Hybrid Catalyst For Oxidation Research Articles

Effect of 4,4′-dialkyl-2,2′-bipyridine ligands on the hydrolysis of dichlorodioxomolybdenum(VI) catalyst precursors and the switch from homogeneous epoxidation to heterogeneous systems

Molybdenum catalysts have been industrially recognized for decades for liquid phase epoxidation, which is an important chemical reaction process, since epoxides are used for many industrial applications. In this work, molybdenum oxide hybrid catalysts, prepared by a reflux hydrolysis methodology, performed effectively as heterogeneous catalysts or reaction-induced self-separating catalysts under mild reaction conditions; in the two cases, the catalyst separation and reuse are facilitated. Specifically, catalysts with the general formula [MoO3(L)], possessing polymeric chain-like (L = 4,4′-dimethyl-2,2′-bipyridine (1)) or oligomeric (L = 4,4′-dinonyl-2,2′-bipyridine (2)) structures comprising corner-sharing {MoO4N2} units, were synthesized and characterized by various complementary techniques (ATR FT-IR, Raman, 13C{1H} CP MAS NMR spectroscopy, PXRD, SEM, TGA, elemental analysis, ICP-OES and N2 sorption isotherms). Small chemical differences in the organic synthesis precursor had important structure directing effects on the type of hybrid material formed. The hybrids promoted olefin epoxidation with H2O2 or tert-butylhydroperoxide (TBHP) as oxidant. For example, 1 catalyzed the conversion of biobased olefins (70 °C) and lignin-based isoeugenol (50 °C) with TBHP to useful bioproducts, in heterogeneous phase, leading to an epoxide yield of 100 % for DL-limonene (3:1 M molar ratio of 1,2-epoxy-p-menth-8-ene to 1,2:8,9-diepoxy-p-menthane), 81 % epoxide yield for fatty acid methyl esters, and 80 % Licarin A selectivity at 40 % isoeugenol conversion. For dienes (DL-limonene, methyl linoleate), kinetic modelling studies suggested that the formation of the monoepoxides was faster than that of diepoxides, accounting for enhanced monoepoxide selectivity.

Selective Synthesis of Formyl‐2‐Furancarboxylic Acid via Enhanced Adsorption of 5‐Hydroxymethylfurfural on Composite Catalysts

5‐Hydroxymethylfurfural (HMF) is a widely used biomass platform chemical that plays a crucial role in bridging biomass and fossil resources. Electrocatalytic oxidation of HMF provides an efficient way to obtain high‐value‐added biomass‐derived chemicals, among which the intermediate product 5‐formyl‐2‐furan carboxylic acid (FFCA) has attracted considerable attention. However, the weak adsorption ability of monometallic nickel oxide (NiOx) to HMF in neutral electrolyte restricts its further development, resulting in low HMF conversion and FFCA yield. In this study, we successfully constructed a novel nickel oxide‐platinum oxide hybrid catalyst supported on carbon felt (NiOx‐PtOx/CF), which exhibits an optimized adsorption ability of HMF, leading to the outstanding FFCA yield up to 77% in the neutral media. The high activity of the NiOx‐PtOx/CF catalyst can be attributed to the redistribution of the electrons and the optimization of the electronic structure on the Ni active site due to the introduction of PtOx on NiOx nanosheets. This study offers valuable insights for the design of efficient multicomponent electrocatalysts for electrocatalytic biomass refinery systems.

Unraveling the Oxygen Vacancy Site Mechanism of a Self-Assembly Hybrid Catalyst for Efficient Alkaline Water Oxidation

Unraveling the Oxygen Vacancy Site Mechanism of a Self-Assembly Hybrid Catalyst for Efficient Alkaline Water Oxidation

Molecular confined synthesis of magnetic CoOx/Co/C hybrid catalyst for photocatalytic water oxidation and CO2 reduction

