Synthesis of 3D Thornbush-like Trimetallic CoAuPd Nanocatalysts and Electrochemical Dealloying for Methanol Oxidation and Oxygen Reduction Reaction

Trimetallic CoAuPd nanocatalysts are synthesized by a classical successive reduction method using P123 as protectant and sodium borohydride as reductant. The structure, composition, and morphology of the nanocatalysts are measured and characterized through different techniques. The obtained results show that the trimetallic CoAuPd nanocatalysts have two kinds of super three-dimensional (3D) structures: the novel nanothornbush and nanocluster structure. The formation of these epitaxial multilevel structures may be attributed to the Co seed crystal ferromagnetism and multilevel self-assembly. The electrocatalytic properties of the CoAuPd nanocatalysts are investigated deeply. Furthermore, the electrochemical dealloying method is also adopted to enhance the electrocatalytic performance. The results of dealloying gradient tests for the methanol oxidation reaction (MOR) demonstrate that the reaction active sites, electrochemical specific active areas, and catalytic activity of the CoAuPd nanocatalysts gradually increased during the dealloying process. In addition, the CoAuPd nano catalysts also present remarkably enhanced activity for oxygen reduction reaction (ORR) activity after the dealloying process. The extraordinary catalytic performance of the dealloyed CoAuPd may be derived from the special epitaxial multilevel structure such as nanothornbush and nanocluster structures, the assembled components of featherness nanoparticles and hollow spherical nanoparticles, as well as plenty of filamentous nanocrystals. Especially, the CoAuPd nanocatalysts have more discovered and exposed active sites, and can form the CoAuPd@AuPd core-shell structure with a rough AuPd alloy surface after electrochemical dealloying. The efficient catalytic performance of the trimetallic CoAuPd nanocatalysts makes them an excellent candidate as electrocatalysts used for a direct methanol fuel cell (DMFC).