Rh1−x Pd x Nanoparticle Composition Dependence in CO Oxidation by NO

Adsorption Forms of NO on Iridium-Doped Rhodium Clusters in the Gas Phase Revealed by Infrared Multiple Photon Dissociation Spectroscopy

The adsorption of an NO molecule on a cationic iridium-doped rhodium cluster, Rh₅Ir⁺, was investigated by infrared multiple photon dissociation spectroscopy (IRMPD) of Rh₅IrNO⁺·Ar_p complexes in the 300-2000 cm^-1 spectral range, where the Ar atoms acted as a messenger signaling IR absorption. Complementary density functional theory (DFT) calculations predicted two near-isoenergetic structures as the putative global minimum: one with NO adsorbed in molecular form in the on-top configuration on the Ir atom in Rh₅Ir⁺, and one where NO is dissociated with the O atom bound to the Ir atom in the on-top configuration and the N atom on a hollow site formed by three Rh atoms. A comparison between the experimental IRMPD spectrum of Rh₅IrNO⁺ and calculated spectra indicated that NO mainly adsorbs molecularly on Rh₅Ir⁺, but evidence was also found for structures with dissociatively adsorbed NO. The estimated fraction of Rh₅IrNO⁺ structures with dissociatively adsorbed NO is approximately 10%, which was higher than that found for Rh₆⁺, but lower than that for Ir₆⁺. The DFT calculations indicated the existence of an energy barrier in the NO dissociation pathway that is exothermic with respect to the reactants, which was considered to prevent NO from dissociating readily on Rh₅Ir⁺. The height of the barrier is lower than that for NO dissociation over Rh₆⁺, which is attributed to the higher binding energy of atomic O to the Ir atom in Rh₅Ir⁺ than to a Rh atom in Rh₆⁺.

Pt–Pd bimetallic effect in PtxPd1−x/(Ce,Zr,La)O2 catalysts for NOx, HC and CO elimination

The bimetallic catalysts show the alloy structure and the surplus precious metals presented as isolated PMO_x species.

The Attractiveness of the Ternary Rh-Pd-Pt Alloys for CO Oxidation Process

Ternary alloys of platinum group metals attract a growing interest due to their unique catalytic properties. The present research is aimed to synthesize a series of Rh-Pd-Pt alloys with varied ratios of metals using a single-source precursor approach. Rhodium and palladium are partly miscible metals, while each of these metals is unlimitedly miscible with platinum. Thermolysis of complex salts used as a precursor results in the formation of metastable systems. The 3D nanostructure alloys are being formed after the complete decomposition of the single-source precursor. High-resolution transmission electron microscopic studies have shown that the nanoalloys are composed of interconnected polycrystalline ligaments with a mean diameter of 50 nm. The single-phase composition is confirmed by an X-ray diffraction analysis. The ratio of metals plays an important role in determining the catalytic activity of alumina-supported alloys and their thermal stability. According to UV-vis spectroscopy data, the higher palladium portion corresponds to worse dispersion of initially prepared, fresh catalysts. Treatment of the catalysts under prompt thermal aging conditions (up to 800 °C) causes redispersion of palladium-rich alloyed nanoparticles, thus leading to improved catalytic activity and thermal stability.

Diamines as interparticle linkers for silica–titania supported PdCu bimetallic nanoparticles in Chan–Lam and Suzuki cross-coupling reactions

The remarkable synergetic effect between Pd and Cu, and basic nitrogen sites on the support effectively stabilize the nanoparticles and enhance the catalytic activity.

Morphology-Controlled Synthesis of Rhodium Nanoparticles for Cancer Phototherapy

Rhodium nanoparticles are promising transition metal nanocatalysts for electrochemical and synthetic organic chemistry applications. However, notwithstanding their potential, to date, Rh nanoparticles have not been utilized for biological applications; there has been no cytotoxicity study of Rh reported in the literature. In this regard, the absence of a facile and controllable synthetic strategy of Rh nanostructures with various sizes and morphologies might be responsible for the lack of progress in this field. Herein, we have developed a synthetic strategy for Rh nanostructures with controllable morphology through an inverse-directional galvanic replacement reaction. Three types of Rh-based nanostructures-nanoshells, nanoframes, and porous nanoplates-were successfully synthesized. A plausible synthetic mechanism based on thermodynamic considerations has also been proposed. The cytotoxicity, surface functionalization, and photothermal therapeutic effect of manufactured Rh nanostructures were systematically investigated to reveal their potential for in vitro and in vivo biological applications. Considering the comparable behavior of porous Rh nanoplates to that of gold nanostructures that are widely used in nanomedicine, the present study introduces Rh-based nanostructures into the field of biological research.

Structural Characterization of Rh and RhAu Dendrimer-Encapsulated Nanoparticles

We report the structural characterization of 1-2 nm Rh and RhAu alloy dendrimer-encapsulated nanoparticles (DENs) prepared by chemical reduction with NaBH₄. In contrast to previously reported results, in situ and ex situ X-ray absorption spectroscopic experiments indicate that only a fraction of the Rh³⁺ present in the precursors are reduced by NaBH₄. Additional structural analysis of RhAu alloy DENs using extended X-ray absorption fine structure spectroscopy leads to a model in which there is significant segregation of Rh and Au within the nanoparticles. In Rh-rich alloy DENs, Au atoms are segregated on the nanoparticle surface.

Improved three-way catalytic activity of bimetallic Ir–Rh catalysts supported on CeO2–ZrO2

The addition of a small amount of Ir caused a significant increase in the TWC performance of Rh/CeO₂–ZrO₂.

Configurational thermodynamics of alloyed nanoparticles with adsorbates

Changes in the chemical configuration of alloyed nanoparticle (NP) catalysts induced by adsorbates under working conditions, such as reversal in core-shell preference, are crucial to understand and design NP functionality. We extend the cluster expansion method to predict the configurational thermodynamics of alloyed NPs with adsorbates based on density functional theory data. Exemplified with PdRh NPs having O-coverage up to a monolayer, we fully detail the core-shell behavior across the entire range of NP composition and O-coverage with quantitative agreement to in situ experimental data. Optimally fitted cluster interactions in the heterogeneous system are the key to enable quantitative Monte Carlo simulations and design.