Shape‐Controlled Synthesis of Colloidal Metal Nanocrystals by Replicating the Surface Atomic Structure on the Seed

Abstract

Controlling the surface structure of metal nanocrystals while maximizing the utilization efficiency of the atoms is a subject of great importance. An emerging strategy that has captured the attention of many research groups involves the conformal deposition of one metal as an ultrathin shell (typically 1-6 atomic layers) onto the surface of a seed made of another metal and covered by a set of well-defined facets. This approach forces the deposited metal to faithfully replicate the surface atomic structure of the seed while at the same time serving to minimize the usage of the deposited metal. Here, the recent progress in this area is discussed and analyzed by focusing on the synthetic and mechanistic requisites necessary for achieving surface atomic replication of precious metals. Other related methods are discussed, including the one-pot synthesis, electrochemical deposition, and skin-layer formation through thermal annealing. To close, some of the synergies that arise when the thickness of the deposited shell is decreased controllably down to a few atomic layers are highlighted, along with how the control of thickness can be used to uncover the optimal physicochemical properties necessary for boosting the performance toward a range of catalytic reactions.

Replicating the Defect Structures on Ultrathin Rh Nanowires with Pt to Achieve Superior Electrocatalytic Activity toward Ethanol Oxidation

“…The less atomic layer number of the Pt shell causes stronger Rh–Pt interaction compression strain and larger electronic ligand effect on the outermost Pt surface, which can dramatically alter the catalytic behavior of the outermost Pt surface leading to the priority of CC bond cleavage. When the Pt shell thickened, the strain effects and ligand effects were gradually released, and the catalytic properties of outermost Pt shell tended to be the nature of pristine Pt, as the geometric strain and ligand effect can only impact surface reactivity over less than a few atomic layers . Thus, the Rh @ Pt 5.3L NW/C catalysts presented the highest capacity for producing acetic acid but poor selectivity toward CO 2 .…”

“…It has been universally recognized that the catalytic behavior of metal nanocrystals is highly dependent on their surface compositions and structures . Metallic nanocrystals with ultrathin Pt skins exhibit extraordinary electronic structures which can drastically improve their electrocatalytic performance .…”

Pd‐Ru Alloy Nanocages with a Face‐Centered Cubic Structure and Their Enhanced Activity toward the Oxidation of Ethylene Glycol and Glycerol

“…As an alternative to the conventional catalysts based upon solid nanoparticles, nanocages have recently emerged as an intriguing class of catalysts for various reactions . The characteristic hollow structure, ultrathin and porous walls of nanocages are advantageous in maximizing the atom utilization efficiency while the well‐controlled surface structures could be leveraged to optimize the active sites . One effective route to the synthesis of nanocages is based upon galvanic replacement, which involves the spontaneous reduction of metal ions at the expense of oxidation of a sacrificial template .…”

Hollow Metal Nanocrystals with Ultrathin, Porous Walls and Well‐Controlled Surface Structures

“…A hollow interior is naturally formed in the product as the sacrificial template is being oxidized and consumed during the galvanic replacement. In the second approach, an ultrathin shell of Pt is conformally deposited on the surface of a well‐defined seed (e.g., Pd nanocube or octahedron), followed by a wet‐chemical etching process to selectively remove the seed from the core. Both approaches are discussed in the upcoming sections, with a focus on the mechanistic understanding and experimental control, as well as the pros and cons of each method.…”

“…Naturally, the production of Pt nanocages enclosed by {100} facets began with perfecting the synthesis of Pd@Pt nL core–shell nanocubes with controllable shell thicknesses . To better control this synthesis, our group compared the deposition kinetics of Pt atoms on Pd nanocubes in both polyol and aqueous solvents .…”