Catalyst development, anode

Amraig various anode catalysts developed, ft-Ru alloys are generally cmisidered as the best candidates for H2/CO and alcohol oxidation these alloy catalysts show high CO tolerance and acceptable durability under FC operating conditions. Several commercial ft-Ru alloy nanoparticles supported on carbon black have been available for applications in PEMFCs, DMFCs, and DEFCs. Efforts to improve the activity and stability of ft-Ru alloy catalysts continuously are being made. Recently, the nanocapsule method has been successfully employed to synthesize ft-Ru nanoparticles with... 

He, C., Venkataraman, R., Kunz, H.R., Fenton, J.M. 1999. CO tolerant ternary anode catalyst development for fuel cell application. Hazardous and Industrial Wastes—Proceedings of the Mid-Atlantic Industrial Waste Conference, June 17, Boca Raton, EL CRC press, pp. 663-668. 

In conclusion, the kinetics of the ORR in alkaline give the advantage of cheaper cathode catalysts, but the significant overpotential for HOR requires anode catalyst development in order to fully utilize the potential of the alkaline fuel cell. 

Development of Anode Catalyst for Internal Reforming of CH4 by CO2 in SOFC System... 

In this work, the catalytic reforming of CH4 by CO2 over Ni based catalysts was investigated to develop a high performance anode catalyst for application in an internal reforming SOFC system. The prepared catalysts were characterized by N2 physisorption, X-ray diffraction (XRD) and temperature programmed reduction (TPR). 

Of particular concern was the finding of a suitable catalyst Owing to the scouting nature, virtually no know-how base was available that time. The investigation gave highly valuable hints for later catalyst development. Actually, they motivated a search for catalysts of higher porosity and better defined composition. As a result, anodically oxidized alumina supports for catalysts were developed (see Sections 3.1 and 3.4.2). 

However, the Pt anode is seriously poisoned by trace amounts of carbon monoxide in reformates (fuel gas reformed from hydrocarbon), because CO molecules strongly adsorb on the active sites and block the HOR [Lemons, 1990 Igarashi et ah, 1993]. Therefore, extensive efforts have been made to develop CO-tolerant anode catalysts and cell operating strategies to suppress CO poisoning, such as anode air-bleeding or pulsed discharging. 

Fujino T. 1996. Development of anode catalysts for PEFCs. MEng Thesis, Yamanashi University. 

Vigier F, Coutanceau C, Perrard A, Belgsir EM, Lamy C. 2004b. Development of anode catalysts for a direct ethanol fuel cell. J Appl Electrochem 34 439-446. 

This survey focuses on recent developments in catalysts for phosphoric acid fuel cells (PAFC), proton-exchange membrane fuel cells (PEMFC), and the direct methanol fuel cell (DMFC). In PAFC, operating at 160-220°C, orthophosphoric acid is used as the electrolyte, the anode catalyst is Pt and the cathode can be a bimetallic system like Pt/Cr/Co. For this purpose, a bimetallic colloidal precursor of the composition Pt50Co30Cr20 (size 3.8 nm) was prepared by the co-reduction of the corresponding metal salts [184-186], From XRD analysis, the bimetallic particles were found alloyed in an ordered fct-structure. The elecbocatalytic performance in a standard half-cell was compared with an industrial standard catalyst (bimetallic crystallites of 5.7 nm size) manufactured by co-precipitation and subsequent annealing to 900°C. The advantage of the bimetallic colloid catalysts lies in its improved durability, which is essential for PAFC applicabons. After 22 h it was found that the potential had decayed by less than 10 mV [187],... 

Catalyst development has lead to formulations more effective than PtRu, especially at higher CO concentrations. As shown in Fig. 14.17, which gives the drop in performance for different anode formulations when increasing amounts of CO are added to hydrogen, both PtPd [64] as well as PtRuMo [65] lead to a strong improvement in tolerance towards CO. 

CO (6). Another approach is to develop a CO tolerant anode catalyst such as the platinum/ruthenium electrodes currently under consideration. Platinum/ruthenium anodes have allowed the cells to operate, with a low level air bleed, for over 3,000 continuous hours on reformate fuel containing 10 ppm CO (23). 