Photosynthesis [6CO2 + 12H2O → (CH2O)6 + 6O2 + 6H2O] in nature contains a light reaction process for oxygen evolution and a dark reaction process for carbon dioxide (CO2) reduction to carbohydrates, which is of great significance for the survival of living matter. Therefore, for simulating photosynthesis, it is desirable to design and fabricate a bifunctional catalyst for promoting photocatalytic water oxidation and CO2 reduction performances. Herein, a molecular confined synthesis strategy is reasonably proposed and applied, that is the bifunctional CoOx/Co/C-T (T = 700, 800 and 900 °C) photocatalysts prepared by the pyrolysis of molecular Co-EDTA under N2 and air atmosphere in turn. Among the prepared photocatalysts, the CoOx/Co/C-800 shows the best photocatalytic water oxidation activity with an oxygen yield of 51.2%. In addition, for CO2 reduction reaction, the CO evolution rate of 12.6 µmol/h and selectivity of 75% can be achieved over this catalyst. The improved photocatalytic activities are attributed to the rapid electron transfer between the photosensitizer and the catalyst, which is strongly supported by the current density-voltage (j-V), steady-state and time-resolved photoluminescence spectra (PL). Overall, this work provides a reference for the preparation and optimization of photocatalysts with the capacity for water oxidation and CO2 reduction reactions.

Mononuclear Cu-complex embedded ordered nano-porous silica based hybrid catalyst for oxidation of benzyl alcohol

A novel mixed ligand copper (׀׀) complex having 2,9-dimethyl-1,10-phenanthroline and nitrate has been successfully synthesized and characterized by single crystal XRD. Following synthesis, this complex was anchored on acid functionalized nano-porous materials such as MCM-41-SO3H and SBA-15-SO3H, and these hybrid materials were characterized using a variety of techniques such as FT-IR, PXRD, BET, SEM, TG, and so on. These modified mesoporous materials (MCM-41-SO3HCu and SBA-15-SO3HCu) were subjected to solvent-free selective benzyl alcohol oxidation with TBHP (Tert-Butyl Hydroperoxide) as an oxidant. Various reaction parameters were investigated to optimize the reaction conditions. MCM-41-SO3HCu was discovered to be an excellent catalyst in terms of benzyl alcohol conversion and benzaldehyde selectivity.

Facile synthesis of polyoxometalate supported on magnetic graphene oxide as a hybrid catalyst for efficient oxidation of aldehydes

In the present study, Anderson-type polyoxometalate [N(C4H9)4] [FeMo6O18(OH)6] (FeMo6) was immobilized on amino-modified magnetic graphene oxide and employed as a new hybrid catalyst in oxidation of aldehydes to carboxylic acids. The synthesized hybrid catalyst Fe3O4/GO/[FeMo6] was characterized using thermogravimetric analysis (TGA), scanning electron microscopies (SEM), Fourier transform infrared (FT-IR), vibrating sample magnetometry (VSM), energy-dispersive X‐ray analysis (EDX), Raman spectroscopy and inductively coupled plasma atomic emission spectroscopy (ICP-OES). The results indicated that our catalyst was quite active in oxidizing the aldehydes to their corresponding carboxylic acids in the presence of hydrogen peroxide. The synthesized catalyst can be easily separated from the reaction medium and reused for six consecutive runs without a significant reduction in reaction efficiency.

A Lindqvist type hexamolybdate [Mo6O19]-modified graphene oxide hybrid catalyst: Highly efficient for the synthesis of benzimidazoles

In this work, a novel organic–inorganic hybrid catalyst ([Mo6O18] @GO-NH2) was synthesized by covalent attachment of Lindqvist type polyoxometalate [(C4H9)4N]2[Mo6O19] on the surface of graphene oxide (GO). To provide the hybrid catalyst, graphene oxide was covalently modified with an aminosilane, followed by treatment with a polyoxometalate complex. The resulting catalyst was identified by different analytical techniques TG, SEM, XRD, BET, EDX, FT-IR, and N2 adsorption–desorption. [Mo6O18] @GO-NH2 was used as an efficient catalyst for the preparation of various benzimidazoles. The result showed high activity, recoverability, reusability, and durability of the designed catalyst under applied conditions.

Facile Synthesis of Trimetallic-Based Cuxmox/Co1−Xo Nanoparticles/Reduced Graphene Oxide Hybrid Catalyst Toward Efficient Oxygen Evolution Reaction

Facile Synthesis of Trimetallic-Based Cuxmox/Co1−Xo Nanoparticles/Reduced Graphene Oxide Hybrid Catalyst Toward Efficient Oxygen Evolution Reaction

Construction of thiol-grafted PProDOT/yolk shell carbon sphere/Pt hybrid catalyst for methanol oxidation

Three-dimensional supports contribute to the uniform loading of Pt nanoparticles (Pt NPs) for use in direct fuel cells (DMFCs). In this paper, a three-dimensional hybrid of thiol-grafted poly (3,4-propylenedioxythiophene)/Yolk-Shell carbon nanosphere (PProDOT-2MeSH/YRFC) was fabricated as Supporting Material for Pt, and the obtained hybrid (PProDOT-2MeSH/YRFC/Pt) catalyst was applied to the methanol oxidation. The hybrid catalyst possessed electrochemically active area of 47 m2/g, and its mass active current density for methanol was 450 mA/mg. Compared with commercial Pt/C, the electro-catalytic activity of hybrid catalyst was greatly improved, which was originated from the contribution of the special morphology of hybrids and the strong interaction occurring in each component.

