Rhodium Atoms Research Articles

Intermediate ytterbium valence in YbRhSn2

Abstract The stannide YbRhSn2 has been synthesized. An arc-melted Rh25Sn48 precursor sample was reacted with ytterbium in a sealed tantalum ampoule in an induction furnace. The structure of YbRhSn2 was refined from single-crystal X-ray diffractometer data: MgCuAl2 type, Cmcm, a = 433.10(3), b = 1076.63(8), c = 739.36(5) pm, wR2 = 0.0676, 444 F 2 values and 16 variables. The rhodium and tin atoms form a three-dimensional [RhSn2] δ− polyanionic network with short Rh–Sn (271–273 pm) and Sn–Sn (301–324 pm) distances. The tin substructure is an orthorhombically distorted lonsdaleite network. YbRhSn2 shows paramagnetic behavior with a reduced magnetic moment of 2.2(1) µB per ytterbium atom, classifying it as an intermediate-valent compound.

Syn and Anti Metal Complexes of 24π Antiaromatic Bis(Dicarbonylrhodium(I))Dithiaamethyrin.

From the reaction of sterically less hindered tetrapropyl[24]dithiaamethyrin(1.0.0.1.0.0) 5, with [Rh(CO)2 Cl]2 , a unique anti form of the bis(dicarbonylrhodium(I)) complex (6-anti), where two rhodium ions are on the opposite faces of the macrocyclic ligand, was isolated for the first time in 12% yield along with the corresponding syn isomer (6-syn, 61% yield). These structures were characterized in detail by single-crystal X-ray structure analysis. Compound 6-syn exhibited a bowl-shaped structure with the two rhodium atoms separated by a distance of ∼4.5 Å. In contrast, 6-anti contained a wave-shaped macrocycle with a distance of ∼5.3 Å between the two rhodium atoms. Furthermore, the 1 H nuclear magnetic resonance spectra and density functional theory calculation results revealed that 6-anti had a stronger paratropic ring current and a more planar structure than 6-syn. The isolation of both 6-anti and 6-syn enabled detailed discussion of the structure-property relationship.

An ab-initio study of electronic and optical properties of RhXO3 (X = Ga, Ag) perovskites

The ab-initio computations were performed to study the electronic and optoelectronic properties of perovskites using WIEN2k code. The has band gap of 2.29 eV, and the behavior of is metallic. The sub-TDOS of the studied materials revealed that rhodium and oxygen atoms have significant contributions in the valence band and conduction band formation of both materials. The silver cation is responsible for the reasonable peaks appearing at the Fermi level of which demonstrated the conducting nature of The dielectric functions, optical conductivity, energy loss function, absorption coefficient, refractive index, extinction coefficient, and reflectivity are computed for these materials to understand the optical behavior of the studied materials. The analysis of optical properties ensure the is a promising material for optoelectronics while has metallic nature.

The effect of precious metals in the NiAl coating on the oxidation resistance of the Inconel 713 superalloy

The rhodium incorporated aluminide coating was produced by the rhodium electroplating (0.5 ?m thick layer) followed by the chemical vapor deposition process on the Inconel 713 superalloy. This coating is composed of the ?-NiAl phase. A part of nickel atoms was replaced by rhodium atoms in the ?-NiAl phase. The plain, rhodium and platinum incorporated aluminide coatings were oxidized at 1100 ?C under the atmospheric pressure. The oxidation kinetics of the rhodium and platinum incorporated aluminide coatings were similar, but different than oxidation kinetic of the plain coating. The ?-Al2O3 was the main product both in rhodium and platinum modified coatings after 360 h of oxidation. Moreover, the ?-Ni3Al phase, besides the ?-NiAl phase, was identified. The presence of 4 at. % rhodium in the coating provided similar oxidation resistance as the presence of 10-20 at. % platinum. Both rhodium and platinum incorporated aluminide coatings produced by the chemical vapor deposition process offer good oxidation protection of the Inconel 713 superalloy.

