Methanol fuel cell and

Direct Methane Conversion, Methanol Fuel Cell, and Chemical Recycling of Carbon Dioxide... 

N. T. Nguyen and S. H. Chan. Micromachined polymer electrolyte membrane and direct methanol fuel cells and mdash a review. Journal of Micromechanics and Microengineering 16 (2006) R1-R12. 

Michael Hickner received his B.S. in Chemical Engineering from Michigan Tech in 1999 and his Ph.D. in Chemical Engineering in 2003 under the direction of James McGrath. Michael s research in Dr. McGrath s lab focused on the transport properties of proton exchange membranes and their structure-property relationships. He has spent time at Los Alamos National Laboratory studying novel membranes in direct methanol fuel cells and is currently a postdoc at Sandia National Laboratories in Albuquerque, NM. 

Equivalent circuits for the catalyst layer are similar to those for porous electrodes, where charge-transfer resistance, capacitance, and Warburg resistance should be considered. The catalyst layer can be conceived of as a whole uniform unit or as a non-uniform circuit. In the case of a uniform unit, the equivalent circuits are similar to the modified ones discussed in Section 4.2.2 2, and the equations in that section apply. In many cases, such as in the presence of adsorbents, the surface is covered by the adsorbed species. For example, in direct methanol fuel cells and in H2/air fuel cells, CO adsorption should be considered. One example is illustrated in Ciureanu s work [7], as shown in Figure 4.31. 

Electrocatalyst selection and design are the key aspects of PEM fuel cells. The most popular catalyst is platinum for the anode and the cathode in pure hydrogen cells. For direct methanol fuel cells and for hydrogen cells with carbon monoxide present, a platinum/ruthenium alloy is used. 

Fig. 7-6 Schematics of the processes in a PEM fuel cell system using methanol (a) indirect methanol fuel cell and (b) direct methanol fuel cell, from [43]...

The mechanism of catalyst dissolution occurs to dilfering degrees, depending upon the degree to which platinum is alloyed and what other elements are included in the alloy. Work by Piela et al. [33] suggests that PtRu alloys, as employed in direct methanol fuel cell and reformate anodes to reduce sensitivity to CO, are extremely unstable and that operation leads to ruthenium... 

Inner water circulation is much fancier, but also harder to realize. Under ordinary operating conditions, both in direct methanol fuel cells and in polymer electrolyte membrane fuel cells, a flow of water from the anode toward the cathode is observed. This flow has two origins water molecules are dragged along by hydrated hydrogen ions moving in the electric field from the anode to the cathode, and water diffuses under the influence of its own concentration gradient. 

The production volume of direct methanol fuel cells and their long-term testing results are yet insufficient for an estimate of the lifetime of such fuel cells. Even so, the researchers mainly look at all the major reasons giving rise to the gradual performance drop and/or premature failure of these fuel cells. The reasons for performance drop... 

Selvarani G, Vinod Selvaganesh S, Krishnamurthy S, Kimthika GVM, Sridhar S, Pitchumani S, Shukla AK (2009) Methanol-tolerant carbon-suppOTted Pt-Au alloy cathode catalyst for direct methanol fuel cells and its evaluation by DFT. J Phys Chem C 113 7461-7468... 

Simoglou A, Argyropoulos P, Martin EB, Scott K, Morris AJ, Taama WM (2001) Dynamic modeling of the voltage response of direct methanol fuel cells and stacks. Part II feasibility study of model-based scale-up and scale down. Oiem Eng Sci 56 6761-6772... 

Table 2 Micro-FC prototypes, incorporating mesoporous silicon in the core system, reported in the hterature for DHFC (direct hydrogen fuel cell), DMFC (direct methanol fuel cell), and RHFC (reformed hydrogen fuel cell). Aacttve is the active surface, OCV the open circuit voltage of the cell, PP the power peak during the test, fuel A and K are the fuels provided at anode (A) and cathode (K), T° is the temperature during the test, RT is the room temperature, MeOH is methanol and EtOFI is ethanol...

Arico AS, Creti P, Antonucci PL, Cho J, Kim H, Antonucci V. Optimization of operating parameters of a direct methanol fuel cell and physico-chemical investigation of catalyst-electrolyte interface. Eleetrochim Acta 1998 43 3719-29. 

