Rhodium Nanoparticles Research Articles

Enhanced performance of novel green synthesized CuS nanostructures decorated with Rh and Pd nanoparticles for energy generation and gas sensing applications

This article investigates the utilization of copper sulfide (CuS) based nanomaterials functionalized with rhodium (Rh) and palladium (Pd) nanoparticles for gas sensing and energy generation applications. CuS nanoparticles, known for their unique properties, were combined with Rh and Pd nanoparticles to enhance hydrogen (H2) gas sensing capabilities. Gas sensing experiments revealed that CuS/Rh/Pd nanocomposites exhibited the highest sensing response of 58.33% to H2, indicating the significant improvement in gas sensing properties due to the combined presence of Rh and Pd nanoparticles in CuS matrices. Moreover, temperature-dependent responses provided insights into optimal operating conditions for effective gas sensing with CuS-based nanocomposites. Comprehensive characterization studies including XPS, Raman, and morphology analysis confirmed the successful synthesis of CuS/Rh/Pd nanomaterials with high purity and desirable structural properties. Dye-sensitized solar cell (DSSC) performance studies demonstrated that CuS/Rh/Pd nanocomposites enhanced the efficiency by minimizing light over-absorption and improving photoanode stability. Overall, this study highlighted the potential of metal nanoparticle-decorated CuS nanocomposites for advanced gas sensing and energy generation applications, paving the way for the development of highly sensitive and efficient gas sensors and solar energy conversion technologies.

Rh nanoparticles confined in triphenylphosphine oxide-functionalized core-crosslinked micelles with a polyanionic shell: Synthesis, characterization, and application in aqueous biphasic hydrogenation

Core-crosslinked micelles (CCMs) with a hydrophilic polyanionic shell made of poly(sodium styrene sulfonate) chains, P(SS−Na+), a triphenylphosphine oxide-functionalized polystyrene core (TPPO@PSt) and crosslinked at the inner end of the polystyrene chains by diethylene glycol dimethacrylate (DEGDMA) were synthesized by reversible addition-fragmentation chain-transfer (RAFT) polymerization as a stable TPPO@CCM-A latex. One-pot synthesis of rhodium nanoparticles (RhNPs) by the reduction of [Rh(COD)(μ-Cl)]2 in the aqueous TPPO@CCM-A latex yielded a stable RhNP-TPPO@CCM-A latex without the need of additional stabilizer or base. This Rh-loaded latex was applied to the catalytic biphasic hydrogenation of styrene under mild conditions with complete selectivity towards ethylbenzene and corrected turnover frequencies (cTOFs) ranging from 3250 to 10,010 h−1 based on the surface atoms of the RhNPs. Importantly, the catalytic phase proved recyclable after product extraction, owing to the efficient retention of the RhNPs by the core TPPO ligands.

Chiral Ligand-Decorated Rhodium Nanoparticles Incorporated in Covalent Organic Framework for Asymmetric Catalysis.

While metal nanoparticles (NPs) have demonstrated their great potential in catalysis, introducing chiral microenvironment around metal NPs to achieve efficient conversion and high enantioselectivity remains a long-standing challenge. In this work, tiny Rh NPs, modified by chiral diene ligands (Lx) bearing diverse functional groups, are incorporated into a covalent organic framework (COF) for the asymmetric 1,4-addition reactions between arylboronic acids and nitroalkenes. Though Rh NPs hosted in the COF are inactive, decorating Rh NPs with Lx creates the active Rh-Lx interface and induces high activity. Moreover, chiral microenvironment modulation around Rh NPs by altering the groups on chiral diene ligands greatly optimizes the enantioselectivity (up to 95.6% ee). Mechanistic investigations indicate that the formation of hydrogen-bonding interaction between Lx and nitroalkenes plays critical roles in the resulting enantioselectivity. This work highlights the significance of chiral microenvironment modulation around metal NPs by chiral ligand decoration for heterogeneous asymmetric catalysis.

