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A novel strategy to support sub-1 nm Pt nanoclusters on N and P co-doped carbon nanotubes was developed. The prepared Pt/NP-CNTs showed highly efficient HER activity and durability in acidic electrolytes, outperforming those of commercial Pt/C.

In this work, heterogeneous catalytic ozonation for the treatment of bio-treated saccharin sodium production wastewater (BSSW) was comprehensively investigated with pilot- and full-scale systems, with special emphasis on the effects of Cu

In this work, both Electrocoagulation (EC) and Fered-Fenton (FF) technologies were used to treat reverse osmosis concentrates (ROC) from petrochemical production. The toxicity reduction capacity and mechanism were comparatively assessed during these two treatments. The results showed that FF exhibited higher capacity to reduce toxicity than EC in the 30 min treatment, which could be attributed to the removal of organic pollutants and heavy metals. The results showed that the ROC contained organics with molecular weight of 1200 g mol−1 and 220 g mol−1, which mainly consisted of the soluble microbial by-product-like and humic acid-like substances. The removal of these organics directly led to the noticeable toxicity reduction. Alkanes, haloalkanes, ketones, PAHs, and other four organic pollutants were the dominant species in the ROC, and the removal of small molecular weight organic pollutants played an essential role in reducing toxicity. FF exhibited stronger capacity to remove PAHs, BTEXS and haloalkanes, and the removal efficiencies for the PAHs were in the following order: 5-ring > 4-ring > 3-ring > 2-ring. The promotion of heavy metals removal appeared to be favorable for decreasing toxicity in ROC. This study illustrated the mechanism of the toxicity reduction and the characteristics of pollutants removal during FF and EC treatments, and provided valuable guidance for petrochemical manufacturing to the toxicity reduction and operation of wastewater treatment facilities.

The synthesis and characterization of a suite of melamine dendrons on FDU-12 and pore-expanded FDU-12 are reported. FDU-12, a mesoporous material with cubic arrays of pores possessing cage apertures of approximately 4 nm is not an efficient support for growing dendrons. However, pore-expanded FDU-12 (PE-FDU-12) is an effective support, and it is an efficient substrate for growing dendrons with high free volumes, i.e., bulkier spacer diamines, as compared to SBA-15. Extensive MALDI-MS and solution NMR on the cleaved dendrons validate the other analytical methods used and confirm that the target fragments are formed. The findings from this work illustrate the effect of the silica support’s pore topology on the synthesis of dendron materials on solid supports.

Oxygen reduction reaction (ORR) plays significant roles in electrochemical energy storage and conversion systems as well as clean synthesis of fine chemicals. However, the ORR process shows sluggish kinetics and requires platinum-group noble metal catalysts to accelerate the reaction. The high cost, rare reservation, and unsatisfied durability significantly impede large-scale commercialization of platinum-based catalysts. Single-atom electrocatalysts (SAECs) featuring with well-defined structure, high intrinsic activity, and maximum atom efficiency have emerged as a novel field in electrocatalytic science since it is promising to substitute expensive platinum-group noble metal catalysts. However, finely fabricating SAECs with uniform and highly dense active sites, fully maximizing the utilization efficiency of active sites, and maintaining the atomically isolated sites as single-atom centers under harsh electrocatalytic conditions remain urgent challenges. In this review, we summarized recent advances of SAECs in synthesis, characterization, oxygen reduction reaction (ORR) performance, and applications in ORR-related H 2 O 2 production, metal-air batteries, and low-temperature fuel cells. Relevant progress on tailoring the coordination structure of isolated metal centers by doping other metals or ligands, enriching the concentration of single-atom sites by increasing metal loadings, and engineering the porosity and electronic structure of the support by optimizing the mass and electron transport are also reviewed. Moreover, general strategies to synthesize SAECs with high metal loadings on practical scale are highlighted, the deep learning algorithm for rational design of SAECs is introduced, and theoretical understanding of active-site structures of SAECs is discussed as well. Perspectives on future directions and remaining challenges of SAECs are presented.

