Oxygen Electroreduction Reaction Catalysts

Ab initio modeling of charge transfer process in the oxygen electroreduction reaction (OER) has achieved some notable stepwise progresses in complexity and in proximity to realistic systems. Initial models only involved a few Pt and reactant atoms. Later, a catalyst slab replaced the Pt cluster. The... 

MEA performance is also seriously limited by the sluggish electroreduction of oxygen on the state-of-the-art Pt/C cathode catalyst in both PEMFCs and DMFCs. As is shown in Figure 22.4, the overpotential for the oxygen reduction reaction (ORR) in a PEMFC contributes about 80% of the total cell voltage loss [30]. In... 

Precious metal catalysts are the most efficient catalysts for the ORR, but their cost is a main issue. Low-cost carbon catalysts are active toward oxygen electroreduction in alkaline environment, but they offer only 2-electron reduction of molecular oxygen to peroxide (see Eq. (4.13)). Carbon catalyst is often used in combination with manganese oxide (Mn02) that promotes the ORR [156]. Mn02 is likely to catalyze a chemical disproportionation reaction of peroxide to... 

Cobalt catalyst precursors are cobalt(III) or cobalt(II) salts ligated to nitrogen and eventually oxygen-containing polydentate molecules like B12, salen, C2(DO)(DOH)p . The III/II electroreduction occurs at around OV vs SCE. Further reduction at ca. — 1 V vs SCE corresponds to the formation of cobalt(I) complexes which are the reactive species involved in the reactions mentioned below. 

For these low-temperature fuel cells, the development of catalytic materials is essential to activate the electrochemical reactions involved. This concerns the electro-oxidation of the fuel (reformate hydrogen containing some traces of CO, which acts as a poisoning species for the anode catalyst methanol and ethanol, which have a relatively low reactivity at low temperatures) and the electroreduction of the oxidant (oxygen), which is still a source of high energy losses (up to 30-40%) due to the low reactivity of oxygen at the best platinum-based electrocatalysts. 

Marcotte, S., D. Villers, N. Guillet, L. Roue, and J.R Dodelet (2004). Electroreduction of oxygen on Co-based catalysts Determination of the parameters affecting the two-electron transfer reaction in an acid medium. Electmchim. Acta 50, 179-188. Zagal, J.H. (1992). Metallophthalocyanines as catalysts in electrochemical reactions. Coord. Chem. Revs. 119, 89-136. 

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