A significant cost advantage of alkaline fuel cells is that both anode and cathode reactions can be effectively catalyzed with nonprecious, relatively inexpensive metals. To date, most low cost catalyst development work has been directed towards Raney nickel powders for anodes and silver-based powders for cathodes. The essential characteristics of the catalyst structure are high electronic conductivity and stability (mechanical, chemical, and electrochemical). 

V. Jalan, J. Poirier, M. Desai, B. Morrisean, "Development of CO and H2S Tolerant PAFC Anode Catalysts," in Proceedings of the Second Annual Fuel Cell Contractors Review Meeting, 1990. 

The definition of reformate tolerance is that, compared to running on pure H2, a fuel cell stack can run on reformate and show no change in performance, apart from that expected for dilution effects (of H2 due to CO2, N2, H2O). This requires the development of reformate-tolerant anode catalysts capable of tolerating the remaining levels of CO and CO2 in the fuel feed. 

A number of recenf reviews of DMFC technology are available. See those by McNicol, Rand, and Williams for earlier developments of catalysts for DMFC, Thomas ef al. for cafhode catalyst development at LANL, and Liu et al. for a summary of anode catalyst preparation and support development. ... 

To measure the current distribution in a hydrogen PEFC, Brown et al. ° and Cleghorn et al. ° employed the printed circuit board approach using a segmented current collector, anode catalyst, and anode GDL. This approach was further refined by Bender et al. ° to improve ease of use and quality of information measured. Weiser et al. ° developed a technique utilizing a magnetic loop array embedded in the current collector plate and showed that cell compression can drastically affect the local current density. Stumper et al."° demonstrated three methods for the determination of current density distribution of a hydrogen PEFC. First, the partial membrane elec-... 

For these low-temperature fuel cells, the development of catalytic materials is essential to activate the electrochemical reactions involved. This concerns the electro-oxidation of the fuel (reformate hydrogen containing some traces of CO, which acts as a poisoning species for the anode catalyst methanol and ethanol, which have a relatively low reactivity at low temperatures) and the electroreduction of the oxidant (oxygen), which is still a source of high energy losses (up to 30-40%) due to the low reactivity of oxygen at the best platinum-based electrocatalysts. 

Primary and secondary high-throughput synthesis and screening workflows have been developed and applied to the search for improved DMFC anode catalysts. 

The electrochemical reaction proceeds most effectively in the presence of a catalyst, and the nature of the catalyst can have a significant effect upon the electrode overpotentials. As a matter of convenience, all of the early work in the electrolyzer development used platinum as both the anode (SO2 oxidation electrode) and cathode (H2 generation electrode) catalyst. It was recognized, however, that although platinum might be a technically satisfactory catalyst for the cathode, it was only marginally suitable as the anodic catalyst. 

Carbon-supported Pt can also be used as the anode catalyst. However, this requires pure H2. Contaminants such as carbon monoxide (CO) poison the catalyst, because CO can strongly adsorb on Pt, blocking the catalytic sites and reducing platinum s catalytic activity. In H2 produced from the reforming of other fuels, CO is always present. Thus, to improve contaminant tolerance, carbon-supported PtRu was developed and now is always used as the anode catalyst. Ru can facilitate the oxidation of CO, releasing the catalytic sites on Pt through the following reactions ... 

This survey focuses on recent catalyst developments in phosphoric acid fuel cells (PAFC), proton exchange membrane fuel cells (PEMFC), and the previously mentioned direct methanol fuel cell (DMFC). A PAFC operating at 160-220 °C uses orthophosphoric acid as the electrolyte the anode catalyst is Pt and the cathode can... 

Develop anode catalyst compositions and structures with higher reformate tolerance and/or a nonprecious metal replacement for Ru, using a catalyst deposition process that easily generates new compositions and structures. 

For the anode and cathode catalyst development, the unique nanostructured support and catalyst coating methods offer many combinations of materials and process conditions to generate new... 

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