Negligible Deactivation Research Articles

Doping Ti into RuO2 to Accelerate Bridged-Oxygen-Assisted Deprotonation for Acidic Oxygen Evolution Reaction.

The development of efficient and durable electrocatalysts for the acidic oxygen evolution reaction (OER) is essential for advancing renewable hydrogen energy technology. However, the slow deprotonation kinetics of oxo-intermediates, involving the four proton-coupled electron steps, hinder the acidic OER progress. Herein, a RuTiOx solid solution electrocatalyst is investigated, which features bridged oxygen (Obri) sites that act as proton acceptors, accelerating the deprotonation of oxo-intermediates. Electrochemical tests, infrared spectroscopy, and density functional theory results reveal that the moderate proton adsorption energy on Obri sites facilitates fast deprotonation kinetics through the adsorbate evolution mechanism. This process effectively prevents the over-oxidation and deactivation of Ru sites caused by the lattice oxygen mechanism. Consequently, RuTiOx shows a low overpotential of 198mV at 10mAcm-2 geo and performance exceeding 1400h at 50mAcm-2 geo with negligible deactivation. These insights into the OER mechanism and the structure-function relationship are crucial for the advancement of catalytic systems.

Insight into the Coordination Environment of Ru Single-Atom for Dry Reforming of Methane.

Dry reforming of methane (DRM), a pivotal process for converting greenhouse gases into syngas is demanding rationally designed catalysts with high stability and ideal catalytic performance for industrial applications due to its stability of reactant molecules and characteristic of carbon deposition. However, the mechanistic understanding of how the coordination environment of the metal in a single-atom catalytic system may influence the catalytic performance remains limited. In this work, high- and low-coordinating Ru-based (RuHC and RuLC) catalysts with distinct Ru-O coordination numbers are prepared using one-pot and two-step methods. The difference in the stability (12.3% and negligible deactivation during 20 h test for RuLC and RuHC catalysts respectively) and selectivity (0.57 and 0.37 of H2/CO ratio) brought by the coordination environment signified the structure-function relationship of single-atom catalysts in DRM. The impact of the structure on the properties is systematically investigated by thorough structural and operando characterization as well as density functional theory (DFT) calculation. The findings contribute to the optimal design of single-atom catalysts for DRM, offering a theoretical basis for industrial catalyst development and the potential to improve the process's environmental impact.

Poly(N‐2‐Aminoethylacrylamide)‐Cu(I) Chelate Grafted from Fe3O4@SiO2 Core‐Shells for the Selective Monoarylation of Anilines via the Ullmann Reaction

AbstractThe present work describes the grafting of a polymer‐metal chelate (PMC) from Fe3O4@SiO2 core‐shells via the Surface Initiated‐Atom Transfer Radical Polymerization (SI‐ATRP). The magnetic core‐shells were silylated by 2‐bromo‐2‐methyl‐N‐(3‐(trimethoxysilyl)propanamide (BTPAm) to give the surface‐anchored ATRP initiator. Acrylamide was polymerized from the Fe3O4@SiO2 surface via the ATRP approach. The grafted magnetic nanoparticles were trans‐amidated with ethylenediamine to give poly(N‐2‐aminoethylacrylamide) grafted magnetic core‐shells, Fe3O4@SiO2‐g‐PAE‐AAm. The grafted chelating polymer ligand (CPL) was treated with an acetonitrile solution of CuI to afford the Fe3O4@SiO2‐g‐PAE‐AAm−Cu(I). The grafted PMC was characterized by FT‐IR, CP/MAS 13C NMR, and thermo‐gravimetric analysis (TGA). The grafted PMC catalyzed the N−C bond formation via the Ullmann‐type N‐arylation reaction of haloarenes and anilines under optimal reaction conditions. Mono N‐arylation product was obtained as the major product with excellent selectivity. The excellent recyclability of the catalyst was shown by negligible deactivation over six runs.

Regulating Strain and Electronic Structure of Indium Tin Oxide Supported IrOx Electrocatalysts for Highly Efficient Oxygen Evolution Reaction in Acid.

