Noble catalysts

PEMFC Polymer 80-110 60 High current and power densities, long operating life C02 intolerance, water management, noble catalyst Transportation, cogeneration... 

PAFC Phosphoric acid 200 40 Technology well advanced Relatively low efficiency, limited lifetime, noble catalyst CHP... 

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 loss of the catalytically active surface of Raney nickel due to recrystallization is a continuously progressing process that can be retarded to some extent in Raney-nickel anodes by dispersing oxide ceramic materials like Zr02 and Ti03 in the nickel matrix. More serious is anodic oxidation for some metals additionally accompanied by dissolution of the catalyst to which even platinum is subject but which is an even more serious hazard for the less noble catalysts as silver and Raney nickel. 

Noble metal ions noble catalysts 6 Reactions of -olefins, structures of... 

Support Effect on Chemisorption and Catalytic Properties of Noble Catalysts... 

PEFC, is that non-noble metals are also stable in an alkaline environment. The greatest advantages of AFCs are that non-noble catalysts can be used and that an expensive and hfetime-reducing ion-conducting membrane can be avoided, thus drastically reducing the material cost. 

Osmieri L, Videla AHAM, Armandi M, Specchia S (2015) A micro-silica reactor (pSi02-R) able to produce highly porous non-noble catalysts for oxygen reduction reaction under alkaline conditions. In challenges towards zero platinum for oxygen reduction. La Grande Motte (France) 14-16/09/2015... 

Dobrzeniecka A, Zeradjanin AR, Masa J, Blicharska M, Wintrich D, Kulesza PJ Schuhmann W Evaluation of kinetic constants on porous, non-noble catalyst layers for oxygen reduction —a comparative study between SECM and hydrodynamic methods. Catal Today. doi 10. 1016/j.cattod.2015.07.043... 

Figure 1.19. Oxygen reduction mechanism on noble catalysts [52]. (Reprinted from Journal of Power Sources, 152(2), Wang Bin, Recent development of non-platinum catalysts for oxygen reduction reaction, 1-15, 2005, with permission from Elsevier.)...

Studies on HOR electrocatalysis have built up a foundation for all modem electrocatalysis. Since the pioneering work of the 1960s, when flie dependence of hydrogen adsorption upon the crystallographic orientation of the platinum surface was discovered, the study of the relationship between electrochemical activity and surface structure has been the main theme of electrochemical research [50]. In this section, we first introduce the electrocatalysis of the HOR on Pt and Pt-alloy electrodes, with detailed discussion of the stmcture-sensitivity of hydrogen adsorption on well-defined Pt surfaces. Then we discuss two types of non-noble catalysts for the HOR carbides and Raney nickels. 

Transition metal alloys, notably Raney nickel, have also been investigated extensively as catalysts because of their interesting electronic and chemical properties [94]. Raney nickel is a solid catalyst, composed of fine grains of a nickel-aluminum alloy, and has been used in many industrial processes. Its application in the fuel cell field has been focused on alkaline fuel cells (AFC) rather than PEM fuel cells, due to potential corrosion in PEM operation media. Raney nickel s unique catalytic activity for the HOR as a non-noble catalyst makes it worth inclusion in this chapter. 

Development of new catalysts such as highly durable non-noble catalysts. For long-term sustainable PEMFC commercialization, non-noble catalysts are the solution because of the limited supply and high cost of Pt. 

Use of noble catalysts (Pt, Ir02) because of the acidity of the membrane... 

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