Pt₃Sn Nanoparticles with Controlled Size: High-Temperature Synthesis and Room-Temperature Catalytic Activation for Electrochemical Methanol Oxidation

Abstract

We report a new method of preparing carbon-supported Pt3Sn nanoparticle catalysts for methanol and CO oxidation. Alloyed Pt3Sn nanoparticles with a cubic phase were synthesized by coreduction of platinum acetylacetonate and tin acetylacetonate in a high-boiling solvent, trioctylamine. Particle sizes in the range of 3.0 to 6.5 nm were controlled by varying the amount of introduced capping agents (oleylamine and oleic acid). The as-prepared particles displayed a narrow size distribution and were catalytically inactive. The ligands were removed to activate the nanoparticles for catalysis by treatment with tetramethylammonium hydroxide (TMAOH) solution. The treated Pt3Sn particles can be stabilized in TMAOH solution and finally loaded on XC-72 carbon support by physical deposition. Cyclic voltammetry and CO-stripping showed that all the Pt3Sn particles exhibited high electrocatalytic activity for methanol and CO oxidation. The size-dependent CO-stripping study indicated COads oxidation started at low potentials (∼50 mV) on all the particles with the 3.5 nm Pt3Sn catalyst having the lowest peak potential. Also, the alloyed catalysts displayed a good stability in acidic environment at low potential (<500 mV).