Incorporating Transition Metal Research Articles

CoNi nano-alloy anchored on biomass-derived N-doped carbon frameworks for enhanced oxygen reduction and evolution reactions

Bifunctional catalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are important for energy conversion systems such as fuel cells, water splitting, and metal-air battery devices. In this work, an earthly abundant and cheap biomass of tobacco-stem was used to prepare a novel porous carbon framework (NiCo@NC) by incorporating transition metal alloy and nitrogen-rich small molecules. The resultant catalyst affords an onset potential of 0.92 V and a half-wave potential of 0.86 V for oxygen reduction reaction in alkaline media, which is better than commercial Pt/C. Besides, the catalyst also exhibits good oxygen evolution reaction performance with a low overpotential of 280 mV @ 10 mA cm−2, and the potential gap between ORR and OER is only 0.65 V. The incorporation of NiCo alloy and N heteroatom modulates the electronic structure of the prepared carbon frameworks, creates abundant active sites, and improves charge redistribution, thus resulting in faster ORR and OER reaction kinetics. The applicability of the prepared NiCo@NC is fully harnessed for use as an air-cathode in a Zn-air battery. This work creates a platform for developing efficient porous and functionalized biomass-derived oxygen electrocatalysts for energy applications.

G-C3N4 templated synthesis of the tubular CoFe/N doped carbon composite as advanced bifunctional oxygen electrocatalysts for zinc-air batteries

Rational incorporating transition metal into porous heteroatom-doped carbon is intensively investigated as an effective strategy to achieve high-performance and bifunctional requirements. Herein, we fabricated the hollow composite that CoFe alloy nanoparticles decorated on the tubular N-doped carbon (denoted as T-CoFe/NC) by soft-templating strategy. In order to effectively incorporate the CoFe alloy into nitrogen doped hollow carbon matrix, g-C3N4 nanotubes were selected as the template to attain high contents of nitrogen doping for tubular carbon matrix. Meanwhile, the coordination effect between tannic acid and metal ions is utilized to limit the metal agglomeration in the process of pyrolysis. Consequently, the resultant catalyst shows an outstanding ORR activity with the half-wave potential of 0.86 V and outstanding stability with only a 2 mV decay after 10,000 cycles. T-CoFe/NC also displays comparable overpotential to the RuO2 at 10 mA cm−2. The high bifunctional electrocatalytic activity is attributed to the unique tubular structure and the combination of Co with Fe can optimize the interaction between the oxygenic species and metal surfaces, enhancing the catalytic activity. And T-CoFe/NC based zinc-air battery exhibits excellent power density, large capacity and good cycling stability.

Heterometallic uranyl-organic frameworks incorporating manganese and copper: Structures, ammonia sorption and magnetic properties

Incorporating transition metal ions into uranyl phosphonate frameworks can bring not only new structure types but also interesting physical or chemical properties. Herein we report two heterometallic uranyl carboxyphenylphosphonates, namely, [Cu2(UO2)3(2-pmbH)2(2-pmb)2(H2O)4]·2H2O (1) and [Mn3(UO2)6(2-pmb)6(H2O)8]·10H2O (2) [2-pmbH3 = 2-(phosphonomethyl)benzoic acid]. Compound 1 shows a two-dimensional layered structure in which uranyl-PO3 chains are linked by {Cu2O2} dimers. Within the uranyl-PO3 chain, {UO6} tetragonal bipyramids and edge-sharing dimers of {UO7} pentagonal bipyramids are connected by edge-sharing {PO3C} tetrahedra. Compound 2 possesses a unique 3D open framework structure, where the Mn-layers are pillared by uranyl-PO3 chains. The uranyl-PO3 chain in 2 is very different from that in 1, which contains trimers of edge-sharing {UO7} and {UO8} polyhedra and {PO3C} linkages. While the Mn-layer consists of chains of {MnO6} octahedra bridged alternatively by carboxylate and phosphonate groups, which are inter-connected by organic moieties of 2-pmb3-. The thermally activated sample of 2 displays strong adsorption capability toward NH3. Magnetic studies revealed dominant antiferromagnetic interactions between the metal centers in both compounds.