Developing nonprecious electrocatalysts with superior activity and durability for electrochemical water splitting is of great interest but challenging due to the large overpotential required above the thermodynamic standard potential of water splitting (1.23 V). Here, in situ growth of Fe

A nano-coating associated with sulfuric acid leaching protocol was developed to prepare N-doped sub-3 nm Co-based nanoparticle catalyst (Co-N/C) using melamine-formaldehyde resin as the N-containing precursor, active carbon as the support, and Co(NO3 )2 as the Co-containing precursor. By thermal treatment under nitrogen atmosphere at 800 °C and leached with sulfuric acid solution, a stable and highly dispersive Co-N coordination structure was uniformly dispersed on the formed Co-N/C catalyst with a Co loading of 0.47 wt % and Co nanoparticle size of 2.55 nm. The Co-N/C catalyst was characterized with XRD, XPS, Raman, SEM, TEM, ICP, and elemental analysis. The Co-N/C catalyst showed extremely high catalytic efficiency with a TON of 257 for the aerobic oxidative coupling of aldehydes with methanol to directly synthesize methyl esters with molecular oxygen as the final oxidant. The Co-N/C catalyst also showed broad substrate range and stable recyclability. After recycling for 7 times, no obvious deactivation was detected. It was confirmed that the sub-3 nm Co-N coordination structure formed between metallic Co nanoparticles and pyridinic nitrogen doping into graphitic layers functions as the active site to activate molecular oxygen for the β-H elimination from generated hemiacetal intermediates to produce methyl esters. The nano-coating associated with acid leaching protocol provides a novel strategy to prepare highly efficient non-precious metal-based catalysts.

Single-atom Fe-N-C electrocatalysts have emerged as the most promising oxygen reduction reaction (ORR) catalyst. However, the low Fe loading and inaccessibility of Fe-N-C sites limit the overall ORR activity. Here, we report an efficient single-atom electrocatalyst (Fe-N-C/N-OMC) with Fe-N-C sites embedded in three-dimensional (3D) N-doped ordered mesoporous carbon framework. Fe-N-C/N-OMC shows high half-wave potential, kinetic current density, turnover frequency and mass activity towards ORR in alkaline electrolyte. Experiments and theoretical calculations suggest that the ultra-high ORR activity stems from the boosted intrinsic activity of FeN4 sites by graphitic N dopants, high density of accessible active site generated by high Fe and N loadings and ordered mesoporous carbon structure as well as facilitated mass and electron transport in 3D interconnected pores. Fe-N-C/N-OMC also shows comparable ORR activity to Pt/C in acidic electrolyte. As the cathode for zinc-air battery, Fe-N-C/N-OMC exhibits high open-circuit voltage, high power density and remarkable durability.

Designing highly efficient electrocatalysts with superior performance on electrochemical water splitting and rechargeable metal-air batteries is an urgent and challenging task due to required large overpotentials. A pulsed direct current with high voltage produced by a layered triboelectric nanogenerator (TENG) provides a novel type of power sources to electrodeposit sub-2 nm Pt nanoclusters onto NiFe-LDH nanosheets in the absence of any capping reagents to improve hydrogen evolution reaction (HER) activity and to electronically reduce part of Fe3+ cations in the lattice of NiFe-LDH to Fe2+ species to enhance oxygen evolution reaction (OER) activity. The particle size of Pt nanoclusters could be easily tuned from 0.8 nm to 1.2 nm by alternating the working frequency of the layered TENG. By loading sub-2 nm Pt nanoclusters onto NiFe-LDH (Pt–NiFe-LDH), the HER overpotential drops from 345 mV to 86 mV at a current density of 50 mA cm−2 in alkaline electrolyte. The synergistic effect between Pt nanoclusters and NiFe-LDH nanosheets on enhancing the cleavage of HO–H bond and recombination of hydrogen intermediates to form molecular hydrogen dramatically improves the HER activity. Meanwhile, benefiting from tuning the local atomic structure and crystal defects by reducing Fe3+ to Fe2+, NiFe-LDH nanosheets demonstrates enhanced OER activity. The deposited sub-2 nm Pt nanoclusters also produces elevated oxygen reduction reaction (ORR) activity with a half-wave potential of 0.84 V (vs RHE). Hence, the as-prepared Pt–NiFe-LDH catalysts exhibits tri-functional properties towards HER, ORR and OER and could be used as the electrode catalysts for overall electrocatalytic water splitting and rechargeable zinc-air batteries. With the optimal catalyst (Pt–NiFe-LDH-0.5-12) as the electrode for overall water splitting, the potential difference between OER and HER drops to 1.63 V at a current density of 50 mA cm−2, much lower than that of the mixed noble-metal catalysts (Pt/C and RuO2, 1.98 V). As an air electrode of rechargeable zinc-air batteries, Pt–NiFe-LDH-0.5-12 exhibits much better performance than that of bare NiFe-LDH in terms of higher open-circuit voltage, higher round-trip efficiency and durability.

