Methanol Fuel Cell Electrodes

Q. Mao, G. Sun, S. Wang, et al. Gomparative studies of configurations and preparation methods for direct methanol fuel cell electrodes. Electrochimica Acta 52... 

REVIEW OF DIRECT METHANOL FUEL CELL ELECTRODES AND CATALYST... 

Tucker MC, Odgaard M, Lund PB, Yde-Andersen S, Thomas JO (2005) The pore structure of direct methanol fuel cell electrodes. J Electrochem Soc 152 A1844-A1844... 

Hyeon T, Han S, Sung Y-E, Park K-W, Kim Y-W. High-performance direct methanol fuel cell electrodes using solid phase synthesized carbon nanocoils. Angew Chem hit Ed 2003 42 4352-6. 

Bang JH, Han K, Skrabalak SE, Kim H, Suslick KS. Porous carbon supports prepared by ultrasonic spray pyrolysis for direct methanol fuel cell electrodes. J Phys Chem C 2007 lll(29) 10959-64. 

In a simple version of a fuel cell, a fuel such as hydrogen gas is passed over a platinum electrode, oxygen is passed over the other, similar electrode, and the electrolyte is aqueous potassium hydroxide. A porous membrane separates the two electrode compartments. Many varieties of fuel cells are possible, and in some the electrolyte is a solid polymer membrane or a ceramic (see Section 14.22). Three of the most promising fuel cells are the alkali fuel cell, the phosphoric acid fuel cell, and the methanol fuel cell. 

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-... 

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. 

Sanicharane S, Bo A, Sompalli B, Gurau B, Smotkin ES. 2002. In-situ 50 °C ETIR spectroscopy of Pt and PtRu direct methanol fuel cell membrane electrode assembly anodes. J Electrochem Soc 149 A554-A557. 

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 same group, in a previous work, reported on the realization of a hybrid anode electrode [197]. An appreciable improvement in methanol oxidation activity was observed at the anode in direct methanol fuel cells containing Pt-Ru and Ti02 particles. Such an improvement was ascribed to a synergic effect of the two components (photocatalyst and metal catalyst). A similar behavior was also reported for a Pt-Ti02-based electrode [198]. Another recent study involved the electrolysis of aqueous solutions of alcohols performed on a Ti02 nanotube-based anode under solar irradiation [199]. 

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. 

Fuel cells o fer important advantages as a power source, such as the potential for high efficiency, clean exhaust gases and quiet operation. In addition, the direct methanol fuel cell offers special benefits as a power source for transportation, such as potential high energy density, no need for a fuel reformer and a quick response. These advantages, however, have not been fully realized yet. One of the problems is the poor performance of the fiiel electrode. Even platimun, which seems the most active single element for methanol oxidation in add media, loses its electrocatalytic activity rapidly by the accumulation of adsorbed partially oxidized products. 

R. X. Liu, and E. S. Smotkin, Array membrane electrode assemblies for high throughput screening of direct methanol fuel cell anode catalysts, J. Electroanal. Chem. 535, 49-55 (2002). 

In electrochemical systems, metal meshes have been widely used as the backing layers for catalyst layers (or electrodes) [26-29] and as separators [30]. In fuel cells where an aqueous electrolyte is employed, metal screens or sheets have been used as the diffusion layers with catalyst layers coated on them [31]. In direct liquid fuel cells, such as the direct methanol fuel cell (DMFC), there has been research with metal meshes as DLs in order to replace the typical CFPs and CCs because they are considered unsuitable for the transport and release of carbon dioxide gas from the anode side of the cell [32]. 

R. Ghen and T. S. Zhao. A novel electrode architecture for passive direct methanol fuel cells. Electrochemistry Communications 9 (2007) 718-724. 

V. Gogel, T. Frey, Z. Yongsheng, et al. Performance and methanol permeation of direct methanol fuel cells Dependence on operating conditions and on electrode structure. Journal of Power Sources 127 (2004) 172-180. 

H. Kim, J. Oh, J. Kim, and H. Ghang. Membrane electrode assembly for passive direct methanol fuel cells. Journal of Power Sources 162 (2006) 497-501. 

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. 

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