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4-Aminophenol (4-AP) is a highly toxic environmental pollutant and contaminant of medicine, which is widely used in industries and daily life. Therefore, the development of a reliable sensor for determining the amount of 4-AP is of great importance for the protection of human and environmental health. Herein, by fabricating a Pd@CeO2 composite on a nanoporous gold-coated carbon fiber paper (NPG/CFP), the sensing properties for 4-AP can be largely enhanced. Combining the significant increase in the catalytic activity of the Pd@CeO2 composite (derived from the strong interactions between Pd and CeO2) with the NPG and NPG/CFP hierarchical porous structure having a high electrochemically active surface area, the electrode achieved excellent detection of 4-AP. It manifested an extremely high sensitivity of 75.4 μA μM−1 and 56.5 μA μM−1 in the concentration range from 0.005 μM to 0.03 μM and 0.03 μM to 9 μM, respectively. The detection limit reached as low as 4 nM under optimized conditions (S/N = 3). The electrode also possesses long-term stability and presents great anti-interference ability. All these results demonstrate that the electrode is a promising candidate for future sensors for monitoring 4-AP in water and pharmaceuticals. [ABSTRACT FROM AUTHOR]

This paper details the preparation of an aluminum-based organic metal complex doped with fluorine and nitrogen (2-Ml/Al–F–N). The synthesis method combines hydrothermal synthesis and calcination for modification. The catalyst was thoroughly characterized for its composition, structure, and morphology using various techniques, including XRD, FT-IR, XPS, SEM, TEM, and others. The electrochemical performance of the material was assessed using an electrochemical workstation, and gas chromatography was employed to analyze the results. DFT calculations were used to compute the material's properties and energy barrier diagram. The findings demonstrate that the catalyst exhibits a carbon nanoline morphology and showcases high catalytic activity in the CO2RR to CO. Notably, the catalyst exhibits excellent performance with a maximum current density of 14.08 mA cm−2 and a peak faradaic efficiency of 90.1% at −1.1 V vs. RHE. The active sites are predominantly located within the nanoline structure. The DFT calculations reveal that the introduction of ammonium fluoride during the synthesis process leads to the formation of a highly efficient fluorinated aluminum metal catalytic center derived from nonahydrate aluminum nitrate. This specific structure demonstrates excellent hydrogen suppression properties and effectively lowers desorption energy barriers, which enhances the CO2RR activity and promotes the electrocatalytic reduction of CO2 to CO. [ABSTRACT FROM AUTHOR]

In this paper, a novel Pt/CoP/C photo-electro synergistic catalyst was successfully synthesized by a hydrothermal method combined with phosphorus doping treatment. The addition of Vulcan XC-72R is in favor of effectively preventing agglomeration of active catalytic sites, resulting in more uniform and smaller Pt and CoP nanoparticles. The as-obtained Pt/CoP/C shows excellent photo-electro catalytic performance for the HER with simulated solar light irradiation. The optimal hydrogen production is 5384.18 mmol h−1 g−1, which is obviously higher than that of the commercial catalyst (20 wt% Pt/C: 4608.52 mmol h−1 g−1). The research results show that introducing cobalt phosphide into the Pt catalyst can improve the electrocatalytic activity and stability for the HER; in particular, the existence of Co3O4 in Pt/CoP/C leads to an efficient photo-electro catalysis under irradiation, which significantly improves the catalytic activity of Pt. The results above provide a novel strategy for the rational design of cost-effective Pt-based composites towards a fast HER. [ABSTRACT FROM AUTHOR]

Sensitive detection of glucose is important for public health, but non-enzymatic glucose biosensors still face significant challenges. In this paper, a novel and sensitive non-enzymatic glucose sensor was developed by in situ preparation of CuO nanorod-supported NiCo LDH nanosheet arrays on copper foam (CuO@NiCo LDH NSAs/CF). Because the hierarchical core–shell nanostructure provides more active sites and increases the exposed surface area of the catalyst, the catalytic activity of the electrode was significantly increased. As a working electrode, the CuO@NiCo LDH NSAs/CF catalyst showed good glucose sensing performance in a linear range of 0.6 μM–3 mM and a detection limit of 0.16 μM (S/N = 3). The sensor also showed repeatable responses over a month with negligible interference, and satisfactory recoveries with real human serum samples. [ABSTRACT FROM AUTHOR]