Highly dispersed rhodium atoms supported on defect-rich Co(OH)2for the chemoselective hydrogenation of nitroarenes

0.54% Rh/Co(OH)2exhibited 100% selectivity for –NO2hydrogenation at >96% conversion for nitroarene hydrogenation. Its excellent catalytic performance is due to the interfacial effect of Rh–Co(OH)2and Rh in the form of single atoms and nanoclusters.

Oxidative carbonylation of methane to acetic acid over micro-mesoporous rhodium-modified zeolites

It was first demonstrated that under liquid-phase conditions, an increase in the mesoporosity of ZSM-5 zeolite boosts a rhodium-containing catalyst activity in the oxidative carbonylation of methane to acetic acid (the acetic acid yield is 570 μmol g cat −1 ). To increase the mesoporosity of zeolite, two approaches were used: ultrasonic treatment and desilication of zeolite. The ultrasonic pretreatment leads to an increase in the acetic acid yield with a decrease in the total yield of oxygenates (methanol/acetic acid molar ratio is 0.2). On the contrary, preliminary desilication contributes to an increase in the total yield of oxygenates, mainly due to methanol (methanol/acetic acid molar ratio is 1.8). The combination of ultrasonic pretreatment and desilication of zeolite improves the total yield of oxygenates with an increase in the acetic acid yield. Such a change in the catalytic properties is attributed both to the acidity of the parent zeolite and the local atomic environment of rhodium. XAS spectroscopy showed that rhodium can be present on the zeolite surface either as nanoclusters giving rise to methanol or as isolated rhodium atoms, which promote the acetic acid formation. • Oxidative conversion of methane to acetic acid with the assistance of СО was studied. • Rhodium-modified microporous and micro-mesoporous zeolite catalysts were used. • Ultrasonic treatment of the zeolite leads to an increase in the yield of acetic acid. • Desilication of the zeolite leads to an increase in the yield of methanol. • The formation of acetic acid is facilitated by the monoatomic distribution of rhodium.

Highly Effective Freshwater and Seawater Electrolysis Enabled by Atomic Rh‐Modulated Co‐CoO Lateral Heterostructures

AbstractAtomic metal‐modulated heterostructures have been evidenced as an exciting solution to develop high‐performance multifunctional electrocatalyst toward water splitting. In this research, a catalyst of continuous cobalt‐cobalt oxide (Co‐CoO) lateral heterostructures implanted with well‐dispersed rhodium (Rh) atoms and shelled over conductive porous 1D copper (Cu) nano‐supports for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in both freshwater and seawater under alkaline condition is proposed. It is found that synergistic effects coming from uniform Rh atoms at doping level and Co‐CoO heterostructures afford rich multi‐integrated active sites and excellent charge transfer, thereby effectively promoting both HER and OER activities. The material requires overpotentials of 107.3 and 137.7 mV for HER and 277.7 and 260 mV for OER to reach an output of 10 mA cm−1 in freshwater and mimic seawater, respectively, surpassing earlier reported catalysts. Compared to a benchmark a Pt/C//RuO2‐based two‐electrode electrolyzer, a device derived from the 1D‐Cu@Co‐CoO/Rh on copper foam delivers comparable cell voltages of 1.62, 1.60, and 1.70 V at 10 mA cm−2 in freshwater, mimic seawater, and natural seawater, respectively, together with robust stability. These results evidence that 1D‐Cu@Co‐CoO/Rh is a promising catalyst for green hydrogen generation via freshwater and seawater electrolysis applications.

