Anode catalyst Future directions

The Direct Methanol Fuel Cell, DMFC, (see Fig. 7-6 in section 7.2.2.4.) is another low temperature fuel cell enjoying a renaissance after significant improvements in current density. The DMFC runs on either liquid or, with better performance but higher system complexity, on gaseous methanol and is normally based on a solid polymer electrolyte (SPFC). R-Ru catalysts were found to produce best oxidation results at the anode, still the power density is relatively low [5, 29]. Conversion rates up to 34 % of the energy content into electricity were measured, an efficiency of 45 % is expected to be feasible in the future. SPFC in the power order of several kW to be used in automobile applications are currently in the development phase. 

Direct methanol fuel cells (DMFCs) are attracting much more attention for their potential as clean and mobile power sources for the near future [1-8], Generally, platinum (Pt)- or platinum-alloy-hased nanocluster-impregnated carbon supports are the best electrocatalysts for anodic and cathodic fuel cell reactions. These materials are veiy expensive, and thus there is a need to minimize catalyst loading without sacrificing electro-catalytic activity. Because the catalytic reaction is performed by fuel gas or fuel solution, one way to maximize catalyst utilization is to enhance the external Pt surface area per unit mass of Pt. The most efficient way to achieve this goal is to reduce the size of the Pt clusters. 

In order to improve the Faradic efficiency and fuel utilization, the desired final product of alcohol oxidation is CO2. However, breaking the C—C bonds of alcohols for direct C2+ alcohol fuel cells remains a great challenge, especially at low temperatures (e.g., <90 °C) and low anode overpotentials. For primary alcohol oxidation, such as ethanol oxidation, nanostructured PtRhSn/C has demonstrated a strong ability to both improve reaction kinetics and break C—C bond. Future research efforts using both combinational chemistry methods and theoretical calculations may lead to the development of efficient ternary or even quarterly PtSn-based catalysts for complete alcohol oxidation. 

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