Transition metal oxygen reduction

The reduction reaction occurs by the transfer of hydrogen atoms bound to the surface of the metal catalyst to the carbonyl oxygen and carbon atoms. We recall that the same types of catalysts are used for the hydrogenation of alkenes, a much faster reaction. Alkenes can be reduced at room temperature under 1 atm. pressure of hydrogen gas. Carbonyl compounds require higher temperatures and pressures as high as 100 atm. Therefore, transition metal-catalyzed reduction of carbonyl compounds that also have a carbon—carbon double bond results in reduction of both functional groups. 

Alonso Vante N, Jaegermann W, Tributsch H, Hoenle W, Yvon K (1987) Electrocatalysis of oxygen reduction by chalcogenides containing mixed transition metal clusters. J Am Chem Soc 109 3251-3257... 

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. 

With respect to non-noble and non-Ru catalysts, transition metal chalcogenides with spinel and pyrite structures have been investigated and shown that these can also be active to oxygen reduction processes. The motivation in the present case is that chalcogen addition might enhance the stability and activity toward the ORR... 

We have already referred to the Mo/Ru/S Chevrel phases and related catalysts which have long been under investigation for their oxygen reduction properties. Reeve et al. [19] evaluated the methanol tolerance, along with oxygen reduction activity, of a range of transition metal sulfide electrocatalysts, in a liquid-feed solid-polymer-electrolyte DMFC. The catalysts were prepared in high surface area by direct synthesis onto various surface-functionalized carbon blacks. The intrinsic... 

Solorza-Eeria O, EUmer K, Giersig M, Alonso-Vante N (1994) Novel low-temperature synthesis of semiconducting transition metal chalcogenide electrocatalyst for multielectron charge transfer Molecular oxygen reduction. Electrochim Acta 39 1647-1653... 

Trapp V, Christensen PA, Hamnett A (1996) New catalysts for oxygen reduction based on transition-metal sulfides. J Chem Soc Earaday Trans 92 4311 319... 

Alonso-Vante N, Tributsch H, Solorza-Eeria O (1995) Kinetics studies of oxygen reduction in acid medium on novel semiconducting transition metal chalcogenides. Electrochim Acta 40 567-576... 

Behret H, Binder H, Sandstede G (1975) Electrocatalytic oxygen reduction with thiospinels and other sulphides of transition metals. Electrochim Acta 20 111-117... 

Reeve RW, Christensen PA, Dickinson AJ, Hamnett A, Scott K (2000) Methanol-tolerant oxygen reduction catalysts based on transition metal sulfides and their appheation to the study of methanol permeation. Electrochim Acta 45 4237-4250... 

Lee K, Savadogo O, Ishihara A, Mitsushima S, Kamiya N, Ota K-I. 2006. Methanol-tolerant oxygen reduction electrocatalysts based on Pd-3D transition metal alloys for direct methanol fuel cells. J Electrochem Soc 153 A20-A24. 

Nilekar AU, Mavrikakis M. 2008. Improved oxygen reduction reactivity of platinum mono-layers on transition metal surfaces. Surf Sci 602 L89-L94. 

The release of N2 occurs within function 3. It involves the dissociation of NO (via a dinitrosyl-adsorbed intermediate), followed by subsequent formation of N2 and scavenging of the adsorbed oxygen species left from NO dissociation. The removal of adsorbed oxygen is due to the total oxidation of an activated reductant (CxHyOz). This reaction corresponds to a supported homogeneous catalytic process involving a surface transition metal complex. The corresponding catalytic sequence of elementary steps occurs in the coordinative sphere of the metal cation. 

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