Platinum loading

The fit of these equations to the data is very good, as seen in Fig. 18. These equations are valid to very small values of CO concentrations, where the reaction becomes first order with respect to CO. In a mixture of CO with oxygen, there should be a maximum in reaction rate when the CO concentration is at 0.2%, as shown in Fig. 19. When the oxidation of olefins and aromatics over a platinum loaded monolith is over 99% complete, the conversion of higher paraffins may be around 90% and the conversion of the intractable methane is only 10%. 

Fig. 1. Performance evaluation of prepared electro-catalysts as an electrode of PEMFC. Cell temperature 70 C, active area 50cm, platinum loading anode(0.3mgPt/cm )/cathode(0.45mg Pt/cm ), fuel utilization H2/O2 = 80%/50%, RH 100% RFl, pressure H2/O2 = 0 psig/0 psig.

In the presence of tin, the number of active platinum sites seems to be superior compared to catalyst B and thus an increase in the space velocity by a factor of ten does not seem to saturate all the sites. These results show the importance of the role played by tin since platinum loading was the same in both cases. It is reasonable to think that in the case of catalyst B, due to the method of deposition, some aggregates of platinum are formed on the surface of the catalyst. In the presence of tin, a part of the aggregates could disappear and some Pt/Sn alloy particles, better dispersed at the surface, could be formed. 

The Pt4f signal obtained with samples with high platinum loading (1 and S%) shows us that despite the low heating rate [0. Scc/min] used during the calcination of the san le, the deconqrosition of the tetramin platinum ion provoked the reduction ofthe ion at sqrerfdal level TPR results (Fig. 6) ow that this did not occur in the bulk... 

Platinum-loaded Ti02 systems can be considered as a short-circuited photo-electrochemical cell where the Ti02 semiconductor electrode and metal Pt counterelectrode are brought into contact [159]. Light irradiation can induce electron-hole (e -h +) pair formation and surface oxidation and also reduction reactions on each Pt/Ti02 particle (Figure 4.11). These powder-based systems lack the advantage of... 

Matsumura, M., Ohnishi, H., Hanafusa, K., and Tsubomura, H., Stabilization of platinum-loaded CdS photocatalyst by addition of EDTA, Bull. Chem. Soc. jpn., 60,2001,1887. 

Fig. 13. Uniform bifunctional platinum-loaded zeolite catalyst. Large white dots (Pt) are 0.5 nm in diameter.

Platinum loadings, reducing, 19 628 Platinum metals plating, 9 822-823 Platinum oxides, volatilized, 17.T80 Platinum-palladium thermocouple, 24 461 Platinum reforming catalysts, rhenium and, 21 695-696... 

Improvements in solid polymer electrolyte materials have extended the operating temperatures of direct methanol PEFCs from 60 C to almost 100 C. Electrocatalyst developments have focused on materials that have higher intrinsic activity. Researchers at the University of Newcastle upon Tyne have reported over 200 mA/cm at 0.3 V at 80 C with platinum/ruthenium electrodes having platinum loading of 3.0 mg/cm. The Jet Propulsion Laboratory in the U.S. has reported over 100 mA/cm at 0.4 V at 60 C with platinum loading of 0.5 mg/cm. Recent work at Johnson Matthey has clearly shown that platinum/ruthenium materials possess substantially higher intrinsic activity than platinum alone (45). 

Johnson Matthey then determined that the platinum loading in the alloyed catalyst could be increased up to 30 wt% while retaining the same amount of platinum without any decrease in... 

T. Ito, K. Kato, S. Kamitomai, M. Kamiya, "Organization of Platinum Loading Amount of Carbon-Supported Alloy Cathode for Advanced Phosphoric Acid Fuel Cell," in Fuel Cell Seminar Abstracts, 1990 Fuel Cell Seminar, Phoenix, AZ, November 25-28, 1990. J.S. Buchanan, G.A. Hards, L. Keck, R.J. Potter, "Investigation into the Superior Oxygen Reduction Activity of Platinum Alloy Phosphoric Acid Fuel Cell Catalysts," in Fuel Cell Seminar Abstracts, Tucson, AZ, November 29-December 2, 1992. 

Using a carbon-supported Pt catalyst to replace Pt black can reduce the platinum loading by a factor of 10—from 4 to 0.4 mg/cm [74]. However, the platinum utilization in this PTFE-bound catalyst layer still remains low in the vicinity of 20% [75,76]. 

O Hayre, R., Lee, J.-J., Cha, S.-W., and Rrinz, R B. A sharp peak in the performance of sputtered platinum fuel cells at ultralow platinum loading. Journal of Power Sources 2002 109 483-493. 

Sasikumar, G., Ihm, J. W., and Ryu, H. Dependence of optimum Nation content in catalyst layer on platinum loading. Journal of Power Sources 2004 132 11-17. 

Wilson, M. S., Valerio, J. A., and Gottesfeld, S. Low platinum loading electrodes for polymer electrolyte fuel cells fabricated using thermoplastic ionomers. Electrochimica Acta 1995 40 355-363. 

Sasikumar, G., Ihm, J. W, and Ryu, H. Dependence of optimum Nation content in catalyst layer on platinum loading. Journal of Power Sources 2004 132 11-17. Taylor, E. J., Anderson, E. B., and Vilambi, N. R. K. Preparation of high-plat-inum-utilization gas diffusion electrodes for proton-exchange-membrane fuel cells. Journal of the Electrochemical Society 1992 139 L45-L46. 

Kumar, G. S., Raja, M., and Parthasarathy S. High performance electrodes with very low platinum loading for polymer electrolyte fuel cells. Electrochimica Acta 1995 40 285-290. 

A continuous process based on hydrodynamic cavitation can be employed to prepare a wide variety of metal oxides in grain sizes of 1 -10 nm, such as iron oxide, bismuth molybdate, perovskites, platinum-loaded zeolite, and other ceramics and superconductors [170]. The method uses a microfluidiser for mechanically generating hydrodynamic cavitation and the internal pressure of the liquid media is elevated from ambient pressure to between 1000 to 25 000 psi. 

Ohno, T., Saito, S., Fujihara, K., Matsumura, M. 1996. Photocatalyzed production of hydrogen and iodine from aqueous solutions of iodide using platinum-loaded TiOj powder. Bull Chem Soc Jpn 69 3059-3064. 

Chao, K.-) Wu, H.-C., and Leu, L-J. (1996) Hydroisomerization oflight normal paraffins over series of platinum-loaded mordenite and beta catalysts. Appl. Catal. A., 143, 223-243. 

Figure 5. Total platinum needed for a 600 MW generating fuel cell for different cell voltages three platinum loadings (mg Pt/cm ) are illustrated...

Fig. 6.7 Dependence of H2 and O2 evolution upon platinum loading. Water = 350 mL Pt/Ti02 = 0.3 g Na2C03 = 80 g. Reproduced with permission from Ref. [ 99].

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