Shape-dependent catalytic activity of palladium nanoparticles for the direct synthesis of hydrogen peroxide from hydrogen and oxygen

In this study, single-crystal Pd nanocubes and nanooctahedrons were prepared by the colloidal method and their catalytic activities were compared in direct hydrogen peroxide synthesis. Using sodium tetrachloropalladate (II) as the Pd precursor, l-ascorbic acid (or formaldehyde) as the reducing agent, potassium bromide as the capping agent, and polyvinylpyrrolidone as the stabilizer, Pd nanocubes were obtained in a uniform size (9 nm). Pd octahedrons (23 nm in edge length) were synthesized via seed-mediated growth of the Pd nanocube, where the morphology of the cube was altered to that of a cuboctahedron, truncated octahedron, and octahedron, in series. The cubes and octahedrons were enclosed by {1 0 0} and {1 1 1} facets, respectively. In activity tests, the Pd octahedron presented higher hydrogen peroxide selectivity and productivity than the Pd cube. It is therefore suggested that the Pd {1 1 1} facet is more active than the Pd {1 0 0} facet in direct hydrogen peroxide synthesis.