Chiral Ligand‐Decorated Rhodium Nanoparticles Incorporated in Covalent Organic Framework for Asymmetric Catalysis

While metal nanoparticles (NPs) have demonstrated their great potential in catalysis, introducing chiral microenvironment around metal NPs to achieve efficient conversion and high enantioselectivity remains a long‐standing challenge. In this work, tiny Rh NPs, modified by chiral diene ligands (Lx) bearing diverse functional groups, are incorporated into a covalent organic framework (COF) for the asymmetric 1,4‐addition reactions between arylboronic acids and nitroalkenes. Though Rh NPs hosted in the COF are inactive, decorating Rh NPs with Lx creates the active Rh‐Lx interface and induces high activity. Moreover, chiral microenvironment modulation around Rh NPs by altering the groups on chiral diene ligands greatly optimizes the enantioselectivity (up to 95.6% ee). Mechanistic investigations indicate that the formation of hydrogen‐bonding interaction between Lx and nitroalkenes plays critical roles in the resulting enantioselectivity. This work highlights the significance of chiral microenvironment modulation around metal NPs by chiral ligand decoration for heterogeneous asymmetric catalysis.

Enhanced hydrogen evolution catalysis on Rh nanoparticles with low loading on graphene nanoplatelets

Hydrogen evolution reaction (HER) was studied on rhodium nanoparticles electrochemically deposited under the same conditions on glassy carbon (Rh/GC) and on graphene nanoplatelets (Rh/GNPs) supports in 0.5 M H2SO4 solution. SEM revealed that the size of Rh nanoparticles ranged from 50 to 350 nm for Rh/GC and 20 to 70 nm for Rh/GNPs. XPS confirmed the presence of Rh in a low amount of 0.9 at% (6.8 wt%) in Rh/GC and 1.2 at% (8.6 wt%) in Rh/GNPs. The potentials for HER at 10 mA/cm2 are −0.076 V, −0.088, and −0.094 V, and the Tafel slopes are 42, 40, and 42 mV dec−1 for Rh/GNPs, Rh/GC, and Rh(poly), respectively. Moreover, the Rh/GNPs electrode exhibits a higher Rh turnover frequency (TOF) of 3.7 H2 sites−1 s−1 than Rh/GC whose TOF value is 2.9 H2 sites−1 s−1. An exceptionally high HER activity and stability of the Rh/GNPs indicates the strong influence of the GNPs support.

Loading Rh nanoparticles onto Bi2MoO6 hollow architectures: Unveiling heterojunction-driven photocatalytic enhancement towards organic dye degradation

A novel photocatalyst composed of bismuth molybdate (Bi2MoO6, BMO) coupled with rhodium (Rh) nanoparticles was synthesized and evaluated for its efficiency in degrading dye contaminant under visible light irradiation. The BMO/Rh composite demonstrated a significant enhancement in photocatalytic performance, achieving a 40 % higher degradation rate of Rhodamine B (RhB) compared to bare BMO. Enhanced charge separation and reduced electron-hole recombination were primarily attributed to the synergistic effects introduced by the Rh nanoparticles. Extensive characterization techniques provided insights into the structural and mechanistic aspects of the photocatalyst. Stability tests confirmed that BMO/Rh maintained over 95 % of its initial activity after five consecutive reaction cycles, highlighting its durability. Scavenger experiments identified superoxide radicals (•O2-) and hydroxyl radicals (•OH) as the primary active species, contributing to the high efficiency of dye degradation. This study underscores the potential of BMO/Rh hybrids as sustainable and effective photocatalysts for environmental remediation.

Nano Technolgy Application to Enhance the Emission Control by Using Activated Carbons Modified by Magnesium Oxide

