Microcalorimetry applied to hydrogen bronzes

Tinet, D.; Partyka, S.; Rouquérol, J.; Fripiat, J. J.

doi:10.1016/0025-5408(82)90036-8

Cited by 10 publications

(7 citation statements)

References 6 publications

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“…This result indicates that the shoulder region, which remains after subtraction of the Pd contribution, arises from formation of H x WO 3 precipitates where the H bonding is weak enough so that there is a measurable equilibrium p H 2 (Figure ). Such shoulder regions are much smaller than the IOed Pd–Mo alloys, indicating that the bonding of the H in the H x WO 3 bronze is weaker than that in the IOed Pd–Mo alloys, which, as pointed out above, is consistent with direct measurements of the heats of formation of these bronzes. , …”

Section: Resultssupporting

confidence: 81%

“…Such shoulder regions are much smaller than the IOed Pd−Mo alloys, 10 indicating that the bonding of the H in the H x WO 3 bronze is weaker than that in the IOed Pd−Mo alloys, which, as pointed out above, is consistent with direct measurements of the heats of formation of these bronzes. 19,27 Initial, more complete, isotherms measured up to large H contents for both of the IOed Pd−W alloys are shown in Figure 7, where it can be seen that there are small shifts to higher H contents in the dilute phase corresponding to the formation of the H-bronzes, which is reflected by the greater H contents in the hydride phase region, but otherwise, the isotherms are similar to those of Pd showing that the alloys have been completely IOed. ■ H DIFFUSION THROUGH THREE-LAYER MEMBRANES Deivation of an Equation for D H,alloy Corresponding to the Inner Layer of a Three-Layer Membrane.…”

Section: ■ Experimental Sectionmentioning

confidence: 99%

“…16 It was found that the IOed Pd 0.97 Mo 0.03 alloy after exposure to H 2 forms an H-bronze corresponding to H 1.7 MoO 3 , 10 which closely agrees with the stoichiometry found by Sermon and Bond 17 who prepared H x MoO 3 by H-spillover. WO 3 is known to form a H-bronze by conventional means, for example, H-spillover, 18 although the amount of occluded H is less than that of MoO 3 , for example, Tinet et al 19 give the stoichiometries as H 0.35 WO 3 when the H bronze is prepared by H-spillover, whereas MoO 3 forms an H-bronze of stoichiometry H 1.7 MoO 3 . Since H-bronze formation from IOed Pd−V 7 and Pd−Mo 10 alloys have been investigated, it seems reasonable to investigate H trapping within a Pd composite by the other well-characterized H-bronze, that is, H X WO 3 .…”

Section: ■ Introductionmentioning

confidence: 99%

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Thermodynamics of Hydrogen Solution and Diffusion in Oxidized and Unoxidized Pd–W Alloys

Flanagan

Wang

2015

J. Phys. Chem. C

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Equilibrium hydrogen isotherms have been measured from 423 to 523 K for two fcc Pd−W alloys, Pd 0.98 W 0.02 and Pd 0.96 W 0.04 , over H content ranges available up to p H 2 ≈ 0.10 MPa. ΔH H and ΔS H values have been determined from the H 2 isotherms as a function of the H content of the alloys. After measurement of the isotherms, the Pd 0.98 W 0.02 and Pd 0.96 W 0.04 alloys were internally oxidized. The H 2 solubilities in the internally oxidized alloys were measured and evidence is given for the formation of Hbronzes, H x WO 3 , from the nanosized WO 3 precipitates within the Pd matrix. Pd−W alloy membranes prepared for H diffusion measurements were partially internally oxidized in order to improve their resistance toward gaseous contaminants. An equation has been derived to obtain the H diffusion constant for the inner, unoxidized alloy layer within the three layer membrane resulting from internal oxidation. This equation has been applied to data for the two internally oxidized Pd−W alloys. Activation energies and pre-exponential factors have been derived for H diffusion constants through the inner, unoxidized Pd−W alloy layers.

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Section: Resultssupporting

confidence: 81%

Section: ■ Experimental Sectionmentioning

confidence: 99%

Section: ■ Introductionmentioning

confidence: 99%

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Thermodynamics of Hydrogen Solution and Diffusion in Oxidized and Unoxidized Pd–W Alloys

Flanagan

Wang

2015

J. Phys. Chem. C

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“…The calorimetric results of Birtell and Dickens reflect a combination of two phase and single phase regions so that they cannot be equated to any given phase or to a two phase region. Tinet et al 11 found an integral enthalpy magnitude of 52.5 kJ/mol of 1 / 2 H 2 for the formation of H 1.6 MoO 3 .…”

Section: Discussionmentioning

confidence: 99%

“…These noble metal particles are sites for the needed H 2 dissociation because the oxides will not absorb hydrogen directly via H 2 . 11 The oxide then receives H by diffusion from the metal. H atoms are reported to diffuse rather fast within H x MoO 3 .…”

Section: Introductionmentioning

confidence: 99%

Hydrogen Bronze Formation within Pd/MoO₃Composites

et al. 2003

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In this study, Pd−Mo alloys have been internally oxidized to form Pd/MoO3 composites, and it is shown for the first time that H2 reacts with these composites to form H-bronzes, for example, H x MoO3, within the Pd matrix. The Pd matrix is the source of mobile H atoms, which react with the oxide precipitates to form H-bronzes. The kinetics of H-bronze formation are extremely fast. Solubilities of H2 in the Pd/MoO3 composites have been measured, and because H2 solution in the oxide is so much more exothermic than that in the Pd matrix, the former can be separated from the latter. The intercept of the solubility plot along the H content axis gives the stoichiometry of the H-bronze formed. Some irreproducibility was found in the p H 2 versus r relationships, which is also found in H-bronzes prepared by other techniques such as H spillover. The relative partial enthalpies of H2 solution, ΔH H, in the H-bronzes have been determined by reaction calorimetry as a function of the H content of the bronze. The ΔH H values decrease sharply in exothermicity with increasing x in H x MoO3.

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