Improving the utilization of metals in heterogeneous catalysts with excellent catalytic performance, high selectivity and good stability represents a major challenge. Herein a new strategy is disclosed by enabling a nanoscale synergy between a transition metal and a noble metal. A novel Ru/Ni/Ni(OH)2/C catalyst, which is a hybrid of Ru nanoclusters anchored on Ni/Ni(OH)2 nanoparticles (NPs), was designed, prepared and characterized. The Ru/Ni/Ni(OH)2/C catalyst exhibited a remarkable catalytic activity for naphthalene hydrogenation in comparison with existing Ru/C, Ni/Ni(OH)2/C and Ru–Ni alloy/C catalysts. This is mainly attributed to the interfacial Ru, Ni and Ni(OH)2 sites of Ru/Ni/Ni(OH)2/C, where hydrogen is adsorbed and activated on Ru while Ni transfers the activated hydrogen species (as a “bridge”) to the activated naphthalene on Ni(OH)2 sites, producing decalin through a highly effective pathway.

Catalytic oxidation can be effectively promoted by the presence of oxygen vacancies on the catalyst surface. In this study, the effect of oxygen vacancies on the catalytic wet air oxidation (CWAO) of phenol was investigated with CeO2 and MnOx–CeO2 as catalysts. CeO2 and MnOx–CeO2 catalysts with different amounts of oxygen vacancies were obtained via hydrothermal methods and applied for the CWAO of phenol. It was found that CeO2 and MnOx–CeO2 nanorods were much more active than the cubic nanorods. The physicochemical properties of the samples were characterized by TEM, XRD, BET, XPS, and H2-TPR techniques. The results revealed that the presence of oxygen vacancies in CeO2 and MnOx–CeO2 catalysts could increase the oxidizing ability of the catalysts surface. The addition of Mn could greatly improve the adsorption ability of CeO2 and more efficiently oxidize phenol and its intermediates. The synergy between Mn and Ce could further improve the catalyst redox properties and produce a larger amount of active oxygen species, which is the reason why MnOx–CeO2 nanorods are the most active catalysts among the catalysts investigated in this study.

•Highly active Ag/Ce-Zr catalyst with ‘Ag/Ce’ structure was successfully synthesized.•Precipitant can affect the size of Ag particles and alter Ag-Ce interaction.•The optimal interaction was beneficial for the increase of superficial Ag+ species.•The catalyst/soot contact for the Ag/Ce-Zr catalyst is expected to be enhanced.•Ag/Ce-Zr catalyst was utilized five times without any appreciable loss of activity.Different to Pt-based catalysts used in diesel particulate filter (DPF), Ag/CeO2-ZrO2 catalyst, whose main feature is a considerable amount of silver species exposed on the surface of catalyst, possesses outstanding soot oxidation performance even in loose contact mode and in the absence of NOx. The Ag/CeO2-ZrO2 catalyst with the special structure and Ag particle ranging from 17 to 35 nm is herein prepared by controlling precipitant, and its combustion temperature T10 and Tmax can be achieved as low as 254 °C and 280 °C in 5.0% H2O/4.8% O2/90.2% N2 and loose contact mode, respectively. The H2-TPR and XPS characterization results show that the interaction between Ag and ceria, controlled by precipitant, leads to the high content of the species of Ag+ and Ce3+. It can be concluded that the distribution of silver species with high superficial Ag+/Ag0 ratio and Ag-Ce interface in Ag/CeO2-ZrO2 catalyst does favor the activation and transfer of oxygen species. It appears that the adsorbed oxygen species play an important role in catalytic performance. Moreover, the catalyst/soot contact for the Ag/CeO2-ZrO2 catalyst is expected to be enhanced due to the transfer of oxygen species. The prepared Ag/CeO2-ZrO2 catalyst is repeatedly used five times without any appreciable loss of activity, thus shows good stability initially.Download high-res image (66KB)Download full-size image

•Hierarchical Ni was prepared via the hydrothermal synthesis method.•Shape of nickel was modulated by changing hydrothermal temperature and solvent.•The Pt/Ni catalysts were obtained via the galvanic replacement reaction method.•Pt/flower-like nickel showed high catalytic activity in hydrogenation reaction.Without any capping agent, surfactant or external magnetic field, hierarchical nickel was successfully prepared via a simple hydrothermal reduction method by using hydrazine hydrate as reducing agent. The structure and morphology of the products (for instance, flower-like, column-like and spherical-like) were controlled by adjusting hydrothermal conditions including reaction temperature and solvent. The morphology transformation mechanism was proposed and discussed. Corresponding platinum/nickel catalysts (Pt/Ni) were obtained by the galvanic replacement reaction method. And the catalytic activity of the platinum/nickel samples was evaluated by using selective hydrogenation of nitrobenzene. It was found that platinum/flower-like nickel showed the most excellent catalytic performance among the as-synthesized catalysts in this work, with good stability as well. Moreover, reasons for the enhancement of platinum/flower-like nickel for nitrobenzene hydrogenation were investigated.Download high-res image (184KB)Download full-size image