Tailoring the supercapacitive behaviors of Co/Zn-ZIF derived nanoporous carbon via incorporating transition metal species: A hybrid experimental-computational exploration

The elaborate design of electrode materials plays a critical role in developing high-performance supercapacitors. In the present work, a convenient avenue is adopted to adjust the supercapacitive behavior of carbon-based electrodes by incorporating transition metals (Co, Nb, Mo, and Fe) into Co/Zn-ZIF derived nitrogen-doped porous carbon (NDPC). The experiment results demonstrated that incorporating transition metal species tuned the microstructure, nanoporous textures, and hydrophilicities of as-prepared Co-NDPC and M/Co-NDPC (M = Nb, Mo, or Fe), which further tailored their supercapacitive performance. Owing to the higher surface area, abundant pores, and superior wettability of Nb/Co-NDPC sample, the corresponding electrode showed the highest specific capacitance of 293 F g−1 at 0.5 A g−1 with an outstanding capacitance retention of 82% at 20 A g−1. All the electrodes displayed remarkable stability over 15,000 charge–discharge cycles. The first-principle density functional theory (DFT) calculations revealed that the superior capacitive behaviors of Nb/Co-NDPC electrode could be attributed to the uneven electrostatic potential surface and robust K+ ion adsorption ability. This work provides an elaborate strategy for designing novel and high-performance electrode materials by adopting DFT calculations for supercapacitors.

Highly Transparent, Robust Hydrophobic, and Amphiphilic Organic-Inorganic Hybrid Coatings for Antifogging and Antibacterial Applications.

The control of surface wettability through a combination of surface roughness, chemical composition, and structural modification has attracted significant attention for antifogging and antibacterial applications. Herein, a two-step spin-coating method for amphiphilic organic-inorganic hybrid materials with incorporated transition metal ions is presented. The coating solution was prepared via photochemical thiol-ene click reaction between the mercapto functional group in trimethylolpropane tris(3-mercaptopropionate) and the vinyl functionalized silica precursor 3-(trimethoxysilyl)propyl methacrylate. In the first step of coating, a glass substrate was coated using a solution of metal nitrate hydrates and subsequently showed hydrophobic properties. As the second step, the spin-coated glass substrate was further coated with silica nanoparticles (SiO2 NPs) and polycaprolactone triol (PCT) suspension, where the contents of SiO2 NPs were fixed at 0.1 wt %, unless otherwise noted. The coated substrate exhibited hydrophilic properties. For comparison, the coating was also formulated with the SiO2 NPs/PCT suspension without SiO2 NPs and with 0.5 wt % SiO2 NPs as well as by adjusting different coating layer thicknesses. The surface morphology and chemical compositions of the obtained coating materials were analyzed by field emission scanning electron microscopy with energy-dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy. The transparency and static contact angle of coated samples were measured by UV-visible spectrophotometry and drop shape analysis, respectively. It was concluded that our novel hybrid coating materials exhibited excellent antibacterial and antifogging properties with extremely high scratch resistance and transparency.

CuSO4 nanoparticles loaded onto poly (toluenesulfonic acid‐formaldehyde)/polyethyleneimine composites: An efficient retrievable catalyst for A3/decarboxylative A3 reactions

Using polymeric composite incorporated transition metal nanoparticles to promote various organic reactions has been found as one of the most powerful strategies in organic synthesis. In this paper, CuSO4 nanoparticles (CuSO4 NPs) anchored on the surface of polymeric composites comprising of water‐insoluble acidic poly (toluenesulfonic acid‐formaldehyde) (PTSAF) and water‐soluble basic polyethyleneimine (PEI) to form the desired PEI/PTSAF‐supported CuSO4 NPs catalyst (CuSO4NPs@PEI/PTSAF) have been fabricated. Characterization of the as‐synthesized catalyst by inductively coupled plasma (ICP), Fourier transform infrared (FTIR), X‐Ray diffraction (XRD), scanning electron microscopy (SEM), energy‐dispersive spectroscopy (EDX) and elemental mapping analysis, transmission electron microscopy (TEM), and thermogravity analysis (TGA) demonstrated successful immobilization of the CuSO4 NPs on the PEI/PTSAF composite. This novel catalyst was highly active in the one‐pot A3 and decarboxylative A3 coupling reactions toward generating corresponding propargylamines in good to excellent yields under solvent‐free reaction. The nature of the well distribution of CuSO4 NPs coordinated with PEI ligand in the CuSO4NPs@PEI/PTSAF composite leads to superior catalytic activity. The present methodology offers several advantages such as high catalytic activity, good to excellent yields, short reaction times, simple operations, compatibility of broad scope of substrates, and environmental friendliness. More importantly, the catalyst can be easily recovered from the reaction mixture by a simple filtration and still exhibits remarkable reusability with only marginal loss of its performance after five consecutive runs.