In this paper, ultrathin layers of carbon nitride were obtained by dissolving urea in different amounts of water and used as a carrier to prepare catalysts for formic acid dehydrogenation. The catalytic activity of the carbon nitride supported Pd catalyst in formic acid dehydrogenation was investigated. The ratio of urea to water played a key role in the type and content of nitrogen-containing functional groups, and then enhanced the catalytic performance by regulating the electronic properties of Pd. The Pd/CN-U1W5 catalyst exhibited excellent catalytic activity for the production of hydrogen from formic acid with an initial TOF of 1058 h−1 at 348 K. It was found that the high catalytic performance of the catalyst could be attributed to the strong interaction between Pd nanoparticles and pyridinic N, small Pd nanoparticle size and highly dispersed Pd nanoparticles. [ABSTRACT FROM AUTHOR]

In this paper, a 3D porous polycalix functionalized with a dual Brønsted–Lewis acidic double-charged DABCO-based ionic liquid group (PC4RA@[SiPrDABCO@BuSO3H](FeCl4)) was synthesized using multiple steps, characterized, and then evaluated by spiro formation for catalytic activity. Initially, the polymeric support was modified using the silylation of its hydroxy groups with (3-chloropropyl)-trimethoxysilane as an organo-silane linker to develop PC4RA-SiPrCl. Then, it was post-functionalized using bi-functional acidic IL groups bearing double-charged diazoniabi-cyclo[2.2.2]octane tetrachloro-ferrate(III) with moving active sites of SO3H groups to deliver PC4RA@[SiPrDABCO@BuSO3H](FeCl4). In the next step, the characterization of the designed catalyst was directed by applying FT-IR, EDX, elemental mapping, WPXRD, LPXRD, FE-SEM, STA, and TEM techniques. The catalytic performance of the porous polymeric system was confirmed using the formation of spiro-fused[4H-pyran] as a highly recyclable and stable di-cationic polymer-supported acidic IL under mild conditions. [ABSTRACT FROM AUTHOR]

The development of noble-metal-free electrocatalysts with high catalytic efficiency, low cost, and high durability in pH-universal media is encountering a bottleneck in practical applications. In this paper, Ni@MoN-700 coral hybrids were prepared using hydrogen evolution reaction (HER) catalysts, which were synthesized by a high-temperature reduction of NiMoO4 nanorods with urea. It was found that the annealing temperature seriously affects the surface morphology and chemical composition of the catalysts. Besides, structural reorganization occurred during the HER, which involved the joining of pyrrolic N, metal nitrogen, Mo3+, and Mo6+, governing the HER performance. Also, during the HER, Ni and Mo could synergistically improve the overall catalytic activity of the catalysts, via electronic interactions. These advantages endow Ni@MoN-700 with exceptional endurance and great HER activity, with a low overpotential of 30 mV and 76 mV at 10 mA cm−2 in alkaline and acidic media. These characteristics are similar to those of Pt under alkaline conditions. NiMoN catalysts show unusual activity and long-term stability, indicating a wide range of potential applications. [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]

Chemical vapor deposition (CVD) and impregnation (IM) methods were applied in the preparation of novel Fe/LTA (Linde Type A) zeolite membrane/paper-like sintered stainless steel fiber (Fe/LTA/PSSF) catalysts for acetone oxidation. The catalysts were characterized using various techniques, such as actual iron loading (AAS), surface morphology (SEM), phase composition and crystallite size (XRD), specific surface area (BET), valence state (XPS) and reducibility (H2-TPR), to investigate the effects of the calcination process, iron loading, preparation methods and supports on their catalytic activity. The calcined catalysts were more active than the non-calcined catalysts in the catalytic oxidation of acetone due to the different oxidation states of the deposited metal species. The catalysts prepared by CVD with an Fe loading of 2.29% exhibited similar activity to the IM-prepared catalysts with Fe loadings of 4.42% and 9.69%, which may be attributed to the superior dispersion of the active Fe2O3 phases, the smaller size of metal oxide and the increased ability for oxygen storage. Among the IM-prepared catalysts, Fe/LTA/PSSF-IM-2 with an Fe loading of 4.42% exhibited the lowest T90 of 230 °C. Additionally, the catalysts coated on LTA/PSSF showed higher activity and contact efficiency (T90 of 249 °C) compared to those on granular zeolite (T90 of 318 °C). [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]

