Synthesis of Palladium Colloidal Nanocrystal Clusters and Their Enhanced Electrocatalytic Properties

Colloidal nanocrystal clusters (CNCs) and nanoparticles of palladium (Pd) were synthesized controllably by using an amino-acid-assisted hydrothermal method in the presence of polyvinylpyrrolidone. Experimental results showed that crystalline Pd nanoparticles were synthesized by adding alanine into the synthetic solutions, whereas sub-micrometer Pd CNCs composed of small nanocrystals were obtained from phenylalanine systems. Electrochemical measurements showed that Pd CNCs displayed a much better electrocatalytic performance than nanoparticles, because CNCs were formed by the in situ self-assembly of primary nanocrystals. The structure of Pd CNCs can also be maintained after electrocatalytic cycle testing. Both Pd-based electrocatalysts showed the highest electrocatalytic activity towards the electrooxidation of ethanol among the used alcohols. The formation mechanisms and electrocatalytic properties of the Pd nanoparticles and CNCs are discussed and analyzed based on the experimental data.