Structural Manipulation of Layered TiS2 to TiS3 Nanobelts through Niobium Doping for High‐Performance Supercapacitors

AbstractUnraveling the influence of incorporating transition metal elements on layered transition metal chalcogenides for energy storage application remains a challenge. Herein, niobium (Nb)‐doped layered titanium disulfide (TiS2) is applied to generate novel compounds Ti1−xNbxS2 (x=0.05, 0.1 and 0.20). Interestingly, TiS3 nanobelts are formed in the resulting materials, which is proven by systematic morphological and structural characterization. It has been found that Nb‐doped TiS2 compounds demonstrate superior electrochemical capacitive activity, reaching up to a 63.2 % increase in gravimetric capacitance in 1 M Na2SO4 electrolyte compared with that of the Nb‐free TiS2. This remarkably enhanced capacity behavior is attributed to Nb doping resulting a structural transition of Layered TiS2 to TiS3 nanobelts.

Influence of temperature and relative humidity on vapor hydration of an AVM nuclear waste glass

The safety assessment of the geological disposal of nuclear waste glasses requires a thorough understanding of the vapor hydration mechanisms of these glasses. In this context, the effect of temperature and relative humidity on vapor hydration of the AVM6 glass, which is the most reactive among the studied French AVM glasses, was investigated in the present study. Polished glass monoliths were vapor hydrated for 1 year (i) at 97% relative humidity (RH), at temperatures 70°C and 90°C to study the effect of temperature and (ii) at 50°C and 50% RH, 76% RH, 88% RH and 97% RH to study the effect of RH. The altered glass samples were characterized by SEM, XRD and ToF-SIMS. The results were compared with published results of AVM6 glass vapor hydrated at 50°C and 95% RH. The nature of the secondary phases that precipitate varied with both temperature and relative humidity, leading to variation in the behavior of elements in the altered layer (gel) but the altered layer morphology is similar at all temperatures studied. The Arrhenius law for temperature dependence is respected between the temperature range 50–90°C and the activation energy suggests that network-hydrolysis is the predominant rate controlling mechanism at these temperatures and duration. The secondary phases that incorporate transition metals and rare-earth elements are identified by XRD only in experiments conducted at lower RH values.

Recent Advances on Metalloporphyrin-Based Materials for Visible-Light-Driven CO2 Reduction.

Photocatalytic CO2 reduction is a promising technology to mitigate environmental issue and the energy crisis. The four nitrogen atoms in the porphyrin ring can incorporate transition metals to form stable active sites for CO2 activation and photoreduction. Nevertheless, the photocatalytic efficiency of metalloporphyrins is still low due to the insufficient photoelectron injection to drive CO2 photoreduction upon visible light irradiation. To address this issue, considerable efforts have been made to introduce photosensitizers for constructing homogeneous or heterogeneous metalloporphyrin-based photocatalytic systems. In this Review, recent advances of metalloporphyrin-based materials for visible-light-driven CO2 reduction were summarized. The methods for the modulation of photosensitizing process at molecular level were presented for the promotion of photocatalytic performance. The mechanism of CO2 activation and photocatalytic conversion was illustrated. Better insight into the structure-activity relationship provides guidance to the design of metalloporphyrin-related photocatalytic systems.

DFT insights into the adsorption properties of toxic gas molecules on pure and transition metal embedded stanene monolayers: Towards gas sensor devices

The first principles calculations were conducted to gain insights into how the interactions of gas molecules can be strengthened over the stanene monolayers upon modifying the surface of stanene by transition metal incorporation. At the first stage, the structures of the transition metal adsorbed stanene monolayers were optimized to obtain the energy favorable frameworks for gas adsorption and sensing. Focused on the band structure results, we found that the Ni-adsorbed stanene monolayers represent semiconductor feature, while the Cu and Au-adsorbed ones exhibit metallic property. Various adsorption sites and directions were examined for the binding of gas molecules to the Au-adsorbed stanene systems. The Au adsorption enhances the adsorption of gas molecules on the stanene system. The difference in the electron densities indicated that the bond in the Au-embedded stanene with adsorbed gas molecules is of covalent nature for the reason that the favored electron accumulation sites are largely located at the middle of the Au-gas molecule bond. Thus, our theoretical findings suggest great potential for Au-adsorbed stanene systems as superior candidates for gas sensing.