Cobalt–nickel alloy crystals with different morphologies, such as flower-like, column-like, mushroom-like and dendrite-like, were prepared by a facile hydrothermal or solvothermal reduction approach without the addition of any surfactant, using hydrazine hydrate as a reducing agent, ethanediamine as a capping agent and a mixture of nickel(II) chloride hexahydrate (NiCl2·6H2O) and cobalt(II) chloride hexahydrate (CoCl2·6H2O) as a precursor. The effect of hydrothermal temperature (120, 150 or 180 °C) and solvent (water or ethanol) on the shape of the CoNi crystals was investigated in this work. The corresponding Ru/CoNi catalysts (Ru-on-CoNi nanocrystals) were obtained via a galvanic replacement reaction. The sizes, element chemical states, morphologies and structures of the CoNi and Ru/CoNi samples were characterized by X-ray diffraction (XRD), scanning electronic microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), and high-sensitivity low-energy ion scattering (HS-LEIS) techniques. The catalytic performance of the as-synthesized catalysts was evaluated by using the benzene hydrogenation reaction. The Ru/CoNi catalyst with a dendrite-like morphology exhibited the highest catalytic hydrogenation activity among the Ru/CoNi catalysts with different shapes. This was mainly due to its high Ru dispersion, many defect sites and positive synergistic effect compared with ruthenium, nickel and cobalt related species. Importantly, the cost of recycling the Ru/CoNi catalysts was relatively low because they could be recycled by magnetic separation.

Cobalt–nickel alloy crystals with different morphologies, such as flower-like, column-like, mushroom-like and dendrite-like, were prepared by a facile hydrothermal or solvothermal reduction approach without the addition of any surfactant, using hydrazine hydrate as a reducing agent, ethanediamine as a capping agent and a mixture of nickel(II) chloride hexahydrate (NiCl2·6H2O) and cobalt(II) chloride hexahydrate (CoCl2·6H2O) as a precursor. The effect of hydrothermal temperature (120, 150 or 180 °C) and solvent (water or ethanol) on the shape of the CoNi crystals was investigated in this work. The corresponding Ru/CoNi catalysts (Ru-on-CoNi nanocrystals) were obtained via a galvanic replacement reaction. The sizes, element chemical states, morphologies and structures of the CoNi and Ru/CoNi samples were characterized by X-ray diffraction (XRD), scanning electronic microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), and high-sensitivity low-energy ion scattering (HS-LEIS) techniques. The catalytic performance of the as-synthesized catalysts was evaluated by using the benzene hydrogenation reaction. The Ru/CoNi catalyst with a dendrite-like morphology exhibited the highest catalytic hydrogenation activity among the Ru/CoNi catalysts with different shapes. This was mainly due to its high Ru dispersion, many defect sites and positive synergistic effect compared with ruthenium, nickel and cobalt related species. Importantly, the cost of recycling the Ru/CoNi catalysts was relatively low because they could be recycled by magnetic separation.

δ-MnO2 with a very high amount of Mn4+ showed high catalytic activity and stability for the catalytic wet air oxidation (CWAO) of phenol at a very low temperature of 70 °C. The abundance of Mn4+ and reactive surface oxygen species in this catalyst, its resistance to Mn leaching, and its repeatable Mn4+/Mn3+ (Mn4+/Mn2+) redox cycles contributed greatly to its remarkable catalytic performance.

The thermal treatment temperature of bimetallic nanocatalysts plays an important role in determining their catalytic performance. In this study, the synthesis of RuNi bimetallic nanoparticles (BNPs) supported on carbon black catalysts (denoted as RuNi BNSC) via hydrazine hydrate reduction and galvanic replacement reaction methods was reported. Then the effect of the annealing temperature in N2 (uncalcined, 160, 230, 280, 380, 480, 580 and 680 °C) of RuNi BNSC on its catalytic activity for the benzene hydrogenation reaction was investigated. It was found that RuNi BNSC calcined at 380 °C exhibited outstanding catalytic activity in the liquid phase hydrogenation of benzene to cyclohexane, which was about 3–4 times higher than that of RuNi BNSC calcined at 680 °C, while RuNi BNSC annealed at 480 °C had no activity for this reaction. The characterization results of the catalysts indicated that various thermal treatment temperatures in N2 affected the RuNi BNP size, chemical states of Ru and Ni, and RuNi bimetallic nanostructures and thus the catalytic properties.