To solve the problem of excessive energy consumption in the process of catalytic water splitting, it is quite essential to exploit high-activity and low-cost electro-catalysts. The present paper proposes a highly catalytically active Ni/Fe hydroxide electro-catalyst for the oxygen evolution reaction (OER), which is in situ formed on the surface of the stainless steel fiber felt using a sacrificial template by adding the oxidizing agent K2S2O8 to the alkaline solution under mild conditions. The electrode prepared using this simple one-step chemical oxidation method obviously shows enhanced catalytic activity for the OER. The overpotentials at 10 mA cm−2 are only 214 mV and 263 mV in KOH and Na2CO3/NaHCO3 solutions, respectively. In addition, the potential and morphology of the electrode remain stable for 180 h at 10 and 100 mA cm−2 in the Na2CO3/NaHCO3 system, demonstrating its ultra-high stability. This new route to prepare OER electrode materials has a promising bright application prospect for large-scale production. [ABSTRACT FROM AUTHOR]

This paper reports the synthesis of a nickel-silver-graphene quantum dot-graphene hybrid. Histidine-functionalized graphene quantum dots (His-GQDs) were bonded to graphene oxide (GO) and then combined with Ni2+ and Ag+ to form a NiAg/His-GQD/GO complex, followed by thermal reduction under N2. The resulting hybrid offers a well-defined three-dimensional structure. The NiAg nanoparticles are uniformly dispersed on the graphene sheets. The special architecture creates high oxidase-like catalytic activity towards the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) into a blue product. Furthermore, the hybrid was used as a mimetic enzyme for colorimetric detection of malathion. In the detection, acetylcholinesterase catalyzes hydrolysis of acetylthiocholine to produce thiocholine. In the presence of malathion, the catalytic activity of acetylcholinesterase was effectively inhibited. This will lead to a reduced thiocholine concentration. As sulfhydryl in the thiocholine can combine with silver and nickel in NiAg/His-GQD/G to form Ag–S and Ni–S bonds, the presence of thiocholine results in a reduced oxidase-like catalytic activity of NiAg/His-GQD/G. With the increase of malathion, NiAg/His-GQD/G gives a higher oxidase-like catalytic activity. This causes a faster rate for oxidation of TMB, indicating an increased absorbance of the blue product. The result shows that the inhibition rate has a good linear relationship with the malathion concentration in the range of 10–120 ng mL−1 and detection limit of 3.10 ng mL−1 (S/N = 3). Meanwhile, the sensing platform was also applied to paper strips for rapid determination of malathion in vegetable samples by using a smartphone application (APP), which provides a promising platform for on-site pesticide detection. [ABSTRACT FROM AUTHOR]

FeCo2O4 is a potential OER catalyst, but its catalytic activity still needs to be further improved due to its poor electrical conductivity and low material utilization. In this paper, we construct oxygen-vacancy-rich two dimensional FeCo2O4 nanosheet materials using a liquid-phase reduction strategy. Benefiting from its large specific surface area, numerous surface catalytic sites, enhanced electrical conductivity, and modulated electronic structure, the catalyst exhibits an overpotential of only 270 mV at a current density of 10 mA cm−2, which is lower than that of the original FeCo2O4 nanosheets (420 mV). At the same time, the catalyst can run steadily for 20 hours without obvious decay. [ABSTRACT FROM AUTHOR]