One of the fundamental processes for planet safety is the catalytic conversion of carbon monoxide (CO). CO has even been named one of the unseen toxins of this century. Inhaling CO can lead to hypoxic damage, neurological break, and even death. CO poisoning decays greenery life and accumulations in global warming and ozone layer depletion. CO is created in the atmosphere by the partial oxidation of carbon-containing mixtures. The primary origin of CO emissions is vehicles. Therefore, oxidizing contaminated CO to nonpoisonous CO2 under ambient conditions is essential for life protection in multiple applications. Additionally, low-temperature CO oxidation is crucial in reducing emissions at the cold start of an internal explosion in the engine. For controlling pollution, the available methods are pre-pollution control and post-pollution. This project depends on the post-pollution control method in Peugeot ROA automobiles using Activated Carbons Modified by Magnesium Oxide as a catalyst. An innovative catalytic converter design activated carbons modified by magnesium oxide nanoparticles as a catalyst to control pollution with different NPs lodgings and carbon structures. This proposed method aims for the reduction environmental pollution contributed by automobiles. It involves using more affordable materials than the existing rhodium nanoparticles, platinum, and palladium technique. The dispersion states of the grafted nanoparticles were examined with scanning electron microscopy (SEM) and X-ray diffraction analysis (XRD), confirming the correlation between high grafted ratio states and improved properties. The nanocomposites' desired properties were significantly enhanced when the graft density was high.

Ratio design of bimetallic Pd‐Rh nanoparticles on MoS2 nanosheets: Excellent electrocatalysts for hydrogen evolution reaction

The decrease in noble metal content presents an efficient approach to attain commercial, effective, and durable electrocatalysts for the hydrogen evolution reaction (HER) at a low fabrication cost. Nonetheless, achieving a proper balance between bimetallic loading ratios and HER performance remains challenging. In this study, a simple and environmentally friendly sonochemical method is employed to successfully synthesize bimetallic palladium–rhodium nanoparticles (Pd‐Rh) with varying ratios, confined within molybdenum disulfide (MoS2) nanosheets. Bimetallic Pd‐Rh/MoS2 composite with different ratios of Pd:Rh is synthesized by adjusting the feed ratio of Pd and Rh precursors (1:4, 1:1, and 4:1). The HER electrocatalytic activity of the bimetallic Pd1‐Rh1/MoS2 composite exhibits the lowest overpotential and a superior Tafel slope, closely rivaling the electrocatalytic activity of the commercial 20 wt% Pt/C. Furthermore, the bimetallic Pd1‐Rh1/MoS2 composite exhibits remarkable stability and durability, with almost negligible performance decay after 2000 cycles. These outstanding HER electrocatalytic properties of the bimetallic composite result from a higher number of active sites, a significantly larger electrochemically active surface area, reduced charge‐transfer resistance, and a larger double‐layer capacitance. These factors collectively facilitate faster adsorption and desorption of hydron on the surface of electrocatalyst.

Comparative catalytic performance of PGM-nanoparticle-doped alumina Xerogels and aerogels for potential application in automotive pollution mitigation

The structural (low density, high porosity), thermal (low thermal conductivity, high temperature stability), and chemical (high degree of tailorability) properties of aerogels make them attractive in a range of applications, including catalysis. The automotive industry relies on three-way-catalysts (TWCs) for automotive pollution mitigation, and TWCs in turn depend heavily on the use of platinum group metals (PGMs). Reduction of the use of PGMs in TWCs would be advantageous. To investigate the effect of aerogel structure and processing on three-way catalytic performance we prepared alumina wet gels doped with ca. 15 nm rhodium and palladium nanoparticles and dried them (1) supercritically to form aerogels and (2) under ambient conditions to form xerogels. Nanoparticle concentration was adjusted to ensure that both forms of the catalyst (aerogel and xerogel) had the same volumetric concentration of PGM after calcination to 800°C. Powder x-ray diffraction and transmission electron microscopy (TEM) confirmed the presence of PGMs. TEM images showed PGM particle agglomeration on the order of 40 to 200 nm in both the aerogel and xerogel materials. Gas adsorption analysis indicated that the aerogels have a surface area of 460 m2/g with most pores in the 2- to 100-nm range, whereas the xerogel surface area was 170 m2/g with a narrow pore distribution around 10 nm. Catalytic performance tests under a range of simulated automotive operating conditions show that, in all cases, the aerogels outperformed the xerogels. The aerogel light-off temperatures (the temperature at which a 50 % conversion is achieved) were 45 to 120 °C lower for the conversion of HCs, 25 to 55 °C lower for the conversion of CO and 40 to 145 °C lower for the conversion of NO. This study provides direct evidence that aerogel processing of catalysts provides catalytic performance benefits separate from the underlying chemistry of the catalysts.

