Shape-controlled synthesis of Pt nanostructures and evaluation of catalytic and electrocatalytic performance

We describe the synthesis of aggregated dendrimer-like and interconnected peanut-like Pt nanostructures by solvothermal routes and their catalytic and electrocatalytic performance. The aggregated dendrimer-like Pt nanostructures with an average size of 10 nm are obtained in ethanol medium in the presence of shape-regulating polymer poly(diallyldimethylammonium chloride). The interconnected peanut-like nanoparticles of similar to 100 nm with porous surface structure are synthesized by a modified polyol route in the absence of any shape-regulating reagents. The nanoparticles are characterized by transmission electron microscopic and electrochemical measurements. The mass specific electrochemically accessible surface area of interconnected peanut-like nanoparticles is 47% higher than the aggregated dendrimer-like nanoparticles. The catalytic performance of these nanoparticles towards hydrogenation of unsaturated alcohols is evaluated. The interconnected peanut-like nanoparticles show a highest turnover frequency (TOF, h(-1)) of 550 at a catalyst loading of 0.1 mole%. The nanoparticles are loaded onto multiwalled carbon nanotubes and their electrocatalytic activity towards the oxygen reduction reaction (ORR) is evaluated in terms of onset potential, specific and mass activities. The kinetics of ORR was examined with a rotating ring-disk electrode (RRDE) system. The interconnected peanut-like nanoparticles have a high positive onset potential of 1.06 V with a specific and mass activity of 279 mu A cm(Pt)(-2) and 47.5 mu A mu g(Pt)(-1), respectively, at a potential of 0.9 V. The specific activity towards ORR of the interconnected peanut-like Pt nanostructures is significantly higher than the aggregated dendrimer-like and quasispherical nanoparticles. Both catalytic and electrocatalytic measurements indicate that the shape and surface structure have a great control over their activity. The remarkable catalytic and electrocatalytic activity is accounted for the large surface area and existence of surface defects.