Synthesis of an active and stable Pt_(shell)-Pd_(core)/G catalyst for the electro-oxidation of methanol

摘要

A Pt_(shell)-Pd_(core)/C catalyst is prepared via electroless deposition and galvanic displacement. The catalyst is active toward the electro-oxidation of methanol and is more stable against CO_(ad)-poisoning than a commercial Pt/C catalyst. The stable activity of Pt_(shell)-Pd_(core)/C is ascribed to the tuned electronic property of the Pt over-layer in the Pt_(shell)-Pd_(core)/C, which leads to weak binding with CO_(ad) and increases the kinetics of OH_(ad) formation. The weakened binding property of the surface Pt with CO_(ad) and the facile oxidation of CO_(ad) by OH_(da) were confirmed by a spectroscopic analysis and in a CO_(ad)-stripping experiment, respectively. The electro-oxidation of CO_(da) by OH_(da) is the rate-determining step of methanol oxidation. Therefore, the accelerated formation of OH_(da) contributes to the overall oxidation reaction, preventing CO_(da)-poisoning. In addition, Pt_(shell)-Pd_(core)/C maintains its activity longer than Pt/C does during a prolonged cycle experiment.