MgO, (NH4)2SO4 or MoO3-modified Ce0.6Zr0.4O2-supported gold catalysts were synthesized and studied for the oxidative esterification of methacrolein with methanol to methyl methacrylate. Although the particle size distribution and oxidative state of the supported Au showed almost no change before and after Ce0.6Zr0.4O2 modification as confirmed by TEM, Raman and XPS technologies, all of the modified Au/Ce0.6Zr0.4O2 catalysts demonstrated highly improved catalytic activities. H2-TPR patterns indicated that the amounts of low-temperature active oxygen species increased in the MgO- and MoO3-modified catalysts. At the same time, the strong interaction between gold and Ce–Zr oxides in the MgO-modified catalyst and the charge transfer between Mo6+ and Ce3+ in the MoO3-modified catalyst were evidenced by XPS characterization. Based on the enhanced synergetic effects between the Au nanoparticles and the support for oxygen activation, the MgO-promoted Au catalyst presented the best performance with a methacrolein conversion of 98% and a methyl methacrylate selectivity of 90% in the absence of a base at 80 °C for 2 h of reaction. Differing from MgO and MoO3, (NH4)2SO4 modification simultaneously increased the acid–base properties of the catalyst and then increased the activity of the catalyst due to the promoted formation of the intermediate hemiacetal.

Uniform large particles (millimeter class) of acid poly ionic liquid (PIL-A) were synthetized, and characterized by FT-IR, XRD, TGA/DCS, and SEM. Thermostability and mechanical strength of PIL-A are much higher than that of commercial resin. Its catalytic properties were investigated through the esterification of methacrylic acid and methanol as the objective reaction. Results showed that the catalytic activity of PIL-A was higher than that of commercial resin. The optimum reaction conditions were as follows: 5 wt% catalyst, 95 degrees C reaction temperature, 3 h reaction time, and methacrylic acid to methanol mole ratio of 1:1.2. The yield of methyl methacrylate is 100%, under optimum reaction conditions. The catalytic activities of PIL-A with different esterifications were also investigated. PIL-A had a higher catalytic activity to different esterification. The catalytic activity of PIL-A did not decrease after it was reused for five times. Continuous reaction to methyl methacrylate (MMA) with a fixed bed reactor was further investigated. The percentage of MMA in the product was >96%. (C) 2015 Elsevier B.V. All rights reserved.

Au nanoparticles supported on Ce–Zr oxides were prepared and characterized in order to study the role of the support in the oxidative esterification of aldehydes in the presence of molecular oxygen. Ce–Zr solid solutions were synthesized by using (NH4)2Ce(NO3)6 as a precursor, while the mixed oxides were obtained by using a Ce(NO3)3 precursor. The solid solutions exhibited a smaller crystallite size, higher BET surface area, larger amount of H2 consumption, and higher acidity and basicity than the mixed oxides at the same Ce/Zr molar ratio due to the incorporation of Zr4+ into the ceria lattice. The effect of the support was investigated because all the samples presented similar Au particle sizes, as confirmed by the HAADF-STEM study. Supports with higher reducibility showed better performance by activating methanol to methoxy and facilitating the β-H elimination of hemiacetal. We also found that the formation of hemiacetal was enhanced by the acidic sites and basic sites of Au catalysts supported on solid solutions possessing similar reducibility. A plausible reaction mechanism for the oxidative esterification of aldehydes on Ce–Zr solid solution-supported Au nanoparticles was proposed. The screened catalyst was also applicable to the oxidative esterification of different benzylic aldehydes, producing high yields. This catalyst could be reused after a simple separation eight times, keeping a high selectivity of above 99%.

A highly efficient Pd2Pb8/alumina catalyst was prepared, which provided the highest turnover number (TON) of 302 for aerobic oxidative coupling of methylacrolein with methanol. The enhanced catalytic efficiency could be attributed to the multi-scale (micron, nano and atom scales) promoting effects of the pre-loaded Pb species.

