Direct methanol fuel cell cathode

Despite the uncertainty regarding the exact nature of the active site for oxygen reduction, researchers have managed to produce catalysts based on heat-treated macrocycles with comparable activities to state-of-the-art platinum catalysts. In numerous cases researchers have shown activity close to or better than platinum catalysts.64,71,73,103,109 Since the active site for the ORR in these materials is not fully understood, there is still potential for breakthrough in their development. Another advantage of this class of materials that should be mentioned is their inactivity for methanol oxidation, which makes them better suited than platinum for use in direct methanol fuel cell cathodes where methanol crossover to the cathode can occur.68,102,104,122-124 While the long-term activity of heat treated materials is... 

Roy S, Christensen PA, Hamnett A, Thomas KM, Trapp V (1996) Direct methanol fuel cell cathodes with sulfur and nitrogen-based carbon functionality. J Electrochem Soc 143 (10) 3073-3079... 

Methanol-tolerant Catalysts for Direct Methanol Fuel Cell Cathodes... 

Thomas S, Ren X, Zelenay P et al (1999) Direct methanol fuel cells cathode evaluation and optimization. In Gottesfeld S, Fuller T (eds) Proton conducting membrane fuel cells II. The Electrochemical Society, Pennington... 

Kulikovsky, A. A. 2012e. A model for mixed potential in direct methanol fuel cell cathode and a novel ceU design. EjectrodunLActa, 79, 52-56. 

Convert P, Countanceau C, Cromgneau P, Gloaguen F, Lamy C (2001) Electrodes modified by electrodeposition of CoTAA complexes as selective oxygen cathodes in a direct methanol fuel cell. J Appl Electrochem 31 945-952... 

A direct methanol fuel cell consists of two electrodes—a catalytic methanol anode and a catalytic oxygen cathode—separated by an ionic conduc-... 

Eickes C, Piela P, Davey J, Zelenay P. 2006. Recoverable cathode performance loss in direct methanol fuel cells. J Electrochem Soc 153 A171-A178. 

PEMFC)/direct methanol fuel cell (DMFC) cathode limit the available sites for reduction of molecular oxygen. Alternatively, at the anode of a PEMFC or DMFC, the oxidation of water is necessary to produce hydroxyl or oxygen species that participate in oxidation of strongly bound carbon monoxide species. Taylor and co-workers [Taylor et ah, 2007b] have recently reported on a systematic study that examined the potential dependence of water redox reactions over a series of different metal electrode surfaces. For comparison purposes, we will start with a brief discussion of electronic structure studies of water activity with consideration of UHV model systems. 

For isolating the overpotential of the working electrode, it is common practice to admit hydrogen to the counter-electrode (the anode in a PEMFC the cathode in a direct methanol fuel cell, DMFC) and create a so-called dynamic reference electrode. Furthermore, the overpotential comprises losses associated with sluggish electrochemical kinetics, as well as a concentration polarization related to hindered mass transport ... 

The electrodes in the direct methanol fuel cell (DMFC) (i.e. the anode for oxidising the fuel and the cathode for the reduction of oxygen) are based on finely divided Pt dispersed onto a porous carbon support, and the electro-oxidation of methanol at a polycrystalline Pt electrode as a model for the DMFC has been the subject of numerous electrochemical studies dating back to the early years ot the 20th century. In this particular section, the discussion is restricted to the identity of the species that result from the chemisorption of methanol at Pt in acid electrolyte. This is principally because (i) the identity of the catalytic poison formed during the chemisorption of methanol has been a source of controversy for many years, and (ii) the advent of in situ IR culminated in this controversy being resolved. 

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],... 

Liu, R, and Wang, C. Y. Optimization of cathode catalyst layer for direct methanol fuel cells Part II Computational modeling and design. Electrochimica Acta 2006 52 1409-1416. 

C. Xu, T. S. Zhao, and Y. L. He. Effect of cathode gas diffusion layer on water transport and cell performance in direct methanol fuel cells. Journal of Power Sources 171 (2007) 268-274. 

Q. Mao, G. Sun, S. Wang, et al. Application of hyperdispersant to the cathode diffusion layer for direct methanol fuel cell. Journal of Power Sources 175 (2008) 826-832. 

A particular version of the PEFC is the direct methanol fuel cell (DMFC). As the name implies, an aqueous solution of methanol is used as fuel instead of the hydrogen-rich gas, eliminating the need for reformers and shift reactors. The major challenge for the DMFC is the crossover of methanol from the anode compartment into the cathode compartment through the membrane that poisons the electrodes by CO. Consequently, the cell potentials and hence the system efficiencies are still low. Nevertheless, the DMFC offers the prospect of replacing batteries in consumer electronics and has attracted the interest of this industry. 

Most of the catalysts employed in PEM and direct methanol fuel cells, DMFCs, are based on Pt, as discussed above. However, when used as cathode catalysts in DMFCs, Pt containing catalysts can become poisoned by methanol that crosses over from the anode. Thus, considerable effort has been invested in the search for both methanol resistant membranes and cathode catalysts that are tolerant to methanol. Two classes of catalysts have been shown to exhibit oxygen reduction catalysis and methanol resistance, ruthenium chalcogen based catalysts " " and metal macrocycle complexes, such as porphyrins or phthalocyanines. ... 

One energy application of methanol in its early stages of development is the direct methanol fuel cell (DMFC). A fuel cell is essentially a battery in which the chemicals are continuously supplied from an external source. A common fuel cell consists of a polymer electrolyte sandwiched between a cathode and anode. The electrodes are porous carbon rods with platinum... 

Strasser, P., Gorer, S., Devenney, M., Electrochemical techniques for the discovery of new fuel-cell cathode materials. In Direct Methanol Fuel Cells, Vol. 4, Narayanan, S.G., Zawodzinski, T. (eds.), The Electrochemical Society Washington, 2001, p 191. 

In the direct methanol fuel cell (DMFC), an aqueous solution of methanol is oxidised at the anode and reduced at the cathode. 

Yu, Hwan Bae Kim, Joon-Hee Lee, Ho-In Scibioh, M. Aulice Lee, Jaeyoung Han, Jonghee Yoon, Sung Pil Ha, Heung Yong. Development of nanophase Ce02-Pt/C cathode catalyst for direct methanol fuel cell. Journal of Power Sources (2005) 140(1) 59-65. 

Direct-methanol fuel cell (DMFC) — This type of -+fuel cell is similar to the - polymer-electrolyte-membrane fuel cell in what concerns the nature of the -> electrolyte -a proton conducting membrane, such as a perfluorosul-fonic acid polymer. In the DMFC the fuel is -> methanol (CH3OH) which is oxidized in the presence of water at the anode and the resulting protons migrate through the electrolyte to combine with the -> oxygen, usually from air, at the cathode to form water ... 

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