Catalysts, Volume 7, Issue 12 (December 2017) – 41 articles

The iminodiacetic acid-modified Nieuwland catalyst not only improves the conversion of acetylene but also increases the selectivity of monovinylacetylene (MVA). A catalyst system containing 4.5% iminodiacetic acid exhibited excellent performance, and the yield of MVA was maintained at 32% after 24 h, producing an increase in the yield by 12% relative to the Nieuwland catalyst system. Based on a variety of characterization methods analysis of the crystal precipitated from the catalyst solution, it can be inferred that the outstanding performance and lifetime of the catalyst system was due to the presence of iminodiacetic acid, which increases the electron density of Cu⁺ and adjusts the acidity of the catalytic solution. Full article

The first steps of oseltamivir synthesis from quinic acid involve acetalization and ester formation. These reactions are catalyzed by either acids or bases, which may be accomplished by heterogeneous catalysts. Sulfonic solids are efficient acid catalysts for acetalization and esterification reactions. Supported tetraalkylammonium hydroxide or 1,5,7-triazabicyclo[4.4.0]dec-5-ene are also efficient base catalysts for lactone alcoholysis and in this work, these catalysts have been applied in two alternative synthetic routes that lead to oseltamivir. The classical route consists of an acetalization, followed by a lactonization, and then a lactone alcoholysis. This achieves a 66% isolated yield. The alternative route consists of esterification followed by acetalization and is only efficient when an acetone acetal is used. Full article

The synthesis of manganese lignosulfonates by a two-step method has been reported. It was based on the conversion of technical sodium derivative of lignosulfonate to its hydrogen form i.e., lignosulfonic acid and its further reaction with manganese hydroxide. The obtained product was electroactive, and could be applied as the precursor of electroactive manganese oxide. The product showed a reversible redox activity in the potential range of 0 to 1 V vs. an Ag/AgCl reference electrode. The electroactivity of the obtained product can be tentatively assigned to the redox activity of both the electrodeposited MnO_x and the presence of lignosulfonate-derived quinones since the energy dispersive spectroscopy (EDS) confirmed the presence of organic matter in the deposit. It also showed substantial electrocatalytic activity towards the anodic oxidation of hydrogen peroxide. This suggests that manganese lignosulfonates could be a valuable compound for the electrochemical preparation of electroactive layers that are suitable in the development of electrochemical sensors. Full article

Nanocomposites of highly reduced graphene oxide (HRG) and ZnO_x nanoparticles doped manganese carbonate containing different percentages of HRG were prepared via a facile co-precipitation method. The prepared sample calcined at 300 °C yielded i.e., ZnO_x(1%)–MnCO₃/(X%)HRG (where X = 0–7), calcination at 400 °C and 500 °C, yielded different manganese oxides i.e., ZnO_x(1%)–MnO₂/(X%)HRG and ZnO_x(1%)–Mn₂O₃/(X%)HRG respectively. The prepared catalyst were subjected to catalytic evaluation and a comparative catalytic study between carbonates and oxides for the liquid-phase aerobic oxidation of benzylic alcohols to corresponding aldehydes using molecular oxygen as an eco-friendly oxidant without adding additives or bases. The influence of various parameters such as percentage of HRG, reaction time, catalyst amount, calcination and reaction temperature was systematically examined to optimize reaction conditions using oxidation of benzyl alcohol as a substrate model. It was found that the catalytic performance is remarkably enhanced after using HRG as catalyst co-dopant for the aerobic oxidation of alcohols, possibly owing to the presence of carbon defects and oxygenated functional groups on HRG surface. The as-synthesized catalysts were characterized by SEM, EDX, XRD, Raman, TGA, BET, and FT-IR. Under optimal conditions, the catalyst with composition ZnO_x(1%)–MnCO₃/(1%)HRG calcined at 300 °C exhibited remarkable specific activity (57.1 mmol·g⁻¹·h⁻¹) with 100% conversion of benzyl alcohol and more than 99% product selectivity within extremely short time (7 min). The as-prepared catalyst was re-used up to five consecutive times without significant decrease in its activity and selectivity. To the best of our knowledge, the achieved specific activity is the highest so far compared to the earlier reported catalysts used for the benzyl alcohol oxidation. A wide range of substituted benzylic and aliphatic alcohols were selectively oxidized into their corresponding aldehydes with complete convertibility and selectivity in short reaction times without over-oxidation to the acids. Due to their significant low cost, superior reproducibility, excellent catalytic efficiency, the ZnO_x(1%)–MnCO₃/(X%)HRG nanocomposites possess several application prospect in other organic chemistry reactions. Full article

