Gold catalysts fuel cells

Titanium dioxide supported gold catalysts exhibit excellent activity for CO oxidation even at temperatures as low as 90 K [1]. The key is the high dispersion of the nanostructured gold particles over the semiconducting Ti02 support. The potential applications of ambient temperature CO oxidation catalysts include air purifier, gas sensor and fuel cell [2]. This work investigates the effects of ozone pretreatment on the performance of Au/Ti02 for CO oxidation. 

According to the procedure of sol deposition described in Section 2.3, more than 10% Au can be deposited on XC72R, thus allowing the use of the catalysts in fuel cells and other electrochemical applications [36]. In all the experiments the common mother gold solution 1 (Section 2.3) was used containing a low PVA amount (PVA Au = 0.05) in order to facilitate the adsorption step. Table 8 shows the results. According to ICP analysis, an almost total gold adsorption was obtained. 

At the next level of abstraction are measurements performed at a thin film of fuel cell catalyst immobilized on the surface of an inert substrate, such as glassy carbon (GC) or gold (Fig. 15.2c). Essentially, three versions of this approach have been described in the fiterature. In the first case (a porous electrode ), an ink containing catalyst and Nafion ionomer is spread onto an inert nonporous substrate [Gloaguen et al., 1994 Gamez et al., 1996 Kabbabi et al., 1994]. In the second case (a thin-fihn electrode ), the ink does not contain Nafion , but the latter is... 

Tabakova, T., Idakiev, V., Tenchev, K., Boccuzzi, F., Manzoli, M., and Chiorino, A. 2006. Pure hydrogen production on a new gold-thoria catalyst for fuel cell applications. Appl. Catal. B Environ. 63 94—103. 

CHAPTER 14. Gold-Based Nanoparticle Catalysts for Fuel Cell... 

For the study of the electrocatalytic reduction of oxygen and oxidation of methanol, our approach to the preparation of catalysts by two-phase protocol " provides a better controllability over size, composition or surface properties in comparison with traditional approaches such as coprecipitation, deposition-precipitation, and impregnation. " The electrocatalytic activities were studied in both acidic and alkaline electrolytes. This chapter summarizes some of these recent results, which have provided us with further information for assessing gold-based alloy catalysts for fuel cell reactions. 

Mkaline Fuel Cell The electrolyte for NASA s space shnttle orbiter fuel cell is 35 percent potassinm hydroxide. The cell operates between 353 and 363 K (176 and I94°F) at 0.4 MPa (59 psia) on hydrogen and oxygen. The electrodes contain platinnm-palladinm and platinum-gold alloy powder catalysts bonded with polytetraflnoro-ethylene (PTFE) latex and snpported on gold-plated nickel screens for cnrrent collection and gas distribution. A variety of materials, inclnding asbestos and potassinm titanate, are used to form a micro-porous separator that retains the electrolyte between the electrodes. The cell structural materials, bipolar plates, and external housing are nsnally nickel-plated to resist corrosion. The complete orbiter fuel cell power plant is shown in Fig. 24-48. 

Maye MM, Luo J, Han L, Kariuki N, Rab Z, Khan N, Naslund HR, Zhong C-J (2004) Gold and alloy nanoparticle catalysts in fuel cell reactions. Div Fuel Chem 49 938-939... 

One of the most daunting issues is the catalyst. The reactions at the electrodes tend to go slowly, and making or coating the electrode with a catalyst is essential to speed things up. Platinum is one of the most effective catalysts because it binds the reactants and holds them in place so that the reaction can proceed. But the problem is cost—platinum is a rare metal and not at all cheap. An ounce (28.6 g) of platinum costs about 1,200 as of May 2009. Compare that to gold, a precious metal that costs about 970 per ounce (28.6 g) as of May 2009. Fuel cell electrodes would be cheaper if they were made of gold (but gold is not an effective catalyst) ... 

However, one application where gold could be most applied is in fuel cells used in electric vehicles, with operating temperatures of 80-100 °C. Another field of application for supported gold catalysts is the production of hydrogen by steam reforming of methanol. 

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... 

However, catalyst cost and availability is an issue in some significant applications such as fuel cells. It is relevant therefore to compare the prices of the precious metals. Since gold is mined in far greater quantities than platinum or palladium, its price has historically been more stable (Figure 14.2) than these metals and industrialists prefer stable prices,... 

The selective oxidation or preferential oxidation of CO in hydrogen-rich stream is another important object for ceria based catalysts. The gas mixture from steam reforming/partial oxidation of alcohols or hydrocarbons, followed by the WGS reaction contains mainly FI2, CO2 and a small portion of CO, H2O, and N2. When such gaseous stream would be taken as input for hydrogen fuel cells, the CO has to be removed to avoid poisoning of the anode electrocatalysts. Ceria based nanomaterials, such as ceria/gold, ceria/copper oxide catalysts exhibit suitable catalytic activities and selectivities for CO PROX process. 

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