Platinum loading reduction

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... 

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. 

Careful inspection of the reported photocatalytic reactions may demonstrate that reaction products can not be classified, in many cases, into the two above categories, oxidation and reduction of starting materials. For example, photoirradiation onto an aqueous suspension of platinum-loaded Ti02 converts primary alkylamines into secondary amines and ammonia, both of which are not redox products.34) ln.a similar manner, cyclic secondary amines, e.g., piperidine, are produced from a,co-diamines.34) Along this line, trials of synthesis of cyclic imino acids such as proline or pipecolinic acid (PCA) from a-amino acids, ornithine or lysine (Lys), have beer. successfuL35) Since optically pure L-isomer of a-amino acids are available in low cost, their conversion into optically active products is one of the most important and practical chemical routes for the synthesis of chiral compounds. It should be noted that l- and racemic PCA s are obtained from L-Lys by Ti02 and CdS photocatalyst, respectively. This will be discussed later in relation to the reaction mechanism. 

Metal(0) deposited at the Ti02 surface may enhance yields and selectivity of the reduction products [28-30], In the presence of copper(0)-loaded Ti02 formaldehyde and methanol were detected as main products [31]. Mercury- and platinum-loaded Ti02 favoured formation of carbon and formaldehyde [28,29], Methane was obtained with a high selectivity in the case of palladium-doped Ti02, whereas in the presence of Rh, Au, and Ru metals acetic acid was also produced [30],... 

This approach would also potentially have two other advantages over current technology. First, if platinum loadings could be reduced, it could produce a welcome reduction in the capital cost of fuel cell catalysts. In recent years, prices for platinum have significantly exceeded those for gold... 

Mukerjee S, Siinivasan S, Appleby AJ (1993) Effect of sputtered film of platinum on low platinum loading electrodes on electrode kinetics of oxygen reduction in proton exchange membrane fuel cell. Electrochim Acta 38(12) 1661-9... 

Figure 7. Platinum, platinum alloy, and ordered platinum alloy catalyst mass oxygen reduction activities at 0.9 V. 0.75 mg Platinum loading on the electrode. Influence of temperature.

Figure 3 Plots of the total number of electrons Ut (a), of the Tafel slope b (b), of the limiting current density IjA,-, (c) and of the exchange current density I/A (d), versus the platinum loading for the reduction of oxygen on a platinum-modified polyaniline-glassy carbon rotating disk electrode (O2 saturated 0.5 M H2SO4 2mVs 25 °C A, is the true surface...

AECL is working with several Canadian PEM developers to apply its heterogeneous catalyst expertise (developed for processes to produce and purify heavy water) to PEM technology. Early work suggests that a significant reduction in platinum loading may be achievable. 

Assessed the potential for reductions in platinum loading by conducting an electrochemical kinetic analysis of the impact of catalyst loading, temperature, and pressure on polarization of the cathode. 

Initially, platinum black has been used as catalyst. However, the noble metal loading was prohibitive for commercial use. Significant reduction of platinum loading from initial values of more than 5 mg cm to currently less than 0.3 mg cm has been achieved by the following accomplishments [23] ... 

Stack and system cost for automotive PEFC are analyzed on a regular basis by the U.S. Department of Energy. At a production rate of 500,000 systems per year stack production cost were estimated 25.30 per kW while system production cost amounted to 51.31 per kW in 2010. Further cost reductions by more than 20 % are foreseen in the future [81]. In this case rather aggressive assumptions with respect to lowering platinum loading and a rather low platinum price has been taken into account. A recent update to the DoF study [82] acknowledged lower power density therefore, at a production volume of 500,000 units per year, the specific stack cost increased to U 27.05 per kW while the total system cost increased to U 54.83 per kW. The overall results of this study are shown in Fig. 14.19 and Table 14.2. It also shows the overall share of platinum metal cost to rise from 5.3 % at an annual production volume of 1000 stacks to 50.3 % at a stack production of 500,000 per year. 

Ye S, Vijh AK, Dao LH (1996) Oxygen reduction on a new electrocatalyst based on highly porous carbonized polyacrylonitrile microcellular foam with very low platinum loading. J Electroanal Chem 415(1-2) 115-121... 

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