Copper containing silica nanostructures are easily produced through a low cost versatile approach by means of hyperbranched polyethyleneimine (PEI), a water soluble dendritic polymer. This dendritic molecule enables the formation of hybrid organic/inorganic silica nanoparticles in buffered aqueous media, at room temperature and neutral pH, through a biomimetic silicification process. Furthermore, the derived hybrid organic/inorganic materials dispersed in water can be easily loaded with various copper amounts, due to the presence of PEI, which, despite having been integrated in the silica network, retains its strong copper chelating ability. Following calcination, the obtained copper loaded nanopowders are characterized by X-ray diffraction (XRD), Scanning electron microscopy (SEM), N₂ adsorption, Temperature programmed reduction (TPR) and UV-Vis diffuse reflectance (UV-Vis-DR) techniques and evaluated for automotive exhaust purification under simulated conditions at the stoichiometric point. Effective control over final materials’ pore structural and morphological characteristics is provided by employing different buffer solutions, i.e., tris(hydroxymethyl)aminomethane (Tris) or phosphate buffer. It was found that the enhancement of the nanopowders textural features, obtained in the presence of Tris buffer, had a great impact on the material’s catalytic behavior, improving significantly its activity towards pollutants oxidation. Full article

Density functional theory (DFT) calculations have been used to investigate the behavior of different transition metals from Groups 8 (Fe and Ru) and 9 (Co and Rh) in an already well-known catalytic mechanism, which is based on an Ru(SIMes)(PPh₃)Cl₂=CH(Ph) complex. As expected, Ru has proven to perform better than their Fe, Co, and Rh counterparts. Even though the topographic steric maps analysis shows no difference in sterical hindrance for any of the metal centers, geometrically, the Fe-based species show a high rigidity with shorter and stronger bonds confirmed by Mayer Bond Orders. The systems bearing Co as a metallic center might present a reactivity that is, surprisingly, too high according to conceptual DFT, which would consequently be a drawback for the formation of the fundamental species of the reaction pathway: the metallacycle intermediate. Full article

Density Functional Theory (DFT) calculations have been carried out in order to unravel the governing reaction mechanism in copper-catalyzed cross-coupling Ullmann type reactions between iodobenzene (1, PhI) and aniline (2-NH, PhNH₂), phenol (2-O, PhOH) and thiophenol (2-S, PhSH) with phenanthroline (phen) as the ancillary ligand. Four different pathways for the mechanism were considered namely Oxidative Addition–Reductive Elimination (OA-RE), σ-bond Metathesis (MET), Single Electron Transfer (SET), and Halogen Atom Transfer (HAT). Our results suggest that the OA-RE route, involving Cu^III intermediates, is the energetically most favorable pathway for all the systems considered. Interestingly, the rate-determining step is the oxidative addition of the phenyl iodide to the metal center regardless of the nature of the heteroatom. The computed energy barriers in OA increase in the order O < S < NH. Using the Activation Strain Model (ASM) of chemical reactivity, it was found that the strain energy associated with the bending of the copper(I) complex controls the observed reactivity. Full article

