Rh Nanoparticles Research Articles

Upcycling of Polyamide Wastes to Tertiary Amines Using Mo Single Atoms and Rh Nanoparticles.

The pursuit of sustainable practices through the chemical recycling of polyamide wastes holds significant potential, particularly in enabling the recovery of a range of nitrogen-containing compounds. Herein, we report a novel strategy to upcycle polyamide wastes to tertiary amines with assistance of H2 in acetic acid under mild conditions (e.g., 180 ºC), which is achieved over anatase TiO2 supported Mo single atoms and Rh nanoparticles. In this protocol, the polyamide is first converted into diacetamide intermediates via acidolysis, which are subsequent hydrogenated into corresponding carboxylic acid monomers and tertiary amines in 100% selectivity. It is verified that Mo single atom and Rh nanoparticles work together to activate both amide bonds of the diacetamide intermediate, and synergistically catalyze its hydrodeoxygenation to form tertiary amine, but this catalyst is ineffective for hydrogenation of carboxylic acid. This work presents an effective way to reconstruct various polyamide wastes into tertiary amines and carboxylic acids, which may have promising application potential.

Urea-induced low crystallization of Rh nanoparticles for efficient H2 production

Developing highly efficient catalysts for the hydrogen evolution reaction (HER) is crucial for advancing renewable hydrogen energy technologies. Heterophase nanomaterials have shown great promise in catalysis, owing to the synergistic effect among various phases and the abundance of active sites located at the phase boundaries or interfaces. However, achieving precise control over these phase structures during synthesis remains a significant challenge. In this work, we explored a one-pot synthesis method for amorphous/crystalline heterophase Rh nanoparticles, with crystallinity tunable by adjusting the quantity of urea and reaction duration. Due to the increased electrochemical active sites, enhanced electron transport, the resulting amorphous/crystalline heterophase Rh exhibits superior HER activities in both acidic (with an overpotential of 27 mV) and alkaline media (with an overpotential of 21 mV), surpassing that of commercial Pt/C and crystalline Rh. Theoretical calculations indicate that the amorphous/crystalline structure reduces the kinetic barrier for water splitting and optimizes adsorption free energy of hydrogen (ΔGH∗), thereby enabling the catalyst to exhibit significantly enhanced HER performance. This exploration offers a valuable reference for designing amorphous/crystalline heterophase structures and demonstrates the great potential of phase engineering strategy in the development of electrocatalysts.

Rh Nanoparticles Encaged in Hollow Porous Silica Nanospheres as Catalysts for Toluene Hydrogenation under Mild Reaction Conditions

Rh Nanoparticles Encaged in Hollow Porous Silica Nanospheres as Catalysts for Toluene Hydrogenation under Mild Reaction Conditions

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.

Engineering of the ferrite-based support for enhanced performance of supported Pt, Pd, Ru, and Rh catalysts in hydrogen generation from NaBH4 hydrolysis

A series of M/NiCo-Ferrite (M: Pt, Pd, Ru, and Rh) nanoparticles were successfully synthesized, through a facile sol–gel auto-combustion followed by impregnation-reduction approach, as a catalyst for hydrogen generation from hydrolysis of NaBH4. All synthesized samples were characterized by XRD, N2 adsorption–desorption method, ICP-OES, FE-SEM, and EDX analysis. Compared to the other samples, it was observed that the Rh/NiCo-Ferrite sample exhibited higher particle distribution and surface area. To evaluate the hydrogen generation rate, the hydrolysis was carried out at a temperature of 35 °C, with an aqueous solution containing 5 wt.% NaBH4 and 3 wt.% NaOH. The experimental findings indicate that the Rh/NiCo-Ferrite sample exhibited a superior rate of hydrogen generation, with an average value of 11,667 mL/min.gcat, compared to the other samples studied. Enhanced catalytic properties may be responsible for its high activity. In addition, the activation energy of hydrolysis of sodium borohydride over the Rh/NiCo-Ferrite sample was 54.5 kJ/mol which is lower than the activation energy of many Ferrite-based catalysts. Moreover, the re-usability test of the Rh/NiCo-Ferrite sample denoted a decline in the catalytic activity after 4 recycling experiments due to the alterations in morphology and the reduction in the quantity of active phase.