Interface engineered Co, Ni, Fe, Cu oxide hybrids with biphasic structures for water splitting with enhanced activity

Developing high-performance catalysts for water splitting via renewable electricity is of great significance for the clean production of hydrogen. This work reports rational design and controllable fabrication of metal oxide hybrid catalyst CoNiFe2O5·2CuO with unique biphasic microstructures for electrochemical water splitting. Benefited from the presence of CuO nanoparticles as the second phase, more defects and active sites were formed around the interfaces of CoNiFe2O5 and CuO, which led to excellent performances for electrocatalytic water splitting. In particular, the catalyst exhibited outstanding activity for hydrogen evolution reaction with a small overpotential of 30 mV to reach a current density of 10 mA cm−2 and showed a higher turnover frequency (0.3 s−1) than commercial catalyst Pt/C (0.1 s−1) under an overpotential of 50 mV. Moreover, it also displayed good activity for oxygen evolution reaction with an overpotential of 264 mV at 10 mA cm−2. Using CoNiFe2O5·2CuO as the catalyst for electrode pair to construct a cell, a very low cell voltage of 1.53 V is enough to achieve overall water splitting at 10 mA cm−2 in 1 M KOH electrolyte, and the cell could maintain the stable performance at 10 mA cm−2 within 100 h. The as-prepared metal oxide hybrids with biphasic microstructures may have promising application potentials in water splitting.

Enhanced hydrogen sorption kinetics of MgH2 catalyzed by a novel layered Ni/Al2O3 hybrid

Metal-containing catalysts have been successfully applied in the Mg-based hydrogen storage materials. Here, a layered Ni/Al2O3 obtained by calcination of NiAl-layered double hydroxide (NiAl-LDH) is firstly reported for enhancing hydrogen sorption kinetics of MgH2. The hybrid catalyst of Ni/Al2O3 with high stability shows better catalytic performance than the corresponding complex oxides: the onset dehydrogenation temperature of MgH2-Ni/Al2O3 (190 °C) is much lower than that of MgH2-NiO/Al2O3 (240 °C) and the as-milled MgH2 (298 °C), and the MgH2-5 wt% Ni/Al2O3 desorbs about 5.6 wt% hydrogen within 3500 s at 275 °C, while only 4.6 wt% hydrogen is released for MgH2-5 wt% NiO/Al2O3 and the undoped MgH2 can hardly dehydrogenate at the same conditions. The catalytic mechanism of Ni/Al2O3 was investigated in detail by combining the experiment and density functional theory (DFT) calculations. The enhanced hydrogen desorption kinetics is mainly due to the destabilizing effect of MgH2 caused by Ni/Al2O3 acting as electron acceptors to capture the electrons in the Mg−H bond, resulting in a weakening of the bond strength. This study might be of interest for designing high-efficiency metal-metal oxide hybrid catalysts applied in the field of hydrogen storage.

The high performance NiFe layered double hydroxides@ Ti3C2Tx/reduced graphene oxide hybrid catalyst for oxygen evolution reaction

A non-precious metal electrocatalyst for oxygen evolution reaction （OER）is achieved by synergistically coupling layered double hydroxides (LDH) and hybrid supports(reduced graphene oxide (rGO) and Ti3C2Tx-MXene). The NiFe LDH/Ti3C2Tx-rGO catalyst exhibits superior activity with a promising low overpotential of 235 mV at a current density of 10 mA cm−2 in alkaline medium. The strong interfacial interaction and electronic coupling with prominent charge-transfer between the NiFe LDH and Ti3C2Tx is identified, which not only improves the conductivity and stability and of the hybrids, but also greatly accelerates the redox process of NiFe LDH for OER.