In this study, we proposed an innovative oxidation–absorption method for low-temperature denitrification (160–240 °C), in which NO is initially catalytically oxidized by hydrogen peroxide (H₂O₂) vapor over titania-based catalysts, and the oxidation products are then absorbed by NaOH solution. The effects of flue gas temperature, molar H₂O₂/NO ratio, gas hourly space velocity (GHSV), and Fe substitution amounts of Fe/TiO₂ catalysts on the denitrification efficiency were investigated by a well-designed experiment. The results indicated that the Fe/TiO₂ catalyst exhibited a combination of remarkable activity and deep oxidation ability (NO converted into harmless NO₃⁻). In order to comprehend the functional mechanism of the Fe dopant’s local environment in TiO₂ support, the promotional effect of the calcination temperature of Fe/TiO₂ on the denitration performance was also studied. A tentative synergetic mechanism could be interpreted from two aspects: (1) Fe³⁺ as a substitute of Ti⁴⁺, leading to the formation of enriched oxygen vacancies at the surface, could significantly improve the adsorption efficiency of •OH; (2) the isolated surface Fe ion holds a strong adsorption affinity for NO, such that the adsorbed NO could be easily oxidized by the pre-formed •OH. This process offers a promising alternative for current denitrification technology. Full article

Copper nanoparticles/fluorine-doped tin oxide (FTO) nanocomposites were successfully prepared by a simple hydrothermal method. The synthesized nanocomposites were characterized by X-ray diffraction (XRD), UV-visible diffuse-reflectance spectrum (UV-VIS DRS), energy dispersive X-ray (EDX), transmission electron microscopy (TEM), Raman spectra, and X-ray photoelectron spectroscopy (XPS). The obtained Cu/FTO nanocomposites exhibit high photocatalytic activity for H₂ evolution under visible light (λ > 420 nm) irradiation. When the content of Cu is 19.2 wt % for FTO, the Cu/FTO photocatalyst shows the highest photocatalytic activity and the photocatalytic H₂ evolution rate is up to 11.22 μmol·h⁻¹. Meanwhile, the photocatalyst exhibits excellent stability and repeatability. It is revealed that the transfer efficiency of the photogenerated electrons is improved greatly because of the intense interaction between Cu NPs and FTO. Furthermore, a possible mechanism is proposed for enhanced photocatalytic H₂ evolution of Cu/FTO photocatalysts under visible light irradiation. Full article

Co₃O₄ particles were supported on a series of activated carbons (G60, CNR, RX3, and RB3). Incipient wetness method was used to prepare these catalysts. The effect of the structural and surface properties of the carbonaceous supports during oxidation of benzyl alcohol was evaluated. The synthetized catalysts were characterized via IR, TEM, TGA/MS, XRD, TPR, AAS, XPS, and N₂ adsorption/desorption isotherm techniques. Co₃O₄/G60 and Co₃O₄/RX3 catalysts have high activity and selectivity on the oxidation reaction reaching conversions above 90% after 6 h, without the presence of promoters. Catalytic performances show that differences in chemistry of support surface play an important role in activity and suggest that the presence of different ratios of species of cobalt and oxygenated groups on surface in Co₃O₄/G60 and Co₃O₄/RX3 catalysts, offered a larger effect synergic between both active phase and support increasing their catalytic activity when compared to the other tested catalysts. Full article

The hierarchical HZSM-5 zeolite was prepared successfully by a simple NaOH treatment method. The concentration of NaOH solution was carefully tuned to optimal the zeolite acidity and pore structure. Under NaOH treatment conditions, a large number of mesopores, which interconnected with the retained micropores, were created to facilitate mass transfer performance. There are very good correlations between the decline of the relative zeolite crystallinity and the loss of micropores volume. The Ni nanoclusters were uniformly confined in the mesopores of hierarchical HZSM-5 by the excessive impregnation method. The direct deoxygenation in N₂ and hydrodeoxygenation in H₂ of the methyl laurate were compared respectively over the Ni/HZSM-5 catalysts. In the N₂ atmosphere, the deoxygenation rate of the methyl laurate on the Ni/HZSM-5 catalyst is relatively slow. In the presence of H₂, the synergistic effect between the hydrogenation function of the metal and the acid function of the zeolite supports can make the deoxygenation level more obvious. The yield of hydrocarbon products gradually reached the maximum with the appropriate treatment concentration of 1M NaOH, which could be attributed to the improved mass transfer in the hierarchical HZSM-5 supports. Full article

