Search

In this study, a piece of filter paper with good flexibility and hygroscopicity was used to support catalysts after a pencil drawing process. A layer of thin Ni film was deposited on the surface of the conductive graphite layer using an electrochemical method at a negative potential. Pd nanoparticles with high electrocatalytic activity for NaBH4 oxidation were introduced by immersing the Ni film-graphite-filter paper (NGF) in PdCl2 solution to obtain a Pd-NGF (PNGF) electrode. The morphology and phase structure of PNGF were characterized using scanning electron microscopy (SEM) equipped with an energy dispersive X-ray spectrometer (EDS), transmission electron microscopy (TEM) and an X-ray diffractometer (XRD). The PNGF electrode was used as the anode in direct borohydride fuel cells (DBFCs), and the electrochemical properties for NaBH4 oxidation were determined by cyclic voltammetry (CV), chronoamperometry (CA) and electrochemical impedance spectroscopy (EIS). The oxidation current density reaches 550 mA cm−2 at −0.4 V when the electrolyte contains 2 mol dm−3 NaOH and 0.10 mol dm−3 NaBH4. [ABSTRACT FROM AUTHOR]

A scalable, and cost-effective method was employed to prepare self-supported CuSn bimetallic catalyst on carbon paper. The obtained CuSn catalyst demonstrates high faradaic efficiency of CO around or above 90% at a broad potential range from −0.7 to −1.8 V vs. reversible hydrogen electrode, greatly surpassing Cu or Sn counterparts. [ABSTRACT FROM AUTHOR]

CuO/CeO2 catalysts were widely studied as an alternative to precious metal catalysts, and the Cu–Ce synergy was essential to improve the catalytic performance. In this paper, the effects of CuO loading on Cu–Ce synergy in CuO/CeO2 nanorod catalysts and their performance in toluene combustion were systematically investigated. It was found that non-equilibrium plasma facilitated the dispersion of CuO active species on the CeO2 surface. With the increase of the CuO loading from 1 wt% to 4 wt%, the Cu–Ce synergistic effect was gradually improved, which generated Cu+/Cu2+ and Ce3+/Ce4+ redox electron pairs. The highest oxygen vacancy concentration and Cu+ content of CuCe-4 (4 wt%) resulting from strong Cu–Ce synergy accelerated the activation of chemisorbed oxygen and consequently improved the efficiency of toluene catalytic combustion. [ABSTRACT FROM AUTHOR]

In this paper, we compare the reactivity of a series of triaryl borates B(OArx)3 as catalysts for the hydroboration of alkenes and alkynes. It was observed that commercially available B(OPh)3 performed the poorest, whereas catalysts with o-F atoms appeared to perform much better. [ABSTRACT FROM AUTHOR]

Developing high-efficiency electrocatalysts for the hydrogen evolution reaction (HER) is of great importance. In this paper, dendrite-free Ni–Cu catalysts were synthesised via one-step pulse electrodeposition under a weak magnetic field (0.5 T). Regardless of the direction of the magnetic field, the ions were affected by the magnetohydrodynamic (MHD) effect, which greatly promoted the mass transfer and dispersion uniformity, and suppressed the uncontrollable agglomeration by electrodeposition. It was found that the nucleation mechanism changed from progressive nucleation under a 0 T magnetic field to instantaneous nucleation under a 0.5 T magnetic field. Large-scale (325 nm, 0 T) dendrite growth on the single-sided plane was successfully suppressed, and replaced by smaller (90 nm, 0.5 T) and uniformly distributed cluster growth around the carbon paper. In addition, the (111) plane was strengthened by the magnetic field. Electrochemical analysis showed that the Ni–Cu catalysts exposed more surface area and exhibited greatly enhanced catalytic activity, which only needed −57.3 mV to deliver the current density of 10 mA cm−2 with a small Tafel slope of 99.4 mV dec−1 in 1 M KOH. Overall, magneto-electrodeposition, especially under weak magnetic field conditions, provides great promise for the preparation of HER catalysts. [ABSTRACT FROM AUTHOR]

Chiral Ph-dbfox (Ph-dbfox = (R,R)-4,6-dibenzofurandiyl-2,2′-bis(4-phenyloxazoline))/Zn(NTf2)2catalyzed enantioselective Friedel–Crafts reactions of β-CF3acrylates with pyrroles and indoles have been investigated, which afforded the corresponding chiral trifluoromethyl pyrrole and indole derivatives in high yields (90–99%) with a range of 66–99% ee values. With the aid of the chiral adduct of the asymmetric Friedel–Crafts reaction, the chiral trifluoromethylated heliotridane has been successfully constructed in good total yield. [ABSTRACT FROM AUTHOR]

The ruthenium catalysed cross-metathesis of terpenoids with methyl acrylate and methyl methacrylate was used to prepare new terpenoids and to improve, to a large extent, the synthesis of known terpenoids. In particular, the cross-metathesis of mono-unsaturated terpenoids was very efficient whereas the transformation of terpenoids incorporating two double bonds was more difficult due to side reactions. The cross-metathesis reactions were carried out under environmentally friendly conditions either in dimethyl carbonate or under solvent-free conditions. [ABSTRACT FROM AUTHOR]

“The best catalyst is no catalyst.” With growing public concern over global warming and the amount of greenhouse gases, it is important to reduce the amount of chemicals and eliminate waste, to obtain better results in a simple, selective, safe, and environmentally benign fashion compared to conventional tedious chemical synthesis. Herein, we disclose an environmentally benign, rapid, catalyst/promoter/coupling reagent-free cyclization procedure of free amino acids to furnish exclusively cyclic dipeptides (2,5-diketopiperazines, DKPs) in excellent or even quantitative yield, along with their solid state self-assembling properties. This process is extremely simple and highly efficient with little or no traditional synthetic skills and without any chromatographic purification. Synthesis of structurally diverse DKPs has been achieved with a dramatic decrease in the reaction time, the amount/number of solvents used, a significant increase in the yield and nearly complete elimination of waste. As a result, this is an excellent example for the environmentally benign, clean and green chemistry concept. The most exciting outcome of our investigation is an unusual case of chiral self-recognition encountered upon the cyclization of rac-pipecolic acid, which resulted in the formation of the meso-product exclusively. [ABSTRACT FROM AUTHOR]