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.

Rh, Co, and N-doped titanium mesh-based carbon nanosheet arrays for enhanced nitrite reduction reaction and ammonia generation

The electrocatalytic transformation of nitrite pollutants into valuable ammonia is crucial for the nitrogen cycle. However, the complex multi-reaction process necessitates the development of highly efficient and selective electrocatalysts. This study focuses on the creation of Rh-doped Co@NC anchored on a titanium mesh as an electrocatalyst to enhance the electrocatalytic nitrite reduction reaction (eNO2RR) for NH3 synthesis. By doping a trace amount of Rh within zeolitic imidazolate framework-67 nanosheets and subsequently pyrolyzing the material, uniformly distributed Rh and Co nanoparticles are anchored onto N-functionalized porous carbon nanosheet arrays. Consequently, the three-dimensional electrode enhances mass and electron transfer while providing abundant surface-exposed active sites for NH3 generation through eNO2RR. The Rh0.6 wt%–Co@NC/TM electrocatalyst, with a minimal Rh loading of 0.6 wt%, exhibits the highest Faradaic efficiency of 98.8 ± 0.7 % at −0.3 V, along with an NH3 yield of 1777.1 ± 7.0 μmol h−1 cm−2 at −0.7 V. Additionally, the electrocatalyst demonstrates exceptional durability over 20 consecutive cycles and remarkable environmental adaptability. Extensive experimental studies reveal that the superior performance of Rh0.6 wt%–Co@NC/TM arises from the synergistic catalysis between Co and Rh, which enhances NO2– adsorption and the production of active hydrogen for eNO2RR to NH3 synthesis. This research highlights that Rh incorporation facilitates the kinetics of eNO2RR and offers valuable insights for the development of efficient electrocatalysts towards NH3 synthesis.

One step synthesis of Rh embedded hollow spherical WO₃ composite for enhanced acetone sensing: A promising approach for non-invasive diabetes monitoring

This study investigated the enhancement of WO₃/Rh composite gas sensors for improved acetone detection. WO₃/Rh composite samples (WO₃/Rh-1, WO₃/Rh-2, WO₃/Rh-3) were synthesized via spray pyrolysis, and materials were studied using XRD, SEM, and TEM. These analyses confirmed successful introduction of Rh nanoparticles and indicated favorable alterations in structure and morphology. Gas sensing tests with varying acetone concentrations (0.1–4 PPM, balanced with simulated exhaled gas with RH% of ∼30 %) demonstrated that Rh introduction significantly improved sensitivity and selectivity. Notably, WO₃/Rh-3 exhibited the highest performance, with enhanced response times and selectivity critical for diabetes monitoring. These results highlight the potential of WO₃/Rh sensors in medical diagnostics, offering a promising approach for the early detection of diabetes through breath analysis.

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.

Alloying and phase separation explored in Au–Rh nanoparticles

Alloying and phase separation explored in Au–Rh nanoparticles

Honeycomb-structured S and N-codoped highly graphitized carbon as a catalyst support for Rh nanoparticles: A new benchmark electrocatalyst for hydrogen evolution reaction

State-of-the-art electrocatalysts are based on catalytically active metal deposited on conductive porous carbon. Herein, we report a new strategy of engineering of a honeycomb-structured S and N dual-doped graphene-like carbon (SNG) as a supporting material for Rh catalysts by a simple low-temperature (850 °C) pyrolysis of S-doped carbon nitride (S-CN) in the presence of Mg. Interestingly, here Mg plays a marvelous dual role not only as a reducing agent for graphitizing the S-CN but also as a precursor for new Mg3N2 and MgS products, which play as pore-generating templates for honeycomb-like structures. This features highly robust graphitized carbon with excellent electrical conductivity, proper S and N content, and porosity, making it highly desirable as catalyst support. Supporting Rh (5.2 wt.%) on SNG outperforms state-of-the-art commercial Pt/C electrodes for hydrogen evolution reaction (HER) under alkaline settings (1.0 M KOH) with an extremely lower overpotential of 13 mV at 10 mA cm−2, a lower Tafel value, and a higher turnover frequency. In addition, Rh/SNG as the cathode for industrial water electrolysis in 6.0 M KOH electrolyte at 70 °C shows excellent performance with only 1.76 Vcell to achieve 500 mA cm−2 and maintains long-term durability with negligible decay. The distinctive properties of SNG, including S and N dual doping, high graphiticity, superior electrical conductivity, and honeycomb-like hierarchical meso‑ and macropore structure, are credited with this remarkable HER performance. The S and N dopants in the SNG framework optimize the electronic structure of the Rh by synergistic interaction between them as illustrated by first-principal density functional theory calculations and electronic structure analysis.

