Reduction Site in Ce
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            + Revealed by Gas Phase Thermal Desorption Spectrometry

Mafuné, Fumitaka; Masuzaki, Daigo; Nagata, Toshiaki

doi:10.1007/s11244-017-0862-5

Cited by 7 publications

(2 citation statements)

References 24 publications

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“…Similar concomitant intensity changes were appreciable above 900 K between Co n H + and Co n + ( n = 5–10) in Figure , although much less pronounced, suggesting that one H atom may be released from Co n H + . The energy required to release one H atom from Co 5 H + was 2.47 eV, Co 5 H + → Co 5 + + normalH goodbreak0em1em⁣ normalΔ E = prefix+ 2.47 0.25em eV On the other hand, the energy required to release one H atom from Co 5 H – was 2.72 eV, Co 5 H − → Co 5 − + normalH goodbreak0em1em⁣ normalΔ E = prefix+ 2.72 0.25em eV which can be too high for the H atom release to be observed clearly below 1000 K. − Moreover, for Co n H – ( n = 7–9) as discussed later, Co n H – increased and Co n – decreased in the abundance fraction with the temperature, which cannot be explained by the H atom release. These changes were surely caused by another mechanism.…”

Section: Discussionmentioning

confidence: 99%

Hydrogen Storage Capacity of Cobalt Cluster Ions

Mafuné,

Wu,

Yamaguchi

et al. 2024

J. Phys. Chem. A

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The adsorption of H 2 on gas-phase Co n ± (n = 5−12) clusters at 300 K and the desorption of H 2 from Co n H m ± upon heating were studied experimentally by combining thermal desorption spectrometry and mass spectrometry to elucidate the hydrogen storage property of the Co clusters. Hydrogen atoms adsorbed well on Co n + (n = 5, 10−12) and Co n − (n = 5−12) at 300 K to form Co n H m± . The atomic ratios, m/n, for Co n H m − (0.9−1.4) were higher than those for Co n H m + (0.2−1.1). According to density functional theory (DFT) calculations, the first few H 2 molecules had a tendency to dissociatively adsorb onto the Co clusters. Further, the bonding nature of the H atoms was ionic, similar to the H atoms in the metallic hydrides. In contrast, H 2 , adsorbed molecularly, was explained in terms of σ complex formation. H 2 molecules were desorbed from the clusters upon heating. The temperature dependences showed that Co n H m − released H 2 at a higher temperature (700−800 K) than Co n H m + (600−700 K), suggesting that Co n − should have a higher affinity to hydrogen than Co n + . The desorption temperatures were lower than those of V n H m + , which was consistent with the fact that the adsorption energies of H 2 were lower for the Co clusters than those for the V clusters. The low adsorption energies were ascribed to their large highest occupied molecular orbital−lowest unoccupied molecular orbital (HOMO−LUMO) gaps in the Co clusters.

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Section: Discussionmentioning

confidence: 99%

Hydrogen Storage Capacity of Cobalt Cluster Ions

Mafuné,

Wu,

Yamaguchi

et al. 2024

J. Phys. Chem. A

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“…In thermal desorption spectrometry experiments, the clusters travel down a 116 mm long extension of the reaction zone formed by a copper tube of larger diameter, which reduces the number of reactive collisions. [76][77][78][79][80][81][82][83][84][85] Crucially, this tube is thermally isolated from the reaction zone and can thus be heated without significantly changing the temperatures of the source and the subsequent reaction zone. In addition, the helium carrier gas cannot escape and forms a thermal link with the heated tube wall, thus ensuring that the reaction products thermalize.…”

Section: Rhodium Cluster Production and Reaction Under Thermalized Co...mentioning

confidence: 99%