Carbon-Supported Mg–Al Oxide Hybrid Catalysts for Aqueous Ethanol Conversion into 1-Butanol in a Flow Reactor

Carbon-supported Mg–Al oxide (hydrotalcite-derived) hybrid catalysts for aqueous ethanol conversion into 1-butanol were prepared and characterized by X-ray diffraction, scanning electron microscopy, low-temperature nitrogen ad(de)sorption, Fourier transform infrared and X-ray photoelectron spectroscopies, and temperature-programmed desorption of NH3, CO2, and H2O. Enhanced catalytic activity and stability of operation over time on stream of the hybrid catalysts versus Mg–Al oxides were achieved using both rectified and aqueous ethanol as feed. Redistribution of the active sites of the Mg–Al oxide phase over a highly dispersed support and increasing their availability for the reagents were suggested to be the causes of the enhanced activity of the hybrid catalysts.

WITHDRAWN: Dicationic ionic liquid-phosphotungstate cross-linked immobilized on chitosan as hybrid catalyst for solvent-free cyclohexane oxidation using molecular oxygen

This article has been withdrawn at the request of the author.The full Elsevier Policy on Article Withdrawal can be found at https://www.elsevier.com/about/our-business/policies/article-withdrawal

Highly dispersive Pd nanoparticles decorated strontium niobate nanosheets: Efficient and recyclable catalyst for base-free aerobic oxidation of benzyl alcohols in water

2D perovskite Sr2Nb3O10 (SNO) nanosheets were synthesized by cation exchange-assisted liquid exfoliation and applied as supports for the immobilization of palladium (Pd) nanoparticles through the electrostatic assembly with Pd(NH3)42+ precursors and successive in-situ photoreduction. Pd nanoparticles with an average diameter of 9.22 nm are uniformly dispersed on the surface of strontium niobate nanosheets. The obtained nanohybrid Pd-SNO could serve as an efficient heterogeneous catalyst for the atmospheric pressure oxidation of benzyl alcohol to benzaldehyde by using air as an oxidizing agent and water as the sole solvent at low temperature (80 °C). Furthermore, the catalyst could be easily separated from the reaction mixture by simple centrifugation and reused five times without significant degradation in catalytic activity under the investigated conditions. We believe that the synthetic strategy described in this work is a feasible means of developing effective noble metal/layered transition metal oxide hybrid catalysts for organic reactions.

Dual stimuli-responsive silver nanoparticles decorated SBA‒15 hybrid catalyst for selective oxidation of alcohols under ‘mild’ conditions

Herein, we develop an efficient and novel catalytic system, i.e. silver nanoparticles (AgNPs) incorporated mesoporous silica SBA‒15/copolymer hybrid material, for selective oxidation of different alcohols to aldehydes or ketones under ‘mild’ conditions. The copolymer of N,-N -dimethylaminoethyl methacrylate and 2-hydroxyethyl acrylate (p(DMAEMA- co -HEA)) was used to graft the surface-modified SBA‒15 (MS) using free radical polymerization method. Then AgNPs were decorated on the polymer grafted SBA‒15. The dual (thermal and pH) responsive behaviors of the AgNPs/p(DMAEMA- co -HEA)/MS catalyst were investigated using the dynamic light scattering technique. The lower critical solution temperature (LCST) of the copolymer was found to be approximately 30–35 °C. The catalytic activity of AgNPs/p(DMAEMA- co -HEA)/MS was investigated for the selective oxidation of different alcohols to aldehydes or ketones. The conversion of catalytic products and selectivity were calculated using gas chromatographic techniques, whereas the molecular structure of products was determined using 1 H and 13 C nuclear magnetic resonance spectroscopy. The catalyst showed improved catalytic activity toward the oxidation of alcohols to aldehydes in aqueous medium below LCST and pKa value (7–7.5) of the copolymer. The selectivity toward the corresponding aldehyde was found to be significantly high (99%). The main advantages of the hybrid catalyst as compared to existing catalysts include outstanding alcohol conversion (up to 99%), short reaction time (1 h), small necessary amount of catalyst (6 mg), and performing the catalytic conversion at room temperature using water as a solvent, which are highly beneficial for organic conversion under mild reaction conditions. • A catalytic system for selective oxidation of alcohols under ‘mild’ conditions was developed. • The catalyst consists of a temperature and pH-responsive copolymer, SBA-15, and Ag nanoparticles. • The catalyst showed outstanding alcohol conversion (up to 99%) within a short reaction time (1 h). • The catalyst performed the catalytic conversion at room temperature using water as a solvent.

