Oxygen platinum-based catalysts

Another key part of a PEM membrane is the thin layer of platinum-based catalyst coating that is used. It makes up about 40% of the fuel cell cost. The catalyst prepares hydrogen from the fuel and oxygen from the... 

In an acidic medium, a PEMFC fed with ethanol allows power densities up to 60 mW cm to be reached at high temperatures (80-120 °C), but this needs platinum-based catalysts, which may prevent wider applications for portable electronic devices. On the other hand, in an alkaline medium, the activity of non-noble catalysts for ethanol or ethylene glycol oxidation and oxygen reduction is sufficient to reach power densities of the order of 20 mW cm at room temperature. This opens up the hope of developing SAMFCs that are particularly efficient for large-scale portable applications. 

The electro-catalytic oxidation of hydrogen, and reduction of oxygen, at carbon supported platinum based catalysts remain essential surface processes on which the hydrogen PEM fuel cell relies. The particle size (surface structure) and promoting component (as adsorbate or alloy phases) influence the activity and tolerance of the catalyst. The surface chemical behavior of platinum for hydrogen, oxygen, and CO adsorption is considered, in particular with respect to the influence of metal adsorbate and alloy components on close packed and stepped (defect) platinum surfaces. Dynamical measurements (employing supersonic molecular beams) of the... 

The sluggish oxygen reduction reaction (ORR) in the cathode catalyst layer (CCL) induces a major fraction of voltage losses in PEFCs. Due to the requirement of sufficient membrane humidification, discussed in Sect. 8.2.2, and the limitation it imposes on the working temperature range (< 100 °C) only platinum-based catalysts can provide acceptable reaction rates. Platinum, however, is costly, and its resources are limited. 

Let us consider the oxygen reduction reaction (ORR) that occurs in the cathode of the polymer electrolyte membrane fuel cell (PEMFC), in an acidic environment. Although a variety of ORR mechanisms have been proposed, the four-electron pathway is primarily used to characterize the behavior of this reaction at a platinum electrode or a glassy carbon electrode coated with a platinum-based catalyst. The overall reaction is given by... 

E. Antolini, T. Lopes, E. R. Gonzalez An overview of platinum-based catalysts as methanol-resistant oxygen reduction materials for direct methanol fuel cells, Journal of Alloys and Compounds , 461, 253-262 (2008). 

As the anion-exchange membrane fuel cell is the alkaline-based system, we can use non-platinum-based catalyst. This is a big advantage to lower the cost of fuel cells. Especially perovskite-type and pyrochlore-type oxides have high performance to oxygen-electrocatalysts which could be applicable to the cathode materials. Some oxides have also bifunctional activities as oxygen electrode catalyst to produce a reversible fuel cell thus, future deployment is expected. While, the big problems are stability of the base... 

Improvement of current platinum-based catalysts for the oxygen reduction reaction (ORR) and the hydrogen oxidation reaction (HOR) or substitution by platinum-group metal (PGM) free catalysts in order to meet the platinum cost and design constraints for commercial applications [1]. 

A.P. (1994) Mechanism of the selective reduction of nitrogen monoxide on platinum-based catalysts in the presence of excess oxygen. AppL Catal. B Environ., 4, 65-94. 

Conversely, the oxygen reduction reaction (ORR) has also been widely studied, in particular for its requirement in proton exchange membrane (PEM) fuel cells. Platinum based catalysts are typically used to increase the sluggish kinetics, although other noble metal catalysts and carbon... 

Neergat N, Sbukla AK, Gandhi KS. 2001. Platinum-based alloys as oxygen-reduction catalysts for solid-polymer-electrolyte direct methanol fuel cells. J Appl Electrochem 31 373-378. 

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