Catalytic Activity Of Cobalt Research Articles

Catalytic activity of the cobalt (2-hydroxybenzylidene)morpholine-4-carbothiohydrazide complex in the hydrogen evolution reaction

The production of hydrogen gas from water holds an important position among green and renewable energy sources, and has been thrust to the forefront because of the rising global need for such sources. The hydrogen evolution reaction (HER) is an attractive technique for producing hydrogen with free CO2 emission. Therefore, scientists have developed various methods to accelerate the hydrogen evolution reaction (HER) with the best achievable yield. In this work, the catalytic activity of cobalt (2-hydroxybenzylidene)morpholine-4-carbothiohydrazide complex was investigated for the hydrogen evolution reaction in the presence of 0.2 M [NBu4][BF4], and deaerated DMF. The activity data confirmed the active profile of the studied cobalt (2-hydroxybenzylidene)morpholine-4-carbothiohydrazide complex as an electrocatalyst for HER. A comparative study of the studied catalysts with the literature further elaborated the significance of the title work.

Molecular Bio-inspired Strategies for the Design of Electrocatalytic Systems.

This perspective article delves into the realm of bio-inspired catalysis, highlighting the valuable insights gleaned from enzymatic systems for the design of advanced electrocatalysts. We focus here on three key aspects to mimic: the structure of enzymatic active sites, the essential functions to enable catalytic activity as well as key elementary steps of reaction mechanisms employed by enzymes to ensure maximum efficiency and selectivity. Our research group's contributions to these areas are highlighted, including the synthesis and catalytic activity of cobalt(III) pyridinethiolate complexes, the exploration of bimetallic sites mimicking biological carbon dioxide reductases and of all-ferrous Fe4S4 clusters as mimics of FeP active sites, and the integration of concerted proton-electron transfer (CPET) mediators for the generation of metal hydride species. We emphasize the potential of these bio-inspired approaches in advancing electrocatalyst design and their relevance to molecular catalysis.

Synthesis, characterization, electrochemical behavior, and catalytic activity of cobalt(II) metal complexes with pincer-type methylbenzamide derivative ligands

The pincer type new benzamide derivative ligands; N,N'-(2,2′-azenidiil-bis(2,1-phenylene))bis(2-methylbenzamide) (H3L1), N,N'-(2,2′-azenidiil-bis(2,1-phenylene))bis(3-methylbenzamide) (H3L2), and N,N'-(2,2′-azenidiil-bis(2,1-phenylene))bis(4-methylbenzamide) (H3L3) were successfully synthesized from bis(2-aminophenyl) amine with addition of different substituent benzoyl chloride derivatives. Cobalt complexes of these ligands were synthesized in an inert atmosphere Glove-Box system. The synthesized compounds have been characterized by 1H NMR, 13C NMR, COSY, HMQC, UV–Vis, and FT-IR techniques. Crystal structure of suitable compounds was also determined by single crystal X-ray diffraction analysis. Electrochemical properties of the ligands and their cobalt complexes were investigated by cyclic voltammetry. The catalytic activities of ligands and K2[Co(H3L1)2], K2[Co(H3L2)2], K2[Co(H3L3)2] complexes were also examined by aerobic oxidation reaction. Triphenylphosphine and diphenyl sulfide were used as substrates in these oxidation reactions. After 24 h, K2[Co(H3L1)2] pincer complex showed highest catalytic activity with 81% conversion of triphenylphosphine to triphenylphosphine oxide.

Boosted methane dry reforming for hydrogen generation on cobalt catalyst with small cerium dosage

Metal-support interface influences the catalytic activity and physical properties of heterocatalysts dramatically. Herein, the effect of cerium on material properties and catalytic activity of cobalt over gamma-alumina applied in dry reforming of methane (DRM) was investigated. The dispersion of cobalt over gamma-alumina was noticeably improved with low cerium dosages ranging from 0.1 to 0.5 wt%. In addition, the presence of Ce promoter on catalyst surface led to an enhancement in reducibility of cobalt oxide to cobalt metal in the catalyst activation. Using CO2-temperature programmed desorption technique, the catalyst basicity was found to increase proportionally with cerium loading. At an optimal dosage of 0.3–0.5 wt%, the cerium promoted cobalt supported on gamma catalyst displayed outstanding performance in DRM with noticeable conversion improvements up to 11% in both methane and carbon dioxide.

