Caesium hydrogen sulfate

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Caesium hydrogen sulfate
CsHSO4 StructureDgm.png
Identifiers
Properties
CsHO4S
Molar mass 229.97 g·mol−1
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Caesium hydrogen sulfate or cesium hydrogen sulfate is the inorganic compound with formula CsHSO4. This colorless solid is the caesium salt of bisulfate. It is obtained by combining Cs2SO4 and H2SO4[1]

Properties[edit]

Above 141 °C, CsHSO4 is a superionic conductor. The rapid ionic conductivity arise especially in the range of these temperatures due to the high activity of protons.[2]

CsHSO4 goes through three crystalline phases that are referred to as phase III, II, and I.[3] CsHSO4 is initially existing in phase III at a room temperature of 21 °C. Phase III ranges from 21 °C to 90 °C with a transition temperature of 90 °C to 100 °C between phase III and phase II. Phase II ranges from 90 °C to 140 °C. At 140 °C, CsHSO4 undergoes a phase shift from phase II to phase I.[4]

Phase III (21 °C to 90 °C) and Phase II (90 °C to 140 °C) are referred to as the monoclinic phases, in which CsHSO4 exhibits its lowest proton conductivity. As the crystalline structure’s temperature is raised, it will show variations in the unit cell volume and the arrangement of its hydrogen bonds, which will alter the ability of a CsHSO4 crystalline structure to allow the displacement of protons.

At 141 °C, the CsHSO4 crystal structure experiences a structural change from monoclinic phase II to a tetragonal phase, becoming phase I. Phase I has more elevated crystal symmetry and widened lattice dimensions.[5] Phase I is noted as the superprotonic phase (strong conducting phase), which triggers an extreme growth in proton conductivity by four orders of magnitude, reaching 10 mS/cm. This makes the conductivity of CsHSO4 ten-fold stronger than the conductivity of a sodium chloride aqueous solution.[6] In the superprotonic phase, the movement of an SO4 tetrahedron generates a disruption of the hydrogen bond network, which accelerates proton transfer.[7] The tetragonal anions available in the structure are accountable for the arrangement of the hydrogen bonds with the moving protons.[8]

Applications[edit]

The maximum conductivity of pure CsHSO4 is 10 mS/cm, which is too low for practical applications. In composites with SiO2, TiO2, and Al2O3) , the proton conductivity below the phase transition temperature was is enhanced by a few orders of magnitude.[9]

Unlike hydrated protonic conductors, the absence of water in CsHSO4 provides a great amount of stability both thermally and electrochemically. Electromotive force (EMF) measurements in a humidified oxygen concentration cell verified the high ionic nature of CsHSO4 in its superprotonic phase.[10] Based on heat rotation, the voltage stayed the same for over 85 hours during the measurement, particularly at the high temperature.[11] These results, demonstrate the thermal independence from humidity-type environments. Additionally, the crystal structure of CsHSO4 allows for quick transport of smaller charged ions, resulting in efficient energy transfer in electrochemical devices.[12] These properties carries many important utilizations of solid electrolytes in electrochemical field such as hydrogen partial pressure sensors, fuel cells, electrocatalytic reactors, batteries, displays, and super-capacitors.[13][14][15][16] Solid state proton conductors rely on the movement of protons, which are commonly found in: hydrogen sulfates, hydrates, hydroxides, and polymers, to elicit currents.[17] Solid state proton conductors can function at temperatures within the range of Earth’s natural climate. This makes them more efficient since relatively small amounts of energy are required to keep the conductor at operational temperatures.[18]

Fuel Cells[edit]

Due to its ability to maintain high proton conductivity in intermediate temperatures (~200℃), CsHSO4 is a candidate for proton transferring agent in proton exchange membrane fuel cells (PEMFC). Transfer of proton across the catalyst layer is the primary limiting step of the cell reaction and electrolysis, thus the high proton conductivity of CsHSO4 can contribute greatly to the cell’s performance.[19] CsHSO4 has advantage over typical low-temperature PEMs, which require water-rich environment limiting them to temperatures below 100 °C.[20] CsHSO4 combined with polymer has been shown to surpass even some other high-temperature PEMFC systems in performance.[21][22]

The negative aspects of CsHSO4 are its high gas permeability that hinders cell reaction and chemical instability under hydrogen-rich atmosphere.[23] Also, CsHSO4 in its superprotonic phase might be degraded to less proton-conductive Cs2S2O7 and water, which will compromise cell performance.[24]