Enzyme-Like Photocatalytic Octahedral Rh/Ag2MoO4 Accelerates Diabetic Wound Healing by Photo-Eradication of Pathogen and Relieving Wound Hypoxia.

The harsh environment of diabetic wounds, including bacterial infection and wound hypoxia, is not conducive to wound healing. Herein, an enzyme-like photocatalytic octahedral Rh/Ag2MoO4 is developed to manage diabetic-infected wounds. The introduction of Rh nanoparticles with catalase-like catalytic activity can enhance the photothermal conversion and photocatalytic performance of Rh/Ag2MoO4 by improving near-infrared absorbance and promoting the separation of electron-hole pairs, respectively. Rh/Ag2MoO4 can effectively eliminate pathogens through a combination of photothermal and photocatalytic antibacterial therapy. After bacteria inactivation, Rh/Ag2MoO4 can catalyze hydrogen peroxide to produce oxygen to alleviate the hypoxic environment of diabetic wounds. The in vivo treatment effect demonstrated the excellent therapeutic performance of Rh/Ag2MoO4 on diabetic infected wounds by removing infectious pathogens and relieving oxygen deficiency, confirming the potential application of Rh/Ag2MoO4 in the treatment of diabetic infected wounds.

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.

Metal-assisted low-temperature cracking of n-hexane over Rh-encapsulated ZSM-5 catalysts

Naphtha cracking is the most common process for producing light olefins such as ethylene, propylene, and butene. This process consumes enormous amounts of energy, so decreasing the energy consumption and operating temperature is an urgent issue. To decrease the reaction temperature for naphtha cracking, we focused on the metal-assisted cracking reaction, in which paraffin is first dehydrogenated into the corresponding olefin on a metal catalyst, and the produced olefin is then decomposed into light olefins. To effectively realize metal-assisted cracking, we considered metal-encapsulated zeolite catalysts to be useful. In metal-encapsulated zeolite catalysts, the dehydrogenation reaction proceeds inside the zeolite particles, and the dehydrogenated intermediates can access the solid-acid sites frequently. In this study, Rh nanoparticle encapsulated ZSM-5 catalysts (Rh@ZSM-5) were employed for the metal-assisted cracking of n-hexane. Rh@ZSM-5 exhibited significantly high activity for n-hexane cracking below 450 °C owing to the metal encapsulation structure and close proximity between the metal and solid-acid sites. Furthermore, the effects of reaction conditions, reaction temperature, amounts of metal and solid-acid sites, and contact time on metal-assisted n-hexane cracking over the Rh@ZSM-5 catalysts were investigated. The highest light-olefin yield of 38.6 carbon mol% was achieved by the conversion of n-hexane over Rh@ZSM-5 using 0.3 wt% Rh loading, an Si/Al ratio of 100, temperature of 450 °C, reaction time of 0.5 h, and W/F of 2 h.

