Surfactant-Free Synthesis of Cube-Like PtRu Alloy Nanoparticles with Enhanced Electrocatalytic Activity Toward Formic Acid Oxidation

Surfactant-free, monodispersed and cube-like PtRu bimetallic nanoparticles were successfully synthesized via a facile, one-step hydrothermal method. The morphology and the crystal structure of the as-prepared PtRu nanoparticles were characterized by TEM, XRD and XPS. The electrochemical studies indicated that the PtRu alloy nanocubes exhibit enhanced electrocatalytic activity toward formic acid oxidation with more negative onset potential, larger oxidation current density, and higher tolerance to CO poisoning effect compared to the commercial Pt/C catalyst in acidic media. The electron transfer kinetics of formic acid oxidation is elaborated with electrochemical impedance spectroscopic measurements. It was found that the diameter of the impedance arcs at the PtRu alloy nanocubes is at least one order of magnitude smaller than that at the commercial Pt/C catalyst, suggestive of lower charge-transfer resistance and thus, higher catalytic activity of the PtRu alloy nanoparticles for formic acid oxidation. Further XPS and CO stripping measurements demonstrated that the enhanced activity of the as-synthesized PtRu nanocrystals could be ascribed to the bifunctional mechanism and the ligand effect. The present work highlights the facile synthesis of surfactant-free PtRu bimetallic alloy nanocubes and their enhanced electrocatalytic performance which makes them potential candidates as anode catalysts in fuel cells.