Role of incorporated transition metal on surface properties and catalytic activity of mesoporous vanadium aluminophosphates in the synthesis of tetrahydroquinolin-5-(1H)-ones

• Preparation, characterization and study of structural and textural properties of various transition metal incorporated aluminophosphates. • Application of these aluminophosphates as a catalyst in the synthesis of tetrahydroquinolin-5-(1 H )-ones. • Optimization of the reaction conditions in terms of the activity of the catalyst, feed ratio of catalyst. • Synthesis of thirteen tetrahydroquinolin-5-(1 H )-one derivatives at 25°C in ethanol within 30 minutes. • Characterization of the products by FT-IR, 1 H NMR, 13 C NMR and ESI-MS analysis. Aluminophosphate incorporated with transition metals (Co, Cu, Fe, V) were synthesized by co-precipitation method. The synthesized materials were characterized by different techniques (pXRD, FT-IR, N 2 adsorption-desorption, NH 3 -TPD) to understand the structural and textural properties. The incorporation of transition metal into aluminophosphate plays an important role in designing the surface properties like pore size, surface area, and surface acidity. The materials were studied as a catalyst for the synthesis of tetrahydroquinolin-5-(1 H )-ones by a one-pot cyclocondensation reaction of dimedone, substituted benzaldehydes, 4-fluoro/4-nitro phenyl acetonitrile, and ammonium acetate in ethanol at 25 °C. The structures of the compounds were identified and confirmed by FT-IR, 1 H NMR, 13 C NMR and ESI-MS spectral data. The mesoporous nature of vanadium aluminophosphate (VAlP) along with a uniform pore size distribution, high surface acidity, surface area attributes to its high catalytic activity when compared to pure aluminophosphates.

Enhanced magnetization in multiferroic nanocomposite Bi0.9Gd0.1Fe0.9Mn0.05X0.05O3 (X= Cr, Co) thin films

In this work, we prepared and investigated the morphology, ferroelectric and magnetic properties of Bi0.9Gd0.1Fe0.9Mn0.05X0.05O3 (X= Cr, Co) nanocomposite thin films. Microstructure study revealed that the surface morphology of the thin films is strongly dependent on the nature of the incorporated transition metal. Room temperature X-ray diffraction and Raman investigations have allowed the identification of formed phases.The local ferroelectric character of these nanocomposites thin films was investigated by piezoresponse force microscopy to get valuable information about the effect of Co3+ and Cr3+ incorporation on ferroelectric domain switching of Bi0.9Gd0.1Fe0.9Mn0.1O3 parent phase. Field dependence of magnetization measurements at room temperature showed that the presence of Co and Cr improved considerably the saturation magnetization with large and narrow open hysteresis loops, respectively. Moreover, the temperature dependence of magnetization measurements revealed the presence of a spin glass behavior in the studied nanocomposites thin films.

Unlocking the therapeutic potential of artificial metalloenzymes.

In order to harness the functionality of metals, nature has evolved over billions of years to utilize metalloproteins as key components in numerous cellular processes. Despite this, transition metals such as ruthenium, palladium, iridium, and gold are largely absent from naturally occurring metalloproteins, likely due to their scarcity as precious metals. To mimic the evolutionary process of nature, the field of artificial metalloenzymes (ArMs) was born as a way to benefit from the unique chemoselectivity and orthogonality of transition metals in a biological setting. In its current state, numerous examples have successfully incorporated transition metals into a variety of protein scaffolds. Using these ArMs, many examples of new-to-nature reactions have been carried out, some of which have shown substantial biocompatibility. Given the rapid rate at which this field is growing, this review aims to highlight some important studies that have begun to take the next step within this field; namely the development of ArM-centered drug therapies or biotechnological tools.

Measuring Interactions Between the Intracellular Domains of the Acid-Sensing Ion Channel

Acid-sensing ion channels (ASICs) are sodium selective, proton activated channels primarily located in the central and peripheral nervous system. To date, there have been numerous structures solved of ASIC1 in the putative open, closed and desensitized states. These structures reveal the trimeric nature and overall fold of the channel but are missing information about the intracellular N- and C- termini which are known to be important for proper channel gating, trafficking and selectivity. Deletion of the channel's N-terminus causes ASICs to become non-functional. Despite a lack of current, channels appear to traffic to the membrane normally. Deletion of the C-terminus causes the channels to enter a prolonged desensitized state sometimes referred to as tachyphylaxis. Here we examine the role of the intracellular domains in ASIC function using a number of approaches. We hypothesize that the intracellular domains make interactions that are important for channel gating. We can show that isolated peptides of the N- and C-terminus interact with a surprisingly high affinity using microscale thermophoresis. We then try to examine this interaction with two techniques in intact channels. First, we use transition metal ion FRET (tmFRET) to measure the proximity between these two domains. To get specific fluorescent labelling of the N-terminus, we use the non-canonical amino acid L-Anap which we have successfully incorporated at many positions along the N-terminus. We then incorporate transition metals using a cysteine reactive high-affinity metal chelator called TETAC at individual sites along the C-terminus of the channel. FRET between these two domains suggests regions where the two domains may be in close proximity and that the position changes with pH. Second, we are using crosslinking to confirm our results and to examine how restricting the movement of these domains might alter channel function.