Use of carboxymethyl cellulose as binder for the production of water-soluble catalysts

Bio-based polymers are materials of high interest given the harmful environmental impact that involves the use of non-biodegradable fossil products for industrial applications. These materials are also particularly interesting as bio-based ligands for the preparation of metal nanoparticles (MNPs), employed as catalysts for the synthesis of high value chemicals. In the present study, Ru (0) and Rh(0) Metal Nanoparticles supported on Sodium Carboxymethyl cellulose (MNP(0)s-CMCNa) were prepared by simply mixing RhCl3x3H2O or RuCl3 with an aqueous solution of CMCNa, followed by NaBH4 reduction. The formation of MNP(0)s-CMCNa was confirmed by FT-IR and XRD, and their size estimated to be around 1.5 and 2.2 nm by TEM analysis. MNP(0)s-CMCNa were employed for the hydrogenation of (E)-cinnamic aldehyde, furfural and levulinic acid. Hydrogenation experiments revealed that CMCNa is an excellent ligand for the stabilization of Rh(0) and Ru(0) nanoparticles allowing to obtain high conversions (>90 %) and selectivities (>98 %) with all substrates tested. Easy recovery by liquid/liquid extraction allowed to separate the catalyst from the reaction products, and recycling experiments demonstrated that MNPs-CS were highly efficiency up to three times in best hydrogenation conditions.

Chitosan as a Bio-Based Ligand for the Production of Hydrogenation Catalysts.

Bio-based polymers are attracting increasing interest as alternatives to harmful and environmentally concerning non-biodegradable fossil-based products. In particular, bio-based polymers may be employed as ligands for the preparation of metal nanoparticles (M(0)NPs). In this study, chitosan (CS) was used for the stabilization of Ru(0) and Rh(0) metal nanoparticles (MNPs), prepared by simply mixing RhCl3 × 3H2O or RuCl3 with an aqueous solution of CS, followed by NaBH4 reduction. The formation of M(0)NPs-CS was confirmed by Fourier Transform Infrared Spectroscopy (FT-IR), Differential Scanning Calorimetry (DSC), Thermal Gravimetric Analysis (TGA), Scanning Electron Microscopy (SEM), Energy-Dispersive X-ray Analysis (EDX), Transmission Electron Microscopy (TEM) and X-ray Diffraction (XRD). Their size was estimated to be below 40 nm for Rh(0)-CS and 10nm for Ru(0)-CS by SEM analysis. M(0)NPs-CS were employed for the hydrogenation of (E)-cinnamic aldehyde and levulinic acid. Easy recovery by liquid-liquid extraction made it possible to separate the catalyst from the reaction products. Recycling experiments demonstrated that M(0)NPs-CS were highly efficient up to four times in the best hydrogenation conditions. The data found in this study show that CS is an excellent ligand for the stabilization of Rh(0) and Ru(0) nanoparticles, allowing the production of some of the most efficient, selective and recyclable hydrogenation catalysts known in the literature.

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.

Evaluation of Pt–Rh Nanoparticle–Based Electrodes for the Electrochemical Reduction of Nitrogen to Ammonia

Ammonia (NH3) is one of the most used chemicals. Industrially, ammonia is produced by hydrogenation of N2 through the Haber–Bosch process, a process in which enormous amounts of CO2 are released and requires a huge energy consumption (~ 2% of the total global energy). Therefore, it is of paramount importance to explore more sustainable and environmentally friendly routes to produce NH3. The electrochemical nitrogen reduction reaction (NRR) to ammonia represents a promising alternative that is receiving great attention but still needs to be significantly improved to be economically competitive. In this work, the NRR is studied on Pt–Rh nanoparticle–based electrodes. Carbon-supported Pt–Rh nanoparticles (2–4 nm) with different Pt:Rh atomic compositions were synthesized and subsequently airbrushed onto carbon Toray paper to fabricate electrodes. The electrochemical NRR experiments were performed in a H-cell in 0.1 M Na2SO4 solution. The results obtained show interesting faradaic efficiencies (FE) towards NH3 which range between 5 and 23% and reasonable and reliable NH3 yield values of about 4.5 µg h−1 mgcat−1, depending on the atomic composition of the electrocatalysts and the metal loading. The electrodes also showed good stability and recyclability (constant FE and NH3 yield in five consecutive experiments).Graphical Pt–Rh nanoparticle–based electrodes were employed for the NRR to NH3 in 0.1 M Na2SO4. Interesting FE towards NH3 and reasonable and reliable NH3 yield values were observed depending on atomic composition and metal loading. Good stability and recyclability (constant FE and NH3 yield in five consecutive experiments) were also observed.