Design of Silica Nanoparticles-Supported Metal Catalyst by Wet Impregnation with Catalytic Performance for Tuning Carbon Nanotubes Growth

The catalytic activity of cobalt and iron nanoparticles for the growth of carbon nanotubes (CNTs) was studied by a specific reproducible and up-scalable fabrication method. Co and Fe catalysts were deposited over SiO2 nanoparticles by a wet-impregnation method and two different annealing steps were applied for the catalyst formation/activation. The samples were calcined at an optimal temperature of 450 °C resulting in the formation of metal oxide nano-islands without the detection of silicates. Further reduction treatment (700 °C) under H2 successfully converted oxide nanoparticles to Co and Fe metallic species. Furthermore, the catalytic efficiency of both supported-metal nanoparticles at 2 and 5% in weight of silica was evaluated through the growth of CNTs. The CNT structure, morphology and size dispersion were tailored according to the metal catalyst concentration.

Cobalt-catalyzed cross-coupling reactions of aryl- and alkylaluminum derivatives with (hetero)aryl and alkyl bromides.

A simple cobalt complex, such as Co(phen)Cl2, turned out to be a highly efficient and cheap precatalyst for a host of cross-coupling reactions involving aromatic and aliphatic organoaluminum reagents with aryl, heteroaryl and alkyl bromides. New C(sp2)-C(sp2) and C(sp2)-C(sp3) bonds were formed in good to excellent yields and with high chemoselectivity, under mild reaction conditions.

Catalytic Activity of Octamethoxy-Substituted Cobalt(II) Tetraphenylporphyrinate in Tetraterpene Oxidation by Hydrogen Peroxide

The catalytic activity of cobalt(II) porphyrinate in the oxidative degradation of β-carotene and lycopene by hydrogen peroxide is studied using spectroscopic methods. The kinetic parameters of the redox process are obtained, and its tentative mechanism is proposed. The catalytic activity is shown to depend on the composition of the coordination site and the presence of additional redox activators. Before oxidative degradation of tetraterpenes takes place, hydrogen peroxide gets coordinated to metal cation of the complex and is subsequently activated. The activation gives rise to a highly reactive intermediate that contains a radical on the methoxy moiety and can initiate free-radical oxidation.

A planar binuclear cobalt(ii) phthalocyanine as a highly efficient catalyst for the oxidation of a mercaptan.

This paper reports on a binuclear Co(ii)Pc which exhibits a previously unknown extremely high catalytic activity for the oxidation of a thiol to the corresponding disulfide. The high activity is explained by an electronic contact between the two Co centres in the complex.

Surface structure of cobalt, palladium, and mixed oxide‐based catalysts and their activity in methane combustion studied by means of micro‐Raman spectroscopy

AbstractThis paper reports the results of the study of surface properties and catalytic activity of cobalt, palladium, and mixed oxide catalysts supported on alumina. Catalytic materials were prepared by the wetness impregnation method directly from solutions of metal salts and using the ultrasound irradiation. The material surface was investigated by micro‐Raman spectroscopy, and the activity in methane combustion was monitored. The results indicated the presence of different metal oxides on the catalysts' surfaces. Cobalt spinel Co3O4 was the main phase of the cobalt catalysts as well as species resulted from interactions with alumina support. In the case of palladium catalysts, the PdO was most prevalent. The article also discusses the observed variation in band position in the Raman spectra and compares the band assignment with literature data. The palladium and mixed oxide catalysts showed average conversion higher than 50% for methane combustion at 673.15 K (400 °C) especially those after sonication.

