Pt/CMS catalyst

Stable performance was demonstrated over 4,000 hours with Nafion membrane cells having 0.13 mg Pt/cm catalyst loading and cell conditions of 2.4 atmospheres H2, 5.1 atmospheres air, and 80 °C (4,000 hour performance was 0.5 V at 600 mA/cm ). Water management was stable, particularly after thinner membranes of somewhat lower equivalent weight became available. Some performance losses may have been caused by slow anode catalyst deactivation, but the platinum catalyst "ripening" phenomenon was not considered to contribute significantly to the long-term performance losses observed in PEFCs (1). 

Fig. 2. Effects of ion dose density on i-V curves. Cathode catalyst loading = 0.2 mg-Pt/cm, H2/air.

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 order to investigate whether COj reacts in a concerted way with surface carbon or whether it dissociates first to CO and adsorbed oxygen and the adsorbed oxygen reacts, infrared spectroscopy, pulse reactor studies and XANES measuremerrts were used. The i.r. spectrum of a prereduced (Ihour at 675K in S /oHj/Nj) Pt/ZrOj catalyst in contact with CO2 at 775K is shown in Fig 6 The spectrum shows the presence of linearly bound CO on Pt at 2053 cm [15]. Additionally, bands of carbonate type species appeared in the region between 1375 and 1540 cm . Over pure supports (in the absence of Pt) the CO band was not seen, but peaks in the carbonate region were observed... 

Figure 11.1 Kinetics of adsorption of CO at a Pt catalyst from a 0.01 M methanol solution at different potentials, (a) Pt black catalyst, with Pt loading 0.8 mg cm . (b) Pto.sRuo.s black catalyst, with catalyst loading 0.8 mg cm (0.1 M H2SO4, T = 298K).

Upon UV light illumination, the photocatalytic reactions were initiated at the surface of the Pt/Ti02 catalyst, resulting in the formation of CO2, H2O, and intermediate species. Because of the overlap of the bands of CH3CH20Had (adsorbed ethanol) with the bands of the intermediate species, the intensity variations in the 1300-1750 cm region can be revealed through the difference spectra obtained by subtracting the spectrum at 0 min (i.e., before the reaction) from the subsequent... 

The membrane electrode assemblies (MEAs), in which the cathode was a commercial Pt/C catalyst (20 wt.%) with a Pt loading of 1.0 mg/cm, were fabricated by... 

Another approach has been developed to fabricate electrodes with loading as low as 0.1 mg Pt/cm (32). The electrode structure was improved by increasing the contact area between the electrolyte and the platinum clusters. The advantages of this approach are that a thinner catalyst layer of 2 to 3 microns and a uniform mix of catalyst and ionomer are produced. For example, a cell with a Pt loading of 0.17 to 0.13 mg/cm has been fabricated. The cell generated 3 A/cm at > 0.4V on pressurized O2 and 0.65 V at 1 A/cm on pressurized air (32,... 

Comparison of oxygen reduction mass and specific activity of a series of carbon supported Pt catalysts with varying metal area as cathodes in MILAs. Activity at 900 mV, 150 kPa O2, 100% RH, 0.4 mg (Pt) cm . ... 

This technique yields a catalyst composed entirely of metal nanoparticles or nanocrystalline thin film, and it allows for control of size and distribution while eliminating the need for a dispersing and supporting medium. The obtained electrodes contained as little as 0.017 mg Pt/cm and performed as well as standard E-TEK electrodes (Pt loading 0.4 mg/cm ). The PLD technique may be of special interest as an alternative to the sputtering process in the production of micro fuel cells. 

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