Rhodium Nanoparticles Research Articles

Effect of Preparation Method and Support on Catalytic Behavior of Rhodium Nanoparticles in Styrene Hydrogenation

The Rh nanoparticles supported on silica were prepared by hydrazine reduction in aqueous medium. The obtained catalysts are characterized by X-ray diffraction, transmission electronic microscopy, and energy dispersive X-ray analysis. Their catalytic performances were evaluated in the hydrogenation of styrene. The results show that the catalytic activity has been greatly affected by the temperature, silica support and the method of preparation. The activity of supported catalyst is about 12 times that of the unsupported systems. Moreover, the catalytic activity of the supported catalysts increases when the Rh loading decreases. This is ascribed to the degree of the metal dispersion, which increases with a decrease in the Rh loading in the catalysts. The results reveal also that the catalyst prepared by programmed temperature reduction seems to be more catalytically active than the catalyst prepared by the isothermal reduction procedure.

Rhodium(0), Ruthenium(0) and Palladium(0) nanoparticles supported on carbon-coated iron: Magnetically isolable and reusable catalysts for hydrolytic dehydrogenation of ammonia borane

We report the synthesis of magnetically isolable ruthenium(0), rhodium(0), and palladium(0) nanoparticles, supported on carbon-coated magnetic iron particles, and their employment as catalysts in hydrolysis of ammonia borane. Carbon-coated iron (C–Fe) particles are obtained by co-processing of iron powders with methane in a radio frequency thermal plasma reactor. The impregnation of ruthenium(III), rhodium(III) and palladium(II) ions on the carbon-coated iron particles followed by aqueous solution of sodium borohydride leads to the formation of respective metal(0) nanoparticles supported on carbon-coated iron, M0/C–Fe NP (M = Ru, Rh, and Pd) at room temperature. M0/C–Fe NPs are characterized using the ICP-OES, XPS, TEM, and EDX techniques and tested as catalysts for hydrolysis of ammonia borane at 298 K. The results reveal that Rh0/C–Fe, Ru0/C–Fe, Pd0/C–Fe catalysts provide turnover frequency of 83, 93, and 29 min−1, respectively, in this industrially important reaction. More importantly, these magnetically separable metal(0) nanoparticles show very high reusability with no noticeable activity loss in subsequent runs of hydrolysis evolving 3.0 equivalent H2 per mole of ammonia borane.

Magnetically Separable Rh0/Co3O4 Nanocatalyst Provides over a Million Turnovers in Hydrogen Release from Ammonia Borane

Cobalt(II,III) oxide nanopowders are used as supporting materials for rhodium(0) nanoparticles forming Rh0/Co3O4 nanocatalysts, which can be prepared by impregnation and sodium borohydride reductio...

Photocatalytic uphill conversion of natural gas beyond the limitation of thermal reaction systems

Dry reforming of methane is one of the key reactions to exploit natural gas feedstocks by their catalytic conversion to synthesis gas (CH4 + CO2 → 2H2 + 2CO), which is used in the production of transportable liquid fuel. However, this reaction suffers from thermodynamic conversion limits and high thermal energy requirements. Herein we report that a SrTiO3-supported rhodium (Rh/STO) catalyst efficiently promotes methane reforming under ultraviolet light irradiation without heat supply at low temperatures, which cannot be achieved by conventional thermal catalysis. The photoexcited holes and electrons are used for CH4 oxidation over STO and CO2 reduction over rhodium, respectively. Isotope analysis clarified that the lattice oxygens (O2−) act as mediator to drive dry reforming of methane. The materials design of Rh/STO can be extended in principle to diverse uphill reactions that utilize photon energy to obtain valued products from different carbon resources. Despite its potential, catalytic dry reforming of methane has not yet reached practical application due to high thermal energy requirements. Now, a photocatalytic method is introduced based on strontium titanate-supported rhodium nanoparticles that afford syngas production solely under light irradiation.

In‐Situ Electrodeposition of Rhodium nanoparticles Anchored on Reduced Graphene Oxide nanosheets as an Efficient Oxygen Reduction Electrocatalyst

A simple, versatile, and cost‐effective one‐pot electrochemical deposition is used to fabricate rhodium (Rh) nanoparticles decorated surface of reduced graphene oxide (rGO) functionalized glassy carbon electrode (GCE) for oxygen reduction reaction (ORR) in alkaline media. The chemical and physical structure of the sample is probed via transmission electron microscopy, rotating disk electrode (RDE), X‐ray photoelectron spectroscopy, linear sweep voltammetry, and Raman spectroscopy. The synergistic effects between the unique properties of Rh nanoparticles and rGO creates such innovative hybrid that exhibits a catalytic activity comparable to that of the commercial platinum electrocatalyst (Pt/C). As a result, the as‐electrodeposited Rh@rGO hybrid exhibits outstanding ORR activity in alkaline media, as evidenced by a larger diffusion‐limited current, greater positive onset potential, much better stability and methanol tolerance than Pt/C under the same conditions.