H2S Electrolysis[edit]

The CsHSO4 cells can be used to electrolyze hydrogen sulfide, which is a common environmental waste. This technology would compete with the Claus Process. A 2008 study shows electrolysis of H2S gas using anode catalyst consisted of RuO2/p-dichlorobenzene/CsHSO4/Pt black.[25] The fact that sulfur has lower melting point (115℃) than phase transition temperature of CsHSO4 (140℃) can also be an advantage since sulfur can be more easily removed and collected as liquid.[26]

References[edit]

  1. ^ Hiroki Muroyama, Toshiaki Matsui, Ryuji Kikuchi, and Koichi Eguchi. "Composite Effect on the Structure and Proton Conductivity for CsHSO4 Electrolytes at Intermediate Temperatures." (n.d.): n. pag. Department of Energy and Hydrocarbon Chemistry, Graduate School of Engineering, Kyoto University, Nishikyo-ku, Kyoto 615-8510, Japan, 13 Apr. 2006. Web.
  2. ^ BALAGUROV, A. M., A. I. BESKROVNYI, B. N. SAVENKO, B. V. MERINOV, M. DLOUHA, S. VRATISLAV, and Z. JIAK. "Physica Status Solidi (a)Volume 100, Issue 1, Article First Published Online: 17 FEB 2006." The Room Temperature Structure of Deuterated CsHSO4 and CsHSeO4. Join Institute of Research, Dubna/Institute of Crystallography, Moscow/ Faculty of Nuclear Physics and Physics Engineering/ Institute of Physics/ Prague, 19 Jan. 1987. Web. 02 Mar. 2015.
  3. ^ Maja Mroczkowska-Szerszeń, Maciej Siekierski, Rafał Letmanowski, Michał Piszcz, Renata Cicha-Szot, Lidia Dudek, Sławomir Falkowicz, Grażyna Żukowska, and Magda Dudek. "Spectroscopic Verification of Extended Temperature Stability of Superionic Phase Obtained in Mechanosyntehsis Process for CsHSO4/Phospho-silicate Glass Composite." Oil and Gas Institute, Ul. Lubicz 25a, 31-503 Cracow, Poland/Warsaw University of Technology Faculty of Chemistry, Inorganic Chemistry and Solid State Technology Division Ul.Noakowskiego 3, 00-640 Warsaw, Poland 3AGH – University of Science and Technology, Faculty of Fuels and Energy, Al. Mickiewicza 30, 30-059 Cracow, Poland, n.d. Web.
  4. ^ Otomo, Junichiro; Shigeoka, Hitoshi; Nagamoto, Hidetoshi; Takahashi, Hiroshi (2005). "Phase transition behavior and proton conduction mechanism in cesium hydrogen sulfate/silica composite". Journal of Physics and Chemistry of Solids. 66 (1): 21–30. doi:10.1016/j.jpcs.2004.07.006. 
  5. ^ Chan, Wing Kee. Structure and dynamics of hydrogen in nanocomposite solid acids for fuel cell applications. TU Delft, Delft University of Technology, 2011.
  6. ^ Otomo, Junichiro; Shigeoka, Hitoshi; Nagamoto, Hidetoshi; Takahashi, Hiroshi (2005). "Phase transition behavior and proton conduction mechanism in cesium hydrogen sulfate/silica composite". Journal of Physics and Chemistry of Solids. 66 (1): 21–30. doi:10.1016/j.jpcs.2004.07.006. 
  7. ^ Otomo, Junichiro; Shigeoka, Hitoshi; Nagamoto, Hidetoshi; Takahashi, Hiroshi (2005). "Phase transition behavior and proton conduction mechanism in cesium hydrogen sulfate/silica composite". Journal of Physics and Chemistry of Solids. 66 (1): 21–30. doi:10.1016/j.jpcs.2004.07.006. 
  8. ^ Chan, Wing Kee. Structure and dynamics of hydrogen in nanocomposite solid acids for fuel cell applications. TU Delft, Delft University of Technology, 2011.
  9. ^ Hiroki Muroyama, Toshiaki Matsui, Ryuji Kikuchi, and Koichi Eguchi. "Composite Effect on the Structure and Proton Conductivity for CsHSO4 Electrolytes at Intermediate Temperatures." (n.d.): n. pag. Department of Energy and Hydrocarbon Chemistry, Graduate School of Engineering, Kyoto University, Nishikyo-ku, Kyoto 615-8510, Japan, 13 Apr. 2006. Web.
