Catalyst Shape Matters

When it comes to catalyzing certain reactions, new research shows that the shape of a nanoparticle catalyst may be more important than its size. Brown University chemistry professor Shouheng Sun and coworkers found that cube-shaped platinum nanoparticles were more efficient than similarly sized Pt polyhedra or truncated cubes for catalyzing the oxygen reduction reaction at the cathode of a polymer electrolyte membrane fuel cell (Angew. Chem. Int. Ed., DOI: 10.1002/anie.200800073). The Pt atoms arrange differently on the faces of the nanocubes than they do on nanopolyhedra or truncated nanocubes, and Sun attributes the nanocubes' superior performance to this phenomenon. The finding could lead to better fuel-cell catalysts. In addition, Sun's group has developed a general synthetic approach for making Pt nanoparticles with uniform shapes and sizes. They reduce platinum acetylacetonate in the presence of oleic acid, oleylamine, and a trace amount of iron pentacarbonyl. The iron pentacarbonyl facilitates Pt nucleation, so by carefully controlling the temperature at which it is added to the reaction mixture, the researchers can direct the precise size and shape of the nanoparticles produced.