Production of Bio Hydrofined Diesel, Jet Fuel, and Carbon Monoxide from Fatty Acids Using a Silicon Nanowire Array-Supported Rhodium Nanoparticle Catalyst under Microwave Conditions

Biodiesel was efficiently produced from biomass fatty acids using renewable gas H2 and a reusable heterogeneous catalyst under low-energy-consumption microwave conditions. As the decarboxylation of...

Rhodium nanoparticles impregnated on TiO2: strong morphological effects on hydrogen production

Rhodium nanoparticles with different morphology were synthesized to assess the influence of the exposed facet towards hydrogen production in aqueous methanolic solution.

Selective hydrogenation of fluorinated arenes using rhodium nanoparticles on molecularly modified silica

Rh nanoparticles prepared on hydrophobic molecularly modified silica act as effective catalysts for the hydrogenation of fluoroarenes to fluorocyclohexane derivatives.

Carbon supported noble metal nanoparticles as efficient catalysts for electrochemical water splitting.

Due to an increasing requirement of clean and sustainable hydrogen energy economy, it is significant to develop new highly effective catalysts for electrochemical water splitting. In alkaline electrolyte, Platinum (Pt) shows a much slower hydrogen evolution reaction (HER) kinetics relative to acidic condition. Here, we show a versatile synthetic approach for combining different noble metals, such as Rhodium (Rh), RhPt and Pt nanoparticles, with carbon forming noble metal nanoparticles/nanocarbon composites, denoted as Rh(nP)/nC, RhPt(nP)/nC and Pt(nP)/nC, respectively. It was found that in alkaline media these composites exhibited higher performance for the HER than the commercial Pt/C. In particular, Rh(nP)/nC displayed a small overpotential of 44 mV at a current density of 5 mA cm-2 and a low Tafel slope of 50 mV dec-1. Meanwhile, it also showed a comparable activity for the oxygen evolution reaction (OER) to the benchmarking catalyst RuO2. The superior HER and OER performance benefits from the very small size of nanoparticles and synergy between carbon support and nanoparticles.

Hollow Nano-Mesosilica Spheres Containing Rhodium Nanoparticles Supported on Nitrogen-Doped Carbon: An Efficient Catalyst for the Reduction of Nitroarenes under Mild Conditions.

Atom efficiency, low temperature, low pressure, and a nontoxic hydrogen source as a reducing agent are ideal reaction conditions for the reduction of nitroarenes. In this work, an efficient catalyst comprising hollow nano-mesosilica spheres loaded with Rh nanoparticles supported on nitrogen-doped carbon was developed. Rh nanoparticles were stabilized and uniformly dispersed by nitrogen atoms, and the inner N-doped carbon shell was used to adsorb reaction substrates and improve catalytic activity. The catalyst showed remarkable activity (maximum yield at 1.5 h) and selectivity (100 %) for the reduction of nitrobenzene at lower temperature (80 °C), atmospheric pressure (1 atm), and without base under aqueous conditions. Moreover, the hydrothermal stability of this nanocatalyst was better than other catalysts in boiling water at 100 °C for 48 h and effectively prevented the aggregation and leaching of Rh NPs during the reaction.

Pore structure dependent activity and durability of mesoporous rhodium nanoparticles towards the methanol oxidation reaction.

This work reports a significant effect of porous structures on the electrocatalytic methanol oxidation performances of Rh-based catalysts. It is demonstrated that a three-dimensional net-like mesoporous structure with ultrathin subunits is beneficial to exposing more active sites and boosting electron transfer inside particles, thus presenting the highest activity.

Hydrogen absorption and desorption on Rh nanoparticles revealed by in situ dispersive X-ray absorption fine structure spectroscopy.

