Plate-Like Colloidal Metal Nanoparticles

The pseudo-two-dimensional (2D) morphology of plate-like metal nanoparticles makes them one of the most anisotropic, mechanistically understood, and tunable structures available. Although well-known for their superior plasmonic properties, recent progress in the 2D growth of various other materials has led to an increasingly diverse family of plate-like metal nanoparticles, giving rise to numerous appealing properties and applications. In this review, we summarize recent progress on the solution-phase growth of colloidal plate-like metal nanoparticles, including plasmonic and other metals, with an emphasis on mechanistic insights for different synthetic strategies, the crystallographic habits of different metals, and the use of nanoplates as scaffolds for the synthesis of other derivative structures. We additionally highlight representative self-assembly techniques and provide a brief overview on the attractive properties and unique versatility benefiting from the 2D morphology. Finally, we share our opinions on the existing challenges and future perspectives for plate-like metal nanomaterials.

Spatially Confined PdHx Metallenes by Tensile Strained Atomic Ru Layers for Efficient Hydrogen Evolution

Hydride metallenes show great potential for hydrogen-related catalytic applications due to favorable electronic structures modulated by interstitial hydrogen atoms and large active surface areas of metallenes. Metallene nanostructures generally have compressive strain relative to bulk, which can affect both the stability and the catalytic behavior of hydride metallenes but in general cannot be controlled. Here, we demonstrate highly stable PdH_x metallenes with a tensile strained Ru surface layer and reveal the spatial confinement effect of the Ru skin by multiple spectroscopic characterizations and molecular dynamics simulations. These PdH_x@Ru metallenes with a 4.5% expanded Ru outer layer exhibit outstanding alkaline hydrogen evolution reaction activity with a low overpotential of 30 mV at 10 mA cm^-2 and robust stability with negligible activity decay after 10,000 cycles, which are superior to commercial Pt/C and most reported Ru-based electrocatalysts. Control experiments and first-principles calculations reveal that the tensile strained Ru outer layer lowers the energy barrier of H₂O dissociation and provides a moderate hydrogen adsorption energy.

Laser induced trace doping of Pd on Ru nanoparticles for an efficient hydrogen evolution electrocatalyst

Improving the activity and stability of electrocatalysts for the hydrogen evolution reaction (HER) plays an essential role in the practical application of electrochemical water splitting under alkaline conditions. Here, trace Pd-doped Ru nanoparticles have been achieved using the pulsed laser ablation in liquid technology, which exhibit efficient HER catalytic performance. It is evidenced that the Pd doping amount is maintained at a trace level and increases nonlinearly with the concentration of the Pd precursor. Molecular dynamics simulations demonstrate that the trace doping of Pd is due to the slow thermal decomposition rate of the Pd precursor. This work improves the mechanistic explanation of the metal doping induced by liquid-phase laser ablation, which may promote the fabrication and application of advanced laser-based nanostructures.

Phase-Controlled Synthesis of Ru Nanocrystals via Template-Directed Growth: Surface Energy versus Bulk Energy

Despite the successful control of crystal phase using template-directed growth, much remains unknown about the underlying mechanisms. Here, we demonstrate that the crystal phase taken by the deposited metal depends on the lateral size of face-centered cubic (fcc)-Pd nanoplate templates with 12 nm plates giving fcc-Ru while 18-26 nm plates result in hexagonal closed-packed (hcp)-Ru. Although Ru overlayers with a metastable fcc- (high in bulk energy) or stable hcp-phase (low in bulk energy) can be epitaxially deposited on the basal planes, the lattice mismatch will lead to jagged hcp- (high in surface energy) and smooth fcc-facets (low in surface energy), respectively, on the side faces. As the proportion of basal and side faces on the nanoplates varies with lateral size, the crystal phase will change depending on the relative contributions from the surface and bulk energies. The Pd@fcc-Ru outperforms the Pd@hcp-Ru nanoplates toward ethylene glycol and glycerol oxidation reactions.

A Novel Cascade Nanoreactor Integrating Two-Dimensional Pd-Ru Nanozyme, Uricase and Red Blood Cell Membrane for Highly Efficient Hyperuricemia Treatment

Nanozyme-based cascade reaction has emerged as an effective strategy for disease treatment because of its high efficiency and low side effects. Herein, a new and highly active two-dimensional Pd-Ru nanozyme is prepared and then integrated with uricase and red blood cell (RBC) membrane to fabricate a tandem nanoreactor, Pd-Ru/Uricase@RBC, for hyperuricemia treatment. The designed Pd-Ru/Uricase@RBC nanoreactor displayed not only good stability against extreme pH, temperature and proteolytic degradation, but also long circulation half-life and excellent safety. The nanoreactor can effectively degrade UA by uricase to allantoin and H₂ O₂ and remove H₂ O₂ by using Pd-Ru nanosheets (NSs) with the catalase (CAT)-like activity. More importantly, the finally produced O₂ from H₂ O₂ decomposition can in turn facilitate the catalytic oxidation of UA, as the degradation of UA is an O₂ consumption process. By integrating the high-efficiency enzymatic activity, long circulation capability, and good biocompatibility, the designed Pd-Ru/Uricase@RBC can effectively and safely treat hyperuricemia without side effects. The study affords a new alternative for the exploration of clinical treatment of hyperuricemia.

Facile Synthesis of PdCuRu Porous Nanoplates as Highly Efficient Electrocatalysts for Hydrogen Evolution Reaction in Alkaline Medium

Ru is a key component of electrocatalysts for hydrogen evolution reaction (HER), especially in alkaline media. However, the catalytic activity and durability of Ru-based HER electrocatalysts are still far from satisfactory. Here we report a solvothermal approach for the synthesis of PdCuRu porous nanoplates with different Ru compositions by using Pd nanoplates as the seeds. The PdCuRu porous nanoplates were formed through underpotential deposition (UPD) of Cu on Pd, followed by alloying Cu with Pd through interdiffusion and galvanic replacement between Cu atoms and Ru precursor simultaneously. When evaluated as HER electrocatalysts, the PdCuRu porous nanoplates exhibited excellent catalytic activity and durability. Of them, the Pd24Cu29Ru47/C achieved the lowest overpotential (40.7 mV) and smallest Tafel slope (37.5 mV dec−1) in an alkaline solution (much better than commercial Pt/C). In addition, the Pd24Cu29Ru47/C only lost 17% of its current density during a stability test for 10 h, while commercial Pt/C had a 59.5% drop under the same conditions. We believe that the electron coupling between three metals, unique porous structure, and strong capability of Ru for water dissociation are responsible for such an enhancement in HER performance.

Catalytic Activity of Bimetallic (Ruthenium/Palladium) Nano-alloy Decorated Porous Carbons Toward Reduction of Toxic Compounds

Chicken feather-derived high-surface-area porous activated carbon (CFAC) material was prepared using chemical activation. A new composite composed of Ru-Pd nanoparticles supported on CFAC (Ru-Pd@CFAC) has been prepared by microwave-thermal reduction in the presence of the support. Characterization by XRD, Raman, BET, FE-SEM/TEM, FT-IR, TGA, XPS, HAADF-STEM-EDS, H₂ -chemisorption, H₂ -TPR, and ICP-AES was used to analyze the catalyst. This catalyst is found to be efficient for the reduction of hexavalent chromium (Cr^VI ), potassium ferricyanide (K₃ [Fe(CN)₆ ]), 4-nitrophenol (4-NP), and pendimethalin (PDM), at room temperature, and remains stable, even after several repeated runs. Moreover, it showed excellent catalytic activity compared with the monometallic counterparts.