Enhanced performance of label-free electrochemical immunosensor for carbohydrate antigen 15-3 based on catalytic activity of cobalt sulfide/graphene nanocomposite

In the present study, an electrochemical sensing platform based on CoS2-GR and AuNPs composites (CoS2-GR-AuNPs) was developed for electrochemical immunosensor. In the proposed immunosensor, AuNPs act as the immobilization site for binding of antibodies. CoS2-GR nanocomposite shows excellent electrocatalytic activity toward the oxidation of catechol and also yielded large surface area, which improve the amount of immobilized CA15-3 antibody. Graphite screen-printed electrodes modified with CoS2-GR-AuNPs and applied to development of the enzyme-free and label-free electrochemical immunosensor for detection of protein biomarker carbohydrate antigen 15-3 (CA15-3). Due to the electrocatalytic activity of CoS2-GR nanocomposite toward the oxidation of catechol as probe, determination of CA15-3 antigen was based on its obstruction to the electrocatalytic oxidation of probe by modified screen-printed electrodes after binding to the surface of electrode through interaction with the CA15-3 antibody. The fabricated immunosensor exhibited a wide linear range of 0.1–150UmL−1 and a low detection limit of 0.03UmL−1. The immunosensor showed good accuracy, stability, specificity and it was successfully applied for CA15-3 detection in serum samples. The proposed immunosensor provides a promising sensitive method for clinical applications.

Catalytic activity of cobalt and cerium catalysts supported on calcium hydroxyapatite in ethanol steam reforming

Abstract In this paper, Co,Ce/Ca10(PO4)6(OH)2 catalysts with various cobalt loadings for steam reforming of ethanol (SRE) were prepared by microwave-assisted hydrothermal and sol-gel methods, and characterized by XRD, TEM, TPR-H2, N2 adsorption-desorption measurements and cyclohexanol (CHOL) decomposition tests. High ethanol conversion (close to 100%) was obtained for the catalysts prepared by both methods but these ones prepared under hydrothermal conditions (HAp-H) ensured higher hydrogen yield (3.49 mol H2/mol C2H5OH) as well as higher amount of hydrogen formed (up to 70%) under reaction conditions. The superior performance of 5Co,10Ce/HAp-H catalyst is thought to be due to a combination of factors, including increased reducibility and oxygen mobility, higher density of basic sites on its surface, and improved textural properties. The results also show a significant effect of cobalt loading on catalysts efficiency in hydrogen production: the higher H2 yield exhibit catalysts with lower cobalt content, regardless of the used synthesis method.

Selective H2O2 oxidation of organic sulfides to sulfoxides catalyzed by cobalt(III)–salen ion

The catalytic activity of cobalt(III)–salen ion catalyzed selective H2O2 oxidation of organic sulfides to sulfoxides is examined using spectrophotometric technique. The catalytic reaction proceeds through Michaelis–Menten kinetics and the rate of the reaction is highly sensitive to the nature of the substituent present in the substrate as well as in the salen ligand. The product analyses show that the aryl methyl sulfides are selectively oxidized to the corresponding sulfoxides. Based on the spectral and kinetic studies two possible mechanisms have been proposed.

Mesoporous hard-templated Me–Co [Me = Cu, Fe] spinel oxides for water gas shift reaction

Copper–cobalt and iron–cobalt oxides, as well as a cobalt oxide sample, were synthesized through the hard template (HT) route by using SBA-15 silica as the HT. Copper- and iron-containing materials with a Me/(Co + Me) atomic ratio of 9 and 17 mol% were obtained and characterized as to their structure, morphology, texture and redox properties by X-ray diffraction, FTIR spectroscopy, transmission electron microscopy, N2-physisorption and H2-temperature programmed reduction, respectively. All the oxides were tested in a fixed-bed reactor for the water gas shift reaction in the 200–350 °C temperature range. All the catalysts showed a spinel structure, with the copper ions occupying exclusively the tetrahedral positions in the Cu–Co spinels and the iron ions being present in both tetrahedral and octahedral positions in the Fe–Co spinels. Segregation (to a minor extent) of maghemite phase was detected only for the high-concentration iron–cobalt oxide. The materials were replicas of the topological structure of the template, the channels being void replicas of the former walls of the SBA-15 host and the oxide appearing as nanorods, arranged in a highly ordered way in the case of Cu–Co oxides. Compared to Co3O4, the copper-containing and the iron-containing spinels were easier and harder to reduce, respectively. While the catalytic activity of cobalt and iron–cobalt spinels was rather poor, a remarkable water gas shift activity, accompanied (to a minor extent) by methanation, was observed over Cu–Co spinels. The influence of the reduction features on the catalytic performance is discussed.