Ru/Co/Co3O4/C (Ru nanoclusters-on-Co/Co3O4 nanoparticles) has an unexpected enhancement of activity for benzene hydrogenation which is about 2500 times higher than Ru–Co nanoalloy/C. Detailed nanostructure characterization of Ru/Co/Co3O4/C has revealed that the high activity originates from a synergetic multifunction of the catalytic Ru, Co and Co3O4 sites on the nanocluster/nanoparticle surfaces.

•The Pt50Au50/C catalysts were prepared using a modified two-phase protocol.•The Pt50Au50/C catalyst with 600 °C treatment temperature has an unprecedented performance.•The above catalyst has higher catalytic activity than Pt/C (J–M, 20 wt%).•Stability tests showed no obvious loss of activity after 500 potential cycles.The design of active and robust bimetallic nanocatalysts requires the control of the nanoscale alloying, phase-segregation and the correlation between nanoscale phase-segregation and catalytic properties. To enhance the performance and durability of formic acid oxidation reaction in fuel-cell applications, we prepared a platinum–gold (PtAu) nanocatalyst with controlled morphology and composition. The catalyst is further treated by calcination under controlled temperature and atmosphere. The morphology of the bimetallic nanoparticles is determined by transmission electron microscopy. The nanoscale phase properties and surface composition are carried out by X-ray diffraction and X-ray photoelectron spectroscopy. Cyclic voltammetry measurements demonstrated that the catalytic activity is highly dependent on the nanoscale evolution of alloying and phase segregation. The mass activity of as-prepared Pt50Au50/C with 600 °C treatment temperature is about 11 times higher than that of commercial Pt/C. Stability tests showed no obvious loss of activity after 500 potential cycles. The high activity and stability are attributed to lattice contraction effect as a result of the high thermal treatment condition. Our findings demonstrate the importance of phase segregation at the nanoscale in harnessing the true electrocatalytic potential of bimetallic nanoparticles.

•Prepared PtFe/C with Fe-rich surface by a one-pot surfactant-free polyol process.•PtFe/C catalyst has high activity for PROX reaction.•The surface Fe enrichment is probably due to the preparation strategy.•The synthesis method can be used for preparing transition metals decorated Pt/C.Rational design and controlled preparation of highly effective catalysts towards the preferential oxidation of CO have significant importance for the utilization of hydrogen energy. In this work, PtFe/C bimetallic catalysts have been successfully prepared by a one-pot surfactant-free polyol process, where Pt metal nanoparticles serve as catalysts to reduce Fe ions to metallic form on the surface. The resulting PtFe/C catalysts are investigated for a PROX CO reaction and characterized by ICP-AES, XPS, XRD, TEM, HS-LEIS. It is found that PtFe/C with an optimal Fe loading shows extremely high activity and stability. These characterization results reveal that PtFe/C adopts a structure of Fe rich surface and Pt dominated cores. The excellent catalytic performances over PtFe/C catalysts are attributed to the efficient activation of O2 by Fe species located on the catalyst surface, indicated by the results of CO and O2 pulse experiments. Additionally, other PtM/C (M = Cu, Ni) catalysts possessing the similar structure with that of PtFe/C can also be synthesized using the established one-pot surfactant-free polyol process.

•A Pt decorated Pd/C with size (5–6 nm) was obtained by galvanic displacement.•The catalyst with Pt:Pd molar ratio 1:250 has an unprecedented performance.•The above catalyst has higher activity and stability than Pt/C and Pd/C.•The controlled decorated structure can significantly reduce Pt use and thus cost.The design of active and durable catalysts for formic acid (FA) electrooxidation requires controlling the amount of three neighboring platinum atoms in the surface of Pt-based catalysts. Such requirement is studied by preparing Pt decorated Pd/C (donated as Pt–Pd/C) with various Pt:Pd molar ratios via galvanic displacement making the amount of three neighboring Pt atoms in the surface of Pt–Pd/C tunable. The decorated nanostructures are confirmed by XPS, HS-LEIS, cyclic voltammetry and chronoamperometric measurements, demonstrating that Pt–Pd/C (the optimal molar ratio, Pt:Pd = 1:250) exhibits superior activity and durability than Pd/C and commercial Pt/C (J-M, 20%) catalysts for FA electrooxidation. The mass activity of Pt–Pd/C (Pt:Pd = 1:250) (3.91 A mg−1) is about 98 and 6 times higher than that of commercial Pt/C (0.04 A mg−1) and Pd/C (0.63 A mg−1) at a given potential of 0.1 V vs SCE, respectively. The controlled synthesis of Pt–Pd/C lead to the formation of largely discontinuous Pd and Pt sites and inhibition of CO formation, exhibiting unprecedented electrocatalytic performance toward FA electrooxidation while the cost of the catalyst almost the same as Pd/C. These findings have profound implications to the design and nanoengineering of decorated surfaces of catalysts for FA electrooxidation.