Covering: 2007 to 2009 [ABSTRACT FROM AUTHOR]

The use of quasi-enantiomeric substrates and ESI-MS as an analytical tool has made it possible to determine the intrinsic enantioselectivity of chiral catalysts by monitoring catalytic intermediates. In this way, potential problems of methods based on product analysis, which may be caused by catalytically active impurities, partial dissociation of a chiral ligand–metal complex, or a non-catalytic background reaction can be avoided. ESI-MS-based screening is fast, reliable, and operationally simple, as it does not require work-up or purification steps. Moreover, mixtures of catalysts with different molecular masses can be screened simultaneously, which is not possible with methods relying on product analysis. In this way catalyst libraries prepared in one batch by combinatorial methods can be screened without the need to synthesize and purify the catalysts individually. This screening method was successfully applied to Pd-catalyzed allylic substitutions and metal-catalyzed and organocatalytic Diels–Alder reactions. [ABSTRACT FROM AUTHOR]

Selective oxidation of tetralin by molecular oxygen over mesoporous CrMCM-41 molecular sieve catalyst using supercritical carbon dioxide (scCO2) solvent has been investigated. CrMCM-41 catalyst gave high selectivity (96.2%) and good yield (63.4%) of 1-tetralone. The presence of scCO2medium improves 1-tetralone selectivity and suppresses leaching of chromium from the CrMCM-41. The activity over recycled CrMCM-41 remains nearly the same under the present experimental conditions. The effect of the reaction parameters on CrMCM-41 was also studied in detail along with comparison of its catalytic activities with other mesoporous catalysts, viz.MnMCM-41, CoMCM-41, microporous CrAPO-5, CoMFI, and macroporous Cr/SiO2catalyst, respectively. In addition this catalytic system was also applied for the oxidation of other benzylic compounds such as indane, fluorene, acenaphthene and diphenylmethane. [ABSTRACT FROM AUTHOR]

Methyltrioxorhenium(VII) (MTO) is a widely employed catalyst for metathesis, olefination, and most importantly, oxidation reactions. It is often preferred to other oxometal complexes due to its stability in air and higher efficiency. The seminal papers of K. B. Sharpless showed that when pyridine derivatives are used as co-catalysts, MTO-catalyzed olefin epoxidation with H2O2 as oxidant, a particularly useful reaction, is accelerated, with pyridine speeding up catalytic turnover and increasing the lifetime of MTO under the reaction conditions. In this paper, combined experimental and theoretical results show that the occurrence of σ-hole interactions in catalytic systems extends to MTO. Four crystalline adducts between MTO and aliphatic and heteroaromatic bases are obtained, and their X-ray analyses display short Re⋯N/O contacts opposite to both O–Re and C–Re covalent bonds with geometries consistent with σ-hole interactions. Computational analyses support the attractive nature of these close contacts and confirm that their features are typical of σ-hole interactions. The understanding of the nature of Re⋯N/O interactions may help to optimize the ligand-acceleration effect of pyridine in the epoxidation of olefins under MTO catalysis. [ABSTRACT FROM AUTHOR]

Chemical catalytic conversion of biomass-derived sugars to lactic acid has attracted considerable attention due to the cheap, abundant and renewable nature of biomass and its huge potential application in the synthesis of biocompatible and biodegradable polylactic acid resins. However, this route is still a huge challenge in view of the transformation efficiency. This paper reports a series of Zn-based catalysts, which are facile and cheap to prepare and highly efficient for the conversion of biomass-derived carbohydrates to ethyl lactate (EL). The microstructure, active site composition and surface properties were characterized by TEM, HRTEM, XRD, NH3-TPD, CO2-TPD, Py-IR, and XPS. The catalytic performance of catalysts in the conversion of biomass-derived carbohydrates to ethyl lactate (EL) and the effect of water content were investigated. It was found that the Zn species played a decisive role in regulating the strengths of the acidic and basic sites to match the rate of each reaction in the tandem reactions. The basic sites are beneficial for isomerization and retro-aldol condensation, while the temperature-responsive released H+ protons are responsible for the dehydration of triose to methylglyoxal, a rate-determining step in the conversion of triose to EL. Addition of a small amount of water could enhance the release of the protons and thus accelerate the dehydration reaction, but excessive water would favor the formation of humins. Using ZnSi-2 as a catalyst under optimal conditions, yields as high as 74.5% of EL from glucose, 81.0% from fructose, 70.9% from mannose, and 80.3% from sucrose could be achieved with tens of times higher productivity than the previously reported values in the literature. DFT calculations revealed that Zn(OEt)Cl, Zn(OH)Cl, and Zn(OH)(OEt) were probably the active components. In addition, the stability of the catalyst as well as the deactivation and regeneration was also studied. The findings in this research provide new insights into the exploration of efficient catalysts for biomass conversion to value-added chemicals. [ABSTRACT FROM AUTHOR]

The development of efficient and stable non-precious-metal-based electrocatalysts is essential for practical water splitting applications. The electrolysis of water for hydrogen production is a green and efficient method, while urea electrolysis can improve energy conversion efficiency. In this paper, W–Ni3S2/NiS catalysts with heterogeneous structures were synthesized via a one-step hydrothermal method using a W-doping-induced phase transition strategy. The doping of W modulates the morphology of the catalyst, which can form uniform nanorod arrays and improve the activity of the electrocatalyst. In an alkaline solution of 1 M KOH and 0.5 M urea, W–Ni3S2/NiS requires a potential of only 1.309 V to achieve a current density of 10 mA cm−2. An electrolyzer containing urea with W–Ni3S2/NiS as both the cathode and anode can drive a current density of 10 mA cm−2 with a potential of only 1.569 V and has relatively good stability after testing for 20 h. Experimental results show that the improvement in the catalytic activity is due to the rapid charge transfer, exposure of more active sites and better conductivity. Density functional theory calculations show that the W–Ni3S2 material exhibits higher urea adsorption energy, indicating that urea is preferentially adsorbed on its surface. The NiS material shows more state density near the Fermi level, indicating that the introduction of this material enhances the conductivity of the W–Ni3S2/NiS material. The synergistic catalysis of the two materials promoted the improvement of the catalytic activity. This work provides new ideas for the development of highly efficient and stable catalysts by means of doping and interface construction. [ABSTRACT FROM AUTHOR]