Among rare earth oxides (REO), mixed-valence praseodymium oxide (Pr3+/Pr4+) has the highest O mobility and very promising applications in multiphase catalysis. In this paper, Pd-loaded praseodymium oxide nanotubes were successfully prepared by immobilizing Pd nanoparticles on modified carriers. XPS characterization showed that the electron transfer process during the reaction could be regulated by changing the Pr3+/Pr4+ ratio of praseodymium oxide. Importantly, the H2-PrxOy carrier surface has much higher Pd electron density, and the electron-rich Pd nanoparticles make it easier to break the C–Br bond and transfer electrons from Pd to C and Br atoms, leading to the formation of ArPdIIBr intermediate complexes. In the Suzuki coupling reaction, Pd/H2-PrxOy exhibited higher catalytic performance under mild conditions. There is a strong correlation between the surface properties of the carriers and the catalytic activity of the Pd nanocatalysts. This provides a new strategy for the preparation of Suzuki coupling reaction catalysts. [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]

This paper mainly studied the influence of the Si/Al ratio on the performance of the Cu/SSZ-13 catalyst synthesized by the ion exchange method. NH3-SCR experimental results show that the catalyst SAR10 has the best catalytic performance, and it can maintain a 100% conversion rate in the range of 250 °C to 600 °C. Although SAR6 samples with low Si/Al ratios have abundant active centers, their low temperature activity is poor due to their poor crystallinity. The decrease of the number of active sites available for exchange in the SAR25 sample with too high an Si/Al ratio results in a decrease in catalytic activity throughout the temperature range. The results of the in situ DRIFTS experiment show that the order of the number of Lewis acid sites and the content of monodentate nitrate adsorption sites is the same as the order of catalytic activity. [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]

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]

The paper reports on multicomponent (Ziegler) catalytic systems based on acetylacetonate complexes of cobalt, nickel or palladium and various aluminum-containing cocatalysts of general formula M(acac)2–Red (where M = Co, Ni, Pd; Red = AlEt3, LiAlH4, AlEt2(OEt), LiAlH(tert-BuO)3), which are active in alkenes hydrogenation under mild conditions (T = 30 °C, P = 2 atm). The key features (size, composition, nature of the ligand shell) of metal-containing nanoscale particles formed during the interaction of the initial components under inert medium and hydrogenation catalysis are considered. Also, the dynamics of the reaction solution changes in the course of catalytic processes as well as the kinetic parameters (activity, productivity, selectivity) of alkenes hydrogenation are described. The models of nanoparticles formed under the hydrogenation catalysis conditions during the interaction of M(acac)2–Red (where M = Co, Ni, Pd; Red = AlEt3, LiAlH4) are discussed. The role of proton-donor compounds (contained in the initial complexes of transition metals or specially introduced into the reaction systems) in the formation of catalytically active sites is explained. In particular, it is shown that the activating effect of these compounds is associated with alcoholysis of the cocatalyst and products of its catalytic decomposition, which are located on the surface of transition metal nanoparticles. A general scheme of activation of the [M]n particles formed by the interaction of M(acac)2 with AlEt3 (M = Ni and Co) is presented. The concept for the directed design of Ziegler catalytic systems is proposed. In order to evaluate the application scope of this concept, the reasons of different catalytic activity and productivity of bimetallic nickel–copper catalysts of the same composition, obtained by sequential and simultaneous reduction of Ni(acac)2 and Cu(acac)2 by LiAlH4, are revealed. In addition, a number of priority issues that should be addressed are discussed to highlight the prospects for the further development of this field of catalysis. [ABSTRACT FROM AUTHOR]

Although graphene quantum dots (GQDs) have attracted great research interest owing to their various applications, the performance of N-doped GQD nanocomposites has rarely been focused on in the catalysis field. A simple one-step chemical strategy for the fabrication of a CuO nanoparticle/ZnO nanorod heterojunction was introduced for the first time in this paper. According to the obtained results, the selection of an appropriate molar ratio, temperature, and pH are the most important factors in the heterojunction preparation procedure. Then, N-doped graphene quantum dots modified with CuO/ZnO nanoarrays were synthesized via a green hydrothermal process. The catalytic activities of the CuO/ZnO heterojunctions, pure N-GQDs, and CuO/ZnO@N-GQDs nanocomposite were compared and, based on the empirical results, it can be concluded that the activities are in the order: CuO/ZnO@N-GQDs > N-GQDs > CuO/ZnO. Therefore, the proposed nanocomposite was used to facilitate the one-pot synthesis of monospiro-2-amino-4H-pyrans in an aqueous system at ambient temperature with excellent yields (89–98%) within a short reaction time. In this multicomponent reaction, three new σ bonds (one C–O and two C–C bonds) were formed in a single operation, which led to the generation of the spiro skeleton. Moreover, the CuO/ZnO@N-GQDs heterogeneous nanocatalyst was also recoverable after seven cycles without significant loss of activity. [ABSTRACT FROM AUTHOR]

