Ligand‐Guided Growth of Alloyed Shells on Intermetallic Seeds as a Route toward Multimetallic Nanocatalysts with Shape‐Control

Abstract

Shape-controlled core@shell PdCu@PtCu nanoparticles (NPs) were synthesized by seed-mediated co-reduction. Specifically, cubic-shaped NPs were achieved by selecting tetraoctylammonium bromide (TOAB) and triphenylphosphine (TPP) as capping ligands. Their roles were investigated by incorporating independently each ligand into the reaction and analyzing the products by transmission electron microscopy (TEM). This analysis revealed that the quasi-spherical PdCu seeds acquired cubic shapes during the synthesis and directed shell deposition. This process was mediated by TPP, which was central to achieving monodisperse NPs with shape-control. The synthesis conditions were modified to tune both the thickness and composition of the shells. Evaluation of the NPs as catalysts for the electrooxidation of formic acid found that the NPs with the thinnest Pt-rich shells gave the highest specific activity, with the nanocubic shape also enhancing performance with respect to the spherical counterpart. These results highlight the benefits of integrating compositional, architectural, and shape-control all in one NP construct. Results and Discussion Synthesis of Core@Shell PdCu@PtCu NPs of Cubic ShapeCore@shell PdCu@PtCu NPs with a well-defined cubic profile were obtained by SMCR, where tetraoctylammonium bromide (TOAB) and triphenylphosphine (TPP) were selected as capping agents to obtain shape control. First, quasi-spherical PdCu seeds [a] S.

Mechanical Reshaping of Inorganic Nanostructures with Weak Nanoscale Forces

“…This indicates a degree of lattice distortion significantly above what is ordinarily considered the limit of elastic bond strain, further confirming the necessity of including plastic deformation in the model for nanoplate mechanics. − In addition, atomically resolved images show lattice planes and atom positions that are severely distorted with respect to a perfect crystal, indicating numerous broken bonds, defects, and plastic mechanical behavior (Figure c). It is important to note that there exist regions of elastically strained metal bonds throughout the structure that are consistent with what has been observed to transform a normally inactive noble-metal surface to one that can catalyze chemical reactions. − This suggests that such curvilinear nanostructures might have a high density of active sites for heterogeneous catalysis.…”

“…Using this in conjunction with simulations and experimental findings, we demonstrate that weak van der Waals forces can indeed provide enough energy to drive mechanical strain and thereby create a new class of curvilinear structures based on substrate topography. Since these objects would be difficult to generate lithographically, they are expected to result in previously inaccessible electromagnetic modes relevant to the nano-optics community. , Furthermore, the gradient of strained bonds in these materials has implications for their performance or study in catalytic systems. − , Overall, this work demonstrates that inorganic nanoparticles may be thought of as being capable of dynamic structural changes, actuated by simple and ubiquitous nanoscale forces.…”

Phase-Controlled Synthesis of Pd–Sn Nanocrystal Catalysts of Defined Size and Shape

“…To begin, we considered that organophosphorus compounds like triphenylphosphine (TPP), trioctylphosphine oxide (TOPO), and TOP have been used as capping agents in the synthesis of cubic metal NPs, in which the expression of {100} facets has been facilitated. − For example, TOP was used to synthesize cubic PdCu NPs in the presence of OLA, whereas spherical PdCu NPs were obtained without TOP. , Then, the synthesis of Pd 2 Sn NPs was carried out with OA omitted to promote the role of TOP in facet expression. Figure a shows a TEM image of the obtained NPs, with nanorhombohedra as the majority product (70% of NPs).…”

Mechanical Reshaping of Inorganic Nanostructures with Weak Nanoscale Forces

“…37,38 Furthermore, the gradient of strained bonds in these materials has implications for their performance or study in catalytic systems. [33][34][35]39 Overall, this work demonstrates that inorganic nanoparticles may be thought of as being capable of dynamic structural changes, actuated by simple and ubiquitous nanoscale forces.…”

“…[30][31][32] It is worth noting that there still exist regions of elastically-strained bonds throughout the structure that are consistent with what has been observed to transform a normally inactive noble metal surface to one that can catalyze chemical reactions. [33][34][35] This suggests that such curvilinear nanostructures might have a high density of active sites for catalysis. In traditional nanoscale systems, there are canonical structures from which more complex architectures can be built (e.g., spheres assembled into a superlattice or rods lithographically fabricated into metamaterial arrays).…”