Synthesis, characterization, and ascorbic acid oxidase biomimetic catalytic activity of cobalt(III) oxime complexes

A new tetradentate tetraaza ligand was prepared via Schiff-base condensation of 3,4-diaminotoluene with 2,3-butandione monoxime in aqueous solution. This ligand coordinates cobalt(III) through nitrogen donors in equatorial positions with loss of one oxime proton with concomitant formation of an intramolecular hydrogen bond. A series of cobalt(III) complexes, [CoLX2] (X = Cl−, Br−, or I−), [SCNCoLBr], [CNCoLBr], [BF2CoLBr], and [YCoLBr]ClO4 (Y = pyridine, thiophene, triphenylphosphine, or n-pentylamine), was synthesized. The compounds were characterized based on the elemental analysis (C, H, N), electrical conductance, magnetic moment measurements, and spectral studies (IR, 1H NMR, and UV-Vis). Thermal stabilities of representative complexes were examined by using thermal analysis (TGA and DTG). The reported complexes are d6 low-spin diamagnetic and a distorted octahedral environment was proposed. All complexes undergo tetragonal distortion as evidenced by splitting of 1T1g and 1T2g levels of the pseudo-octahedral symmetry. The ligand field parameters such as DqE , DqA , and the tetragonal splitting Dt have been computed and correlated with the nature of the coordinated axial ligands. The reported cobalt(III) complexes exhibit promising catalytic activity toward aerobic oxidation of ascorbic acid to the corresponding dehydroascorbic acid. The oxidase catalytic activity is linked to both the tetragonal splitting parameter Dt and the Lewis-acidity of cobalt(III) created by the nature of the coordinated axial ligands. The probable mechanistic implications of the catalytic oxidation reactions are discussed.

The dependence of catalytic activity of cobalt and copper oxides in the soot oxidation reaction on the method of adding the catalysts

The paper addresses the kinetics of air oxidation of soot in the presence of copper and cobalt oxides which were added in the form of metal acetates or nitrates. The activity of oxides is assessed by the catalytic constants for only the catalytic reaction picked out from the overall process. The oxides derived from nitrates are more active, and the activity ratio between the copper and cobalt oxides depends on the precursor from which they were produced.

Catalytic activity of cobalt and iron phthalocyanines or porphyrins supported on different carbon nanotubes towards oxygen reduction reaction

Non-noble metal catalysts for O 2 reduction were prepared by dispersing iron(II) phthalocyanine, cobalt(II) tetra- tert-butylphthalocyanine, cobalt(II) 2,3,7,8,12,13,17,18-octaethyl-porphine, and cobalt(II) 5,10,15,20-tetrakis(4- tert-butylphenyl)-porphyrine on carbon nanotubes (CNTs) used as high surface area support. Different types of CNTs (SWCNTs, DWCNTs and MWCNTs) were investigated as an effective substitute for commonly used carbon black in carbon-supported phthalocyanines and porphyrins. The oxygen reduction reaction (ORR) activity of those CNT-supported catalysts in alkaline and acidic solutions was studied. The results show that: (i) all catalytic systems including MWCNTs are more efficient for O 2 reduction than those with SWCNTs and DWCNTs, (ii) the oxidative chemical treatment of the CNTs increases the electrocatalytic performance of the corresponding CNT-supported catalysts, (iii) similarly to Vulcan-supported catalysts, iron(II) phthalocyanine gives the best electroactivity among the investigated CNT-supported materials and (iv) finally, the MWCNT-supported iron(II) phthalocyanine catalyst chemically treated in oxidative conditions shows an ORR catalytic activity comparable to a commonly used Pt/C catalyst with similar current densities and a very low overpotential (60 mV).

