Platinum alloy catalysts, for

Gurau B, Viswanathan R, LiuR, Lafrenz TJ, Ley KL, Smotkin ES, Reddington E, Sapenza A, Chan BC, Mallouk TE, Sarangapani S (1998) Stmctural and electrochemical characterization of binary, ternary, and quaternary platinum alloy catalysts for methanol electro-oxidation. J Phys Chem B 102 9997-10003... 

Kocha SS, Gasteiger HA (2004) Platinum alloy catalysts for PEMFCs. Htany B. Gonzalez Convention Center, San Antonio, TX. http //www.fijelcellst3niiiar.e(Hn ast-eonferences/ 2004.aspx... 

Wei ZD, Guo HT, Tang ZY. Heat treatment of carbon-based powders carrying platinum alloy catalysts for oxygen reduction influence on corrosion resistance and particle size. J Power Sources 1996 62 233-6. 

Platinum Alloy Catalysts for Direct Methanol Fuel Cell Anodes... 

H4-135642 Paul Stonehart, Kazunori Tsurumi, Tosbihide Nakamura, Akira Sato Platinum Alloy Catalyst and Process for Preparing (Pt-Ni-Co-Mn) 26 Sept 1990 11 May 1992 Tanaka Kikinzoku Kogyo Stonehart Associates... 

Rheniu, s used W-Re thermocouples 3 a Pt-Re alloy catalyst for petroleum rv ruling" aid to have a longer lifetime than platinum alone. 

Janssen MMP, Moolhuysen J (1976) Platinum-tin catalysts for methanol fuel cells prepared by a novel immersion technique, by electrocodeposition and by alloying. Electrochim Acta... 

This selected brief review will be focused on the research and development progress on ORR kinetics. The origin of the problem related with the low ORR activity of platinum will be discussed, followed by a review of recent progress in making more active, more durable platinum-based ORR catalysts. These include platinum alloy catalysts, platinum monolayer catalysts, platinum nanowire and nanotube catalysts, and the more recent shape- and facet-controlled platinum-alloy nanocrystal catalysts. The progress in the mechanistic understanding on the correlation between the activity and the electronic and structural properties of surface platinum atoms will be reviewed as well. The future direction of the research on platinum-based catalysts for PEM fuel cell apphcation will be proposed. 

Platinum-based Alloy Catalysts for PEM Fuel Cells... 

Platinum-based Alloy Catalysts for PEM Fuel Cells 637 13.2.2.2 The OHads Inhibition Effect... 

Carbon corrosion and platinum dissolution in the acidic electrolyte at elevated temperatures are well recognized from the early years of research on PAFCs and are definitely relevant to HT-PEMFCs based on the acid-doped FBI membranes. Both mechanisms are enhanced at higher temperatures and higher electrode potentials. This should be taken into account when platinum alloy catalysts are considered for the HT-PEMFC. More efforts are also needed to develop resistant support materials based on either structured carbons or non-carbon alternatives. 

As mentioned earher, since the platinum (and other precious metals) loading reduction cannot overcome the price increment, the development of a nonprecious catalyst is perhaps the most feasible solution for PEM fuel cell commercialization. The nonprecious catalysts generally include carbides, nitrides, oxides, carbonitrides, oxynitrides, materials derived from macrocycles and porphyrins, and composites of these materials (Borup et al., 2007). However, unlike the platinum alloy catalysts that have already shown both the improved reaction activity and stability, none of the nonprecious catalysts demonstrated both good reaction activity and stability to the best of the authors knowledge. Some nonprecious catalysts have reasonable reaction activity but poor stability (e.g., some transition metal carbides), and... 

Platinum has been widely used for PEMFCs owing to its excellent oxygen reduction catalytic activity. Platinum is usually implemented in the form of Pt/C catalysts because of its significantly higher surface area compared with that of platinum black catalysts. Furthermore, platinum alloy catalysts are also employed to enhance oxygen reduction activities. Pt black, Pt/C, and Pt/C alloys will be discussed in this section. 

Commercial PEFC electrodes contain dispersed platinum or platinum-alloy catalysts supported on high surface area carbon. High platinum surface area is required to minimize the overpotential for the ORR. Examination of the Pourbaix diagram for platinum indicates that dissolution is expected to occur in a triangular region where pH < 0 and the electrode potential is between approximately 1 and 1.2 V at 25 °C (Pourbaix 1974). 

Ruthenium nowadays finds many uses in the electronics industry, particularly for making resistor tracks. It is used as an ingredient in various catalysts and, importantly, in electrode materials, e.g. Ru02-coated titanium elements in the chloralkali industry. Osmium tetroxide is a very useful organic oxidant and, classically, is used as a tissue stain. Both elements are employed in making certain platinum alloys. 

The Industrial Revolution was made possible by iron in the form of steel, an alloy used for construction and transportation. Other d-block metals, both as the elements and in compounds, are transforming our present. Copper, for instance, is an essential component of some superconductors. Vanadium and platinum are used in the development of catalysts to reduce pollution and in the continuing effort to make hydrogen the fuel of our future. 

Electro-catalysts which have various metal contents have been applied to the polymer electrolyte membrane fuel cell(PEMFC). For the PEMFCs, Pt based noble metals have been widely used. In case the pure hydrogen is supplied as anode fuel, the platinum only electrocatalysts show the best activity in PEMFC. But the severe activity degradation can occur even by ppm level CO containing fuels, i.e. hydrocarbon reformates[l-3]. To enhance the resistivity to the CO poison of electro-catalysts, various kinds of alloy catalysts have been suggested. Among them, Pt-Ru alloy catalyst has been considered one of the best catalyst in the aspect of CO tolerance[l-3]. 

The catalysts at the anode can be made less sensitive to CO poisoning by alloying platinum with other metals such as ruthenium, antimony or tin[N.M. Markovic and P.N. Ross, New Flectro catalysts for fuel cells CATTECH 4 (2001) 110]. There is a clear demand for better and cheaper catalysts. Another way to circumvent the CO problem is to use proton-exchange membranes that operate at higher temperatures, where CO desorbs. Such membranes have been developed, but are not at present commercially available. 

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