Electrocatalysts for Fuel Cells

Fuel cell technology holds the promise of low to zero emission energy for power plants, backup generators, and in the transportation sector. Fuel cells will also offer fuel efficiency in the order of 50% or more. With the increasing interest in fuel cells as alternative energy sources for stationary power, portable, and automotive applications, there is a need to develop new anode and cathode electrocatalysts. The cost of the current precious metal-based electrocatalysts is a considerable hurdle to the successful commercialization of fuel cells.

The oxidation of methanol in fuel cells has been extensively studied for several decades. At present, however, the commercialization of the direct methanol fuel cell (DMFC) is beset by several problems. Given the lower electrochemical activity of methanol in comparison with hydrogen, much higher loading levels of noble metal catalysts must be employed. The most efficient anode systems for the complete electro-oxidation of methanol consist of the platinum metals and mixtures or alloys thereof. Notwithstanding the high cost issues, presently employed anode systems suffer from complications due to catalyst poisoning by CO, which leads to both an unacceptable loss in cell voltage and degradation in long-term performance. Numerous studies have indicated that the most promising anode systems consist of either a supported or unsupported binary alloy of Pt/Ru [189, 190].

The traditional approach to evaluating anode materials has involved the relatively time-consuming and laborious practice of synthesizing and characterizing materials one at a time. Mallouk, Smotkin, and coworkers developed a rapid combinatorial synthesis and fluorescent screening method for the exploration of ternary and quaternary anode electrocatalysts for the DMFC (Fig. 32.20) [157]. The authors created libraries of alloys by using automated inkjet deposition of metal precursor aliquots onto a conducting fiber paper, followed by reduction of the metal salts with a borohydride reagent. The authors created 135 unique ternary compositions

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