A two-dimension model of carbon corrosion induced by the partial coverage of hydrogen on the anode is presented. In proton exchange fuel cells, this degradation mode is caused principally by two mechanisms: 1) blockage of hydrogen from a portion of the anode under steady-state conditions, and 2) transitioning between the off state and a normal operating state. Whereas, corrosion of anode supports because of insufficient fuel is well known, corrosion of the cathode supports under these conditions is less well understood and likely a larger contributor of degradation than commonly expected. Under certain conditions the overpotential in the cell may reach values greater than 1.5 V.
Room temperature molten salts consisting of 1-methyl-3-propylimidazolium chloride and aluminum chloride have been examined as possible electrolytes for a room temperature design of the sodium/metal chloride battery; however, the coulombic efficiency of the sodium couple is less than 95%. This work examines the reduction and oxidation efficiency of the sodium couple from a 1-methyl-3-propylimidazolium chloride/aluminum chloride neutral melt. Most of the work was performed on a tungsten substrate using cyclic voltammetry. The coulombic efficiency of the sodium couple was improved by treating the melt with gaseous HC1 using a closed electrochemical cell which allowed for quantification of the effect of HC1 on the electrochemical behavior of sodium. Thionyl chloride was also found to induce sodium plating and stripping in 1-methyl-3-propylimidazolium chloride/aluminum chloride melts. Optical microscopy was used to examine the surface of the tungsten electrode during sodium deposition, open-circuit periods, and sodium stripping. In comparison to the stability of sodium in two other imidazolium melts, (1,2-dimethyl-3-propylimidazolium chloride and 1-methyl-2-ethylimidazolium chloride) the 1-methyl-3-propylimidazolium chloride system was found to have the widest stability window.
Room temperature molten salts consisting of 1-methyl-3-ethylimidazo]ium chloride (MEIC) and aluminum chloride (A]C13) have been examined as possible electrolytes for a room temperature design of the sodium/iron(II) chloride battery. This work examines the conditions required to achieve efficient reduction and oxidation of sodium from a sodium chloride buffered, neutral melt. Two substrates were examined, tungsten and 303 stainless steel, using both cyclic voltammetry and chronopotentiometry. Melts were protonated using a closed electrochemical cell to allow quantification of the effect of dissolved HC1 on the efficiency of the sodium couple. A threshold of approximately 6 Torr HC1 partial pressure was observed for sodium plating-stripping. Below this threshold, the sodium couple was not observed. The results show that the sodium plating-stripping efficiency increases with increasing current density; however, the efficiency reaches a maximum and is adversely affected by high overpotentials and extended exposure of the sodium to the melt. It appears that some passivation occurs as even a very thin layer of plated sodium exhibits a steady open-circuit voltage over long periods in the melt.) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 138.251.14.35 Downloaded on 2015-03-22 to IP ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 138.251.14.35 Downloaded on 2015-03-22 to IP
Room temperature molten salts consisting of 1,2-dimethyl-3-propylimidazolium chloride and aluminum chloride have been examined as possible electrolytes for a room temperature design of the sodium/iron(II) chloride battery This work examines the conditions which provide the most efficient reduction and oxidation of sodium from a sodium chloride buffered, neutral melt. Most work was performed on a tungsten substrate using cyclic voltammetry. Melts were treated with gaseous HC1 using a closed electrochemical cell which allowed for quantification of the effect of HC1 on the electrochemical behavior of sodium in the molten salt. The HCI threshold partial pressure was less than 1 kPa for sodium plating. This result was complicated by the slow equilibrium between gaseous HC1 and that dissolved in the molten salt; the effect of HC1 addition was found to last for months, demonstrating the slow equilibrium. Small amounts of water contamination were found to produce a similar effect. At elevated temperatures the melt had higher conductivity, an order of magnitude higher current densities, and higher coulombic efficiency. ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 137.222.24.34 Downloaded on 2015-03-16 to IP ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 137.222.24.34 Downloaded on 2015-03-16 to IP
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