In this work, Ag–Fe₂O₃ catalysts were successfully prepared using several different methods. Our main intention was to investigate the effect of the preparation methods on the catalysts’ structure and their catalytic performance for CO oxidation. The catalysts were characterized by X-ray diffraction (XRD), N₂ adsorption–desorption, transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), H₂-temperature program reduction (H₂-TPR) and inductively coupled plasma optical emission spectroscopy (ICP-OES). Ag–Fe catalysts prepared by impregnating Ag into MIL-100 (Fe) presented the best catalytic activity, over which CO could be completely oxidized at 160 °C. Based on the characterization, it was found that more metallic Ag species and porosity existed on Ag–Fe catalysts, which could efficiently absorb atmospheric oxygen and, thus, enhance the CO oxidation. Full article

Novel allyl cobalt complexes, i.e., (η³-C₄H₇)(η⁴-C₄H₆)Co(PCyPh₂) (1), (η³-C₄H₇)(η⁴-C₄H₆)Co(PMePh₂) (2) and (η³-C₅H₉)(η⁴-C₅H₈)Co(PMePh₂) (3), were synthesized by reacting CoCl₂(PRPh₂)₂ (R = methyl, cyclohexyl) with 1,3-butadiene or isoprene in presence of metallic zinc. The complexes were fully characterized by Nuclear Magnetic Resonance (NMR) spectroscopy (¹H and 2D experiments); in case of 1, single crystals, suitable for X-ray analysis, were obtained and the molecular structure was determined. The allyl cobalt phosphine complexes alone gave highly crystalline 1,2 polymers from 1,2-propadiene, but they did not polymerize 1,3-dienes. Nevertheless, in the presence of a stoichiometric amount of methylaluminoxane (MAO), they were able to polymerize 1,3-butadiene and substituted 1,3-butadienes such as isoprene, (E)-1,3-pentadiene, (E)-1,3-hexadiene, and (E)-3-methyl-1,3-pentadiene. Specifically, 1/MAO gave predominantly syndiotactic 1,2 polymers from 1,3-butadiene and terminally substituted 1,3-butadienes (e.g., 1,3-pentadiene and 1,3-hexadiene), but it was practically not active in the polymerization of internally substituted 1,3-butadienes (e.g., isoprene and 3-methyl-1,3-pentadiene); 2/MAO and 3/MAO exhibited instead an opposite behavior, giving predominantly isotactic 1,2 polymers from 3-methyl-1,3-pentadiene, and showing very low activity in the polymerization of 1,3-butadiene, 1,3-pentadiene and 1,3-hexadiene. The results obtained are interesting from the mechanistic point of view, and some hypotheses to explain this particular behavior were formulated. Full article

This review focuses on recent advances in the field of direct carboxylation reactions of C(sp³)-H and C(sp²)-H bonds using CO₂ encompassing both transition-metal-catalysis and base-mediated approach. The review is not intended to be comprehensive, but aims to analyze representative examples from the literature, including transition-metal catalyzed carboxylation of benzylic and allylic C(sp³)-H functionalities using CO₂ which is at a “nascent stage”. Examples of light-driven carboxylation reactions of unactivated C(sp³)-H bonds are also considered. Concerning C(sp³)-H and C(sp²)-H deprotonation reactions mediated by bases with subsequent carboxylation of the carbon nucleophile, few examples of catalytic processes are reported in the literature. In spite of this, several examples of base-promoted reactions integrating “base recycling” or “base regeneration (through electrosynthesis)” steps have been reported. Representative examples of synthetically efficient, base-promoted processes are included in the review. Full article

