Nanostructured Transition Metal Nitride (MN) As a Potential Support for Pt(Ru) Anode Electro-Catalyst for Direct Methanol Fuel Cells (DMFCs)
Currently, Pt(Ru) alloy has been identified as a most active anode electro-catalyst for methanol electro-oxidation in DMFC. The synthesis of high surface area Pt(Ru) electro-catalyst is important to improve the reaction kinetics. In addition, efficient utilization of electro-catalyst by achieving high electrochemical active surface area is important, which can be accomplished by dispersing Pt(Ru) electro-catalyst on support with high surface area and superior electrical conductivity. The present study explores highly conductive nanostructured transition metal nitride (MN) as a potential support for Pt(Ru) electro-catalyst for methanol eletcro-oxidation.
High surface area Pt(Ru)/MN (~125 m2/g) has been synthesized by wet chemical approach employing non-halide precursors of Pt and Ru. The electrochemical characterization has been carried out in 1 M methanol and 0.5 M sulfuric acid, used as fuel and electrolyte, using Pt wire as counter electrode and Hg/Hg2SO4 as reference electrode (+0.65 V with respect to NHE) and Pt loading of 0.3 mg/1cm2 at 400C. Pt(Ru)/MN shows promising performance for methanol oxidation, showing ~52% improved catalytic activity at ~0.65 V (vs NHE) in half-cell configuration and ~56% higher maximum power density in single DMFC study (Fig. 1) than that of commercial JM-Pt(Ru). This is attributed to well-dispersion of Pt(Ru) on MN (support of surface area of ~125 m2/g) offering high utilization of noble metals Pt and Ru, along with superior electrochemical active surface area and low charge transfer resistance for Pt(Ru)/MN than that of JM-Pt(Ru). Pt(Ru)/MN also shows superior electrochemical stability in half-cell configuration and single DMFC study than JM-Pt(Ru) electro-catalyst. Thus, the present study demonstrates the potential of MN as a support in improving the electrochemical activity of Pt(Ru) electro-catalyst, in the aim of achieving superior electrochemical performance and stability with reduced noble metal content for the electro-catalyst of DMFC.
This portends significant reduction in the overall capital cost of DMFC system. Results of the synthesis, structural characterization and electrochemical activity of these electro-catalysts will be presented and discussed.
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Research supported by the U.S. Department of Energy, Office of Basic Energy Sciences, Division of Materials Sciences and Engineering under Award DE-SC0001531. PNK also acknowledges the Edward R. Weidlein Chair Professorship funds, NSF and the Center for Complex Engineered Multifunctional Materials (CCEMM) for partial support of this research.