Perovskite-Based Catalysts for Direct Methanol Fuel Cells

As an effort to further explore the possible complex oxide catalysts for methanol electrooxidation, a library of perovskites (ABO3; A = Ba, Ca, Sr, La; B = Fe, Ru) were synthesized and tested. A novel screening strategy, featuring energy-efficient and rapid solution combustion (SC) synthesis techniques in combination with a throughput catalyst activity testing method, was employed. It was demonstrated that most of these mixed-conductor complex perovskites with ruthenium on the B-site are promising candidates for the development of effective catalysts. A possible reaction pathway on the perovskite (e.g., ARuO3) surface is proposed in analogy to the well-established reaction mechanism of methanol oxidation on a Pt surface. Additional experiments by using ethanol and formic acid as fuels were conducted to give further insights on the proposed reaction pathway. Furthermore, composite perovskite−Pt compositions were also synthesized directly by the SC method for the design of multifunctional catalysts, where the optimum amount of noble metal was found to be ∼10 wt %. These novel catalysts, containing 4 times less platinum, display comparable apparent catalytic activity to standard Pt−Ru alloy. Structure and surface properties of these novel catalysts were also studied by using X-ray photoelectron spectroscopy and X-ray diffraction techniques. The above findings strongly suggest that the proposed approach for design of multifunctional catalysts is practical and effective.