Infrared spectroscopic and density functional theoretical study on the binary rhodium–oxygen Rh2O9+ cation

The mass-selected dirhodium oxide Rh2O9+ was prepared from the reaction of laser ablation of rhodium atoms with O2/He mixtures. Infrared spectra of Rh2O9+ are measured by infrared photodissociation spectroscopy in the rhodium-oxygen and OO stretching frequency region observed at 1254, 876 and 1536 cm−1. To assign the experimental spectra, total 43 tautomeric isomers with doublet, quartet, sextet and octet states are optimized and analyzed to compare the experimental with simulated spectra derived from density functional calculations. Further CCSD(T) single point energy confirmed the most stable isomer was the dinuclear sextet Rh2O9+ cation with a pseudo five-numbered ring as well as one Rh-O-Rh core terminally bonded to one superoxide, two terminal Rh-O, and two dioxygen groups. The three observed bands at 876, 1254 and 1536 cm−1 bands are exactly assigned to the terminal Rh-O, superoxide OO and weak dioxygen OO stretching modes compared to calculated vibration frequencies of the sextet Rh2O9+ cation(isolmer 29). Bonding analysis indicate that both rhodium of the Rh2O9+ cation observed display + 5 and + 3 formal oxidation state, respectively.

Rhodium atoms for alkane dehydrogenation

Catalysis Nanoparticles of rhodium dispersed on metal oxides are generally poor catalysts for alkane dehydrogenation because the reactants bind too strongly to the metal. Hannagan et al. performed first-principle calculations indicating that single rhodium atoms in a copper surface should be stable and selective for conversion of propane to propene and hydrogen. Model studies of single rhodium atoms embedded in a copper (111) surface revealed a very high selectivity to propene and high resistance to the formation of surface carbon that would deactivate the catalyst. Science , abg8389, this issue p. [1444][1] [1]: /lookup/doi/10.1126/science.abg8389

First-principles design of a single-atom–alloy propane dehydrogenation catalyst

Rhodium atoms for alkane dehydrogenation Nanoparticles of rhodium dispersed on metal oxides are generally poor catalysts for alkane dehydrogenation because the reactants bind too strongly to the metal. Hannagan et al. performed first-principle calculations indicating that single rhodium atoms in a copper surface should be stable and selective for conversion of propane to propene and hydrogen. Model studies of single rhodium atoms embedded in a copper (111) surface revealed a very high selectivity to propene and high resistance to the formation of surface carbon that would deactivate the catalyst. Science , abg8389, this issue p. 1444

Single Atom Catalysts: Surface Reduction State Determines Stabilization and Incorporation of Rh on α‐Fe2O3(11¯02) (Adv. Mater. Interfaces 8/2021)

Rhodium atoms adsorbed on a model iron oxide surface sinter to nanoparticles already at room temperature. Redispersion into isolated single atoms is induced by oxygen annealing. The resulting atoms are incorporated in the first subsurface layer of the oxide, rather than the surface. More details can be found in article number 2001908 by Gareth S. Parkinson and co-workers.

An Iminophosphonamido-Chlorosilylene as a Strong σ-Donating NHSi Ligand: Synthesis and Coordination Chemistry.

The N-heterocyclic silylene (NHSi) [Ph2 P(t BuN)2 ]SiCl (1), supported by an iminophosphonamide ligand, was obtained from the dehydrochlorination of [Ph2 P(t BuN)2 ]SiHCl2 (2) with LiN(SiMe3 )2 . NHSi 1 contains an extremely high-energy HOMO level and consequently displays unique coordination behavior toward RhI complexes. When 1 was treated with 1/4 of an equivalent of [RhCl(cod)]2 (cod=1,5-cyclooctadiene), the 14-electron Y-shaped bis(chlorosilylene) RhI complex 5 was obtained as dark purple crystals. The reaction of 1 with 1/6 of an equivalent of [RhCl(cod)]2 yielded the cationic tris(silylene)-RhI complex [6]+ ⋅Cl- as red crystals, wherein a two-coordinated silylene ligand engages in a Si=Rh double bond. A structural analysis of 5 and [6]+ ⋅Cl- revealed that the central rhodium atoms adopt trigonal and square-planar coordination geometries, respectively, with considerably shortened Si-Rh bonds [5: 2.1605(5) Å; [6]+ : 2.133(1) Å].