One‐Pot Synthesis of Rh Nanoparticles in Polycationic‐Shell, Triphenylphosphine Oxide‐Functionalized Core‐Crosslinked Micelles for Aqueous Biphasic Hydrogenation

AbstractCationic‐shell core‐crosslinked micelles (CCM−C) with rhodium nanoparticles (RhNPs) anchored to core‐linked triphenylphosphine oxide (TPPO) ligands were synthesized by a facile one‐pot approach by the reduction of [Rh(COD)(μ‐Cl)]2/toluene in the presence of an aqueous TPPO@CCM−C latex. The resulting RhNP‐TPPO@CCM−C latex showed to be performant for the aqueous biphasic hydrogenation of styrene with an average corrected turnover frequency (cTOF) up to 23600 h−1 based on the RhNP surface atoms. The catalyst system also proved reusable in multiple catalytic runs without any visible RhNP loss during the recycling process as well as applicable to the hydrogenation of other selected alkenes, alkynes and carbonyl substrates (average cTOF of 1000–3200 h−1), thus demonstrating a high versatility.

Callistemon citrinus: A plant‐mediated synthesis of sustainable Rhodium nanoparticles and their antimicrobial activity

AbstractThis work investigates the potential of using Callistemon citrinu flower extract, commonly known as bottlebrush, in the environmentally friendly synthesis of Rhodium nanoparticles (Rh NPs). Callistemon citrinu flower extract contains a high concentration of flavonoids and other phytochemicals. Hence, the extract was used to provide the essential components for an environmentally, sustainable synthesis method of Rh NPs. Different characterization analyses were used to evaluate the different properties of the synthesized particles. UV spectroscopy analysis demonstrated a continuous UV absorption spectrum attributed to the formation of Rh NPs. The XRD data and SAED analysis showed an amorphous nature of the synthesized Rh NPs. The HRTEM imaging provided morphological information about the Rh NPs tested sample, where the efficiency of Callistemon citrinu flower extract as a capping agent was reported. Furthermore, Raman spectra displayed the characteristic vibrational bands of the synthesized Rh NPs. The antimicrobial activity of the synthesized samples was tested against several dental pathogens, that play a role in dental caries, Staphylococcus aureus (SA), Bacillus subtilis (BS), Candida albicans (CA), Escherichia coli (Eco), and Staphylococcus epidermidis (S. Epi). In comparison with the control, Chlorhexidine (CHX), Rh NPs showed a greater impact on C. albicans (20 ≤ Zone of inhibition (ZOI) (mm) ≤ 26). The statistical analysis demonstrated that Rh NPs had a greater mean ZOI than the Callistemon citrinu flower extract. These results reveal the considerable potential and biological capacity Rh NPs have as an antifungal agent for dental applications.

Nanocomposite materials based on amorphous SiC-containing DLC structures modified with rhodium nanoparticles

From the 1980s to the present, interest in carbon has remained very high. The variety of polytypic forms of carbon is expected to have a large number of possible applications. The creation of electronic and optical devices based on them is a promising direction. One of the most interesting carbon materials could be amorphous diamond-like carbon (DLC) films. This work considers nanocomposite materials based on DLC with nanostructures of SiC components. Thin composite DLC:Si films modified with Rhodium nanoparticles (Rh NPs) were synthesized by magnetron sputtering. The structure of the films has been studied by transmission electron microscopy, Raman and X-ray photoelectron spectroscopy (XPS). It is shown that a diamond-like carbon matrix with inclusions of SiC nanostructures and Rh nanocrystals is formed. Significant influence of Rh NPs on the structures of the carbon matrix and SiC during the formation of the DLC: Si matrix is revealed. In addition, X-ray photoelectron spectroscopy shows a considerable effect of Rh NPs on the edge of the valence zone and the density of localized states. The significant effect of rhodium nanoparticles on the electronic component of the valence band of DLC:Si films can be used in the development of new optoelectronic devices.