To unveil the origin of the hydrogen-storage properties of rhodium nanoparticles (Rh NPs), we investigated the dynamical structural change of Rh NPs using in situ dispersive X-ray absorption fine structure spectroscopy (XAFS). The variation of the Rh–Rh interatomic distance and Debye–Waller factor of Rh NPs with a size of 4.0 and 10.5 nm during hydrogen absorption and desorption suggested that they have a different mechanism for hydrogen absorption, which is that the hydrogen absorption on the inner site has a greater contribution than that on a surface for Rh 4.0 nm. In the case of Rh 10.5 nm, it is opposed to Rh 4.0 nm. This study demonstrates a powerful in situ XAFS method for observing small local structural changes of metal nanoparticles and its importance for understanding of the hydrogen-absorption properties of Rh NPs with an interesting hydrogenation mechanism.

Asymmetric 1,4‐Addition of Arylboronic Acids to β,γ‐Unsaturated α‐Ketoesters using Heterogeneous Chiral Metal Nanoparticle Systems

AbstractAsymmetric 1,4‐addition reactions with β,γ‐unsaturated α‐ketoesters are valuable because the resulting chiral ketoester compounds can be converted into various useful species that are often used as chiral building blocks in drug and natural product synthesis. However, β,γ‐unsaturated α‐ketoesters have two reactive points in terms of nucleophilic additions, which will lead to the 1,4‐adduct, the 1,2‐adduct and to the combined 1,4‐ and 1,2‐adduct. Therefore, controlling this chemoselectivity is an important factor for the development of these transformations. Here, we developed an asymmetric 1,4‐addition of aryl boronic acids to β,γ‐unsaturated α‐ketoesters by using heterogeneous chiral rhodium nanoparticle systems with a chiral diene ligand bearing a secondary amide moiety. The newly developed polydimethylsilane‐immobilized rhodium nanoparticle catalysts showed high activity, high chemoselectivity, and excellent enantioselectivity, and this is the first heterogeneous catalytic system for this asymmetric reaction. Metal nanoparticle catalysts were recovered and reused without loss of activity or leaching of metal.magnified image

Graphene Supported Rhodium Nanoparticles for Enhanced Electrocatalytic Hydrogen Evolution Reaction

Current research on catalysts for proton exchange membrane fuel cells (PEMFC) is based on obtaining higher catalytic activity than platinum particle catalysts on porous carbon. In search of a more sustainable catalyst other than platinum for the catalytic conversion of water to hydrogen gas, a series of nanoparticles of transition metals viz., Rh, Co, Fe, Pt and their composites with functionalized graphene such as RhNPs@f-graphene, CoNPs@f-graphene, PtNPs@f-graphene were synthesized and characterized by SEM and TEM techniques. The SEM analysis indicates that the texture of RhNPs@f-graphene resemble the dispersion of water droplets on lotus leaf. TEM analysis indicates that RhNPs of <10 nm diameter are dispersed on the surface of f-graphene. The air-stable NPs and nanocomposites were used as electrocatalyts for conversion of acidic water to hydrogen gas. The composite RhNPs@f-graphene catalyses hydrogen gas evolution from water containing p-toluene sulphonic acid (p-TsOH) at an onset reduction potential, Ep, −0.117 V which is less than that of PtNPs@f-graphene (Ep, −0.380 V) under identical experimental conditions whereas the onset potential of CoNPs@f-graphene was at Ep, −0.97 V and the FeNPs@f-graphene displayed onset potential at Ep, −1.58 V. The pure rhodium nanoparticles, RhNPs also electrocatalyse at Ep, −0.186 V compared with that of PtNPs at Ep, −0.36 V and that of CoNPs at Ep, −0.98 V. The electrocatalytic experiments also indicate that the RhNPs and RhNPs@f-graphene are stable, durable and they can be recycled in several catalytic experiments after washing with water and drying. The results indicate that RhNPs and RhNPs@f-graphene are better nanoelectrocatalysts than PtNPs and the reduction potentials were much higher in other transition metal nanoparticles. The mechanism could involve a hydridic species, Rh-H− followed by interaction with protons to form hydrogen gas.

Surface Engineering of Rh Catalysts with N/S-Codoped Carbon Nanosheets toward High-Performance Hydrogen Evolution from Seawater

In this study, rhodium (Rh) nanoparticles modified by N/S-codoped carbon nanosheets were prepared as a high performance hydrogen evolution reaction (HER) interface electrocatalyst in seawater. Such...