Fe, N co-doped carbon electrocatalyst is one of the most attractive alternatives to Pt/C catalysts due to its high catalytic activity, excellent stability and low cost. However, obtaining stable and efficient Fe, N co-doped carbon oxygen reduction reaction (ORR) catalysts based on simple processes is still a challenge. Herein, Fe, N co-doped porous carbon (Fe–N–C) with an open macroporous frame structure is prepared by using inorganic molten salts (FeCl3·6H2O and ZnCl2) and ethylenediaminetetraacetic acid as the template and nitrogen-containing carbon precursor, respectively. The open pore structure of the Fe–N–C material precisely tailored with the inorganic molten salt template exhibits high specific surface area (676.5 m2 g−1) and appropriate pore size, which can promote oxygen adsorption and expand the oxygen reduction interface, resulting in the acceleration of the electron/charge transfer processes and an improved electrocatalytic performance. The optimized Fe3–N–C-800 electrocatalyst exhibits good catalytic activity for ORR, such as high onset potential of 0.998 V and half wave potential of 0.84 V in alkaline media, as well as high stability and methanol tolerance. Furthermore, a novel Zn–air battery assembled with carbon paper containing Fe3–N–C-800 electrocatalyst as air cathode shows high open-circuit voltage (1.485 V), high specific capacity (870 mA h g−1 at 10 mA cm−2), excellent reversibility and stability. The proposed synthetic strategy provides new opportunities to design and construct carbon frame materials with the desired open macroporous structure to improve their electrocatalytic performance. [ABSTRACT FROM AUTHOR]

We report on the activity of fullerene-supported OsO4catalysts in the achiral dihydroxylation of olefins using N-methylmorpholine N-oxide as co-oxidant. The fullerene-supported OsO4catalysts can selectively dihydroxylate olefins with conversions up to 95% after 48 h without leaching, and the catalysts can be recovered and recycled several times. [ABSTRACT FROM AUTHOR]

Chiral bifunctional phase transfer catalysts introducing bis(diarylhydroxymethyl) substituents at 3,3′-positions of the chiral binaphthyl core were successfully applied to asymmetric fluorination of cyclic β-keto esters with high enantioselectivities. [ABSTRACT FROM AUTHOR]

A homodinuclear Ni2-Schiff base 1complex (0.1–1 mol%) promoted the direct catalytic asymmetric aldol reaction of β-keto esters with formaldehyde, giving hydroxymethylated adducts in 94–66% ee. [ABSTRACT FROM AUTHOR]

α′-Hydroxyenones undergo clean, catalytic amidations with amines promoted by the combination of an N-heterocyclic carbene and 1,2,4-triazole. [ABSTRACT FROM AUTHOR]

It is of great significance for chemical energy storage devices, especially for the practical application of rechargeable zinc–air batteries (ZABs), to find efficient and economical bifunctional catalysts. Metal–organic frameworks (MOFs) have recently become hot research materials, and are often used as precursors of catalysts. This paper reports a carbon skeleton-coated bimetallic sulfide derived from MOF nanostructures that were used as cathode catalysts for ZABs. The N,S co-doped carbon-loaded FeS2,CoS2 ((Co,Fe)S2/CNS) catalysts exhibit excellent electrochemical properties in alkaline solutions due to the protection of metal sulfides by the carbon structure, the synergy of bimetallic Fe and Co, and the high surface area of the carbon skeleton. (Co,Fe)S2/CNS catalysts show a very low potential difference (ΔE = 0.68 V), a high specific capacity (759.1 mA h g−1) and good charge–discharge cycling performance (360 cycles/120 h) when applied to ZABs. This indicates that the prepared (Co,Fe)S2/CNS catalysts have a broad application prospect in the field of ZABs. [ABSTRACT FROM AUTHOR]

Liquid phase oxidation of 2-methylnaphthalene (2-MN) is a common synthetic route for the preparation of 2-methyl-1,4-naphthoquinone (2-MNQ). Metal-free carbon materials doped with heteroatoms have been proven to have excellent catalytic potential in various reaction fields. In this paper, the catalytic performance of N, F co-doped benzoxazine carbon materials for the selective oxidation of 2-MN was studied. The results show that the catalyst obtained at a carbonization temperature of 700 °C has the best catalytic performance. Under optimized conditions, the 2-MN conversion is 97.9%, and the 2-methyl-1,4-naphthoquinone selectivity is 84.3%. In addition, this catalyst still exhibits good catalytic activity after five cycles. Based on the experimental and characterization results, graphitic nitrogen species play a key role in the catalytic reaction and there is an almost linear relationship between the F content and the selectivity of 2-MNQ. This work provides a greener and more efficient method for the preparation of 2-MNQ with N/F co-doped mesoporous carbon. [ABSTRACT FROM AUTHOR]

In 2011, Zhang's research team, in cooperation with Li and Liu, reported the Pt1/FeOx atomically dispersed catalysts for the first time in the world, and based on this, proposed the concept of "single-atom catalysts". Single-atom catalysts (SACs) have a wide range of industrial application prospects in the catalytic synthesis of fine chemicals due to their high atomic utilization rate and special catalytic activity. With the deepening of the research, the preparation methods of SACs emerge in an endless stream, but it is still an urgent problem to realize the industrial production of highly stable SACs prepared in small batches (gram level) or even in large batches (kilogram level). In this review paper, several typical solvent-free green synthetic strategies (e.g., ball milling, physical mixing, gas migration, and pyrolyzing coordination polymers (including MOFs)) for the batch preparation of SACs are introduced. And typical catalytic application of SACs in green synthesis of fine chemicals by means of oxidation reaction, hydrogenation reaction, coupling reaction and other reactions are also introduced. This is the first review paper focusing on the mass preparation techniques of SACs and their applications in fine chemicals production. [ABSTRACT FROM AUTHOR]

