Controlled Synthesis of Nanosized Palladium icosahedra and Their Catalytic Activity towards Formic‐Acid Oxidation

Abstract

Pd icosahedra with sizes controlled in the range of 5-35 nm were synthesized in high purity through a combination of polyol reduction and seed-mediated growth. The Pd icosahedra were obtained with purity >94 % and uniform sizes controlled in the range of 5-17 nm by using ethylene glycol as both the reductant and solvent. The studies indicate that the formation of Pd nanocrystals with an icosahedral shape was very sensitive to the reaction kinetics. The success of this synthesis relies on the use of HCl to manipulate the reaction kinetics and thus control the twin structure and shape of the resultant nanocrystals. The size of the Pd icosahedra could be further increased up to 35 nm by seed-mediated growth, with 17 nm Pd icosahedra serving as seeds. The multiply twinned Pd icosahedra could grow into larger sizes, and their shape and multiply twinned structure were preserved. Thanks to the presence of twin defects, the Pd icosahedra showed a catalytic current density towards formic-acid oxidation that was 1.9 and 11.6 times higher than that of single-crystal Pd octahedra, which were also fully covered by {111} facets, and commercial Pd/C, respectively.

Scalable Synthesis of Palladium Icosahedra in Plug Reactors for the Production of Oxygen Reduction Reaction Catalysts

“…As established in our previous studies, Pd icosahedra could be synthesized in ethylene glycol (EG) or diethylene glycol (DEG) using batch reactors . The synthesis typically involved the reduction of a precursor (e.g., Na 2 PdCl 4 ) by aldehyde derived from the oxidation of EG or DEG in air .…”

“…They can also serve as seeds to generate bimetallic nanocrystals with enhanced properties . Over the past decade, Pd nanocrystals with a variety of shapes, including cubes, octahedra, right bipyramids, icosahedra, and plates, have been reported, albeit most of the protocols were based on batch reactors such as flasks and vials. Although uniform, well‐controlled products could be obtained, the reproducibility and quantity cannot be guaranteed from batch to batch, making it a grand challenge to apply the nanocrystals to large‐scale applications .…”

Generation of subsurface voids and a nanocrystalline surface layer in femtosecond laser irradiation of a single-crystal Ag target

“…Beyond the mechanical properties, the high sensitivity of catalytic activity of metal surfaces and nanoparticles to their atomic structure [ 99,100] suggests that the presence of a broad spectrum of atomic configurations on nanostructured surfaces produced by femtosecond laser processing may lead to an enhanced catalytic activity of the surface. The presence of twins, in particular, have been found to result in a substantial enhancement of hydrogen absorption [ 101 ] and electrocatalitic activity of icosahedral nanoparticles [102,103].…”

Shape-Controlled Metal Nanocrystals for Heterogeneous Catalysis

“…Furthermore, we studied the impact of twin defects on the FAO catalytic activity (49). Our group recently synthesized Pd decahedra, icosahedra, and right bipyramids with purity exceeding 90% (52)(53)(54). Specifically, the decahedra and icosahedra were prepared by manipulating the initial reduction rate of a synthesis.…”