Ein ,altes‘ Rhodiumsulfid mit überraschender Struktur: Synthese, Kristallstruktur und elektronische Eigenschaften von Rh3S4

Beck, Johannes; Hilbert, Tobias

doi:10.1002/(sici)1521-3749(200001)626:1<72::aid-zaac72>3.0.co;2-i

Cited by 27 publications

(22 citation statements)

References 9 publications

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“…51 The Rh 3 S 4 material resides between the nonmetallic Rh 2 S 3 and metallic Rh 17 S 15 phases and exhibits properties akin to both of its brethren. RhS 6 octahedra ͑essentially Rh 2 S 3 ͒ serve as the backbone in the Rh 3 S 4 phase and anchor metallic Rh 6 eaves.…”

Section: A431mentioning

confidence: 63%

X-Ray Absorption Spectroscopy Studies of Water Activation on an Rh[sub x]S[sub y] Electrocatalyst for Oxygen Reduction Reaction Applications

Ziegelbauer

Gatewood

Gullá³

et al. 2006

Electrochem. Solid-State Lett.

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The prototype chalcogenide electrocatalyst Rh x S y was probed in situ via a synchrotron-based X-ray absorption near-edge structure ͑XANES͒ technique to elucidate specific sites and modes of water activation during oxygen reduction reaction. X-ray diffraction revealed a mixture of phases ͑Rh 2 S 3 , Rh 3 S 4 , and Rh 17 S 15 ͒. Theoretically generated XANES on a variety of geometries of O͑H͒ adsorption on the predominant Rh 3 S 4 phase were compared to the experimental data. We show for the first time that the electrocatalyst first adsorbs O͑H͒ in a onefold configuration at lower potentials and n-fold at potentials greater than 0.80 V. This expectedly has important consequences for oxygen reduction reaction on alternative chalcogenide materials.The current state-of-the-art materials for low-and mediumtemperature fuel cell cathodes are platinum or platinum-transition metal alloys. Platinum has a high activity for oxygen reduction reaction ͑ORR͒, ͑i 0 Ϸ 10 −5 mA cm −2 ͒ and tends predominantly towards the 4 e − oxygen reduction process. Unfortunately, platinum is extremely expensive, low in abundance, and easily poisoned. Even small amounts of contaminants severely depolarize platinum cathodes; this is a major issue in the context of direct methanol fuel cells ͑DMFCs͒. Methanol crossover through the proton exchange membrane and the resulting depolarization of a platinum-based catalyst causes overpotential losses of the order of approximately 300 mV vs reference hydrogen electrode ͑RHE͒. It is also important to note that in the case of electrolyzers such as those used for chlorine generation, cathodic oxygen reduction is preferred from both energysaving and safety perspectives. 1,2 Here, Pt-based electrocatalysts are not applicable due to their inherently higher solubility and susceptibility to poisoning in chlorine-saturated HCl. 1,2 As a result of these economic and technical issues, many groups are currently searching for new materials to replace platinum in these applications, such as transition metal chalcogenide clusters. 3,4 A wealth of research has generally pointed to pseudobinary M x Ru y Se z clusters ͑where M = transition metal͒ as exhibiting the best performance ͑i 0 :Ru x Se y /C = 2.22 ϫ 10 −5 , 0.5 M H 2 SO 4 ͒. 5,6 While these clusters are active towards ORR and exhibit a high degree of methanol tolerance, the pertinent structure/property relationships are still unclear. 7 One of the important variables to full 4 e − ORR is the water activation pathway. In the case of Pt-based electrolcatalysts, the adsorption of OH ͑as well as halide ions͒ on the electrocatalyst surface acts as a surface poison towards O 2 adsorption. 8 These effects on Pt and Pt-alloy systems have been extensively studied. 9,10 A recent study examined the effects of OH adsorption on Pt and Pt alloys by varying the concentration of water in a trifluoromethane sulfonic acid ͑TFMSA͒ electrolyte ͑where 6 M corresponds to a 4:1 mol % H 2 O/SO 3 − ratio͒. 9 The ϳ60 mV/dec Tafel slope observed at low overpotentials was related to OH͑ads͒...

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Section: A431mentioning

confidence: 63%

X-Ray Absorption Spectroscopy Studies of Water Activation on an Rh[sub x]S[sub y] Electrocatalyst for Oxygen Reduction Reaction Applications

Ziegelbauer

Gatewood

Gullá³

et al. 2006

Electrochem. Solid-State Lett.

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“…This is a monoclinic structure with space group C2/m (#12, C 2h ). It corresponds to a metal that shows a weak paramagnetism down to 4.5 K. 26 Recently, the mineral kingstonite of ideal composition Rh 3 S 4 has been found by the Bir Bir river in Ethiopia, although again with Ir and Pt substituting to some degree Rh atoms. 27 In the following we apply a first-principles method to investigate the three materials described (Rh 2 S 3 , Rh 3 S 4 , and Rh 17 S 15 ).…”

Section: B Rh-s Compoundsmentioning

confidence: 99%

First-principles characterization of the structure and electronic structure ofα−Sand Rh-S chalcogenides

Diéguez

Marzari

2009

Phys. Rev. B

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We have used first-principles calculations to study the structural, electronic, and thermodynamic properties of the three known forms of Rh-S chalcogenides: Rh2S3, Rh3S4, and Rh17S15. Only the first of these materials of interest for catalysis had been studied previously within this approach. We find that Rh17S15 crystallizes in a Pm3m centrosymmetric structure, as believed experimentally but never confirmed. We show band structures and densities of states for these compounds. Finally, we also investigated the ground state structure of solid sulfur (α-S), one of the few elements that represents a challenge for full first-principles calculations due to its demanding 128-atom unit cell and dispersion interactionis between S8 units.

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“…The experimentally determined Rh-S bond length (0.2059 nm) is somewhat smaller than the estimate given by density functional theory [10]. The only previous estimate of a Rh-S bond length comes from an X-ray crystallographic study of Rh 3 S 4 where single bond values range from 0.2256 to 0.2367 nm [16]. …”

Section: Treatment Of Datamentioning

confidence: 99%

A visible spectrum of jet-cooled rhodium monosulfide

Balfour

Hopkins

et al. 2005

Journal of Molecular Spectroscopy

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Ein ,altes‘ Rhodiumsulfid mit überraschender Struktur: Synthese, Kristallstruktur und elektronische Eigenschaften von Rh3S4

Cited by 27 publications

References 9 publications

X-Ray Absorption Spectroscopy Studies of Water Activation on an Rh[sub x]S[sub y] Electrocatalyst for Oxygen Reduction Reaction Applications

X-Ray Absorption Spectroscopy Studies of Water Activation on an Rh[sub x]S[sub y] Electrocatalyst for Oxygen Reduction Reaction Applications

First-principles characterization of the structure and electronic structure ofα−Sand Rh-S chalcogenides

A visible spectrum of jet-cooled rhodium monosulfide

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