In this paper, the effects of Zr, Al or Sr doped Mn/MCM-41 on NH3-SCR activity, SO2/H2O resistance and mechanism were studied. The results showed that Mn/Zr-MCM-41 has 100% NOx conversion at 175–300 °C while Mn/Al-MCM-41 achieves about 94% N2 selectivity at 120–400 °C. Zr doping significantly enhances the resistance to SO2 at 200 °C while Sr plays a negative role. Doped metal does not change the ordered hexagonal arrangement of MCM-41, but can cause the specific surface area enrichment of Mn while Al doping leads to the entry of Mn into the channel of MCM-41. Mn/MCM-41 has only Lewis acid sites, but Zr, Al or Sr doped catalysts have Lewis and Brønsted acid sites. Moreover, the reaction path on Mn/MCM-41 and Mn/Zr-MCM-41 mainly conforms to the L–H mechanism while Mn–Al or Mn–Sr doped catalysts follow L–H and E–R mechanisms. However, the deposited sulfates change the progress of the NH3-SCR process and cause a decline of SCR activity. [ABSTRACT FROM AUTHOR]

Hydrogen (H2) is a new type of renewable energy that can meet people's growing energy needs and is environmentally friendly. In order to improve the industrial application prospects and electrochemical performance of hydrogen evolution catalysts, extensive research on transition metal materials has been carried out. Among the many catalytic materials, cobalt is an element with potential for the hydrogen evolution reaction (HER) due to its abundant reserves, low cost, and small energy barrier for H adsorption. This review classifies the latest research on cobalt-based catalysts according to the types of compound, including cobalt-based sulfides, phosphides, carbides, borides, oxides, etc., and summarizes the latest research progress of cobalt-based compound catalysts in acidic and alkaline media. Strategies to tune the properties of cobalt-based compound catalysts for high catalytic activity for HER are focused on, including structural engineering, defect engineering, and doping, etc. The advantages and limitations of each modified approach are reviewed. Not only that, but also the catalytic activity and advantages of the catalyst are evaluated by using density functional theory (DFT) calculation-related descriptors, activity evaluation parameters, etc. Finally, limitations and challenges of cobalt-based materials for HER are presented, as well as prospects for future research. This paper aims to understand the chemical and physical factors that affect cobalt-based catalysts, and to find directions for future research on cobalt-based catalysts. [ABSTRACT FROM AUTHOR]

In this paper, the effects of sulfuric acid treatment of a ZrO2 support (ZrO2-S) on the Ca resistance of CeO2 catalysts were investigated. The results showed that the CeO2/ZrO2-S catalyst exhibited much better SCR activity and Ca resistance compared with the CeO2/ZrO2 catalyst. To further reveal the Ca resistance mechanism, BET, XRD, Raman, XPS, H2-TPR, NH3-TPD and in situ DRIFTS were used to characterize the changes in structure and properties of the CeO2/ZrO2 and CeO2/ZrO2-S catalysts before and after the Ca deactivation tests. The Ca poisoning of the CeO2/ZrO2 catalysts was mainly due to the decrease in specific surface area and surface acidity, the loss of reducibility and the enhanced stabilization of adsorbed nitrate/nitrite species. The treatment of ZrO2 with sulfate acid led to an increased specific surface area and highly-dispersed Ce species at the catalyst surface. It was also beneficial to inhibiting the transformation of ZrO2 from the tetragonal to the monoclinic phase. Moreover, it also enhanced the redox properties, Ce3+ species ratio, total surface acidity (especially Brønsted acid sites), and adsorption of NH3 species. The SCR reactions via both Langmuir–Hinshelwood (L–H) and Eley–Rideal (E–R) mechanisms could proceed well even after the CeO2/ZrO2-S catalysts were subjected to Ca poisoning. [ABSTRACT FROM AUTHOR]

Fossil fuels have been increasingly consumed since the industrial revolution, causing rapid increases in carbon dioxide emissions and disrupting the global carbon cycle. With increasing attention being paid to the harmful effects of carbon dioxide as a "greenhouse gas", its use as a feedstock for basic chemical production is an attractive topic. Nature benefits humans through "crops brought by thunderstorms". Combining these two methods to produce urea containing nitrogen is the focus of this paper. In this paper, a series of catalysts supported on the substituted corrole substrates in the form of a double transition metal are investigated by DFT calculations. The best catalyst was selected and combined with carbon and nitrogen reduction to further explore the catalytic performance of urea synthesis. Based on this study, it was found that the synergistic catalytic strategy of double active sites had broad prospects in urea synthesis, and could also provide new development strategies for the design of other efficient molecular catalysts. [ABSTRACT FROM AUTHOR]

In this work, the effect of catalyst viscosity on diamond growth was studied by simulating and analyzing the catalyst convection field in a diamond synthesis chamber in different viscous catalyst systems. The results showed that the low-viscosity catalyst had a high convection velocity, fast carbon flow, and large crystal growth volume, but it easily produced defects during long growth times. The convection velocity in the high-viscosity catalyst was slow, the precipitation rate of carbon was moderate, and the crystal quality was good. It is suitable for growing high-quality large-sized diamond single crystals. The structural properties of the synthesized samples were characterized by optical microscopy and Raman spectroscopy. The synthesis experiment and simulation results were consistent. In this experiment, a new viscosity concept is proposed to control the quality of diamond crystals, in which the crystal morphology is controlled by adjusting the flow field in the catalyst. This is not limited to controlling the synthesis of crystals with different morphologies by changing the temperature gradient in the diamond synthesis chamber. Therefore, this paper establishes the characteristics of a convection field suitable for the growth of diamond crystals using different viscous catalysts and provides an important theoretical reference for cavity optimization and the design of flow fields for new catalysts. [ABSTRACT FROM AUTHOR]

In this paper, a Ce-W/TiO2-mSiO2 catalyst was prepared by a co-precipitation method with the addition of silicon acid to enhance and broaden the denitrification (deNOx) efficiency and temperature range of the Ce-W/TiO2 catalyst. The test results of deNOx performance showed that temperature ranges of the 80% and 90% deNOx efficiencies of the Ce-W/TiO2 catalyst with 30% silicic acid were increased by 35 °C and 30 °C, respectively, and the highest deNOx efficiency was increased to 99.53% compared with that without silicic acid. Moreover, the XRD, BET, SEM, XPS, NH3-TPD and H2-TPR analysis revealed that strong water absorption of silicic acid provided more SiO2 for the catalyst to increase its specific surface area. Meanwhile, the volume of a TiO2 cell increased and the crystallinity of CeO2 decreased, which enhanced the number of Lewis and Brønsted acid sites on the catalyst surface and promoted the deNOx reaction. Besides, the ratios of Ce3+ and Oα on the catalyst surface were about doubled with the addition of 30% silicic acid, thus improving the deNOx performance of the catalyst. [ABSTRACT FROM AUTHOR]