Arico, A., Creti, R, Antonucci, R, et al. (1998). Optimization of Operating Rarameters of a Direct Methanol Fuel Cell and Physico-chemical Investigation of Catalyst-electrolyte Interface, Electrochim. Acta, 24, pp. 3719-3729. 

A drop in ionic conductivity of the electrol5de for example, of the polymer membrane in proton-exchange membrane and direct methanol fuel cells and that is caused by its gradual oxidative destruction... 

Apart from these practical aims, an electrochemical reduction of CO2 is of great cognitive interest, since it is analogous to the photochemical reduction of CO2 to carbohydrates accomplished by chlorophyll in plants. The two fields of work—development of methanol fuel cells and investigations into cathodic CO2 reduction—have practically no mutual connections and have most often been associated with different groups of scientists. 

These preliminary results are a first demonstration that the shape-selected particles concept may work in a realistic fuel cell environment. Future research will focus on degradation and stability tests of the novel materials as well as their application in other fuel cell types, as for instance direct methanol fuel cells and high-temperature pol)uner electrolyte membrane fuel cells. Moreover, the effect of the surfactant requires special attention, as the surfactant molecules may also influence the electrocatalysis by a ligand effect or an ensemble effect directing the adsorption of reactants to specific surface sites. 

In comparison with the extensive research and development of catalysts for PEMFC and DMFC, the development of catalysts for DEFCs has drawn a surge of interest recently in recent years due to its bio-fuel characteristic, its ability to eliminate the toxicity issue of methanol as in direct methanol fuel cells, and its high energy density. Carbon-supported PtRu, a well-known catalyst for DMFCs, was naturally studied for DEFCs [59], but lacks high activity for ethanol oxidation due to a high propensity of Ru to form RuOH at the oxidation potential region. 

Research on direct methanol fuel cells and SOFCs at federal laboratories, university and private industry... 

Nafion , which is one of the best PEMs available today, satisfies requirements b (for gases only) d and e, and perhaps even requirement c. However, the conductivity of Nafion drops rapidly with decreasing relative humidity (RH), methanol permeability through Nafion is very high (a disadvantage for direct methanol fuel cells), and the material is presently extremely expensive ( 700 m ), although cost reductions with increased production rates have been projected by the manufacturer. These drawbacks have prompted an extensive effort to improve the properties of Nafion and identify alternate materials to replace Nafion . 

Typically, micro fuel cells use methanol as fuel alfhough hydrogen-fed micro fuel cells have also been developed. The choice of the type of fuel cell to use in portable devices may be limited to low-temperature fuel cells such as PEMFC (proton exchange membrane fuel cell/polymer electrolyte membrane fuel cell) and DMFC. However, micro reformed methanol fuel cells and miniature SOFCs have also been developed. 

HjSO, but the magnitude of the current density was not affected largely up to a concentration of lOmmol dm . With 2-propanol, the current due to the alcohol oxidation was superimposed on the ORR current, and the potential shifted by approximately 0.5 V at 0.1 mol dm . Both 2-propanol and acetone are MEA components because 2-propanol is added to the catalyst ink, and acetone is produced by oxidation of 2-propanol on the platinum cathode. The effects are, however, not serious because their concentration is less than lOmmol dm . Methanol is used as a fuel in direct methanol fuel cells, and crossover through the polymer electrolyte membrane is known to cause a degradation of the ORR at the cathode, when the concentration of the fuel is as high as 5 mol dm . 

Recent fuel-cell membrane research efforts have been focused on three areas [2] (1) membranes for hydrogen/air fuel cells that operate above 100 °C at low humidity conditions, (2) high proton conductivity and low methanol permeability membranes for direct methanol fuel cells and (3) low-cost alternatives to perfluorosulfonic acid membranes for both DMFCs and hydrogen/air fuel cells. 

Includes direct methanol fuel cell and direct alcohol fuel cells. 

Figure 6.52 Schematic of direct methanol fuel cell and associated mass transfer processes. (Courtesy of K. Sharp, Penn State University.)...

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