In this paper, a series of ZnxCe1−xO2 (x = 0.00, 0.05, 0.10, 0.15, and 0.20) nanoparticles were synthesized via an aqueous-phase coprecipitation method. The ZnxCe1−xO2 nanoparticles were coated on honeycomb ceramics to prepare monolithic catalysts, and the catalytic activity of the monolithic catalysts was investigated for the direct synthesis of dimethyl carbonate (DMC) from CO2 and methanol in a continuous tubular fixed-bed reactor. The as-prepared catalysts were fully characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), N2 adsorption/desorption isotherms, H2-temperature-programmed reduction (H2-TPR), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and CO2-temperature-programmed desorption (CO2-TPD). The characterization results showed that doping Zn ions into the ceria lattice formed a fluorite-like solid solution and modified the structure and surface properties of the catalysts. Among all the monolithic ZnxCe1−xO2 catalysts, the monolithic Zn0.10Ce0.90O2 catalyst showed the highest catalytic activity with a methanol conversion of 20.5% with DMC selectivity of 82.1% at 160 °C and 2.4 MPa in the absence of any dehydrating agents. This superior catalytic activity was mainly attributed to a series of better properties, such as larger specific surface area (i.e. 179.9 m2 g−1), higher oxygen vacancy concentration, and the unique structure of the monolithic catalyst (e.g., removing by-product of water in time). This study provides a valuable design strategy for highly efficient direct synthesis of DMC using monolithic catalysts in the fixed-bed reactor. [ABSTRACT FROM AUTHOR]

Highly effective bifunctional oxygen electrocatalysts play a key role in fuel cells (FCs), metal–oxygen batteries, and water splitting devices. In this paper, metal organic layer (MOL) derived Co/Co9S8 nanoparticles coated with N,S co-doped graphene-like carbon nanosheets were synthesized with the help of the space-confinement effect of montmorillonite (MMT). The as-prepared material shows excellent electrocatalytic activity both for oxygen reduction and oxygen evolution reactions in 0.1 M KOH solution: its ORR onset potential is 0.93 V (vs. RHE) and the limiting diffusion current density is 4.7 mA cm−2. Moreover, the retention of current for the as-prepared material is 85% after a stability test for 10 000 s for the ORR, while those of the template free catalyst and commercial Pt/C glided below 80%. Additionally, its Tafel slope is 265 mV dec−1, which is much smaller than that of the control sample, suggesting the excellent OER kinetics. The excellent catalytic activity and stability can be attributed to the relatively higher specific surface area, higher number of pyridinic-N and Co–Nx active sites, and higher graphitization degree compared to the template free catalyst. [ABSTRACT FROM AUTHOR]

In this paper, the synthesis of a novel imidazolium based N-heterocyclic carbene (NHC) containing imidazopyridine substitutes using a three-component reaction is described. This compound was immobilized on magnetic graphene oxide (GO) to make a heterogeneous catalyst for the direct aerobic amidation of benzaldehyde derivatives under solvent-free conditions, as well as the intra- and intermolecular cross dehydrogenative coupling of aldehydes. In addition, the catalytic activity of the NHC catalyst was homogeneously studied in the presence of Fe3O4 nanoparticles under the same conditions, and showed good activity with lower yields than the heterogeneous catalyst. [ABSTRACT FROM AUTHOR]