Redox-Active Monolayers Self-Assembled on Gold Electrodes-Effect of Their Structures on Electrochemical Parameters and DNA Sensing Ability.

The background: The monolayers self-assembled on the gold electrode incorporated transition metal complexes can act both as receptor (“host” molecules) immobilization sites, as well as transducer for interface recognitions of “guest” molecules present in the aqueous solutions. Their electrochemical parameters influencing the sensing properties strongly depend on the transition metal complex structures. The objectives: The electrochemical characterization of the symmetric terpyridine–M2+–terpyridine and asymmetric dipyrromethene–M2+–terpyridine complexes modified with ssDNA probe covalently attached to the gold electrodes and exploring their ssDNA sensing ability were the main aims of the research presented. The methods: Two transition metal cations have been selected: Cu2+ and Co2+ for creation of redox-active monolayers. The electron transfer coefficients indicating the reversibility and electron transfer rate constant measuring kinetic of redox reactions have been determined for all SAMs studied using: Cyclic Voltammetry, Osteryoung Square-Wave Voltammetry, and Differential Pulse Voltammetry. All redox-active platforms have been applied for immobilization of ssDNA probe. Next, their sensing properties towards complementary DNA target have been explored electrochemically. The results: All SAMs studied were stable displaying quasi-reversible redox activity. The linear relationships between cathodic and anodic current vs. san rate were obtained for both symmetric and asymmetric SAMs incorporating Co2+ and Cu2+, indicating that oxidized and reduced redox sites are adsorbed on the electrode surface. The ssDNA sensing ability were observed in the fM concentration range. The low responses towards non-complementary ssDNA sequences provided evidences for sensors good selectivity. The conclusions: All redox-active SAMs modified with a ssDNA probe were suitable for sensing of ssDNA target, with very good sensitivity in fM range and very good selectivity. The detection limits obtained for SAMs incorporating Cu2+, both symmetric and asymmetric, were better in comparison to SAMs incorporating Co2+. Thus, selection of the right transition metal cation has stronger influence on ssDNA sensing ability, than complex structures.

Analysis of the Kinetics of Devitrification and Crystallization of a Melilite Mold Powder Slag for Medium Carbon Steel Billet Casting

High-speed continuous casting of steel billets entails considerable turbulence in the liquid core, which results in significant slag entrapment unless high viscosity slags are used. It has been suggested that such slags remain glassy or crystallize slightly under the prevailing mold cooling, temperature and residence time conditions. Slags whose composition lead to formation of melilite minerals (i.e., to formation of calcium sodium magnesium aluminum iron disilicates), as the main crystalline phase, possess viscosities > 0.5 Pa/s at 1573 K (1300 °C), are low or do not contain F, and incorporate transition metal oxides (e.g., FeO, MnO and TiO) to absorb infrared radiation and soften steel shell-to-mold heat transfer. In this work, a commercial melilite mold powder, for casting medium carbon steels round billets, is selected to carry out detailed analysis of the kinetics of precipitation of crystalline phases from glassy—devitrification—and super-cooled liquid slags—crystallization—under non-isothermal and isothermal conditions. High-temperature confocal laser scanning microscopy is used in both cases and differential scanning calorimetry just in non-isothermal ones. Assessment of amorphous and crystalline phases in treated samples is done by quantitative X-ray powder diffraction analysis. It is found that even after prolonged treatment (» 36,000 seconds) at 1248 K (975 °C) approximately 13 wt pct of the slag remains amorphous. Additionally, the results indicate that nucleation of crystalline phases in super-cooled liquid and glassy slags occurs on the surface. Thus, it is found that crystallization kinetics is strongly influenced by the topography of the surface with which the super-cooled liquid is in contact, as well as, by shearing actions imposed on the liquid slag surface, which contribute by developing nucleation sites. Devitrification tends to be stronger on surfaces contacting foreign walls and over cracks. Moreover, it is found that predictions of the kinetic model, developed for estimating time–temperature–transformation diagrams from non-isothermal differential scanning calorimetry data, portray reasonably well experimental results of crystallization, as well as devitrification of consolidated samples.