An Iminophosphonamido‐Chlorosilylene as a Strong σ‐Donating NHSi Ligand: Synthesis and Coordination Chemistry

AbstractTheN‐heterocyclic silylene (NHSi) [Ph2P(tBuN)2]SiCl (1), supported by an iminophosphonamide ligand, was obtained from the dehydrochlorination of [Ph2P(tBuN)2]SiHCl2(2) with LiN(SiMe3)2. NHSi1contains an extremely high‐energy HOMO level and consequently displays unique coordination behavior toward RhIcomplexes. When1was treated with 1/4 of an equivalent of [RhCl(cod)]2(cod=1,5‐cyclooctadiene), the 14‐electron Y‐shaped bis(chlorosilylene) RhIcomplex5was obtained as dark purple crystals. The reaction of1with 1/6 of an equivalent of [RhCl(cod)]2yielded the cationic tris(silylene)‐RhIcomplex [6]+⋅Cl−as red crystals, wherein a two‐coordinated silylene ligand engages in a Si=Rh double bond. A structural analysis of5and [6]+⋅Cl−revealed that the central rhodium atoms adopt trigonal and square‐planar coordination geometries, respectively, with considerably shortened Si‐Rh bonds [5: 2.1605(5) Å; [6]+: 2.133(1) Å].

XPS study of Rh/In2O3 system

The effect of surface modification of In2O3 films by rhodium atoms deposited by electron beam sputtering on the XP spectra is considered. The surface coverage with rhodium ranged from 0 to 0.1 ML. It was shown that the main changes in the XP spectra occur in the Rh3d region and are caused by the dimensional effect of rhodium particles. With an increase in the surface coverage with rhodium, Rh particles grow from an atomically dispersed state to relatively large clusters. As the particle size increases, its electronic structure tends to approach the state corresponding to the bulk Rh. Such a process is accompanied by a decrease in BE Rh3d5/2 by 0.3–0.6 eV, which behaviour depends on the surface structure of the used In2O3 films.

Reversible Hydride Migration from C5Me5 to RhI Revealed by a Cooperative Bimetallic Approach.

The use of cyclopentadienyl ligands in organometallic chemistry and catalysis is ubiquitous, mostly due to their robust spectator role. Nonetheless, increasing examples of non‐innocent behaviour are being documented. Here, we provide evidence for reversible intramolecular C−H activation at one methyl terminus of C5Me5 in [(η‐C5Me5)Rh(PMe3)2] to form a new Rh−H bond, a process so far restricted to early transition metals. Experimental evidence was acquired from bimetallic rhodium/gold structures in which the gold center binds either to the rhodium atom or to the activated Cp* ring. Reversibility of the C−H activation event regenerates the RhI and AuI monometallic precursors, whose cooperative reactivity towards polar E−H bonds (E=O, N), including the N−H bonds in ammonia, can be understood in terms of bimetallic frustration.

Reversible Hydride Migration from C5Me5 to RhI Revealed by a Cooperative Bimetallic Approach

AbstractThe use of cyclopentadienyl ligands in organometallic chemistry and catalysis is ubiquitous, mostly due to their robust spectator role. Nonetheless, increasing examples of non‐innocent behaviour are being documented. Here, we provide evidence for reversible intramolecular C−H activation at one methyl terminus of C5Me5 in [(η‐C5Me5)Rh(PMe3)2] to form a new Rh−H bond, a process so far restricted to early transition metals. Experimental evidence was acquired from bimetallic rhodium/gold structures in which the gold center binds either to the rhodium atom or to the activated Cp* ring. Reversibility of the C−H activation event regenerates the RhI and AuI monometallic precursors, whose cooperative reactivity towards polar E−H bonds (E=O, N), including the N−H bonds in ammonia, can be understood in terms of bimetallic frustration.

Density Functional Theoretical Study on the Electronic Structure of Rh2O7 + with Low Oxidation States.