Reasonable design and synthesis of high-efficiency nanocatalysts are of great significance for the electrocatalytic analysis of fungicides. In this paper, La-doped Nd2O3 (La-Nd2O3) nanomaterials are synthesized by a hydrothermal method and characterized via SEM, TEM, EDS, XPS and XRD. The results confirm that the trigonal Nd2O3 and La-Nd2O3 are successfully synthesized, and La is localized on the surface of the Nd2O3 lattice. Compared with Nd2O3, La-Nd2O3 nanomaterials have a larger surface area. In addition, the prepared Nd2O3 and La-Nd2O3 catalysts coated on a carbon paste electrode (CPE) are used as working electrodes to investigate their electrochemical performance for carbendazim (CBZ). Probably due to the synergistic electronic transfer process and dual-function effects of La-Nd2O3, the La-Nd2O3 modified electrode exhibits a stronger redox signal and faster electron transfer rate, thus resulting in superior electrocatalytic activity against CBZ. The proposed CBZ sensor produces a wide linear range of 0.08 to 50 μM and a low detection limit (0.027 μM, S/N = 3) by differential pulse voltammetry (DPV). Moreover, the La-doped catalyst has a long-term electrochemical activity and catalytic stability under steady state conditions, which indicates that La-Nd2O3 is a promising catalyst in electrocatalysis and sensing applications. [ABSTRACT FROM AUTHOR]

Oxidation of sp3 C–H bonds has attracted increasing attention, and the aim of our work is to prepare catalysts for oxidation of sp3 C–H bonds using O2 without an initiator. In this paper, a series of Co–Cu bimetal oxides with different Co/Cu ratios were synthesized by a sol–gel method and tested for catalytic oxidation of fluorene to fluorenone using molecular oxygen as an oxidant in the absence of a radical initiator. The best catalytic performance was achieved over the Co0.7Cu0.3 catalyst and the catalysts could be reused without significant loss of the catalytic activity. The characterization results indicated that some Cu entered the Co3O4 lattices, leading to more high-valence metal ion sites (Co3+ and Cu2+) and surface oxygen species (O2−, O22−, and O−) as well as promoted redox ability, which all enhanced the catalytic activity. In addition, the catalysts were also efficient for the oxidation of other benzylic C–H containing aromatic hydrocarbons such as tetralin, indan, diphenylmethane and ethylbenzene. [ABSTRACT FROM AUTHOR]

The production of methyl glycolate (MG) from the catalytic hydrogenation of dimethyl oxalate (DMO) derived from syngas (H2 + CO) as an environmentally benign and economical route has attracted tremendous interest in the modern chemical industry. Silica-supported noble and transition metal elements have been employed as efficient catalyst materials for this reaction. In this paper, we used a novel, highly efficient and eco-friendly sonochemical approach to synthesize noble metal-free, ultra-small and highly dispersed Cu nanodots wrapped on porous SiO2 catalysts. The hydrothermal method as a well-known conventional approach is used to synthesize the same catalyst of Cu/SiO2. The synthesized catalysts were exposed to the industrially relevant vapor-phase hydrogenation reaction of dimethyl oxalate, and then the calcined, reduced and spent catalysts were fully characterized using XRD, TEM, HR-TEM, N2 physical adsorption, FTIR, XPS, Cu-LMM and H2-TPR. Notably, the obtained results confirmed that the sonochemically synthesized noble metal-free Cu/SiO2 catalyst displayed remarkably high MG selectivity of 94% and a turnover frequency (TOF) of 5.08 h−1 compared with 81% MG selectivity and 3.45 h−1 TOF for the hydrothermally synthesized catalyst. These results could be attributed to the synergistic and high value of the Cu+/(Cu+ + Cu0) ratio for the synthesized catalyst and the high dispersion and surface area of the nanoparticles. Our ultrasonication technique holds promise for the synthesis of highly dispersed and efficient heterogeneous catalytic materials in aqueous medium with a short reaction time. [ABSTRACT FROM AUTHOR]