The UV Plasmonic Behavior of Rhodium Tetrahedrons—A Numerical Analysis

Rhodium (Rh) nanoparticles have attracted a lot of attention due to their strong and ambient-stable UV plasmonic response. Very recently, the synthesis of Rh tetrahedra with and without concave defect-rich surfaces serving in plasmon assisted photocatalytic energy conversion has been reported. In this work, we perform a systematic numerical study on plasmonic behavior and surface charge distribution in order to optimize the use of Rh tetrahedra in surface-enhanced spectroscopies and photocatalysis. We analyze the effect of the edges and corners reshaping, a deformation already reported to appear in Rh nanocubes which have been repeatedly re-used in photocatalytic processes. It is demonstrated that rounding the edges and corners weakens both the near-field enhancement and surface charge densities in these locations, which in turn are the more reactive regions due to the presence of uncoordinated sites. In addition, we study how the near-field and charge density is redistributed on the surface of the tetrahedra when concavities of different sizes and depths are introduced. Through this study, we show that, in order to simultaneously maximize the near-field enhancement and surface charge densities in the concavity and at external edges and corners, medium size deep concavities are needed.

Reduction of Nitroarenes on Goethite-Supported Rhodium Nanoparticles

Reduction of Nitroarenes on Goethite-Supported Rhodium Nanoparticles

0.2 V Electrolysis Voltage-Driven Alkaline Hydrogen Production with Nitrogen-Doped Carbon Nanobowl-Supported Ultrafine Rh Nanoparticles of 1.4 nm.

The development of highly effective and low-cost electrocatalysts for energy-saving hydrogen production via water splitting is still a great challenge. Herein, porous nitrogen-doped carbon nanobowls (N-CBs) have been designed and used for the controlled growth of ultrafine rhodium (Rh) nanoparticles. With the aid of interfacial bonding of Rh and N, ultrafine Rh nanoparticles with an average size of 1.4 nm have been successfully immobilized on the N-CBs. This Rh/N-CB electrocatalyst shows superior activity and high stability for the hydrogen evolution reaction (HER) and the hydrazine oxidation reaction (HzOR). More importantly, the Rh/N-CBs exhibit high activity for hydrogen production from water electrolysis, marking with a cell voltage of 0.2 V to achieve a current density of 20 mA cm-2 when they serve as cathodic electrocatalysts for the HER and anodic electrocatalysts for the HzOR in 1 M KOH with 0.5 M hydrazine. The density functional theory calculations demonstrate that a near-zero hydrogen adsorption free energy produced by the chemical bonding of Rh with the pyrrole-N doped in N-CBs is responsible for the excellent HER activity of Rh/N-CBs electrocatalysts.

Emission Control In Diesel Engine using Magnesium as a Catalyst

Most cities in the world are subjected to rapid urbanization and a majority of the country’s population is estimated to move towards the cities within a span of the two decades. Majority of Population in all over country expects to live in a city, Such that most cities face rapid Urbanization. The fast growth in urban cities has stemmed in an incredible growth in the quantity of motor vehicles. In some major cities, the motor vehicles are doubled in the last decade. The numbers of vehicles used in cities have almost tripled its usage in a number of Automobiles by few decades. The majority of environmental pollution is caused by two-wheelers in large number. This results in a massive environmental pollution. A serious prerequisite for most effective precautionary measures has to be carried out. The emission controlled by dual techniques to control the pollution specifically, pre-pollution and post pollution control. Here the investigation is conceded out by establishing the post pollution control method for the two-wheeler automobiles via magnesium as a catalyst. To accomplish this objective, a pioneering proposal of catalytic converter is offered using magnesium as a catalyst for two-wheeler automobiles. The projected technique is precise operational in the deterrence of conservational pollution contributed from two-wheeler automobiles. It encompasses the consumption of magnesium which is economical than the, palladium, platinum and rhodium nano-particles used in automobiles.

Synthesis of 3D-Ordered Macro/Microporous Yolk-Shelled Nanoreactor with Spatially Separated Functionalities for Cascade Reaction.

Constructing three-dimensional (3D) hierarchical materials with spatial compartmentalization of multiple catalytic functionalities effectively facilitates the chemical processes' intensification, especially for bulky-molecule-involved cascade reaction. Herein, a facile and novel core-shell colloidal crystal templating strategy was developed to synthesize highly ordered arrays of integrated yolk-shelled nanoreactor consisting of monolithically interconnected ZIF-8 shell and sulfonated polystyrene yolks decorated with rhodium nanoparticles. The obtained nanoreactor achieves efficient catalytic one-pot cascade Knoevenagel condensation-hydrogenation reactions for larger molecules, by taking advantage of the superior mass diffusion properties of the hierarchical macro/microporous metal-organic framework (MOF) skeleton, robust monolith nature, and spatially separated functionalities. This work offers an important strategy for preparing MOF-based composites with a hierarchical framework, accelerating various applications of MOFs, such as electrochemical applications, photothermal conversion, and heterogeneous catalysis.