Rh2On+ (n = 2–10) species are prepared by the reaction of the laser-ablated rhodium atoms with oxygen; furthermore, they are characterized by employing time-of-flight mass spectroscopy. To reveal the stable electronic structure, in this study, we performed the density functional theory calculations for the possible isomers of Rh2O7+. A total of 29 geometries were obtained including cyclic Rh2O3, cyclic Rh2O2, and ring-opening structures with doublet, quartet, sextet, and octet states. It is noteworthy that no Rh–Rh bond was observed for all the optimized Rh2O7+ isomers including oxides, peroxides, superoxides, and oxygen groups. The optimized geometries were also confirmed to exhibit minimum structural energies by employing harmonic frequency analysis at the same energy level. Generally, two types of oxygen-bridged geometries were discovered with cyclic and pseudo-linear Rh2O7+, which contained one or more than one O2 groups. It is concluded that the cyclic structure comprises a lower energy than that observed in pseudo-linear structures. In addition, Rh2O7+ tends to be unstable when the coordination groups change from O2 to O2– unit. Finally, the localized orbital bonding analysis indicates that Rh has oxidation states of 1 or 2 in cyclic Rh2O7+ structures; this is true even in the presence of O2–, O2–, and O22– groups.

Stabilization of atomically dispersed rhodium sites on ceria-based supports under reaction conditions probed by in situ infrared spectroscopy

In this work, atomically dispersed rhodium over co-precipitated ceria-based supports were prepared by wet impregnation. The structural and surface properties of materials were investigated by X-ray diffraction, N2 physisorption isotherms, and X-ray photoelectron spectroscopy. The fraction of isolated sites was quantified by infrared spectroscopy using CO as a probe molecule. The formation of a defective surface by incorporation of 15% (mol/mol) of zirconium on ceria structure increased ~5-fold the fraction of isolated sites on catalyst compared to unmodified ceria. The doped-support efficiently trapped rhodium atoms avoiding agglomeration and increasing stability during CO oxidation reaction in a wide range of temperatures (30–200 °C) when compared to single-sites deposited on silica.

Characterization of none and yttrium-modified Ni-based catalysts for dry reforming of methane

Monometallic and bimetallic RhNi catalysts supported on γ-alumina and yttria-modified alumina were developed. The relation between the support kind, the structure and catalytic properties of the catalysts in dry reforming of methane was studied by using different techniques such as: N2 isotherms, UV–vis DRS, XRD, TPD-NH3, TPR-H2, XPS and HRTEM. Variation in the electronic environment of the nickel, rhodium and yttrium atoms as a function of the catalyst pretreatment and support kind was observed. It was shown that the couple pairs of Nio/Nin+ and/or Rho/Rhn+ act as active sites. The difference in the catalytic behaviors of catalysts was connected with the distribution of metal particles. Y-loaded monometallic Ni catalyst showed higher activity and stability than alumina supported Ni due to the proximity of nickel to yttrium oxide species expressed by the increase of metal dispersity. The close contact between Rh and Ni leaded to better catalytic behavior of bimetallic RhNi/Al catalyst due to the better reducibility of nickel oxide species and homogeneous distribution of the particles with average diameter size of ∼ 5 nm.

Distance Synergy of MoS2‐Confined Rhodium Atoms for Highly Efficient Hydrogen Evolution

AbstractPerturbing the electronic structure of the MoS2 basal plane by confining heteroatoms offers the opportunity to trigger in‐plane activity for the hydrogen evolution reaction (HER). The key challenge consists of inducing the optimum HER activity by controlling the type and distribution of confined atoms. A distance synergy of MoS2‐confined single‐atom rhodium is presented, leading to an ultra‐high HER activity at the in‐plane S sites adjacent to the rhodium. By optimizing the distance between the confined Rh atoms, an ultra‐low overpotential of 67 mV is achieved at a current density of 10 mA cm−2 in acidic solution. Experiments and first‐principles calculations demonstrate a unique distance synergy between the confined rhodium atoms in tuning the reactivity of neighboring in‐plane S atoms, which presents a volcanic trend with the inter‐rhodium distance. This study provides a new strategy to tailor the activity of MoS2 surface via modulating the distance between confined single atoms.