Electrochemical Hydrogen Insertion in Substoichiometric Titanium Carbide TiC0.6: Influence of Carbon Vacancy Ordering

Abstract : Substoichiometric titanium carbide of formula TiC0.6 with different degrees of carbon vacancy ordering has been synthesized first by reactive sintering at high temperature (2100 °C) and then by annealing at low temperature (730 °C) for different durations. The effect of annealing on the structure of the carbide and its capacity to electrochemically insert hydrogen has been investigated. The XRD study reveals two phase transitions in the carbide during annealing. First, annealing of disordered TiC0.6 (space group Fm3̅m) for 40 h leads to a trigonal superstructure of space group R3̅m thanks to ordering of carbon vacancies. After the longest annealing time of 120 h, the structure of the carbide becomes cubic anew, but with a space group of Fd3̅m. The electrochemical hydrogen insertion in these different types of TiC0.6, as studied by cyclic voltammetry, strongly depends on the crystalline structure of the carbide. The maximum storage capacity is obtained for 40 h, corresponding to the R3̅m ordered phase. Because the R3̅m structure consists of alternately empty and full (111) carbon atomic planes, we show that the hydrogen insertion and diffusion in the material is rendered possible by the presence of vacant (111) planes. This behavior is very similar to that of a cation-ordered manganese-nickel spinel vis-à-vis lithium ion insertion.
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Soumis le : jeudi 13 février 2014 - 16:16:11
Dernière modification le : mercredi 14 février 2018 - 16:29:38

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J. Nguyen, Nicolas Glandut, Cédric Jaoul, Pierre Lefort. Electrochemical Hydrogen Insertion in Substoichiometric Titanium Carbide TiC0.6: Influence of Carbon Vacancy Ordering. Langmuir, American Chemical Society, 2013, 29 (38), pp.12036-12042. ⟨10.1021/la402043x⟩. ⟨hal-00946526⟩

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