Mechanism Of Catalyst Formation Research Articles

Surface morphology and interface electronic structure tailoring of cobalt carbonate hydroxide via Ce doping for enhanced oxygen evolution reaction

As a high-quality green and clean energy source, hydrogen is produced from electrochemical water splitting. The superior activity is significant for the non-precious-metal electrocatalyst in water electrolysis process. Herein, cerium-doped cobalt carbonate hydroxide nanohybrids on nickel foam (Co2CexCH/NF) have been synthesized by a one-step hydrothermal method. The cobalt carbonate hydroxide (CoCH)/cerium fluoride (CeF3) heterostructure preparation was achieved and characterized by physical and chemical characterization. The doping of cerium facilitates nucleation, resulting in a unique hierarchical morphology that exposes more active sites. And the mechanism of catalyst formation was investigated. Tailoring the electronic structure of the cobalt active center and producing the layered nanowire array/flower-like ball structure is favorable to enhance the oxygen evolution activity of the Co2Ce0.06CH/NF electrocatalyst. In 1.0 M KOH, the Co2Ce0.06CH/NF electrocatalyst presents efficient OER activity with a lower onset potential of 1.48 V vs. RHE during the electrochemical water splitting and an overpotential of only 304 mV at a current density of 100 mA cm−2. Besides, the Co2Ce0.06CH/NF electrocatalyst exhibits a Tafel slope of 81 mV dec−1 as well as good stability and durability. This research offers a possible method for the design and synthesis of OER catalysts.

Bi2S3 nanoribbons-hybridized {001} facets exposed Bi2WO6 ultrathin nanosheets with enhanced visible light photocatalytic activity

Bi2S3 nanoribbons were dispersed in situ on Bi2WO6 ultrathin nanosheets with exposed {001} facet via a simple one-set hydrothermal route forming Bi2S3/Bi2WO6 heterojunctions with high active surface, in which the quantity of Bi2S3 nanoribbons was tuned by changing the amount of thiourea in solution. The obtained composites were characterized by various measurements and their photocatalytic activities under visible-light irradiation were also investigated. The 7%-Bi2S3/Bi2WO6 nanocomposites exhibited excellent photocatalytic activities in degradation of ofloxacin (OFL). A plausible degradation pathway for OFL was proposed via combining LC-MS and GC–MS detections with Gaussian calculations. The probable photocatalytic and formation mechanism of catalysts were discussed on the basis of the obtained experimental results and density function theory (DFT) calculations. An enhanced photocatalytic mechanism attributed to the synergistic effect between the exposed {001} facet and heterojunction with shape-crystalline integrity, significantly improving band structure and visible light absorption, increasing reactive sites, and suppressing the recombination of charges. The findings provide new insights for designing highly active and stable heterojunction catalysts to remove environmental pollutants and promote solar energy conversion efficiently.

Structured Au/FeO x/C Catalysts for Low-Temperature CO Oxidation

Innovative structured catalysts based on nanoparticles of gold supported on activated carbon fibers (ACF) in the form of woven fabrics are presented for low-temperature CO oxidation. Gold was deposited by adsorption from aqueous solution of ethylenediamine complex [Au(en) 2]Cl 3 followed by reduction in hydrogen. The catalysts were studied under transient reaction conditions and characterized by high-resolution transmission electron microscopy (HRTEM) and X-ray energy dispersive analysis (EDS). HRTEM-EDS shows that gold is present on the surface of Au/ACF catalyst in the form of metallic particles with sizes of ∼2.5–5 and ∼30–50 nm. A predeposition of iron oxide on the ACF was beneficial for the Au dispersion and catalytic activity in CO oxidation. Gold particles in the Au/FeO x /ACF samples were not in direct contact with the Fe 2O 3 phase and their size was smaller than without doping by iron oxide. The mechanism of catalyst formation, its morphology, and the influence of preparative conditions are discussed. The activity of Au/FeO x /ACF was substantially higher as compared to Au/Al 2O 3 and Au/FeO x /Al 2O 3 catalysts. A reductive pretreatment with H 2 was necessary to activate the catalyst, but the activity decreased rapidly in CO/O 2 atmosphere. Addition of hydrogen or water vapors to the reaction mixture increases the catalyst activity.

The development of a novel range of metal—carbon catalysts

This paper describes a new range of metal-carbon catalysts which consist of a three dimensional array of small metal particles dispersed throughout the bulk of a carbon matrix. This structure confers a number of potential advantages over conventional metal-carbon systems. The mechanism of catalyst formation has been studied and ESR has been used to characterise the copper-carbon precursor which determines the physical nature of the final catalyst. The activation of the carbon matrix of the copper-carbon catalysts has been optimised in a series of statistically designed experiments. The materials have been characterised by AA, XRD and SEM. Measurements have been made of metal particle size and area, total surface area and pore volume. Catalytic activity has been assessed using a model reaction.

ChemInform Abstract: Pd+2/Poly(acrylic acid) Thin Films as Catalysts for Electroless Copper Decomposition: Mechanism of Catalyst Formation.

AbstractIn the described method for the initiation of the electroless Cu deposition onto dieletric substrates, the substrate is coated with a poly(acrylic acid) film by dipping, followed by immersion in 0.1 M PdSO4 solution.

Pd+2/Poly(acrylic acid) Thin Films as Catalysts for Electroless Copper Deposition: Mechanism of Catalyst Formation

The mechanism involved in the initiation of electroless copper deposition onto dielectric substrates using Pd+2/ poly(acrylic acid) thin films is described. Dielectric substrates are catalyzed by dip‐coating in aqueous poly(acrylic acid) to deposit a 50–300 nm thick film of the polymer on the surface; the coated substrate is then immersed in aqueous . It is shown that uptake of palladium in the poly(acrylic acid) film occurs by H+/Pd+2 ion exchange. The active catalyst is identified by x‐ray photoelectron spectroscopy as zerovalent palladium, formed when the Pd+2‐exchanged polymer film is immersed in an electroless copper deposition bath.

The mechanism of catalyst formation from tungsten hexachloride and cocatalyst in olefin metathesis

The mechanism of the catalyst formation in hept-2-ene metathesis was investigated by gas chromatographic analysis of the products from reactions of tungsten hexachloride with R4Sn(R = Ph, n-Bu), RLi, RMgl (R = n-Bu) or R3Al(R = Et) as cocatalyst. The products are chiefly RH, RCl and RR species, and the highest catalytic activity is observed for an equimolar ratio of products to tungsten hexachloride. The facts suggested that the active catalyst, a WCl4 species, is formed by the elimination of two R groups from R2WCl4 and/or one R group and chlorine from RWCl5. The total quantity and composition of the products varies with the cocatalyst:WCl6 ratio, and the difference between the behavior of tetra-n-butylstannane and n-butyllithium in the catalyst formation is explainable on the basis of their relative nucleophilicities. Gas chromatographic analysis of the organotin compounds resulting from the WCl6:: Bu4Sn system shows that tetra-n-butylstannane provides only one butyl group per mole of WCl6.