The rational design of high-efficiency electrocatalysts for application in water oxidation in alkaline media remains a great challenge. In this paper, Ni3+-rich nanograss-like Mo-doped Ni3S2/NiS/VS arrays grown on nickel foam (denoted as Mo-NiVS@NF) have been successfully constructed through a hydro/solvothermal method. Interestingly, Mo-NiVS@NF exhibits superior catalytic OER performance, needing an overpotential of 217 mV to drive a current density of 10 mA cm−2, outperforming most previously reported NiS-based electrocatalysts. The result indicates that the Ni3+-rich active sites caused by the modulation of the electronic structure environment via the introduction of V and high-valency Mo play an important role in the high activity for the OER. Moreover, this catalyst shows high long-term electrochemical durability. [ABSTRACT FROM AUTHOR]

Exploring active catalyst components is very important to develop high-performance and highly stable ORR electrocatalysts to replace costly Pt-based catalysts, though it remains an ongoing challenge. In this paper, three ORR catalysts with different active components were obtained by calcination of different proportions of mixed precursors simply and delicately. Among them, precursor 1 (bimetallic polymer Fe/Zn-ZIFs@ZnCO3) played the role of a self-sacrificing template, while precursor 2 (an N, P-co-doped polymer) played the role of a volatile atmosphere. Precursor 2 also embedded N and P heteroatoms into the carbon framework during high-temperature volatilization, which resulted in subtle changes in the active catalyst components. Finally, a hybrid of metal Fe and α-Fe2O3 nanoparticles embedded in N, P-codoped carbon nanotubes with many separated gullies (named α-Fe2O3/Fe@NPC) exhibited excellent ORR catalytic activity in an alkaline solution as compared to commercial Pt/C. This work provides a new strategy for designing controllable active components using volatile precursors. [ABSTRACT FROM AUTHOR]

Although cobalt(I) bis-phosphine complexes have been implicated in many selective C–C bond-forming reactions, until recently relatively few of these compounds have been fully characterized or have been shown to be intermediates in catalytic reactions. In this paper we present a new practical method for the synthesis and isolation of several cobalt(I)-bis-phosphine complexes and their use in Co(I)-catalyzed reactions. We find that easily prepared (in situ generated or isolated) bis-phosphine and (2,6-N-aryliminoethyl)pyridine (PDI) cobalt(II) halide complexes are readily reduced by 1,4-bis-trimethylsilyl-1,4-dihydropyrazine or commercially available lithium nitride (Li3N), leaving behind only innocuous volatile byproducts. Depending on the structures of the bis-phosphines, the cobalt(I) complex crystallizes as a phosphine-bridged species [(P∼P)(X)CoI[μ-(P∼P)]CoI(X)(P∼P)] or a halide-bridged species [(P∼P)CoI[μ-(X)]2CoI(P∼P)]. Because the side-products are innocuous, these methods can be used for the in situ generation of catalytically competent Co(I) complexes for a variety of low-valent cobalt-catalyzed reactions of even sensitive substrates. These complexes are also useful for the synthesis of rare cationic [(P∼P)CoI-η4-diene]+ X− or [(P∼P)CoI-η6-arene]+ X− complexes, which are shown to be excellent single-component catalysts for the following regioselective reactions of dienes: heterodimerizations with ethylene or methyl acrylate, hydroacylation and hydroboration. The reactivity of the single-component catalysts with the in situ generated species are also documented. [ABSTRACT FROM AUTHOR]

In this paper, a Co--Fe LDO catalyst was prepared by combining K2Cr2O7 and Cr(NO3)3 to modify the LDH precursor. The catalytic activity of NOx and o-DCB was systematically studied, and the effect of gas composition on the catalytic activity was investigated. The prepared Cr (0.25)/Co--Fe LDO catalyst showed the best catalytic performance, with conversion efficiencies of NOx and o-DCB of 89.0% and 81.6% at 250 °C, respectively. The catalysts were characterized by XRD, BET, SEM, XPS, H2-TPD and NH3-TPD to explore the reaction activity. In addition, the interaction between NH3-SCR and o-DCB oxidation was investigated by changing the gas atmosphere. The results showed that the inhibition at low temperature (< 200 °C) could be attributed to the residues of the by-products of incomplete oxidation. The further oxidation of NO to NO2, and the dissociation of NH3 are the reasons for the mutual promotion of the two reactions in the middle and high temperature sections. Water vapor has little effect on the reaction and the introduction of SO2 will cause irreversible inactivation of the catalyst. [ABSTRACT FROM AUTHOR]

Due to the synergistic effects of different metal sites, the double atom or multiple atomic catalysts are very promising for use in electrocatalysis. This paper focuses on the synthesis of urea [CO(NH2)2] under the synergistic effects of bimetallics. The heteronuclear diatomic molecular catalysts were designed and screened, and the details and energy information of the elementary reactions were provided from the atomic level using theoretical simulation, which provided a new understanding for the study of the reaction mechanism. It was found that the NbVN6C catalyst was the best catalyst for the electrosynthesis of CO(NH2)2 (0.37 eV < 0.44 eV < 0.67 eV < 0.74 eV < 0.84 eV for NbVN6C, TaVN6C, WVN6C, MoVN6C, ReVN6C, respectively), and the optimal path was * → *N2 → *NN → *NNH → *NNH2 → *HNNH2 → *H2NNH2 → *H2NNH2–CO2 → *H2NNH2–COOH → *H2NCONH2. At the same time, compared with the homonuclear diatomic catalyst V2N6C, the heteronuclear diatomic molecular catalyst NbVN6C had a smaller limiting potential (−0.37 V and −0.59 V), which demonstrated the usefulness of this study. [ABSTRACT FROM AUTHOR]