The development of proton exchange membrane water electrolysis is a promising technology for hydrogen production, which has always been restricted by the slow kinetics of the oxygen evolution reaction (OER). Although IrOx is one of the benchmark acidic OER electrocatalysts, there are still challenges in designing highly active and stable Ir-based electrocatalysts for commercial application. Herein, a Ru-doped IrOx electrocatalyst with abundant twin boundaries (TB-Ru0.3Ir0.7Ox@ITO) is reported, employing indium tin oxide with high conductivity as the support material. Combing the TB-Ru0.3Ir0.7Ox nanoparticles with ITO support could expose more active sites and accelerate the electron transfer. The TB-Ru0.3Ir0.7Ox@ITO exhibits a low overpotential of 203 mV to achieve 10 mA cm-2 and a high mass activity of 854.45 A g-1noblemetal at 1.53 V vs RHE toward acidic OER, which exceeds most reported Ir-based OER catalysts. Moreover, improved long-term stability could be obtained, maintaining the reaction for over 110 h at 10 mA cm-2 with negligible deactivation. DFT calculations further reveal the activity enhancement mechanism, demonstrating the synergistic effects of Ru doping and strains on the optimization of the d-band center (εd) position and the adsorption free energy of oxygen intermediates. This work provides ideas to realize the trade-off between high catalytic activity and good stability for acidic OER electrocatalysts.

Self-Assembly Intermetallic PtCu3 Core with High-Index Faceted Pt Shell for High-Efficiency Oxygen Reduction.

Rational design of well-defined active sites is crucial for promoting sluggish oxygen reduction reactions. Herein, leveraging the surfactant-oriented and solvent-ligand effects, we develop a facile self-assembly strategy to construct a core-shell catalyst comprising a high-index Pt shell encapsulating a PtCu3 intermetallic core with efficient oxygen-reduction performance. Without undergoing a high-temperature route, the ordered PtCu3 is directly fabricated through the accelerated reduction of Cu2+, followed by the deposition of the remaining Pt precursor onto its surface, forming high-index steps oriented by the steric hindrance of surfactant. This approach results in a high half-wave potential of 0.911 V versus reversible hydrogen electrode, with negligible deactivation even after 15000-cycle operation. Operando spectroscopies identify that this core-shell catalyst facilitates the conversion of oxygen-involving intermediates and ensures antidissolution ability. Theoretical investigations rationalize that this improvement is attributed to reinforced electronic interactions around high-index Pt, stabilizing the binding strength of rate-determining OHads species.

Enhanced cobalt MOF electrocatalyst for oxygen evolution reaction via morphology regulation

Developing productive and stable catalysts using common elements for the production of hydrogen via water splitting is highly desirable. Due to their well-designed composition, unique morphology, and highly crystalline structure, metal–organic frameworks (MOFs) exhibit good electrocatalytic performance and have attracted significant research interest as OER catalysts. The optimized Co-MOF-C catalyst reported herein exhibited a smaller overpotential at 10 mA cm−2 and Tafel slope (342 mV, 119 mV dec−1) than Co-MOF-A and Co-MOF-B in an alkaline solution for OER. Moreover, Co-MOF-C showed better long-term durability and stability with negligible deactivation compared with the other MOF catalysts. The apparent laminar nanomorphology of Co-MOF-C provided more accessible active metal centers, better electrical conductivity, and improved kinetics, explaining its better performance as an OER electrocatalyst.

Oxygen-Bridged Stabilization of Single Atomic W on Rh Metallenes for Robust and Efficient pH-Universal Hydrogen Evolution.

Highly efficient and durable electrocatalysts are of the utmost importance for the sustainable generation of clean hydrogen by water electrolysis. Here, we present a report of an atomically thin rhodium metallene incorporated with oxygen-bridged single atomic tungsten (Rh-O-W) as a high-performance electrocatalyst for pH-universal hydrogen evolution reaction. The Rh-O-W metallene delivers ascendant electrocatalytic HER performance, characterized by exceptionally low overpotentials, ultrahigh mass activities, excellent turnover frequencies, and robust stability with negligible deactivation, in pH-universal electrolytes, outperforming that of benchmark Pt/C, Rh/C and numerous other reported precious-metal HER catalysts. Interestingly, the promoting feature of -O-W single atomic sites is understood via operando X-ray absorption spectroscopy characterization and theoretical calculations. On account of electron transfer and equilibration processes take place between the binary components of Rh-O-W metallenes, fine-tuning of the density of states and electron localization at Rh active sites is attained, hence promoting HER via a near-optimal hydrogen adsorption.