Novel MgO-SBA-15 supported catalysts were prepared for oxidative esterification of methacrolein (MAL) with methanol to methyl methacrylate (MMA). The MgO-SBA-15 supports were synthesized with different magnesia loadings from different magnesium precursors and hydrochloric acid molar concentrations. The MgO-SBA-15 supports and Pd-Pb/MgO-SBA-15 catalysts were characterized by several analysis methods. The results revealed that the addition of MgO improved the ordered structure of SBA-15 supports and provided surface alkalinity of SBA-15 supports. The average size of the Pd3Pb particles on magnesia-modified Pd-Pb/MgO-SBA-15 catalysts was smaller than that on the pure silica-based Pd-Pb/SBA-15 catalysts. The experiments on catalyst performance showed that the magnesia-modified Pd-Pb/MgO-SBA-15 catalysts had higher activity than pure silica-based Pd-Pb/SBA-15 catalysts, showing the strong dependence of catalytic activity on the average size of active particles. The difference of activity between Pd-Pb/SBA-15 catalysts and Pd-Pb/MgO-SBA-15 catalysts was due to the discrepant structural properties and surface alkalinity provided by MgO, which led to the different Pd3Pb particle sizes and then resulted in the different number of active sites. Besides magnesia loadings, other factors, such as hydrochloric acid molar concentration and magnesium precursors, had considerable influences on the catalytic activity. (C) 2014 The Chemical Industry and Engineering Society of China, and Chemical Industry Press. All rights reserved.

Developing nonprecious electrocatalysts with superior activity and durability for electrochemical water splitting is of great interest but challenging due to the large overpotential required above the thermodynamic standard potential of water splitting (1.23 V). Here, in situ growth of Fe2+ -doped layered double (Ni, Fe) hydroxide (NiFe(II,III)-LDH) on nickel foam with well-defined hexagonal morphology and high crystallinity by a redox reaction between Fe3+ and nickel foam under hydrothermal conditions is reported. Benefiting from tuning the local atomic structure by self-doping Fe2+ , the NiFe(II,III)-LDH catalyst with higher amounts of Fe2+ exhibits high activity toward oxygen evolution reaction (OER) as well as hydrogen evolution reaction (HER) activity. Moreover, the optimized NiFe(II,III)-LDH catalyst for OER (O-NiFe(II,III)-LDH) and catalyst for HER (H-NiFe(II,III)-LDH) show overpotentials of 140 and 113 mV, respectively, at a current density of 10 mA cm-2 in 1 m KOH aqueous electrolyte. Using the catalysts for overall water splitting in two-electrode configuration, a low overpotential of just 1.54 V is required at a benchmark current density of 10 mA cm-2 . Furthermore, it is demonstrated that electrolysis of the water device can be drived by a self-powered system through integrating a triboelectric nanogenerator and battery, showing a promising way to realize self-powered electrochemical systems.

Herein, we report for the first time that a La–Mg composite oxide modified extra-large mesoporous FDU-12 supported Au–Ni bimetallic catalyst exhibits excellent performance for oxidative coupling of aldehydes (including benzyl and aliphatic aldehydes) with methanol to directly produce methyl esters.

Hydrodeoxygenation of sunflower oil was performed in an autoclave over 5.0 wt.% Pd/Al-SBA-15 (Si/Al molar ratios from 22 to 300) and Pd/HZSM-5(22). The effects of acidity of the catalysts and the reaction temperatures on the activity of the catalysts were investigated. Pd/Al-SBA-15(Si/Al = 300) showed a high activity as 74.4% liquid yield and 72.9% C15–C18 diesel-like hydrocarbons yield at 250 °C. At 300 °C, the higher activity over Pd/Al-SBA-15(Si/Al = 50, 100 and 300) catalysts compared with that over Pd/Al-SBA-15(22) and Pd/HZSM-5(22) indicated that strong acidity of the catalysts was not favorable for converting sunflower oil into C15–C18 diesel-like hydrocarbons at a high temperature.

In the paper, we report for the first time that the conversion of renewable oils into diesel-like hydrocarbon mixtures can be realized on molybdenum carbides with high activity and selectivity. The molybdenum carbide catalyst exhibited much better resistance to leaching than noble metals and could be reused consecutively for sixteen times without deactivation. Mechanism investigations indicated that molybdenum carbide and palladium showed different reaction selectivities and it was speculated that the level of difficulty in acyl-to-alkyl rearrangement of surface acyl intermediates on molybdenum carbide and palladium resulted in the different product selectivity.

