Synthesis of complex cesium hydrosulfatophosphates

Abstract

478Compounds with proton conductivity have been of a special interest for researchers due to their high potential for use as materials for electrolytes (mem branes) of fuel cells [1].Today, fuel cells compare favorably with the energy sources in current use in terms of their high efficiency, as well as environmental and operational safety.The qualifying standards for the fuel cell materials are diverse due to the diversity of their performance. In other words, there are no rigid limits for temperature parameters or the physical state of the material. Ionic transport with adequate conductivity is the major requirement. Compoundswith the general formula M m H n (AO 4 ) (m + n)/2 ⋅ xH 2 O (M = K, NH 4 , Rb, Cs; A = S, Se, P) are an example of these materials [2]. Con ductors based on cesium hydrogen salts, mostly, on cesium hydrophosphates and hydrosulfates, have recently been of special interest. Single crystals of CsH 2 PO 4 , CsHSO 4 , and complex hydrosulfatophos phates Cs 2 (HSO 4 )(H 2 PO 4 ), α(β) Cs 3 (HSO 4 ) 2 (H 2 PO 4 ) and Cs 5 (HSO 4 ) 3 (H 2 PO 4 ) 2 have been prepared [3][4][5][6][7][8][9]. Superionic transition temperatures were determined for some of these compounds.This study presents the results of synthesis and characterization of complex cesium hydrosulfato phosphates. The CsH 2 PO 4 -CsHSO 4 -H 2 O ternary system was studied at 25.0°С over the entire concen tration range using an isothermal method to investi gate the interaction between the initial components (CsH 2 PO 4 and CsHSO 4 ). Single crystals of the result ing phases were grown and analyzed. EXPERIMENTAL Cesium hydrosulfate CsHSO 4 (high purity grade, technical specifications TU 6 09 04 198 83) and cesium dihydrophosphate CsH 2 PO 4 (high purity grade, technical specifications TU 6 09 04 201 82) were used to study the interaction between the compo nents of the CsHSO 4 -CsH 2 PO 4 -H 2 O system and to grow single crystal samples. Cesium in the liquid phase and the solid residue was determined gravimet rically as cesium tetraphenylborate [10]; phosphate anion was determined photocolorimetrically [11].X ray diffraction analysis was carried out on an XRD 6000 Shimadzu diffractometer (bent graphite monochromator, CuK α on a diffracted beam, contin uous scan mode 1 deg/min, increment 0.02° over the 2θ angle range of 10°-80°, no sample rotation).The elemental analysis of single crystal samples was carried out on a Quanta 200 3D atomic force microscope using energy dispersive X ray analysis (EDAX) according to the standard absorption coeffi cients; a CsH 2 PO 4 (CDP) single crystal was used as the reference; tube voltage was 15 kV; scanning time 500 s; refinement using the ZAF system.Intercomponent interactions in the CsHSO 4 -CsH 2 PO 4 -H 2 O system were studied under isothermal equilibrium conditions at 25.0°С. Temperature was maintained constant using a thermostat; the time required to attain equilibrium was 24 h.Weighed portions of the compounds were placed into 50 mL round bottom flasks and kept in the ther mostat; stirring was provided...

MmHn(XO4)(m + n)/2crystals: structure, phase transitions, hydrogen bonds, conductivity. II. Structure and properties of Cs3(HSO4)2(H2PO4) and Cs4(HSO4)3(H2PO4) single crystals

“…The elemental compositions were calculated using EDAX with corrections to the atomic number, absorption and fluores-research papers cence. The crystal compositions were also confirmed by chemical analysis of SO 4 2À and PO 4 3À groups using the technique reported in Komornikov et al (2012). Based on the preliminary data, the chemical formulae of these compounds were determined to be Cs 3 (HSO 4 ) 2 (H 2 PO 4 ) and Cs 4 (HSO 4 ) 3 (H 2 PO 4 ) in the first approximation.…”

“…The Cs 3 (HSO 4 ) 2 (H 2 PO 4 ) compound is incongruently soluble and exists in a limited temperature range (298-313 K) in comparison to Cs 4 (HSO 4 ) 3 (H 2 PO 4 ) which is congruently soluble and exists in a wider temperature range (Komornikov et al, 2012). When growing Cs 3 (HSO 4 ) 2 (H 2 PO 4 ) crystals with a controlled decrease in temperature, the upper temperature limit should be restricted to 313 K and the component ratio CsHSO 4 :CsH 2 PO 4 = 1:1; when growing Cs 4 (HSO 4 ) 3 (H 2 PO 4 ), the component ratio CsHSO 4 :CsH 2 PO 4 = 3:1.…”

Investigation of the structure of Cs3(HSO4)2(H2PO4) single crystals

“…The elemental composition was calculated using the EDAX program with corrections to the atomic number, absorption, and fluorescence. The crystal composition was also confirmed by chemical analysis for the and groups using the technique reported in [16]. Based on the preliminary data, the chemical formula of the compound was determined to be Cs 3 (HSO 4 ) 2 (H 2 PO 4 ) in the first approximation.…”

“…The Cs 3 (HSO 4 ) 2 (H 2 PO 4 ) compound is incongruently soluble and exists in a limited temperature range (298-313 K) [16]. When growing its crystals with a controlled decrease in temperature, one should be restricted to a value of 313 K as the upper temperature limit and the component ratio CsHSO 4 : CsH 2 PO 4 = 1 : 1.…”

Study of phase equilibria in the Rb3H(SO4)2-RbH2PO4-H2O system

“…For example, the CsHSO 4 -CsH 2 PO 4--H 2 O water-salt system was systematically investigated only recently [4]. As a result of that investigation, a new compound, Cs 6 (H 2 SO 4 ) 3 (H 2 PO 4 ) 4 , with high proton conductivity was found [5,6].…”