A New Bis‐(NHC)‐P(II) Complex Supported on Magnetic Mesoporous Silica: An Efficient Pd(II) Catalyst for the Selective Buchwald‐Hartwig Monoarylation of Ammonia

AbstractWe report the synthesis and identification of a new bis(NHC)‐Pd(II) catalyst supported on magnetic SBA‐15 (Fe3O4@SBA‐15). The surface of magnetic SBA‐15 was subsequently treated with (3‐aminopropyl) triethoxysilane (APTES), cyanuric chloride (CC), imidazole, and 2‐bromopyridine. The modified magnetic mesoporous material was then further treated with separately prepared trans‐[Pd(Cl)2(SMe2)2] complex to give Fe3O4@SBA‐AP‐CC‐bis(NHC)‐Pd(II) as a supported bis(NHC)‐Pd(II) complex. The catalyst was fully characterized by common spectroscopic methods. X‐ray photoelectron spectroscopy (XPS) revealed that some imine nitrogens interact with palladium atoms. The supported Pd(II) complex catalyzed the direct monoarylation of ammonia with iodo‐, bromo‐, and chloroarenes, selectively. The effects of reaction components and parameters were investigated to establish the optimal reaction conditions. The catalyst was separated by a magnet, washed, and applied in the subsequent run. It exhibited noticeable stability and reused over seven catalytic cycles with negligible deactivation. A small Pd leaching (1.04 %) was observed in the first run.

Nanostructured Layered Lithium Iridates as Electrocatalysts for Improved Oxygen Evolution Reaction

We report for the first time the synthesis pathway of nanostructured lithium iridates in molten salts with tunable particle and crystal sizes. The structural analysis confirms that these materials are phase-pure, with a layered α-Li2IrO3 structure and a surface area 2 orders of magnitude higher than that of the materials obtained by traditional solid-state methodology. Improved OER activities were obtained compared to the bulk counterpart, given the improved surface area. Intriguingly, the electrocatalytic behavior of this nanoscaled α-Li2IrO3 significantly differs from the bulk counterpart. Such a different behavior may arise from the small size of the synthesized materials; thus, surface reactions play a key role. Additionally, the nanoscaled α-Li2IrO3 shows good chemical and structural stability; thus, negligible deactivation was observed in KOH and H2SO4 electrolytes with low electrode catalyst loading during 24 h of chronopotentiometry. Besides this stability, these materials show enhanced iridium intrinsic activity with 336 and 181 A gIr–1 in H2SO4 and KOH electrolytes, respectively. This work shows how the design of high-temperature colloidal synthesis yields nanoscaled materials with enhanced and different electrocatalytic properties compared to bulk counterparts and pave the way to the design of electrocatalysts with enhanced mass activity.

Upgrading biogas into syngas via bi-reforming of model biogas over ruthenium-based nano-catalysts synthesized via mechanochemical method

The upgrading of biogas to value-added syngas via reforming of biogas is of great significance from the perspective of green carbon science. A series of Ru based nano-catalysts (Ru/MgO, Ru/La2O2CO3, Ru/CeO2) with relatively low Ru loading and high dispersion were successfully prepared by mechanochemical method, and applied in the bi-reforming of model biogas reaction. The representative catalysts were comprehensively characterized by XRD, N2 physical adsorption, ICP-OES, SEM, XPS, H2-TPR, CO2-TPD, HRTEM, FTIR of CO adsorption, TPSR, TG, and Raman spectroscopy, etc. Ascribed to the appropriate basicity of MgO, homogeneous Ru dispersion with ultra-small particle size, and strong interaction between Ru ultra-small nano particles and MgO support, Ru/MgO exhibit higher CO2 adsorption and activation, higher CH4 activation and dissociation, compared with Ru/La2O2CO3, Ru/CeO2, which facilitate the formation of active oxygen species and intermediate coke removal, thus enhance the resistance to coke deposition and sintering. At reaction conditions of T = 750 °C and weight hourly space velocity = 32,400 mLgCat−1 h−1, 0.5Ru/MgO catalyst exhibit satisfying catalytic activity (initial CH4/CO2 conversation rate of 87/48%) and superior stability (stable for 150 h) with negligible deactivation rates.