The synthesis of three N-heterocyclic carbene complexes by stepwise grinding is described in this paper. The benzimidazolium salts ([H2L]Br2 and [H2L](PF6)2 ([H2L] = 1,1′-di(2-picolyl)-3,3′-methylenedibenzoimidazolium)) were initially prepared. Their reactions with Ni(OAc)2·4H2O by grinding afforded three nickel complexes, [NiL]Br2·CH3OH (1), [NiL]Br2·2H2O (1′) and [NiL](PF6)2·0.5CH3CN (2), respectively. A five-coordinated complex [NiLBr]PF6 (3) was further obtained by grinding NH4PF6 with complex 1 or 1′, or grinding KBr with complex 2. Complex 3 can also be obtained by direct grinding of complexes 1/1′ and 2. Complex 3 was subsequently used as a catalyst in the C–S bond cross-coupling of 2-bromoacetophenone and 2-mercaptobenzothiazole. The entire procedure from the synthesis to the catalytic reaction was performed by mechanochemistry. The green metrics E-factor and EcoScale close to ideal values showed the eco-friendly nature of the entire procedure. [ABSTRACT FROM AUTHOR]

The treatment of mercury pollutants in water has been wide concern. Adsorption is a promising method for mercury removal that has been extensively studied. Nevertheless, the secondary application of the immobilized Hg is seldom investigated. In this paper, the Hg adsorption behavior of UiO-66 bearing sulfhydryl groups is studied. The research shows that the porous structure and sulfhydryl groups of UiO-66-SH can effectively promote the removal of mercury from water. In addition, this work also pushes forward the sequential application of the recovered adsorbent, which contains the adsorbed mercury that may cause secondary pollution. The recovered waste adsorbent, UiO-66-S-Hg, was successfully used as an efficient catalyst for transfer vinylation, which produces value-added products, vinyl benzoates. Eight vinyl esters have been successfully synthesized with a yield of up to 89%. This methodology provides a promising way for not only the treatment of mercury contamination, but also secondary pollution protection and the resource utilization of immobilized Hg. [ABSTRACT FROM AUTHOR]

In this paper, 2-methylquinoline compounds were synthesized continuously from nitroarenes and the ethanol/water system by a simple hydrogen transfer reaction in the presence of the Ru–Fe/γ-Al2O3 catalyst. This new simple synthesis reaction was heterogeneous and continuous. At the same time, green solvents were used, and strong acids, oxidants, and other environmentally harmful substances were not added, which conformed to the principles of green chemistry. Through the impregnation method, the nanocatalysts with a smaller particle size and uniform dispersion were obtained on the γ-Al2O3 particles (1–2 mm) and had good activity. The effects of the alcohol water volume ratio, pressure, flow rate and Ru–Fe mass ratios on the yields of 2-methylquinoline compounds in the reaction were investigated. The reaction can proceed smoothly for nitroarenes with different substituents, and a moderate to good yield (46%–88%) was obtained. [ABSTRACT FROM AUTHOR]

The isomerization–dehydration cascade conversion on the saccharide platform is a pivotal route for biomass valorization, although it exhibits a specific reaction complexity that makes achieving an efficient conversion a highly technical challenge. The rational design of novel versatile solid acids is deemed to be the key to improving the cascade catalytic performance. In this paper, a dual-functional carbon-based solid acid catalyst (DFCSA) with tunable Brønsted/Lewis acid sites was developed for the cascade conversion of saccharides. The combined modification of H3PO4 and HNO3 on the carbon substrate contributed to the grafting of protonated moieties with a reasonably porous structure. With the aid of AlPO4, which has an orthorhombic crystal structure, the newly developed catalyst was able to achieve good performance for the subsequent hydrothermal conversion. Under optimal conditions, glucose and xylose were transformed with high product yields: 38.2 mol% levulinic acid and 69.7 mol% furfural, respectively. In addition, the catalyst displayed excellent hydrothermal stability, with only a slight degradation in activity after 10 cycles, which was ascribed mainly to the high thermal stability of AlPO4 and the firm grafting of the surface functional groups. As shown by the kinetic analysis, the DFSCA catalyst had a higher conversion rate and lower activation energy in the cascade conversion of xylose than that of glucose, leading to a better yield of furfural. [ABSTRACT FROM AUTHOR]

The development of advanced carbon materials as metal-free catalysts holds great importance for mercury catalyst replacement in acetylene hydrochlorination. In this paper, we transform discarded cigarette butts into a porous nitrogen-doped carbon material (N-CB-800), exhibiting characteristics of high specific surface area, large N doping amount, defective structure and strong C2H2 chemical adsorption ability. These unique features endow N-CB-800 with a high catalytic performance with an acetylene conversion of 71.8% at 220 °C and an acetylene space velocity of 100 h−1, making it one of the most active metal-free catalysts. This work will be of great value for the recycling of living waste and provide meaningful guidance for the development of non-mercury catalysts for acetylene hydrochlorination. [ABSTRACT FROM AUTHOR]

The synthesis of propargylamines by traditional methods is limited by several drawbacks such as anhydrous conditions, low temperatures and by-products. A3-coupling reactions (aldehydes, amines, and alkynes), that involve a catalytic amount of metal complexes, have been recently recognized as a powerful alternative for the synthesis of these important scaffolds. In this paper, four new silver and gold complexes (3a, 4a, 3b and 4b), bearing N-heterocyclic carbene (NHC) ligands, were tested in A3-coupling reactions, combining the use of harmless metals as catalysts with sustainable reaction conditions (neat conditions or water as solvent). NHC silver(I) and gold(I) complexes were synthesized and characterized by 1H and 13C NMR spectroscopy, ESI-MS and elemental analysis. The molecular structure of the NHC gold(I) complex 4b was determined by single crystal X-ray diffraction. A comparison of the catalytic behavior in A3-coupling reactions among the synthesized complexes disclosed the higher efficiency of gold catalysts. Computational studies shed light on species possibly involved in the catalytic mechanism. [ABSTRACT FROM AUTHOR]