Fabrication of NIPMAM based polymer microgel network assisted rhodium nanoparticles for reductive degradation of toxic azo dyes

The aim of this study was to prepare poly-N-isopropylmethacrylamide-co-acrylic acid-acrylamide [p-(NIPMAM-co-AA-AAm)] via precipitation polymerization in an aqueous medium. Rhodium nanoparticles were formed in the microgel network by an in-situ reduction technique with the addition of sodium borohydride as a reducing agent. Pure p-(NIPMAM-co-AA-AAm) and hybrid microgels [Rh-(p-NIPMAM-co-AA-AAm)] microgels were examined by using UV–Visible, FTIR (Fourier Transform Infrared), SEM (Scanning Electron Microscopy), TEM (Transmission Electron Microscopy), DLS (Dynamic Light Scattering) and XRD (X-Ray Diffraction) techniques. The catalytic activities of the hybrid microgel [Rh-(p-NIPMAM-co-AA-AAm)] for the degradation of azo dyes such as alizarin yellow (AY), congo red (CR), and methyl orange (MO) were compared and the mechanism of the catalytic action by this system was examined. Various parameters including the catalyst amount and dye concentration influenced the catalytic decomposition of azo dyes. In order to maximize the reaction conditions for the dye's quick and efficient decomposition, the reaction process was monitored by spectroscopic analysis. The rate constants for reductive degradation of azo dyes were measured under various conditions. When kapp values were compared for dyes, it was found that [Rh-(p-NIPMAM-co-AA-AAm)] hybrid microgels showed superior activity for the degradation of MO dyes compared to the reductive degradation of CR and AY.

Utilization of Magonia pubescens extracts in the synthesis of rhodium NPs on Fe3O4@MgO support: A novel catalyst for 4-nitrophenol hydrogenation

This study reports the development of three distinct nanoparticulate catalysts, each comprising a biosynthesized Fe3O4 nanoparticle magnetic core with an average diameter of 17 nm, showcasing superparamagnetic behavior. This magnetic core was further encased in a spherical magnesium oxide (MgO) layer through a bio-inspired strategy, leading to the Fe3O4@MgO support structure. Rhodium (Rh) nanoparticles, with diameters between 1.0 and 1.5 nm, were then fabricated to act as the main catalytic entities. These were subsequently affixed to the Fe3O4@MgO support, yielding Fe3O4@MgO-Rh, using three distinct methodologies. Remarkably, the bio-inspired processes employed for the creation of Fe3O4@MgO-Rh harnessed the infusion and extract from Magonia pubescens A St. Hil leaves, colloquially termed “Timbó”. These natural extracts played dual roles as reducing and stabilizing agents during the catalyst generation, leading to three variants: CI, CW, and CS. Comprehensive characterization of these catalysts was achieved using XPS, TEM, EDS, and VSM techniques. The ensuing evaluation involved the hydrogenation of 4-nitrophenol, which served to assess the efficiency and resilience of the bio-inspired catalysts vis-à-vis conventionally-produced counterparts. Notably, under benign conditions of a molecular H2 atmosphere (an ecologically sound hydrogen atom source) and moderate temperatures (60 °C), conversion rates exceeding 97 % were consistently observed for the substrate within a time frame of 0 to 15 min. For a more granular comparison of efficiency among the rhodium-centric catalysts, Turnover Frequency (TOF) and Total Turnover Number (TTON) computations were undertaken. Herein, the CI catalyst, originating from infusion, displayed a TTON value of 1263.24, underscoring its preeminence in 4-NF hydrogenation reactions. This was closely trailed by the CS catalyst, which boasted a TTON of 873.63, synthesized with a commercial surfactant.

Rhodium and Rhodium-Alloy Films and Nanoparticles: Part I

Noble metals are key to various research fields and noble metal nanomaterials are directly relevant to optics, catalysis, medicine, sensing and many other applications. Rhodium-based nanomaterials have been less studied than metals such as gold, silver or platinum. There have been many improvements in characterisation tools over the years and knowledge about rhodium chemistry and nanomaterials is growing rapidly. Rhodium nanoparticles are widely used as catalysts for automotive emissions control and for hydrogen and oxygen precipitation reactions in electrolytic cells. Novel applications in electronics, anticancer drugs and aerospace are being revisited. In Part I of this two-part review, we cover different strategies for the synthesis of rhodium films and nanoparticles.

