Proton conduction mechanism and the stability of sol–gel titanium phosphates

Hogarth, Warren H.J.; Muir, Sean S.; Whittaker, Andrew K.; Costa, João C. Diniz da; Drennan, John; Lu, Gao Qing

doi:10.1016/j.ssi.2006.10.015

Cited by 30 publications

(9 citation statements)

References 32 publications

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“…In contrast, the effect of larger amount of absorbed water in pure SPEEK membranes was found to be negligible for temperatures lower than 100 °C. The E a values indicate that proton transport occurs through a Grotthuss mechanism, expected to be dominant at high hydration levels − …”

Section: Resultsmentioning

confidence: 99%

Titania Nanosheets (TNS)/Sulfonated Poly Ether Ether Ketone (SPEEK) Nanocomposite Proton Exchange Membranes for Fuel Cells

et al. 2009

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Sulfonated polyetheretherketone (SPEEK)-based composite membranes containing various amounts of titania nanosheets (TNS) as inorganic filler have been prepared and investigated for proton exchange membrane applications. The SPEEK degree of sulfonation was DS = 0.58 and the TNS content was in the range 0.95-10.00 wt. %. The two-dimensional titanium oxide sheets, have been prepared as stable colloidal suspensions produced by the action of a quaternary ammonium ion, such as tetrabutylammonium, TBA þ . SPEEK/TNS composites have been prepared by casting from DMA (dimethylacetamide). The samples have been characterized in terms of thermal stability (TG/ DTA, DSC), proton exchange capacity (P.E.C., by titration), water uptake, proton conductivity (EIS), and structural (XRD) and microstructural (SEM) features. Acid treated composites, at the lowest inorganic additive contents, exhibited improved properties in terms of proton conductivity and water uptake with respect to pure SPEEK. The best performing nanocomposite was the membrane containing only 1.67 wt.% TNS showing conductivity value of 4.14 10 -2 Scm -1 at 140°C and at 100% of relative humidity (RH), whereas pure SPEEK membrane exhibited a value of 1.76 Â 10 -2 Scm -1 at the same temperature and RH conditions. The volume swelling (VS), measured at 90°C for the composite membrane containing 1.67 wt. % TNS, was reduced by ca. 80% with respect to that of a reference SPEEK membrane. The improved electrochemical properties of TNS nanocomposites have been associated to the unique nature of the two-dimensional nano structured inorganic additive. †

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Section: Resultsmentioning

confidence: 99%

Titania Nanosheets (TNS)/Sulfonated Poly Ether Ether Ketone (SPEEK) Nanocomposite Proton Exchange Membranes for Fuel Cells

et al. 2009

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“…This promotes the formation of a dynamic hydrogen-bonded network, providing high proton conductivity even at elevated temperatures in the absence of water. The replacement of polymeric matrixes by more stable solid acid proton conductors like phosphates (zirconium and titanium phosphates, cesium dihydrogen phosphate, and also tin or cerium pyrophosphate) − is also a subject of ongoing research.…”

Section: Introductionmentioning

confidence: 99%

Structure-Independent Proton Transport in Cerium(III) Phosphate Nanowires

Pusztai

Haspel

Tóth

et al. 2015

ACS Appl. Mater. Interfaces

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Understanding of water-related electrical conduction is of utmost importance in applications that utilize solid-state proton conductors. However, in spite of the vast amount of theoretical and experimental work published in the literature, thus far its mechanism remained unsolved. In this study, the structure-related ambient temperature electrical conduction of one-dimensional hydrophilic nanostructures was investigated. Cerium phosphate nanowires with monoclinic and hexagonal crystal structures were synthesized via the hydrothermal and ambient temperature precipitation routes, and their structural and surface properties were examined by using high-resolution transmission electron microscopy, X-ray diffractometry, nitrogen and water sorption, temperature-programmed ammonia desorption, and potentiometric titration techniques. The relative humidity (RH)-dependent charge-transport processes of hexagonal and monoclinic nanowires were investigated by means of impedance spectroscopy and transient ionic current measurement techniques to gain insight into their atomistic level mechanism. Although considerable differences in RH-dependent conductivity were first found, the distinct characteristics collapsed into a master curve when specific surface area and acidity were taken into account, implying structure-independent proton conduction mechanism in both types of nanowires.

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“…Recently, there has been a remarkable progress in the synthesis of nanomaterials and their exploitation for various applications. 1 Titanium phosphates (TiPs) have been extensively studied with respect to their diverse structures and wide applications in some areas such as ion exchange, 2,3 intercalation, 4 proton conduction, 5 catalysis, 6,7 and so forth. 8,9 TiPs with layered 10,11 and mesoporous 3 structures have already been prepared by different methods.…”

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confidence: 99%