Catalysts methanol-tolerant

In addition to the slow methanol oxidation kinetics, methanol that crosses over from the anode to the cathode side through the membrane can react with 02 at the cathode catalyst, leading to a mixed potential at the cathode side and thereby reducing cell performance. To solve this problem, methanol-tolerant catalysts as well as membranes with low methanol permeability have been investigated. However, these materials are still in the research stages and commercial applications have not been developed. 

If AEMs are shown to be stable in fuel cells over thousands of hours, an in-depth investigation into effective and cheaper non-noble metal catalysts (e.g., Ni, Ag etc.) is indicated. There would also be a greater chance of finding methanol-tolerant catalysts for use in the cathodes than in related PEM-based DMFCs. 

Wippermann K, Richter B, Klafki K, Mergel J, Zehl G, Dorbandt I, Bogdanoff P, Fiechter S, Kaytakoglu S (2007) Carbon supported Ru - Se as methanol tolerant catalysts for DMFC cathodes part II preparation and characterization of MEAs. J Appl Electrochem 37 1399-1411... 

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

The permeation of methanol through the membrane from the anode to the cathode (cross-over) represents a source of severe performance loss. The combined reaction of methanol and oxygen on the cathodic platinum catalysts (or platinum-based alloys) leads to a mixed potential formation that reduces the maximum achievable potential considerably by up to 200 mV. Two strategies are followed to circumvent this phenomenon. On the one hand the general avoidance of methanol permeation through the membrane allows the use of standard catalysts. The other strategy is the use of methanol-tolerant catalysts for the cathode of DMFCs these materials are characterized by a complete inactivity towards methanol, which does not react on these catalyst surfaces. For the development of methanol-tolerant catalysts, several prerequisites have to be fulfilled to obtain competitive products the new material not only has to be as active as a comparable catalyst (platinum-based) but also the stability and cost aspect have to be considered. Recently, selenium-modified rathenium particles (RuSe ) were found to be a suitable alternative to platinum-based alloys where the addition of selenium increases the activity of pure rathenium particles to shift these catalysts in a competitive regime. ... 

Xia, D., Chen, G., Wang, Z., Zhang, J., Hui, S., Ghosh, D. Wang, H. Synthesis of ordered intermetallic PtBi2 nanoparticles for methanol-tolerant catalyst in oxygen electroreduction. Chem. Mater. 18 (2006), pp. 5746-5749. 

Whipple et al. [35] Methanol (0.1-15M) Air Sulfuric acid (0.5 M) Air breathing 62 4 Using Ru, ej, as methanol-tolerant catalyst for cathode... 

For DMFC, methanol crossover is one of the main obstacles to its development Several efforts have been made to avoid or reduce the effect of methanol crossover on the DMFC s cathode performance [50-55], including the development of methanol-tolerant catalysts such as macrocycles or chalcogenides [34-37] and modification of Pt catalyst by adding another metal such as Fe, Co, Ni, and... 

Other methanol-tolerant catalysts have been found in iron poiphyiine-type materials supported on high surface area carbon [69,70]. These catalysts were tested in fuel cell conditions and it was found that no deterioration of the electrode performance could be seen when utilizing methanol in the ceU. The catalysts are insensitive to methanol. These catalysts were also combined with a new cell concept whereby the anode and the cathode reside in the same compartment. Both electrodes are in contact with the same side of the membrane, thus eliminating most of the ohmic resistance in the cell. The fuel efficiency in the ceU at low current densities was much higher than for a normal bipolar plate design. A methanol-tolerant cathode is a prerequisite to make this concept feasible. 

We have already referred to the Mo/Ru/S Chevrel phases and related catalysts which have long been under investigation for their oxygen reduction properties. Reeve et al. [19] evaluated the methanol tolerance, along with oxygen reduction activity, of a range of transition metal sulfide electrocatalysts, in a liquid-feed solid-polymer-electrolyte DMFC. The catalysts were prepared in high surface area by direct synthesis onto various surface-functionalized carbon blacks. The intrinsic... 

Reeve RW, Christensen PA, Hamnett A, Haydock SA, Roy SC (1998) Methanol tolerant oxygen reduction catalysts based on transition metal sulfides. J Electrochem Soc 145 3463-... 

Ozenler SS, Kadirgan F (2006) The effect of the matrix on the electro-catalytic properties of methanol tolerant oxygen reduction catalysts based on ruthenium-chalcogenides. J Power Sources 154 364-369... 

Selvarani, G., Maheswari, S., Sridhar, P., Pitchumani, S., and Shukla, A.K. (2009) Carbon-supported Pt-Ti02 as a methanol-tolerant oxygen-reduction catalyst for DMFCs. Journal of the Electrochemical Society, 156 (11),... 

Since the formation of strongly bonded surface CO constitutes the major kinetic hurdle for the oxidation of methanol at low overpotentials, model calculations of the CO tolerance should also give guidance in the development of ternary methanol oxidation catalysts. In fact, model calculations of the CO tolerance of ternary Pt-Ru-X alloys have been performed (Fig. 11.14) [18] revealing activity trends similar to those observed in the experimental combinatorial methanol oxidation study (Fig. 11.13) Figs 11.13 and 11.14 identify Pt-Ru-Co ternary composi-... 

The preparation of Cu/ZnO catalysts and precursors for the methanol synthesis reaction have been described [87, 88], while others [89] used a mixture of Pt, Ru and a leachable metal such as A1 to prepare catalysts for CO-tolerant catalysts for fuel cells. 

SULFUR POISONING AND TOLERANCE OF METHANOL SYNTHESIS CATALYSTS CHAI GUOYONO. AIDAGANG, and LI CHENGYlJE ... 

Only a few studies of the poisoning of copper/zinc oxide catalysts have been reported (refs. 4-6). Whether copper or zinc is most su.sceptible to attack by sulfur is still a question, Tlte literature findings on the sulfur tolerance of methanol synthesis catalyst are inconsistent with industrial experience. For example, observations from indusirinl production suggest that a... 

This paper addresses sulfur poisoning and sulfur tolerance of methanol synthesis catalysts under laboratoiy and commercial conditions, effects of catalyst formulation on sulfur tolerance and the forms of sulfur compounds in poisoned catalysts. 

L. R. Radovic and M. A. Vannice, Sulfur Tolerance of Methanol Synthesis Catalysts, Appl. Catal. 29(1987)1-20. 

Cu/ZnO/A Os and the reduced Pd catalysts that are seriously deactivated in the presence of H2S 12,13). In the case of Pdi6S7, it was found to preserve a constant methanol yield even in the presence of H2S 100 ppm in concentration. Thus, Pd sulfide is a new type of sulfur tolerant catalysts. However, the space-time yield of methanol obtained with Pdi6S7 was 80 g kg- cat h at 613 K and... 

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