Surface/Lattice Oxygen Synergism of Durable CuO Catalysts for Tandem Dehydrogenation–Oxidation of Glycerol to Carboxylic Acids in Oxygen-Free Medium

Catalytic dehydrogenation–oxidation of bio-oxygenates to carboxylic acids and green H2 has been considered a key technology for biorefineries. Composition, size, and morphology are critical parameters for solid catalysts. However, the synergism of surface/lattice oxygen in inexpensive metal oxide catalysts is largely unexplored in this area. In this work, a systematic study on the surface/lattice oxygen synergism of crystallized CuO catalysts has been performed using glycerol dehydrogenation as an example. The key finding is that surface oxygen contributes to enhanced C–H bond activation, while lattice oxygen is key for tandem dehydrogenation–oxidation reactions. Thus, the crystallized CuO catalysts display a 2-fold enhancement in activity and 7-fold improvement in the durability of CuO catalysts, leading to almost 93% reduction of Cu leaching with negligible deactivation. The methodology discussed in this work will provide insights into the rational design of cost-effective CuO materials for other important aqueous dehydrogenation reactions in the chemical industry.

High selective oxidation of 5-hydroxymethyl furfural to 5-hydroxymethyl-2-furan carboxylic acid using Ag-TiO2

Production of 5-hydroxymethyl-2-furan carboxylic acid (HMFCA) from 5-hydroxymethylfurfural (HMF) selective oxidation using Ag-TiO2 were investigated under oxygen atmosphere. The novel catalyst was prepared by a simple sol-gel method, different characterizations were performed, which included N2 adsorption and desorption measurements, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), NH3/CO2 temperature-programmed desorption (NH3/CO2-TPD), scanning electron microscope (SEM), and high revolution transmission electron microscope (HR-TEM). Reaction parameters, such as temperature, base content, oxygen pressure, catalyst loading and reaction time were investigated. 99% HMF conversion, 96% HMFCA yield, and 97% HMFCA selectivity obtained under optimum condition (25 mg Ag-TiO2, 4 eq. Na2CO3, 1 MPa O2, 80 °C, 32 h). Catalyst stability experiment revealed negligible deactivation (90% HMF conversion and 85% HMFCA yield in fourth time). The appropriate proportion of acidic/basic sites, large surface areas, and strong synergistic interaction between Ag+, metallic Ag and TiO2 for oxygen activation attributed to high catalytic activation.

Highly Active MgP Catalyst for Biodiesel Production and Polyethylene Terephthalate Depolymerization

AbstractA highly active heterogeneous catalyst was designed and employed for two relevant transesterification reactions. i. e. biodiesel production and depolymerization of polyethylene terephthalate (PET). The material was prepared in the presence of pectin by the co‐precipitation method followed by calcination at 600 °C (MgP). MgP is efficient for biodiesel production, with a yield of ≈99 % in 6 h/65 °C, and with a molar ratio methanol: oil of 21 : 1. The reference material (MgR, prepared in absence of pectin) showed a poor catalytic performance in the same experimental conditions. For the methanolysis of PET, 100 % PET conversion was obtained with 3 wt % catalyst, 200 : 1 methanol: PET molar ratio at milder conditions 160 °C/4 h, compared to a 33 % conversion without the presence of a catalyst. The catalyst showed remarkable stability and negligible deactivation after five consecutive runs. Materials were characterized by SEM, XRD, IR, TGA, and BET.

