Studies of layered uranium(VI) compounds. I. High proton conductivity in polycrystalline hydrogen uranyl phosphate tetrahydrate
01 Jun 1979-Journal of Solid State Chemistry (Academic Press)-Vol. 28, Iss: 3, pp 345-361
TL;DR: In this paper, a Grotthus-type mechanism of conduction is proposed which involves intermolecular transfer steps (hopping) and inter-parallel transfer steps in comparable numbers, the former facilitated by the high concentration of H 3 O + ions in the structure, and the latter most likely facilitated by high H-bond vacancies.
Abstract: We have found that hydrogen uranyl phosphate tetrahydrate HUO 2 PO 4 ·4H 2 O has a high proton conductivity. The ac conductivity was 0.4 ohm −1 m −1 at 290°K measured parallel to the faces of sintered disks of the compound. The activation energy was found to be 31 ± 3 kJ mole −1 . The values of conductivity were between 3 and 10 times lower when measured perpendicular to the disk faces due to preferred orientation of the plate-like crystals. Both the powder and sintered disks are stable in air and insoluble in phosphoric acid solution of pH 2.5. Experiments are described which enable possible grain boundary contributions to the conductivity to be determined in such hydrates. The extrinsic grain boundary contribution to the conductivity was found to be small from experiments in which the pH in a solution cell was varied. The abnormally high bulk H + conductivity thus inferred is attributed primarily to the high concentration of H + , which exists as H 3 O + in the interlamellar hydrogen-bonded network. A Grotthus-type mechanism of conduction is proposed which involves intermolecular transfer steps (hopping) and intramolecular transfer steps, in comparable numbers, the former facilitated by the high concentration of H 3 O + ions in the structure, and the latter most likely facilitated by the high concentration of H-bond vacancies.
TL;DR: In this paper, a review of the proton conductivity in materials and the elements of proton conduction mechanisms are discussed with a special emphasis on proton chemistry, including structural reorganization and diffusional motion of extended moieties.
Abstract: In this review the phenomenon of proton conductivity in materials and the elements of proton conduction mechanismsproton transfer, structural reorganization and diffusional motion of extended moietiesare discussed with special emphasis on proton chemistry. This is characterized by a strong proton localization within the valence electron density of electronegative species (e.g., oxygen, nitrogen) and self-localization effects due to solvent interactions which allows for significant proton diffusivities only when assisted by the dynamics of the proton environment in Grotthuss and vehicle type mechanisms. In systems with high proton density, proton/proton interactions lead to proton ordering below first-order phase transition rather than to coherent proton transfers along extended hydrogen-bond chains as is frequently suggested in textbooks of physical chemistry. There is no indication for significant proton tunneling in fast proton conduction phenomena for which almost barrierless proton transfer is suggest...
TL;DR: The role of polymers as gas sensors, pH sensors, ion-selective sensors, humidity sensors, biosensor devices, etc., are reviewed and discussed in this article, and current trends in sensor research and also challenges in future sensor research are discussed.
Abstract: Because their chemical and physical properties may be tailored over a wide range of characteristics, the use of polymers is finding a permanent place in sophisticated electronic measuring devices such as sensors. During the last 5 years, polymers have gained tremendous recognition in the field of artificial sensor in the goal of mimicking natural sense organs. Better selectivity and rapid measurements have been achieved by replacing classical sensor materials with polymers involving nano technology and exploiting either the intrinsic or extrinsic functions of polymers. Semiconductors, semiconducting metal oxides, solid electrolytes, ionic membranes, and organic semiconductors have been the classical materials for sensor devices. The developing role of polymers as gas sensors, pH sensors, ion-selective sensors, humidity sensors, biosensor devices, etc., are reviewed and discussed in this paper. Both intrinsically conducting polymers and non-conducting polymers are used in sensor devices. Polymers used in sensor devices either participate in sensing mechanisms or immobilize the component responsible for sensing the analyte. Finally, current trends in sensor research and also challenges in future sensor research are discussed.
...nH2O, PVA/H3PO4, Nafion H2 [26–30]...
... Howe AT, Shilton MG....
TL;DR: 1 demonstrated a combination of two of the concepts by introducing NH(4)(+) ions using the anionic framework and putting carboxyl end groups of adipic acid in a honeycomb-shaped void, showing a superprotonic conductivity of 10(-2) S cm(-1) at ambient temperature.
Abstract: A novel metal−organic framework (MOF), (NH4)2(adp)[Zn2(ox)3]·3H2O (1) was synthesized and its structure was determined. We propose three types of rational design to introduce proton carriers into MOFs. The simplest method is to introduce them directly as counterions such as NH4+, H3O+, and HSO4− into the pores of frameworks (type I). The second is to put acid groups on frameworks, the protons being provided from them (type II). The third is to incorporate acidic molecules into voids (type III). 1 demonstrated a combination of two of the concepts by introducing NH4+ ions using the anionic framework (type I) and putting carboxyl end groups of adipic acid in a honeycomb-shaped void (type III). 1 showed a superprotonic conductivity of 10−2 S cm−1 at ambient temperature, comparable to organic polymers such as Nafion, which is in practical use in fuel cells. This is the first example of an MOF to exhibit a superprotonic conductivity of 10−2 S cm−1 at ambient temperature.
TL;DR: This level of conductivity exceeds that of any proton-conducting MOF reported to date and is equivalent to the conductivity of the most effective known electrolyte, Nafion.
Abstract: Facile postsynthetic oxidation of the thiol-laced UiO-66-type framework UiO-66(SH)2 enabled the generation of UiO-66(SO3H)2 with sulfonic acid groups covalently linked to the backbone of the system. The oxidized material exhibited a superprotonic conductivity of 8.4×10−2 S cm−1 at 80 °C and 90 % relative humidity, and long-term stability of the conductivity was observed. This level of conductivity exceeds that of any proton-conducting MOF reported to date and is equivalent to the conductivity of the most effective known electrolyte, Nafion.
01 Jan 1945
01 Jan 1971
TL;DR: In this article, it was shown that the layered hydrate HUO2PO4 is a rapid proton conductor with a room temperature conductivity of 4 × 10−3ohm−1cm−1.
Abstract: We have found that the layered hydrate HUO2PO4. 4H2O is a rapid proton conductor. The room temperature conductivity of 4 × 10−3ohm−1cm−1 is higher than that of Na+ in β alumina. The activation energy is 30± 3 kJ mol−1. The material is insoluble, and presses into transluscent discs suitable for solid electrolyte applications.
TL;DR: In this paper, it was found that a large fraction of the total current was transported by the surface counter-ions, their mobility being ⩾10 4 times that of the internal ones.
Abstract: The specific conductance of zirconium phosphate decreases considerably with increase in the degree of crystallinity; however the energy of activation for the conduction apparently does not depend on the degree of crystallinity and is surprisingly low (11–13 KJ/mole) In order to explain these results, different samples of Zr(HPO 4 ) 2 ·H 2 O of the same degree of crystallinity but having different specific surface area were obtained by sedimentation and the amount of surface counter-ions per cm 3 of microcrystals and the specific conductance measured It was found that a large fraction of the total current was transported by the surface counter-ions, their mobility being ⩾10 4 times that of the internal ones Thus, the low activation energy for ionic conduction in the crystalline material is due essentially to the transport of surface counter-ions These results demonstrate that the counter-ions present at the surface of microcrystals of zirconium phosphate make an important contribution to the total conduction, to the activation energy, and to the electrochemical properties of membranes consisting of microcrystals of zirconium phosphate