Ruthenium chalcogenides

Ozenler SS, Kadirgan F (2006) The effect of the matrix on the electro-catalytic properties of methanol tolerant oxygen reduction catalysts based on ruthenium-chalcogenides. J Power Sources 154 364-369... 

Most studies reported on ruthenium chalcogenides containing Se, S, and Te relate, so far, to the acid medium. It is, however, interesting to compare some feamres from the cyclic voltammetry results generated in acid as well as in alkaline media for the metal core as well as the selenium coordinated to the metallic core (Fig. 14.11). 

Gago AS, Morales-Acosta D, Arriaga LG, Alonso-Vante N (2011) Carbon supported ruthenium chalcogenide as cathode catalyst in a microlluidic fOTuiic acid fuel cell. J Power Sources 196(3) 1324-1328... 

Binary systems of ruthenium sulfide or selenide nanoparticles (RujcSy, RujcSey) are considered as the state-of-the-art ORR electrocatalysts in the class of non-Chevrel amorphous transition metal chalcogenides. Notably, in contrast to pyrite-type MS2 varieties (typically RUS2) utilized in industrial catalysis as effective cathodes for the molecular oxygen reduction in acid medium, these Ru-based cluster materials exhibit a fairly robust activity even in high methanol content environments of fuel cells. 

Carbonyls. Related to the chalcogenide and metal cluster studies are the carbonyl studies for ORR.189 I92-198-201 The majority of the carbonyl work has been reported by several Mexican research groups. This body of work appears to have developed from studies on ruthenium-containing chalcogenide catalysts in the mid-1990 s. The precursors used for these catalysts involved Ru-carbonyls.202... 

Heterometal alkoxide precursors, for ceramics, 12, 60-61 Heterometal chalcogenides, synthesis, 12, 62 Heterometal cubanes, as metal-organic precursor, 12, 39 Heterometallic alkenes, with platinum, 8, 639 Heterometallic alkynes, with platinum, models, 8, 650 Heterometallic clusters as heterogeneous catalyst precursors, 12, 767 in homogeneous catalysis, 12, 761 with Ni—M and Ni-C cr-bonded complexes, 8, 115 Heterometallic complexes with arene chromium carbonyls, 5, 259 bridged chromium isonitriles, 5, 274 with cyclopentadienyl hydride niobium moieties, 5, 72 with ruthenium—osmium, overview, 6, 1045—1116 with tungsten carbonyls, 5, 702 Heterometallic dimers, palladium complexes, 8, 210 Heterometallic iron-containing compounds cluster compounds, 6, 331 dinuclear compounds, 6, 319 overview, 6, 319-352... 

Physico-Chemical Properties of Novel Nanocrystalline Ruthenium Based Chalcogenide Materials... 

As an example, Fig. 5.6 depicts a typical diffraction spectrum. It is evident that long range order does not exist in our chalcogenide samples. However, the broad difffactrogram peak centered at 20 = 42.5° has the characteristic of a nanodivided ruthenium metal [22]. This points out that the active center in this chalcogenide materials is essentially of metallic nature. The material, either in powder or colloidal form, was analyzed by the EXAFS technique [11]. The local range order of this technique allowed for some structural determination of our samples. Thus, for example, the co-ordination distances for ruthenium-selenium and ruthenium-ruthenium are R(RU-se) = 2.43 A y R(ru.rU) = 2.64 A, respectively. The metal-metal co-ordination distance is of the same order of magnitude as that of well known cluster based materials such as the Chevrel phase [35, 37], cf. Fig. 5.2b. This testifies that the used chemical route leads to the formation of cluster-like materials. 

Figure 14. Design of an air-breathing laminar flow fuel cell (LFFC) showing the laminar flow profile of the anode side. Adapted with permission from Devin T. Whipple, Ranga S. Jayashree, Daniela Egas, Nicolas Alonso-Vante and Paul J.A. Kenis, Ruthenium cluster-like chalcogenide as a methanol tolerant cathode catalyst in air-breathing laminar flow fuel cells. Electrochi mica Acta 54 (2009) Copyright (2009), with permission from Elsevier.

The reduction of the overpotential in alkaline on chalcogenide ruthenium metal centers is certainly the result of the generation of H02 species, via the outer-sphere reaction mechanism, phenomentMi that also occurs on oxide-covered surfaces. This is apparently the rational of the kinetics facility in alkaline media in comparison to the acid medium. 

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