Heterojunction or homojunction construction has been demonstrated to be an effective method to boost photocarrier separation and transfer, leading to a greatly enhanced photocatalytic activity. However, the photocatalytic performance of conventional heterojunction or homojunction photocatalysts usually faces some challenges, such as low surface area, insufficient active sites, and poor interface contact area. In this research, for the first time, a novel graphitic carbon nitride/graphitic carbon nitride (g-C3N4/g-C3N4) metal-free homojunction was successfully synthesized by calcining the supramolecular precursor self-assembly formed between hydrothermal melamine and dicyandiamide. The novel g-C3N4/g-C3N4 metal-free homojunction features a nanomesh morphology with a high specific surface area, which is not detected in the other g-C3N4/g-C3N4 composites. In addition, the in situ formation of the homojunction creates abundant interface contact, which improves the charge transfer ability. As expect, the as-prepared sample exhibited significantly enhanced visible light activity for rhodamine B degradation compared to the use of g-C3N4 alone and was 4.3 times as active as conventional g-C3N4/g-C3N4 composites. The results presented in this paper demonstrate that the novel supramolecular pre-organization route is valuable for the creation of a g-C3N4 isotype homojunction with a large specific surface area and abundant interface contact. The feasibility of developing different supramolecular precursors for efficient C3N4 photocatalysis using simple hydrothermal melamine and other nitrogen-rich precursors is proposed. [ABSTRACT FROM AUTHOR]

In this paper, a simple colloidal crystal-templating method assisted by a hydrothermal process has been proposed to prepare novel three-dimensionally ordered macroporous (3DOM) TiO2@nanosheet SnS2 heterojunction photocatalysts. The photoactivities of all the obtained samples were measured by the photodecomposition of rhodamine B (RhB), the photoreduction of Cr(vi) and photocatalytic hydrogen generation from water splitting. In comparison with pure SnS2 nanosheets and 3DOM TiO2, the 3DOM TiO2@SnS2 sample with a Sn/Ti molar ratio of 7.5 : 100 showed the highest photocatalytic activity for wastewater purification (kapp for RhB solution = 0.035 min−1 and for Cr6+ solution = 0.0845 min−1) and hydrogen generation under visible light irradiation. By means of ultraviolet-visible diffuse reflectance spectra (UV-vis DRS), photoluminescence (PL) spectra, transient photocurrent spectra, electron paramagnetic resonance (EPR) measurements and photocatalytic experiments, a suggested mechanism for the charge generation and transfer in the 3DOM TiO2@nanosheet SnS2 heterojunction was proposed. The improved charge separation and enhanced photocatalytic activity for the as-prepared TiO2@SnS2 composition can be attributed to the well-defined 3DOM heterojunction structure and the spatial transfer of the visible-light excited high energy electrons of SnS2 to TiO2. This work will provide a novel route to prepare highly active heterojunction photocatalysts and a new insight into the study of electron migration paths in TiO2@SnS2 composites. [ABSTRACT FROM AUTHOR]

This paper demonstrates the preparation of core-shell nanocomposites (NCs) of Aucore-Agshell (Au@Ag) and Agcore-Aushell (Ag@Au) for measuring their catalytic activity and electro-kinetic properties relative to their respective monometallic counterparts. A significant blue-shift (530 → 408 nm) and a red-shift (420 → 550 nm) of the surface plasmon band for Au@Ag and Ag@Au NCs, respectively, were observed due to increased size of binary composites depending on the nature of the core and shell material. The thickness of the deposited Ag shells varied from B3-10 nm on the Au core leading to the formation of Au@Ag NCs. On the other hand, the Ag core served as a sacrificial template, where Ag@Au NCs were converted to hollow Ag-Au alloy shells (∼15 nm) because of the galvanic reaction between them due to the difference in their redox potential. An increased zeta potential was found for resulting Au@Ag (+57.8 mV) and hollow Ag-Au alloy shell (-20.13 mV) NCs in comparison to monometallic Au (-6.13 mV) and Ag nanospheres (-5.74 mV) due to surface passivation with aqueous AgNO3 and AuCl4- solution, respectively. These bimetallic NCs exhibited ∼2 times higher catalytic activity than the monometallic nanoparticles depending on the shell thickness and the core of the respective metals for the nitrobenzene and 1,3-dinitrobenzene reduction. [ABSTRACT FROM AUTHOR]