Precious metal nanoparticles (NPs) are attractive for use in the field of catalysis because of their precisely controlled sizes and shapes. However, NPs exhibit insufficient anti-sintering properties under common operating conditions due to their poor thermal stability at elevated temperatures. In this paper, the preparation of noble metallic NPs (Pd and Au) incorporated inside the pores of an SBA-15 support via a sol-immobilization method, which prevents their aggregation, is reported. The Pd NPs retain their size of ∼5 nm within the channels of SBA-15, even after aging at 800 °C for three days under an air atmosphere. However, Au NPs aggregated at a temperature of calcination above 500 °C. Using a set of characterization methods comprising XRD, STEM, HRTEM, TPR, and DRIFTS analysis, it is revealed that Pd on SBA-15 exhibits better anti-sintering properties than the Au supported system. The catalytic activity and durability of M/SBA-15 (M: Pd or Au) catalysts were studied using CO oxidation with and without steam (10 vol%). Interestingly, a hydrothermally treated (Pd/SBA-15-750-H2O-3d) catalyst leads to the partial re-dispersion of Pd. This helps to attain smaller particles of ∼1.6 nm, which play a prominent role in the catalytic performance. This work provides insight into the design of sintering-resistant metal catalysts, which would be suitable for industrial applications under harsh conditions. [ABSTRACT FROM AUTHOR]

Owing to the advantage of atomic utilization, the single-atom catalyst has attracted much attention and been employed in multifarious catalytic reactions. Its definite site configuration is favorable for exploring the actual active centers and corresponding reaction mechanism. At the atomic scale, the tunable site configuration, from central metal atoms, coordinated heteroatoms, peripheral dopants, and feasible polymetallic centers to the synergetic intrinsic carbon defects, can effectively augment the intrinsic activity for oxygen reduction reaction (ORR). From a practical viewpoint, the propagation strategies of single-atom sites, the loading-activity relation and the structural retention during practical tests are crucial for the industrial applications. Furthermore, the activity contribution of multiple additional active centers including the active carbon sites and the pony-size well-wrapped metal species should be acknowledged. From the perspective mentioned above, this paper thoroughly analyses the consensuses, controversies, challenges and possible solutions based on the current research progress, thereby providing inspiration and guidance for the active center engineering of single-atom catalysts. [ABSTRACT FROM AUTHOR]

In this paper we introduce the use of molecular metal clusters as precursors for the in situ formation of nanoparticles with a high activity and surprising stability as electrocatalysts in energy conversion. The work is relevant in the present quest for remediation of greenhouse gas production and global warming, where fuel cells and metal and lithium air batteries are intended to play a crucial role. The research for an increased efficiency of these devices needs to solve the problems linked to the Oxygen Reduction Reaction (ORR), which plays a key role in these processes, due to its sluggish electrochemical kinetics that must be increased by a suitable electrocatalyst. Here we describe the facile synthesis of a new cathode material for fuel cells based on CO–Pt molecular clusters that are strongly bound to Vulcan XC72R®. The Pt–CO bond can be removed just after the synthesis, by thermal treatment at 450 K, or once in solution, leaving low-coordinated, highly reactive surface Pt atoms. The materials are investigated thoroughly using identical-location transmission electron microscopy, X-ray diffraction (with pair distribution function) and X-ray absorption measurements, revealing an extremely small, yet controlled, particle size (1–2 nm), with high structural and morphological stability, and lack of any aggregation process after thermal treatment. The surprising stability is related to the quite large number of Pt–C bonds that the nanoparticles form with the support, allowing them to attach stably onto the carbonaceous moiety. At the same time, the nanoparticles are particularly strained, and enclose a high defect density, thus enhancing their catalytic properties. The best performing composite presents a mass activity of 225 mA mgPt−1 @ 0.9 V vs. RHE for the ORR, and a less cathodic onset potential compared with a conventional Pt nanoparticle cathode, used as a benchmark under the same experimental conditions, while in turn having a lower noble metal content. [ABSTRACT FROM AUTHOR]

Dissolved oxygen (DO) is a primary corrosive substance in the transportation process of urban reclaimed water by pipelines. MCM-41 is widely used as a catalyst carrier because of its high specific surface area and low mass transfer resistance. The catalyst, namely Cu/Al-MCM-41 was prepared by doping Cu and Al in MCM-41 using one-step hydrothermal method and was used to catalyze reducing DO in reclaimed water by carbohydrazide. The effects of reaction temperature, the mass concentration of carbohydrazide, the initial pH value of water, and the mass concentration of catalyst on the removal rate of DO from reclaimed water were investigated in this paper. The reusability and catalytic mechanism of Cu/Al-MCM-41, the fresh catalyst, were determined and the used catalyst was characterized by XRD, FTIR, SEM, NH3-TPD, and BET methods. It was concluded that Cu and Al were successfully doped into MCM-41, and the synthesized molecular sieves had a highly ordered hexagonal mesoporous structure. Moreover, the doping of Al metal into MCM-41 improved the acid strength and acid centers significantly. The DO removal rate could reach 98.54% under the temperature of 45 °C, which is 3 times the theoretical feed amount of carbohydrazide, at the initial pH value of 8.5 and the mass concentration of 0.7 g L−1 of the catalyst after 60 min. The Cu/Al-MCM-41 catalyst still showed high catalytic activity after three tests. The active metal Cu could catalyze the decomposition of carbohydrazide into carbon dioxide, nitrogen, and hydrogen atoms The increase of hydrogen atom concentration adsorbed on the catalyst surface led to the rapid reduction of DO. [ABSTRACT FROM AUTHOR]

Carbon materials show great potential in catalytic applications, due to their advantages of wide raw material sources, stable chemical properties, and large specific surface area. In this paper, N-doped biochar was prepared from Pennisetum giganteum for supporting PdLa bimetallic nanoparticles to achieve efficient conversion of acetylene. The results showed that the conversion and ethylene selectivity of the Pd0.25La0.25/N-pgBC bimetallic catalyst could reach 100% and 94.2%, respectively. From the characterization results, it could be inferred that the electron transfer from lanthanum to palladium can weaken the ethylene adsorption onto the negatively charged Pd sites and thus improve the selectivity of Pd0.25La0.25/N-pgBC. It is noted that the bimetallic PdLa/N-pgBC catalyst showed strong component dependence, which may be caused by the difference in electronic or geometric modification caused by different metal ratios. This work has shown that the active site separation effect formed by doping inert metals is of great significance to the whole catalytic field. [ABSTRACT FROM AUTHOR]