Rhodium and Rhodium-Alloy Films and Nanoparticles: Part II

Part I of this review covered the synthesis methods for synthesis of rhodium films and nanoparticles (). In Part II, we review the literature on the current and potential applications of rhodium and rhodium alloy films and nanoparticles in catalysis, components for the glass, chemical and electronic industries, thermal sensors and anticancer drugs.

Advancing rhodium nanoparticle-based photodynamic cancer therapy: quantitative proteomics and in vivo assessment reveal mechanisms targeting tumor metabolism, progression and drug resistance.

Rhodium nanoparticles have been recently discovered as good photosensitizers with great potential in cancer photodynamic therapy by effectively inducing cytotoxicity in cancer cells under near-infrared laser. This study evaluates the molecular mechanisms underlying such antitumoral effect through quantitative proteomics. The results revealed that rhodium nanoparticle-based photodynamic therapy disrupts tumor metabolism by downregulating key proteins involved in ATP synthesis and mitochondrial function, leading to compromised energy production. The treatment also induces oxidative stress and apoptosis while targeting the invasion capacity of cancer cells. Additionally, key proteins involved in drug resistance are also affected, demonstrating the efficacy of the treatment in a multi-drug resistant cell line. In vivo evaluation using a chicken embryo model also confirmed the effectiveness of the proposed therapy in reducing tumor growth without affecting embryo viability.

Porous aluminum decorated with rhodium nanoparticles: preparation and use as a platform for UV SERS

Non-porous aluminium decorated with rhodium nanoparticles show potential as plasmonic substrates for UV SERS. Adenine (absorption maxima ∼250 nm) makes for an ideal resonant analyte for probing using a 266 nm laser.

Effect of adenosine monophosphate on visible-light driven nicotinamide mononucleotide reduction in a system of water-soluble zinc porphyrin and colloidal rhodium nanoparticles

Effect of adenosine monophosphate on visible-light driven nicotinamide mononucleotide reduction in a system of water-soluble zinc porphyrin and colloidal rhodium nanoparticles dispersed with polyvinylpyrrolidone was clarified.

Confinement of Rh nanoparticles in triphenylphosphine oxide-functionalized core-crosslinked micelles for aqueous biphasic hydrogenation catalysis

The introduction of phosphine oxide as anchoring groups in the hydrophobic core of amphiphilic star-block copolymers leads to greatly improved confinement of rhodium nanoparticles (RhNPs) inside the nanoreactors with a benefit in aqueous biphasic catalysis. The copolymers are specially designed core-crosslinked micelles (CCMs) forming a stable latex by reversible addition-fragmentation chain-transfer (RAFT) polymerization. They possess a hydrophilic shell made of polycationic 4-vinyl-N-methylpyridinium iodide P(4VPMe+I−) chains, a triphenylphosphine oxide (TPPO)-functionalized polystyrene core and are crosslinked at the inner end of the polystyrene chains by diethylene glycol dimethacrylate (DEGDMA) (TPPO@CCM-C). Ex-situ synthesized RhNPs readily cross the hydrophilic shell and remain anchored within the CCM nanoreactor cores. The RhNP-loaded TPPO@CCM-C latex was applied as catalyst in the hydrogenation of styrene under mild conditions with complete selectivity towards ethylbenzene and average turnover frequency (TOF) up to 12000 h−1, corresponding to a corrected TOF (cTOF) up to 16800 h−1 based on only surface atoms of the RhNPs. Moreover, the catalytic phase proved recyclable after product extraction with diethyl ether, demonstrating efficient retention of the RhNPs by the core TPPO ligands. Although the activity decreased after the first catalytic run, it converged to a stable average TOF of ca. ∼1025 h−1 (cTOF of ca. ∼1440 h−1), which was similar to that of an extensively pre-washed RhNP-TPPO@CCM-C latex. This phenomenon is attributed to a promoter effect of adsorbed ligands, which were used as stabilizer for the RhNPs synthesis and were gradually removed during the work-up washings between recycles.