding associated with contamination of PEM fuel cells. A brief overview of contamination issues, along with reference to the material in this book, is included in this section. 

Contamination of the membrane is mainly through the introduction of cationic species, either through contaminated air and fuel streams, or from the leaching of metal materials within the fuel cell system. Metal contamination may be present in the stack or cell component materials, such as in the carbon catalyst support or gas diffusion layer. Seal and gasketing materials may contain silicone, which can decompose and contaminate the membrane. The key effect of cationic contaminants... 

These selection and evaluation criteria were applied systematically to four technological fields, three of which contribute to new energy-efficient solutions. Passive houses, for example, with their major components of insulation solutions, window systems, ventilation and control techniques are close to market diffusion within the next ten years. Fuel cells for mobile uses in vehicles, however, are still a long way from market introduction, for instance, because of unresolved problems regarding the deactivation of the membrane electrode assembly (MEA) and the need for cost reductions by about one order of magnitude. Other types of fuel cells for stationary uses may be closer to market introduction, owing to less severe technical bottlenecks and better economic competitiveness. 

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