Ag₄Bi₂O₅/MnO₂ nano-sized material was synthesized by a co-precipitation method in concentrated KOH solution. The morphology characterization indicates that MnO₂ nanoparticles with a size of 20 nm are precipitated on the surface of nano Ag₄Bi₂O₅, forming a structure like corn on the cob. The obtained material with 60% Mn offers slightly higher initial potential (0.098 V vs. Hg/HgO) and limiting current density (−5.67 mA cm⁻²) at a rotating speed of 1600 rpm compared to commercial Pt/C (−0.047 V and −5.35 mA cm⁻², respectively). Furthermore, the obtained material exhibits superior long-term durability and stronger methanol tolerance than commercial Pt/C. The remarkable features suggest that the Ag₄Bi₂O₅/MnO₂ nano-material is a very promising oxygen reduction reaction catalyst. Full article

Single-layer, ultrasmall ReS₂ nanoplates embedded in amorphous carbon were synthesized from a hydrothermal treatment involving ammonium perrhenate, thiourea, tetraoctylammonium bromide, and further annealing. The rhenium disulfide, obtained as a low dimensional carbon composite (ReS₂/C), was tested in the hydrodesulfurization of light hydrocarbons, using 3-methylthiophene as the model molecule, and showed enhanced catalytic activity in comparison with a sulfide CoMo/γ-Al₂O₃ catalyst. The ReS₂/C composite was characterized by X-ray diffraction (XRD), Raman spectroscopy, N₂ adsorption–desorption isotherms, scanning electron microscopy (SEM), scanning transmission electron microscopy (STEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS). The improved catalytic performance of this ReS₂/C composite may be ascribed to the presence of a non-stoichiometric sulfur species (ReS_2−x), the absence of stacking along the c-axis, and the ultra-small basal planes, which offer a higher proportion of structural sulfur defects at the edge of the layers, known as a critical parameter for hydrodesulfurization catalytic processes. Full article

Nitrogen doping in combination with the brookite phase or a mixture of TiO₂ polymorphs nanomaterials can enhance photocatalytic activity under visible light. Generally, nitrogen-dopedanatase/brookite mixed phases TiO₂ nanoparticles obtained by hydrothermal or solvothermal method need to be at high temperature and with long time heating treatment. Furthermore, the surface areas of them are low (<125 m²/g). There is hardly a report on the simple and direct preparation of N-doped anatase/brookite mixed phase TiO₂ nanostructures using sol-gel method at low heating temperature. In this paper, the nitrogen-doped anatase/brookite biphasic nanoparticles with large surface area (240 m²/g) were successfully prepared using sol-gel method at low temperature (165 °C), and with short heating time (4 h) under autogenous pressure. The obtained sample without subsequent annealing at elevated temperatures showed enhanced photocatalytic efficiency for the degradation of methyl orange (MO) with 4.2-, 9.6-, and 7.5-fold visible light activities compared to P25 and the amorphous samples heated in muffle furnace with air or in tube furnace with a flow of nitrogen at 165 °C, respectively. This result was attributed to the synergistic effects of nitrogen doping, mixed crystalline phases, and high surface area. Full article

Development of inexpensive and robust electrocatalysts towards oxygen reduction reaction (ORR) is crucial for the cost-affordable manufacturing of metal-air batteries and fuel cells. Here we show that cross-linked CoMoO₄ nanosheets and reduced graphene oxide (CoMoO₄/rGO) can be integrated in a hybrid material under one-pot hydrothermal conditions, yielding a composite material with promising catalytic activity for oxygen reduction reaction (ORR). Cyclic voltammetry (CV) and linear sweep voltammetry (LSV) were used to investigate the efficiency of the fabricated CoMoO₄/rGO catalyst towards ORR in alkaline conditions. The CoMoO₄/rGO composite revealed the main reduction peak and onset potential centered at 0.78 and 0.89 V (vs. RHE), respectively. This study shows that the CoMoO₄/rGO composite is a highly promising catalyst for the ORR under alkaline conditions, and potential noble metal replacement cathode in fuel cells and metal-air batteries. Full article