Hollow bifunctionalized silica nanosphere as catalyst for the aerobic oxidation of cyclohexane with molecular oxygen

Hollow bifunctionalized silica nanosphere was prepared through a one-step reverse microemulsion method. Surface hydrophobicity or superhydrophobicity was obtained with the introduction of various organic groups on its surface, and the catalytic active sites were created with the incorporation of cobalt ions in the bulk phase of SiO2. At the same time, a hollow structure was constructed to facilitate the diffusion of the substrate and oxygenated products. With this hollow superhydrophobic bifunctionalized material as catalyst for the selective oxidation of inert cyclohexane using molecular oxygen, high catalytic activity was successfully obtained with a good selectivity to cyclohexanone and cyclohexanol under mild conditions. The results indicated the potential for intentional design of the catalytic environment at a nanometer level with the combination of transition metal incorporation, surface organic modification, and hollow structure construction.

Optical properties of CsPbCl3 nanocrystals in phosphate glass

CsPbCl3 nanocrystals embedded glasses have potential to incorporate transition metal ions and lead to efficient spectral conversion for applications as solar concentrator materials in building. Here, CsPbCl3 nanocrystals were precipitated through heat-treatment in phosphate glasses with potential application in building. X-ray diffraction patterns confirm that CsPbCl3 nanocrystals were formed in glasses. By changing the heat-treatment conditions, absorption peaks of the CsPbCl3 nanocrystals can be tuned from 3.06 eV (405 nm) to 3.25 eV (381 nm). Upon 255–325 nm UV light excitation, photoluminescence in the range of 350–530 nm was observed. Upon 325–375 nm UV light excitation, CsPbCl3 nanocrystals exhibited narrow band photoluminescence centering at 405–410 nm with Stokes shift almost linearly dependent on the band gap energy of CsPbCl3 nanocrystals.

Smart Control of Composition for Double Perovskite Electrocatalysts toward Enhanced Oxygen Evolution Reaction.

Double perovskites have emerged as efficient candidates for catalyzing the electrochemical oxygen evolution reaction (OER). Smart control of the composition of a B-site ordered double perovskite can lead to improved catalytic performance. By adopting a facile co-doping strategy, the OER-active elements are simultaneously introduced into the B-site and B'-site of a B-site-ordered double perovskite (A2 BB'O6 ), leading to an enhancement of the exposed reactive sites and an optimum surface chemical state. As a result, a model system built from the substitution of Co for Mo and Fe in the Sr2 FeMoO6-δ double perovskite (with a composition of Sr2 Fe0.8 Co0.2 Mo0.6 Co0.4 O6-δ ) shows significantly enhanced OER activity in alkaline media compared with the host material, requiring an overpotential of 345 mV to reach a 10 mA cm-2 current density (catalyst loading≈0.232 mgcat cm-2 GEO ) and a cell voltage of 1.57 V to afford the same current density for the overall water splitting when coupled with a Pt/C cathode (catalyst loading≈2 mg cm-2 ). It also demonstrates excellent electrochemical stability. The generalizability of the compositional control methodology has also been demonstrated in double perovskites incorporating transition metals other than Co (e.g., Ni).

Methane Decomposition Over Modified Carbon Fibers as Effective Catalysts for Hydrogen Production

Catalyzed thermal decomposition of methane to produce hydrogen was studied. The carbon microfibers with embedded Ni, Cu and Co metals and metal phosphides were introduced as the novel catalysts. The catalysts were prepared by needle-less electrospinning being a versatile method for fibers production in large scale. The efficiency of methane decomposition by utilization of micro fiber carbon supported metal catalysts was studied by the pyrolysis-capillary gas chromatography method. The experiment was carried out in the temperature range from 973.15 to 1073.15 K. Kinetic parameters were calculated based on the Demitcheli kinetic model. It was found that the morphology, schedule of heat treatment and type and content of incorporated transition metals and metal phosphides may be the controlling parameter in the catalytic decomposition of methane. The highest conversion rates about 54% were achieved using carbon microfibers doped with cobalt and cobalt phosphide nanoparticles. The catalyst was heat treated in argon atmosphere followed by the hydrogen reduction. The second highest conversion rates were achieved with carbon microfibers doped with nickel and nickel phosphide nanoparticles carbonized only under argon atmosphere.