A series of Ca/SBA-15 samples with Ca/Si atomic ratios of 0.1, 0.2, 0.3, 0.4 and 0.5 were prepared by using a one-pot synthesis method. They were used in the transesterification of sunflower oil with methanol. For comparison, 0.3Ca/SBA-15 was also synthesized by an incipient impregnation method (0.3Ca/SBA-15-IM). Small-angle XRD, N 2 adsorption, TEM, SEM, TG-DTA, FTIR, CO 2 -TPD techniques were used to determine the textual structure and physicochemical properties of Ca/SBA-15 samples. The mesoporous structure of SBA-15 was well preserved with Ca/Si ratios up to 0.5. Compared with 0.3Ca/SBA-15-IM sample, the Ca/SBA-15 showed not only a better calcium species distribution, but also higher BET surface area and larger medium basic sites. A biodiesel yield of as high as 99.1% was achieved on the 0.5Ca/SBA-15 catalyst at a reaction temperature of 200 °C for 8 h. In the meantime, no deactivation was found after five cycles on Ca/SBA-15 sample prepared by one-pot synthesis method in the transesterification reaction, which showed a much better stability than that of prepared by conventional impregnation method. Besides, a water content of up to 5% and/or free fatty acids (FFAs) content of 3% did not affect the catalytic activity of Ca/SBA-15 catalyst in the transesterification reaction.

A size-controlled palladium nanoparticle catalyst prepared by adsorption of colloidal palladium nanoparticles on barium sulfate is efficient and highly selective in transforming vegetable oils into diesel-like fuel. Preliminary kinetic investigations using model compounds indicated that decarboxylation of aliphatic esters on palladium in a hydrogen-rich atmosphere showed a zero-order rate. Hydrogen temperature-programmed desorption measurements revealed that the high-temperature desorption of hydrogen species might be the rate-determining step.

Ordered mesoporous carbon (OMC)-supported molybdenum carbide catalysts were successfully prepared in one pot using a solvent-evaporation-induced self-assembly strategy accompanied by a carbothermal hydrogen reduction reaction. Characterization with nitrogen sorption, small-angle XRD, and TEM confirmed that the obtained materials had high surface areas, large pore volumes, ordered mesoporous structures, narrow pore size distributions, and uniform dispersions of molybdenum carbide particles. With nitrogen replaced by hydrogen in the carbothermal reduction reaction, the formation temperature of molybdenum carbide could be reduced by more than 100 °C. By changing the amount of molybdenum precursor added from less than 2 % to more than 5 %, molybdenum carbide structures could be easily regulated from Mo(2) C to MoC. The catalytic performance of OMC-supported molybdenum carbide catalysts was evaluated by hydrodeoxygenation of vegetable oils. Compared with Mo(2)C, MoC exhibited high product selectivity and excellent resistance to leaching in the conversion of vegetable oils into diesel-like hydrocarbons.

Carbon nanofiber-supported molybdenum carbide catalysts (Mo2C/CNF) with different loadings were prepared by the carbothermal hydrogen reduction method. Characterizations with Raman, XRD, N2-TGA, SEM, TEM and HAADF-STEM confirmed that Mo2C nanoparticles were successfully supported on the carbon nanofibers. The optimal reaction conditions with model compounds on Mo2C/CNF had a conversion of 98.03% and yield of 95.26%. It is interesting to note that a low evaporation rate positions the Mo2C nanoparticles on the outside of the CNF due to the capillary effect and the Mo2C nanoparticles on the outside of the CNFs showed high catalytic activity compared to ones on the inside of the CNFs. The Mo2C/CNF catalyst was recycled 5 times without any apparent loss of catalytic activity. Catalytic performances of Mo2C/CNF, Mo2C/AC (activated carbon) and Mo2C/CNT (multi-walled carbon nanotubes) were examined using methyl palmitate and maize oil. The results showed that molybdenum carbide could be a potential substitute for noble metals in transformation of vegetable oils.

Nanostructured molybdenum carbides supported on multi-walled carbon nanotubes (Mo2C/CNTs) with different loadings were prepared by carbothermal hydrogen reduction method and characterized with SEM, Raman, HAADF-STEM and XRD. Raman spectra showed that the specific G-band structure of carbon nanotubes promoted the formation of molybdenum carbide at lower temperatures. Compared with noble metals, molybdenum carbide exhibited better catalytic activity and resistance to leaching. The Mo2C/CNTs catalyst also showed high activity and selectivity for one-step conversion of vegetable oils into branched diesel-like hydrocarbons, which provided a promising approach to prepare high-grade diesel fuels from renewable resources.

An effective and highly selective decarboxylation approach to convert higher aliphatic esters into diesel-like paraffins has been developed. The results showed that palladium supported on barium sulfate was a potent catalyst to transform aliphatic esters into high-energy alkanes in supercritical hexane at a much lower temperature. Based on the comprehensive analysis to gas and liquid products, a decarboxylation mechanism was proposed. The methodology described in this paper provides a new protocol to the utilization of biomass-based resources, especially to the second generation biodiesel production.