Cellulase from Aspergillus niger was immobilized on a synthesized TiO₂–lignin hybrid support. The enzyme was effectively deposited on the inorganic–organic hybrid matrix, mainly via physical interactions. The optimal initial immobilization parameters, selected for the highest relative activity, were pH 5.0, 6 h process duration, and an enzyme solution concentration of 5 mg/mL. Moreover, the effects of pH, temperature, and number of consecutive catalytic cycles and the storage stability of free and immobilized cellulase were evaluated and compared. Thermal and chemical stability were significantly improved, while after 3 h at a temperature of 50 °C and pH 6.0, the immobilized cellulase retained over 80% of its initial activity. In addition, the half-life of the immobilized cellulase (307 min) was five times that of the free enzyme (63 min). After ten repeated catalytic cycles, the immobilized biocatalyst retained over 90% of its initial catalytic properties. This study presents a protocol for the production of highly stable and reusable biocatalytic systems for practical application in the hydrolysis of cellulose. Full article

Global climate change and increasing demands for clean energy have brought intensive interest in the search for proper electrocatalysts in order to reduce carbon dioxide (CO₂) to higher value carbon products such as hydrocarbons. Recently, transition-metal-centered molecules or organic frameworks have been reported to show outstanding electrocatalytic activity in the liquid phase. Their d-orbital electrons are believed to be one of the key factors to capture and convert CO₂ molecules to value-added low-carbon fuels. In this review, recent advances in electrocatalytic CO₂ reduction have been summarized based on the targeted products, ranging from homogeneous reactions to heterogeneous ones. Their advantages and fallbacks have been pointed out and the existing challenges, especially with respect to the practical and industrial application are addressed. Full article

The nanostructure of β-gallium oxide crystals influences the conversion to carbamates; specifically, for the synthesis of alkyl carbamates (like propyl N-octylcarbamate) from CO₂ and n-propanol in the absence of phosgene. The nanostructures with variable aspect ratios (length (L)/width (D); from 2 to 18) were prepared by the controlled addition of neutral and cationic surfactants during gallium oxide synthesis. These catalysts displayed selectivities to the corresponding carbamates as high as ~70%, superior to non-nanostructured Ga₂O₃ catalysts. The conversion was found to be inversely proportional to the square of the relative crystallinity. The catalysts retained their structure and catalytic performance upon recycling. Full article

Although Si nanowires (NWs) arrays are superior candidates for visible light photocatalysis, reports about the photodegradation activity of various crystal-orientated Si NWs are still insufficient. Here, light-doped hydrogen-terminated Si NWs arrays with different crystal orientations were prepared via a metal-assisted chemical etching method (MACE), which simply modulated the concentration of the oxidizer, H₂O₂. Their dye photodegradation activities were systematically and comprehensively investigated. When compared with Si NWs arrays with crystal orientations of (110) and (111), Si NWs arrays with (100) crystal orientation exhibit a superior photodegradation activity and stability due to the anisotropy of optical and physical properties. The n-type Si NWs arrays exhibit better photodegradation activity than the p-type Si NWs arrays of the same crystal orientation and similar length. The results provide a further understanding of the synthesis of Si NWs arrays with various orientations, and the relationships between photodegradation activity/stability and crystal orientations. Full article

ZSM-5 zeolite is widely used in catalytic cracking of hydrocarbon, but the conventional ZSM-5 zeolite deactivates quickly due to its simple microporous and long diffusion pathway. Many studies have been done to overcome these disadvantages recently. In this review, four main approaches for enhancing the catalytic performance, namely synthesis of ZSM-5 zeolite with special morphology, hierarchical ZSM-5 zeolite, nano-sized ZSM-5 zeolite and optimization of acid properties, are discussed. ZSM-5 with special morphology such as hollow, composite and nanosheet structure can effectively increase the diffusion efficiency and accessibility of acid sites, giving high catalytic activity. The accessibility of acid sites and diffusion efficiency can also be enhanced by introducing additional mesopores or macropores. By decreasing the crystal size to nanoscale, the diffusion length can be shortened. The catalytic activity increases and the amount of carbon deposition decreases with the decrease of crystal size. By regulating the acid properties of ZSM-5 with element or compound modification, the overreaction of reactants and formation of carbon deposition could be suppressed, thus enhancing the catalytic activity and light alkene selectivity. Besides, some future needs and perspectives of ZSM-5 with excellent cracking activity are addressed for researchers’ consideration. Full article