An enhanced activity of Pt/CeO2/CNT triple junction interface catalyst prepared by atomic layer deposition for oxygen reduction reaction

Pt and metal oxide hybrid catalysts based on strong metal support interactions have been proved to be an effective way to improve oxygen reduction reaction (ORR) performance of Pt. In this work, Pt/CeO2/CNT-A triple junction interface catalyst was obtained by atomic layer deposition. Compared with Pt/CeO2/CNT-W (wet chemical method) and Pt/C, Pt/CeO2/CNT-A shows the highest catalytic activity and stability for ORR. As expected, the enhanced ORR performance can be attributed to unique triple junction interface structure which Pt has contact with CNT and ultra-small CeO2. Therefore, ALD method could be a promising strategy to construct effective triple junction interface.

Cu-SSZ-13 zeolite–metal oxide hybrid catalysts with enhanced SO2-tolerance in the NH3-SCR of NOx

The relatively low SO2-tolerance of Cu-SSZ-13 zeolite limits its broader applications in NH3-SCR. In this study, Cu-SSZ-13 zeolite-metal oxide hybrids with different metal oxide components (Mn, Co, Ni, Zn) were prepared using the sol-dispersion method. After poisoning with 50 ppm SO2, ZnTi10Ox-Cu-SSZ-13(1:5) catalyst shows a NO conversion of 73 %, which is significantly higher than in Cu-SSZ-13. Regeneration tests together with TGA and SO2-TPD results suggest that ZnTi10Ox in the hybrid catalyst might serve as a sacrificial component that undergoes preferential reaction with SO2, thereby sparing the Cu2+ active sites from sulfur deactivation. ZnTi10Ox-Cu-SSZ-13(1:5) prepared using the sol-dispersion method exhibits higher NO conversion after SO2 poisoning versus mechanically mixed and co-precipitated hybrid catalysts, which may be due to stronger interactions between Cu2+ and the SSZ-13 support. Our results suggest that ZnTi10Ox-Cu-SSZ-13 may be a promising hybrid catalyst for deNOx due to its high reactivity and decreased sensitivity towards SO2.

Insert Zn2+ in Tetrahedral Sites of Bi-metal Zn-Co Spinel Oxides with High Oxygen Catalytic Performance for Liquid and Flexible Zinc-Air Batteries

Nowadays, it is very challenging to develop a low-cost, highly active and stable bi-functional catalyst for accelerating oxygen reduction reaction (ORR) and oxygen evolution (OER) reaction during the charge and discharge process of zinc-air battery. Herein, we successfully design a novel bi-metal oxide hybrid catalyst (ZnCo2O4-CNT) by inserting Zn ions. Benefiting from the robust synergetic effects between porous ZnCo2O4 and CNTs, the high conductivity and the unique nanostructure, the ZnCo2O4-CNT shows lots of accessible active sites and improved reactants and electrons transfer. As expected, the hybrid shows higher ORR and OER performances with larger limited diffusion current density (5.72 mA cm−2) and lower OER over-potential (0.49 V) than Pt/C and other ZnCo2O4-CNT samples. In addition, rechargeable zinc-air battery assembled with the bi-functional catalyst exhibits a high power density of 249.4 mW cm−2, a strong discharge durability and charge-discharge stability of 240 cycles. Notably, the flexible zinc-air battery also shows good battery performances with high power density and good flexibility. Hence, exploiting efficient bi-functional catalytic materials with excellent ORR and OER performance and assembling flexible devices will improve the development of current zinc-air batteries battery industry.

Microwave-assisted catalytic conversion of glucose to 5-hydroxymethylfurfural using “three dimensional” graphene oxide hybrid catalysts

Hybrids of reduced graphene oxide (rGO) and metal/metal oxide (Pt, NiO/Ni(OH)2, CoO, Fe3O4) nano particle were prepared by reduction of graphene oxide (GO) and metal ion (Pt2+, Ni2+, Co2+, Fe2+) hybrids. The M-rGO hybrids (M = Pt, Ni–, Co and Fe) were justified for the transformation of glucose to 5-hydroxymethylfurfural (5-HMF). High glucose → 5-HMF conversion was yielded depending on the nature of the M-rGO catalyst. The Ni-rGO showed the highest 5-HMF yield. The conversion reaction tuned to the optimized state under a microwave-assisted reaction accomplished by using Ni-rGO. In such case, the conversion rate was 99% with a 5-HMF yield of 75%. In order to improve both the conversion and yield, NiGO-FD was prepared by a freeze-dry method. The NiGO-FD remarkably showed the highest conversion of 99% and 5-HMF yield of 95%. Beside the biomass transformation process, the physico-chemical strategy employed herein for multiplying the catalytic efficiency might be justified for catalyzing similar reactions.