Ni/SiO2 catalysts derived from carbothermal reduction of nickel phyllosilicate in the hydrogenation of levulinic acid to γ-valerolactone: The efficacy of nitrogen decoration

Ni catalysts derived from the carbothermal reduction of nickel phyllosilicate were investigated and their application in the hydrogenation of levulinic acid (LA) to γ-valerolactone (GVL) was revealed. The most effective catalyst (S3M1.5@NiPS-600) was prepared by using a sucrose-melamine mixture (molar ratio = 2:1) as the reducing agent with a proper thermal treatment (maintained at 600 °C for 2 h). By using S3M1.5@NiPS-600, a high GVL productivity (1387 mmol GVL/g surface Ni/h), good recyclability (4.9% loss of initial activity in five cycles), and a negligible deactivation rate were observed. The promising outcome was attributed to grafted carbon and nitrogen species on the carbothermally reduced Ni/SiO2 catalyst. Grafted carbon species improve catalyst stability whereas immobilized nitrogen species induce Niδ+ (δ>2) with a strong Lewis acidity. Paired Niδ+ and Ni0 sites are active in the reduction of the ketone group of LA, thereby enhancing the production of GVL.

Enhanced catalytic activity and stability of nanoshaped Ni/CeO2 for CO2 methanation in micro-monoliths

Coupling inherently fluctuating renewable feedstocks to highly exothermic catalytic processes, such as CO2 methanation, is a major challenge as large thermal swings occurring during ON- and OFF- cycles can irreversible deactivate the catalyst via metal sintering and pore collapsing. Here, we report a highly stable and active Ni catalyst supported on CeO2 nanorods that can outperform the commercial CeO2 (octahedral) counterpart during CO2 methanation at variable reaction conditions in both powdered and μ-monolith configurations. The long-term stability tests were carried out in the kinetic regime, at the temperature of maximal rate (300 °C) using fluctuating gas hourly space velocities that varied between 6 and 30 L h−1·gcat−1. Detailed catalyst characterization by μ-XRF revealed that similar Ni loadings were achieved on nanorods and octahedral CeO2 (c.a. 2.7 and 3.3 wt. %, respectively). Notably, XRD, SEM, and HR-TEM-EDX analysis indicated that on CeO2 nanorods smaller Ni-Clusters with a narrow particle size distribution were obtained (∼ 7 ± 4 nm) when compared to octahedral CeO2 (∼ 16 ± 13 nm). The fast deactivation observed on Ni loaded on commercial CeO2 (octahedral) was prevented by structuring the reactor bed on μ-monoliths and supporting the Ni catalyst on CeO2 nanorods. FeCrAlloy® sheets were used to manufacture a multichannel μ-monolith of 2 cm in length and 1.58 cm in diameter, with a cell density of 2004 cpsi. Detailed catalyst testing revealed that powdered and structured Ni/CeO2 nanorods achieved the highest reaction rates, c.a. 5.5 and 6.2 mmol CO2 min−1·gNi−1 at 30 L h−1·gcat−1 and 300 °C, respectively, with negligible deactivation even after 90 h of fluctuating operation.

Aqueous Electrochemical Partial Oxidation of Hydrocarbons By a Gas Diffusion Electrode Carrying Ru-Doped Covalent Triazine Framework