Catalytic activity of cobalt on nanotextured polymer films for hydrogen production

We describe the mechanism of cobalt and ligand binding on nanotextured poly(chloro-p-xylylene) (PPX) films as supports for catalytic release of H2 from alkaline aqueous solutions of sodium borohydride. Cobalt catalysts are prepared on nanotextured PPX substrates via electroless plating using a Sn-free Pd(II) colloid with adsorbed pyridine ligand as an adhesion promoter. Gas physisorption studies on PPX, using N2 and CO2 as probe gases, indicate the presence of micropores (∼1 to 2nm width) responsible for the adsorption and non-covalent stabilization of pyridine molecules on the nanotextured surface. The strongly adsorbed pyridine molecules promote Co adhesion onto the PPX surface during subsequent electroless deposition, thereby retaining the metal's catalytic activity for H2 evolution even after multiple reaction cycles. In contrast, conventionally deposited PPX is devoid of any nanotexture and contains fewer micropores capable of stabilizing pyridine adsorption, resulting in poor metallization and catalytic activity for H2 evolution. We also demonstrate the effect of patterning the PPX substrate as a means to further improve the activity of the Co catalyst to achieve H2 evolution rates comparable to those obtained using precious metal catalysts.

Metal-induced graphitization by methane pyrolysis: Its application as a catalyst for single-walled carbon nanotubes

Abstract This paper investigated the catalytic activity of cobalt and its alloy with molybdenum for the growth of single-walled carbon nanotubes (SWCNT) using the CVD process. The phase transformation of the Co–Mo catalyst was monitored during high temperature methane pyrolysis to determine the catalytic activity of each element for graphitization, and the results can be applied to synthesize SWCNT with high efficiency. Structural changes through the formation of the intermetallic compound Co 3 Mo and decomposition during the CVD reaction generated the internal instability of the metal catalyst, and this played a crucial role in the nucleation of a graphitic structure and the promotion of SWCNT growth.

Quantitative determination of glycine in commercial dosage forms by kinetic spectrophotometry

A kinetic method for the determination of nanogram quantities of amino acid glycine (Gly) is described. The catalytic activity of cobalt in the reaction of oxidation of purpurin (1,2,4-trihydroxyantraquinone, PP) by hydrogen peroxide in alkaline buffer solution decreases in the presence of micro quantities of glycine. Operating conditions for the successful determination of glycine were optimized and yielded a theoretical detection limit of 6.5 ng/mL. Kinetic equations are proposed for the investigated process. The interference effects of certain foreign ions and amino acids upon the reaction rate were studied in order to assess the selectivity of the method. The procedure was successfully applied to the determination of glycine in various pharmaceutical samples. The unique features of this procedure are that the determination can be carried out rapidly at room temperature and analysis time is short. The procedure is simple, inexpensive and efficient for use in the analysis of a large number of samples.

Metallic phases of cobalt-based catalysts in ethanol steam reforming: The effect of cerium oxide

Abstract The catalytic activity of cobalt in the production of hydrogen via ethanol steam reforming has been investigated in its relation to the crystalline structure of metallic cobalt. At a reaction temperature of 350 °C, the specific hydrogen production rates show that hexagonal close-packed (hcp) cobalt possesses higher activity than face-centered cubic (fcc) cobalt. However, at typical reaction temperatures (400–500 °C) for ethanol steam reforming, hcp cobalt is transformed to less active fcc cobalt, as confirmed by in situ X-ray diffractometry (XRD). The addition of CeO2 promoter (10 wt.%) stabilizes the hcp cobalt structure at reforming temperatures up to 600 °C. Moreover, during the pre-reduction process, CeO2 promoter prevents sintering during the transformation of Co3O4 to hcp cobalt. Both reforming experiments and in situ diffuse-reflectance infrared Fourier transform spectroscopy (DRIFTS) showed that the surface reactions were modified by CeO2 promoter on 10% Ce–Co (hcp) to give a lower CO selectivity and a higher H2 yield as compared with the unpromoted hcp Co.