  10. ^ Uda, Tetsuya, Dane A. Boysen, and Sossina M. Haile. "Thermodynamic, thermomechanical, and electrochemical evaluation of CsHSO 4." Solid State Ionics 176.1 (2005): 127-133.
  11. ^ Uda, Tetsuya, Dane A. Boysen, and Sossina M. Haile. "Thermodynamic, thermomechanical, and electrochemical evaluation of CsHSO 4." Solid State Ionics 176.1 (2005): 127-133.
  12. ^ Tetsuya Uda, Dane A. Boysen, and Sossina M. Haile. "Thermodynamic, Thermomechanical, and Electrochemical Evaluation of CsHSO4." SOLID STATE IONICS. Materials Science MC 138-78, California Institute of Technology, Pasadena, CA 91125, USA, 27 Apr. 2004. Web.
  13. ^ Tetsuya Uda, Dane A. Boysen, and Sossina M. Haile. "Thermodynamic, Thermomechanical, and Electrochemical Evaluation of CsHSO4." SOLID STATE IONICS. Materials Science MC 138-78, California Institute of Technology, Pasadena, CA 91125, USA, 27 Apr. 2004. Web.
  14. ^ Baranov, A. I., L. A. Shuvalov, and N. M. Shchagina. "Superion Conductivity and Phase Transitions in CsHSO4 and CsHSeO4 Crystals." (n.d.): n. pag. Institute of Crystallography, Academy of Sciences of the USSR, 13 Oct. 1982. Web.
  15. ^ Tetsuya Uda, Dane A. Boysen, and Sossina M. Haile. "Thermodynamic, Thermomechanical, and Electrochemical Evaluation of CsHSO4." SOLID STATE IONICS. Materials Science MC 138-78, California Institute of Technology, Pasadena, CA 91125, USA, 27 Apr. 2004. Web.
  16. ^ Baranov, A. I., L. A. Shuvalov, and N. M. Shchagina. "Superion Conductivity and Phase Transitions in CsHSO4 and CsHSeO4 Crystals." (n.d.): n. pag. Institute of Crystallography, Academy of Sciences of the USSR, 13 Oct. 1982. Web.
  17. ^ Norby, Truls; Friesel, Milan; Eric Mallander, Bengt (1995). "Proton and deuteron conductivity in CsHSO4 and CsDSO4 by in situ isotopic exchange". Solid State Ionics. 77: 105–110. doi:10.1016/0167-2738(94)00228-K. 
  18. ^ Norby, Truls; Friesel, Milan; Eric Mallander, Bengt (1995). "Proton and deuteron conductivity in CsHSO4 and CsDSO4 by in situ isotopic exchange". Solid State Ionics. 77: 105–110. doi:10.1016/0167-2738(94)00228-K. 
  19. ^ Ecklund-Mitchell, Lars E. Development of thin CsHSO4 membrane electrode assemblies for electrolysis and fuel cell applications. Diss. University of South Florida, 2008. 23, 35, 96, 101.
  20. ^ Barron, Olivia, et al. "CsHSO4 as proton conductor for high-temperature polymer electrolyte membrane fuel cells." Journal of Applied Electrochemistry 44.9 (2014): 1037-1045. 1
  21. ^ Barron, Olivia, et al. "CsHSO4 as proton conductor for high-temperature polymer electrolyte membrane fuel cells." Journal of Applied Electrochemistry 44.9 (2014): 1037-1045. 1
  22. ^ Qingfeng, Li, Hans A. Hjuler, and Niels J. Bjerrum. "Oxygen reduction on carbon supported platinum catalysts in high temperature polymer electrolytes." Electrochimica Acta 45.25 (2000): 4219-4226. pp.1-3
  23. ^ Boysen, Dane Andrew. Superprotonic solid acids: structure, properties, and applications. Diss. California Institute of Technology, 2004. 127-128.
  24. ^ Ecklund-Mitchell, Lars E. Development of thin CsHSO4 membrane electrode assemblies for electrolysis and fuel cell applications. Diss. University of South Florida, 2008. 23, 35, 96, 101.
  25. ^ Mbah, Jonathan, et al. "Electrolytic splitting of H2S using CsHSO4 membrane." Journal of The Electrochemical Society 155.11 (2008): E166-E170.
  26. ^ Ecklund-Mitchell, Lars E. Development of thin CsHSO4 membrane electrode assemblies for electrolysis and fuel cell applications. Diss. University of South Florida, 2008. 23, 35, 96, 101.