The oxidative functionalization of organic substrates to valuable chemicals has attracted global interest from both fundamental and practical viewpoints. One of the promising approaches for the C-H oxidative functionalization is an aqueous electrochemical method because it can operate under mild conditions without toxic oxidants or flammable solvents. However, there are two major challenging issues for the further dissemination of electrochemical hydrocarbon oxidation in aqueous solution. The first one is the low solubility of raw organics in aqueous media. Here, we focus on gas diffusion electrodes (GDEs) that have been originally developed for hydrogen/oxygen fuel cells in an attempt to overcome this problem. The other major issue is that highly reactive species on an electrocatalyst are required for the activation of stable C−H bonds of hydrocarbons. Although high-valency ruthenium-oxo species (RuIV=O or RuV=O) are known to catalyze O-atom insertion into stable C-H bonds, Ru-based molecular electrocatalysts generally exhibit poor robustness and also catalyze the competitive oxygen evolution reaction (OER) in aqueous solutions. Our group has recently reported that singly isolated Ru-doped covalent triazine frameworks (Ru-CTF) effectively oxidize benzyl alcohol in aqueous electrolytes without the OER[1]. Besides, Ru-CTF displayed higher stability than an organometallic complex immobilized on an electrode because of the covalently cross-linked structure of CTF. In this study, we attempt to realize the electrochemical oxidation of vaporized hydrocarbons in aqueous solutions using a GDE that supports Ru-CTFs (Ru-CTF/GDE).A mixture of 1.0 g ZnCl2, 100 mg 2,6-dicyanopyridine, and 100 mg Ketjenblack was filled into a vacuum glass tube and then heated at 400 °C for 40 hours to prepare a CTF. Ru atoms were then impregnated into the CTF using 0.91 mM RuCl3 ethanol solution for 6 h at 90 °C. A catalyst ink was prepared by dispersing 4.0 mg Ru-CTF in 38 μL 5% Nafion solution and 400 μL ethanol, which was then added dropwise onto the GDE.Ethylbenzene (EB)-saturated (1.2×103 Pa) argon gas was supplied from the backside of GDE as a model substrate. Reaction products in liquid phases after electrolysis were quantitatively analyzed using high-performance liquid chromatography. When the GDE electrode carrying Ru-CTF was applied at 1.5V vs. RHE, acetophenone was generated as the product of ethylbenzene oxidation. The amount of generated acetophenone reached up to 4.7 µmol after 6 h electrolysis. In contrast, generated acetophenone was almost negligible in the absence of ethylbenzene or for bare CTF (without Ru). These results indicated that the Ru atoms in CTF served as the active center for ethylbenzene oxidation. For comparison, electrochemical measurements of Ru-CTF/GDE with 0.2 mM EB in the electrolyte instead of gaseous EB were also conducted using the same GDE electrochemical cell. In this case, the gas chamber was filled with pure argon gas. Although the EB concentration of 0.2 mM is about one-seventh lower than the saturated concentration (solubility of EB in water: 1.4 mM), the amount of acetophenone generated from gaseous EB was over 40-fold larger than that from the electrolyte. This result demonstrates that a GDE is effective for the aqueous electrochemical oxidation of hydrophobic organic compounds. The stability of Ru-CTF on GDE was investigated by the repeated tests in which an EB oxidation reaction was performed over four consecutive cycles with the replacement of the electrolyte every 12 h. Ru-CTF on GDE had negligible deactivation for both current-time profiles and acetophenone generation with repeated use. These results indicate that Ru-CTF on GDE has good stability at 1.5 V vs. RHE.In summary, gaseous EB was successfully oxidized to acetophenone in aqueous electrolytes using a GDE that supported Ru-CTF. Singly isolated Ru-atoms coordinated with nitrogen atoms in Ru-CTF were converted to high-valency Ru=O by water oxidation, and O-atom insertion into the C-H bond of EB was facilitated. Considering that Ru-CTF is highly stable during the long-term electrolysis in aqueous solution, Ru-CTF is a novel platform as a heterogeneous electrocatalyst for partial hydrocarbon oxidation reactions. This is the first demonstration of electrochemical hydrocarbon oxidation in aqueous electrolytes using GDEs. The three-dimensional microstructures in the GDE maximized the transportation of gaseous hydrocarbons, and the oxidation reaction occurred at the triple-phase boundary. The present results clearly demonstrate that GDEs are a promising approach for the electrochemical oxidative upgrading of hydrophobic organics.Reference:[1] S. Yamaguchi et al. Chem. Commun. 2017, 53, 10437-10440.Figure. (a) Schematic illustration of GDE carrying Ru-CTF (left), Molecular structure of Ru-CTF (right), (b) The amount of acetophenone generated as a function of time with gaseous EB (Black), with 0.2 mM aqueous EB (Gray). Figure 1

Catalytic performance of silica covered bimetallic nickel-iron encapsulated core-shell microspheres for hydrogen production

