Platinum metal chalcogenides

Dey S, Jain VK. Platinum group metal chalcogenides. Platinum Metals Rev 2004 48 16-29. 

The platinum metal chalcogenides in general are easier to prepare than the corresponding oxides. Whereas special conditions of temperature and pressure are required to prepare many of the oxides, the platinum metals react most readily with S, Se, and Te. A number of additional differences concerning the chemistry of the chalcogenides and the oxides are summarized as follows The metal—sulfur (selenium, tellurium) bond has considerably more covalent character than the metal-oxygen bond and, therefore, there are important differences in the structure types of the compounds formed. Whereas there may be considerable similarity between oxides and fluorides, the structural chemistry of the sulfides tends to be more closely related to that of the chlorides. The latter compounds... 

It will not be possible, in this paper, to deal with all of the platinum metal chalcogenides. Instead, a number of examples will be chosen and their electrical as well as magnetic properties correlated with the atomic positions in the various structures formed. The first group of compounds to be discussed crystallize with the pyrite structure, which is shown in Figure 1. This structure is similar to the NaCl structure if we replace Na by Fe and each Cl by an S2 group. However, the S-S distance within... 

Several platinum metal chalcogenides of the type MX crystallize with the NiAs structure. They include RhSe, RhTe, and PdTe. This structure is shown in Figure 6. Each cation is coordinated by six anion neighbors... 

Normally, the kinetics of ORR and OER occurring at the cathode of fuel cells, including direct methanol fuel cells (DMFCs) is very slow. In order to speed up the ORR kinetics to reach a practical usable level in a fuel cell, ORR catalyst is needed at the air cathode. Platinum (Pt)-based materials are the most practical catalysts used in PEM technology. These Pt-based catalysts are too expensive to make fuel cells commercially viable, and hence extensive research over the past several decades has been focused on development of alternative catalysts. These alternative electrocatalysts include noble metals and allo37S, carbon materials, quinone and its derivatives, transition metal macrocyclic compounds, transition metal chalcogenides, transition metal carbides and transition metal oxides. In this chapter, we focus on both noble and nonnoble electrocatalysts being used in air cathodes and the kinetics and mechanisms O2 reduction/oxidation reaction (both ORR and OER), catal37zed by them. 

The platinum group metals form several binary, pseudo-binary, and ternary chalcogenides. The outstanding features of these compounds as related to catalysis and materials science have been widely reported and reviewed [88],... 

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... 

A nonactive electrode may include noble metals such as gold, silver, and platinum, the so-called sp-metals such as In, Ga, Cd, Bi, as well as transition (or d) metals such as nickel or cobalt. Carbon electrodes and semiconductors such as indium tin oxide [1], diamond [2], and conducting polymers may fall into the category of nonactive electrodes in appropriate solutions, as do composite materials that contain metal oxides or chalcogenides. The behavior of active electrodes in nonaqueous solution is discussed separately in the next chapter. 

Numerous types of materials have been made by CVD techniques, such as metal carbides, borides, silicides, oxides, nitrides, and chalcogenides, as well as films of pure metals.27 For example, thermolysis of Cp PtMe3 deposits films of platinum on glass or silicon wafer substrates,28 while Pd(hfacac)2 (hfacac = 1,1,1,5,5,5-... 

R301 B. Devreese and J. Van Beeumen, Mass Spectrometric Methods for the Study of Non-Co valent Interactions of Proteins and Other Biomolecules , Int. J. Bio-Chromatogr., 2000, 5, 313 R302 S. Dey, S. Narayan, A. Singhal and V, K. Jain, Palladium and Platinum Organochalcogenolates and their Transformation into Metal Chalcogenides , Proc.-Indian Acad. Sci., Chem. Sci., 2000, 112, 187... 

Partial or complete replacement of platinum for ORR has attracted a lot of interest in order to enhance electrocatalytic activity and reduce materials costs. Therefore, some non-platinmn promising electrocatalysts for ORR have been developed, i.e., using car-bides, " nitrides,macroeycle materials, " and other preeious metals, such as Pd" " or Ru-based materials, " as well as non-precious metal chalcogenides. ... 

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