Electrocatalytic water splitting, which is driven by renewable energy input to produce oxygen, has been widely regarded as a promising strategy in the future energy portfolio. The two-dimensional structure based on CoOOH nanosheets is easy to handle in the preparation process, low in cost, and has a small overpotential during water decomposition. Therefore, CoOOH two-dimensional materials have been widely used as electrocatalysts for the oxygen evolution reaction (OER). In this paper, we summarize the application of two-dimensional CoOOH nanosheets in the field of oxygen production from electrocatalytic water splitting. First, the different preparation methods of two-dimensional CoOOH nanosheets are briefly introduced. The structure–activity relationship of the two-dimensional CoOOH catalyst was analyzed from different viewpoints, such as doping, defects, etc. Finally, different catalytic mechanisms of CoOOH-based catalysts are discussed, and studies at the density functional theory (DFT) level are also provided to support the above mechanisms. To improve the readability of this review, a concise overview at the end of each section is given to illustrate some of the characteristics and trends of the studies in the corresponding part. The opportunities and challenges of two-dimensional CoOOH as an electrocatalyst in the future are summarized in the Conclusion section. This work will provide new insights and perspectives to the readers to understand the role of CoOOH nanosheets in the OER process. [ABSTRACT FROM AUTHOR]

Single-atom catalysts (SACs) with atomically dispersed metals have emerged as a new class of heterogeneous catalysts and have attracted considerable interest because they offer 100% metal atom utilization and show excellent catalytic behavior compared with traditionally supported nano-particles. However, it is challenging to explore the active sites and catalytic mechanisms of SACs through common characterization methods due to the isolated single atoms. Therefore, employing theoretical calculations to determine the nature of SACs' active sites and the reaction mechanisms is particularly meaningful. This paper describes the nature of SACs by summarizing the diverse applications and properties of SACs, which starts from computational simulation on a couple of important applications of SACs. Then the distinctive and fundamental properties of SACs are discussed. At last, the challenges and future perspectives of computational calculations for SACs are outlined. [ABSTRACT FROM AUTHOR]

Pd/C catalysts are one of the most efficient catalysts for direct synthesis of H2O2 from H2 and O2 (DSH), while pretreating the activated carbon by HNO3 will influence the performance of the Pd/C catalyst. In this paper, a series of HNO3-pretreated and N2-calcinated activated carbon-supported Pd catalysts were prepared and evaluated for the DSH reaction at ambient temperature. The experimental results showed that using HNO3-pretreated activated carbon as the support enhanced H2O2 selectivity greatly, and the highest H2O2 selectivity of 90% was obtained on 20 wt% HNO3-pretreated catalyst. The catalysts were systematically characterized by multiple techniques including transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), N2 adsorption–desorption, Boehm titration and other techniques. It was found that the textural properties of activated carbon did not affect the catalytic performance, while the effects of acid functional groups of activated carbon were supposed to improve the H2O2 selectivity, and lower H2O2 decomposition and hydrogenation capacities of the catalyst. [ABSTRACT FROM AUTHOR]

This paper demonstrates the potential of Eu2O3 and Gd2O3 as catalysts for non-oxidative propane dehydrogenation to propene. They reveal a higher activity than the state-of-the-art bare ZrO2-based catalysts due to the higher intrinsic activity of Gdcus or Eucus in comparison with that of Zrcus (cus = coordinatively unsaturated). [ABSTRACT FROM AUTHOR]

It is highly desirable for porous coordination polymers (PCPs), including metal–organic frameworks (MOFs) and Prussian blue analogues (PBAs), to retain their intrinsic characteristics in electrocatalysis, instead of being used as precursors or templates for further total conversion to other compounds via high-temperature calcination. Here, a S-treated two-dimensional (2D) CoFe bimetallic PBA grown on carbon fiber paper (CFP) (named S-CoFe-PBA/CFP) is assembled and applied as a highly efficient oxygen evolution reaction (OER) electrocatalyst in 1 M KOH. The resultant S-CoFe-PBA/CFP demonstrates significantly improved OER catalytic activity; overpotentials of only 235, 259, and 272 mV are needed to drive current densities of 10, 50, and 100 mA cm−2, respectively, with a super low Tafel slope of 35.2 mV dec−1. Even more noteworthy, a current density of 90 mA cm−2 can be achieved when a potential of 1.5 V vs. RHE is applied, which is 6.4 times higher than that of commercial Ir/C in the same environment. The outstanding electrocatalytic performance can be ascribed to two reasons caused by the S-treatment process. On one hand, H+ from intermediates of *OH and *OOH can be captured by –SOx distributed on the surface of the catalyst, thus accelerating the breaking of O–H; on the other hand, partial phase transformation of CoFe-PBA leads to the in situ formation of amorphous CoSx nanogauze on the surface, and the resultant electronic interactions between the two phases contribute much to the improvement of charge transfer and adsorption for OER intermediates. This work provides a new avenue for the design of highly efficient PCP-based OER electrocatalysts. [ABSTRACT FROM AUTHOR]

In this paper, the effect of the hierarchical arrangement of nanocrystallites on CO oxidation and soot combustion activity has been investigated. Hierarchically structured star-shaped particles (HS stars) were compared with microemulsion-derived, loosely arranged nanoparticles (NPs). Star-like Ce0.9REE0.1O1.95 mixed oxides were synthesized by oxidative thermolysis of Ce0.9REE0.1(HCOO)3 mixed formates. The study of the synthesis, structure and catalytic activity of the porous, star-like ceria-based mixed oxides was presented for the first time. It was shown that each level of the hierarchical structure of the star-like mixed oxides has its own functionality and it is vulnerable to modifications. In-depth characterization of as-synthesized ceria allowed determination of the relationship between the hierarchically structured nature of the material and its catalytic activity in CO oxidation and soot combustion. It was concluded that the presence of the 3D structure composed of ceria nanocrystals significantly improves the stability and catalytic activity of the star-like material in comparison to the nanopowder. Moreover, introduction of the trivalent RE ion into the ceria structure led to further improvement of the CO oxidation performance. Finally, the key–lock catalysis concept was applied to explain the enhanced activity of the hierarchically structured star-shaped ceria particles as a catalyst in the soot combustion process in comparison to nanocrystalline CeO2. [ABSTRACT FROM AUTHOR]