Supported nickel-iron catalysts with core/shell structures (Ni,Fe/SiO2, and Ni/SiO2, Fe (Imp.)) were synthesized by sol-gel microencapsulation and sol-gel microencapsulation-impregnation methods, respectively. Sol-gel microencapsulation resulted in the formation of Ni and Fe containing alloys, where both Fe and Ni were in the core (Ni,Fe/SiO2). In the case of combined microencapsulation-impregnation Ni was placed in the center where Fe was on the shell side (Ni/SiO2, Fe (Imp.)). BET, XRD, SEM, TGA and Raman Spectroscopy techniques were used for catalysts characterization. Catalysts were tested in dry reforming of methane (DRM) reaction which was specially selected to provide a comprehensive utilization of methane and carbon dioxide. The catalytic activity tests were carried out at 750 °C and atmospheric pressure, using stainless steel, temperature-controlled tube reactor. After 3 h of reaction, Ni,Fe/SiO2 bimetallic core-shell microsphere catalysts with Ni/Fe ratio of 4/1 and 2/1 indicated the highest CH4 conversions (74% and 68%, respectively) and H2/CO (0,72 and 0,69) ratios. Ni,Fe/SiO2 catalysts showed higher activity compared to Ni/SiO2, Fe (Imp.) catalysts and an activity increase for both types of catalysts were observed due to increasing Ni amount in catalyst structure. Ni,Fe/SiO2 catalysts were also determined to be highly resistant against coke formation. A significant resistance against coke formation on active sites was achieved via SiC formation during reaction. The catalyst with best performance (4Ni,1Fe/SiO2) was regenerated after use and tested on following three successive cycles under identical experimental conditions. Results indicated similar activity values with negligible deactivation.

Catalytic oxidation of glucose over highly stable AuxPdy NPs immobilised on ceria nanorods

The catalytic performance of AuxPdy nanoparticles prepared by colloidal synthesis and immobilised on ceria nanorods (Ce-NR) in the selective oxidation of glucose has been studied under initially basic and relatively mild conditions. Activity was found to be strongly dependent on the bimetallic composition with Au-rich catalysts being more active in glucose oxidation. Catalyst recycling revealed negligible deactivation or metal loss from leaching, and continuing high selectivity to gluconic acid (≥97.7%). Defects on the Ce-NR surface appear to serve as anchoring sites for Au-Pd NPs giving rise to small and very stable NPs.

Nanomagnetic biochar dots coated silver NPs (BCDs-Ag/MNPs): A highly efficient catalyst for reduction of organic dyes

The design and synthesis of metal nanocomposites have attracted enormous attention due to their wide application in environmental fields and water treatment. In this study, synthesis of BCDs-Ag/MNPs has been investigated by a green and economical technique for water treatment. Leaf extract of the Pistacia atlantica plant has Afterward as a capping and reducing agent for the formation of Ag nanoparticles on the surface of magnetic biochar dots. Characterization of the synthesized nanocatalyst was confirmed by X‐ray diffraction (XRD), Fourier-transform infrared (FT-IR), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The BCDs-Ag/MNPs has been successfully developed for effective reduction of methyl orange (MO), methyl red (MR) and methyl blue (MB) in the presence of NaBH4. The calculated kinetic data for the reduction of these dyes were appropriate to the first-order rate equation in the presence of BCDs-Ag/MNPs and NaBH4. In addition, this catalyst showed excellent magnetic separately and reusability without negligible deactivation after at least eight cycles of the reduction reaction.

A high-performance ternary ferrite-spinel material for hydrogen storage via chemical looping redox cycles

Chemical looping has been proposed as an emerging technology for large-scale hydrogen storage with the advantages of high volumetric hydrogen storage density, environmental compatibility, and safety. However, to ensure sufficient redox activity, conventional oxygen carrier materials must be operated at a temperature higher than 800 °C, leading to the rapid deterioration on the storage capacity over several cycles. In this work, we report a ternary ferrite-spinel material Cu0.5Co0.5Fe2O4 for chemical looping hydrogen storage and production. The material exhibits high volumetric hydrogen storage density (65.58 g·L−1) and average hydrogen production rate (142 μmol·g−1·min−1) at 550 °C. The performance is maintained with negligible deactivation over repetitive redox cycles. The high performance can be attributed to the ability of Cu and Co to improve the reduction and the reversible phase change during the oxidation stage at moderate temperatures. The performance of the Cu0.5Co0.5Fe2O4 is comparable to the state-of-the-art Rh-FeOx containing rare earth metals, which enables its potential in industry application.