A series of vanadium(III) complexes bearing monodentate tertiary phosphine ligands of the type VCl₃(PR_nPh_3-n)₂ (n = 0 (1a); n = 1 and R = Me (1b), Et (1c), ⁱPr (1d), Cy (1e); n = 2 and R = Me (1f), Et (1g), Cy (1h)), and VCl₃(PR₃)₂ (R = Cyp (2a), Cy (2b), ⁿPr (2c), ^tBu (2d)) were synthesized and characterized. In the case of 1c, 1g and 2a single crystals were also obtained and their molecular structures were determined. All the complexes were used, in combination with methylaluminoxane (sMAO) or AlMe₃–free MAO (dMAO), for the polymerization of 1,3-butadiene, exhibiting rather good activity and giving polymers with different microstructure depending on the nature of the phosphine ligand and the type of co-catalyst employed. Full article

Novel NiO/GDC (Gadolinium-doped Ceria) cermet catalysts were developed by the Weak Acid Resin (WAR) method using an ion exchange resin template. In addition, the specific surface area of these tunable materials was enhanced by NiO partial dissolution in aqueous acid solution. The whole procedure highly improved the micro-structural properties of these materials compared to previous studies. Catalysts with high metal loadings (≥10%), small Ni nanoparticles (<10 nm), and high specific surface areas (>70 m²/g) were achieved. These properties are promising for catalytic applications such as methane steam reforming for H₂ production. Full article

The development of cheap and efficient catalytic electrodes is of great importance, to promote the sluggish overall water-splitting systems associated with the large-scale application of clean and renewable energy technologies. In this work, we report the controlled synthesis of pyrite-type bimetallic Ni-doped CoS₂ nanoneedle (NN) arrays supported on stainless steel (SS) (designated as Ni_xCo_1−xS₂ NN/SS, 0 ≤ x ≤ 1) and the related compositional influence on electrocatalytic efficiencies for the oxygen and hydrogen evolution reaction (OER/HER). Impressively, the Ni_0.33Co_0.67S₂ NN/SS displays superior activity and faster kinetics for catalyzing OER (low overpotential of 286 mV at 50 mA cm⁻²; Tafel value of 55 mV dec⁻¹) and HER (low overpotential of 350 mV at 30 mA cm⁻²; Tafel value of 76 mV dec⁻¹) than those of counterparts with other Ni/Co ratios and also monometallic Ni- or Co-based sulfides, which is attributed to the optimized balance from the improved electron transfer capability, increased exposure of electrocatalytic active sites, and favorable dissipation of gaseous products over the nanoneedle surface. Furthermore, the conductive, flexible SS support and firmly attached in-situ integrated feature, result in the flexibility and remarkable long-term stability of as-prepared binder-free Ni_0.33Co_0.67S₂ NN/SS electrode. These results demonstrate element-doping could be an efficient route at the atomic level to design new materials and further optimize the surface physicochemical properties for enhancing the overall electrochemical water splitting activity. Full article

Ene-yne cross-metathesis from alkynes and ethylene is a useful method to produce substituted conjugated butadiene derivatives. If this method has been used with aliphatic alkynes, it has however never been used starting from diarylacetylenes as internal alkynes. We show that the ene-yne cross-metathesis catalyzed by the second generation Hoveyda ruthenium catalyst provides the 2,3-diarylbuta-1,3-dienes under 3 atm of ethylene at 100 °C. The scope and limitations of the reaction have been evaluated starting from unsymmetrical functionalized diarylacetylene derivatives hence leading to unsymmetrical 2,3-diarylbuta-1,3-dienes in a straightforward and environmentally acceptable manner. Full article