Catalytic Activity of Carbon-Supported Pt Nanoelectrocatalysts. Why Reducing the Size of Pt Nanoparticles is Not Always Beneficial

Carbon-supported Pt catalysts prepared by the impregnation method in water−dimethyl sulfoxide (DMSO) solutions were investigated. Using X-ray diffraction (XRD) technique for estimation of the particle size and shapes, we show that morphology of the Pt/C catalysts depends strongly on the DMSO content in the solutions. The average particles size reduces and a shape of the Pt nanocrystals changes from a truncated octahedron to a cuboctahedron and eventually to a truncated cube with increasing DMSO concentration in the reaction mixture. Antibate effects of the size and shape cause nonmonotonic dependence of the catalytic activity for the oxygen reduction reaction (ORR) with electric current maximum at an average particle size of 2.7 nm.