A series of CaO/Al2O3 base catalysts with different crystal phases is prepared via thermal treatment. The as-prepared base catalysts are tested through Baeyer–Villiger oxidation of cyclohexanone to ε-caprolactone in liquid-phase using a mixture of aqueous hydrogen peroxide and benzonitrile as oxidant. The corresponding results show that the CaO/Al2O3 catalysts with high thermal treatment temperature (e.g. 900 °C) exhibit excellent activity as well as stability. Upon these, the catalysts are characterized by TG–DTG, XRD, N2-physisorption, SEM and CO2-TPD techniques. The characterization results clearly suggest that such a stable and efficient catalytic performance is beneficial from the formation of calcium aluminate phase, thus overcoming one of base catalyst application barriers, that Ca or CaO species loss (leach) from CaO-based catalysts during reactions. Correspondingly, it can be inferred that the treatment of the catalysts at different temperatures results in the diverse distribution of basic strength. Furthermore, it is also demonstrated that the suitable base strength (medium strength is good for the reaction selected in the work) plays a critically role in the improvement of catalytic performance. Finally, the effects of operation conditions on catalytic activity and product selectivity are also determined and discussed.

•CO2 expanded carbonation technique used to synthesize mesoporous alumina.•Alumina particles were flower-like and honey-comb-like due to different volume expansions.•Efficient catalytic oxidation of cyclohexanone to ɛ-caprolactone.•Hydrolysis of ɛ-caprolactone could be avoided.A CO2 expanded carbonation technique is proposed for direct synthesis of alumina powders that does not require structure directing substances or templates. Mesoporous amorphous flower-like alumina was synthesized at relatively low volume expansions (lower ethanol to water volume ratio), whereas mesoporous crystalline honey-comb-like alumina was synthesized at high volume expansions. The alumina powders exhibited high surface area and pore size with small crystallite sizes. The alumina structures were stable from 400 to 800 °C. Experimental tests showed that the alumina powders could catalytically convert cyclohexanone to ɛ-caprolactone efficiently. The use of the calcined catalysts (at 400 and 800 °C; flower-like alumina) at equal ethanol to water volume ratio avoids the usual and inevitable hydrolysis of ɛ-caprolactone to ɛ-hydroxyhexanoic acid. The catalyst was recyclable and stable for up to five reaction cycles.

One of the most challenging problems for the fuel cells commercialization is the preparation of active, robust, and low-cost electrocatalysts. This work reports a novel electrocatalyst of Pd decorated Fe/C catalyst, donated as Pd-Fe/C, for formic acid electrooxidation. The Pd-Fe/C is prepared by a spontaneous displacement process, and characterized by an array of analytical techniques including transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. Cyclic voltammetric and chronoamperometric measurements demonstrated that the activity of Pd-Fe/C (Pd:Fe = 1:5) (5.10 A mg−1) is about 11 times of Pd/C (0.46 A mg−1) at a given potential of 0.227 V vs. SCE for formic acid electrooxidation. The enhanced electrocatalytic activity and stability are attributed to synergistic effect due to the replacement of Fe atoms by Pd atoms in the outer layer of the Fe nanoparticles, resulting in higher propensity of Fe and lower propensity of Pd to surface oxidation to weaken the CO adsorption.

A prepared 0.024%Ru–1.00%Ni/C nano-bimetallic catalyst reported in this work is a highly efficient and stable catalyst for the hydrogenation of benzene to cyclohexane, with an unprecedented TOF up to 7905 h−1 under mild reaction conditions (20 °C, 40 psi H2) without adding any solvent. The method for the preparation of catalyst is very simple and low-cost. Therefore, this cyclohexane synthetic approach is potentially more environmentally friendly and economical than existing technology.

•Ru–RuO2/C shows an excellent hydrogen generation rate of 16.8 L H2 min−1 gcat.−1.•Reducible RuO2(110) crystal plays important roles in NaBH4 hydrolysis reaction.•A synergetic effect of RuO2 and Ru results in high hydrolysis activity of NaBH4.How to efficiently hydrolyze NaBH4 to H2 has been greatly concerned due to its theoretically high hydrogen storage capacity (10.8 wt. %). In this work, Ru–RuO2/C catalyst is prepared by the galvanic replacement reaction of Ni based material. By evaluating the hydrolysis activity, analyzing the structure and component of the catalysts and exploring the possible reaction channels, we find that Ru–RuO2/C has the excellent hydrolysis activity of 16.8 L H2 min−1 gcat.−1 in 5 wt. % NaBH4 and 1 wt. % NaOH solution at 323 K, which is higher than most data in open literature. The more reducible RuO2 (110) crystal at about 423 K plays an important role in the high hydrolysis activity of Ru–RuO2/C. The ruthenium oxide facilitates the dissociation of water, a rate-determining step of NaBH4 hydrolysis to H2, while Ru acts as an active phase for NaBH4 dissociation. A synergetic effect of RuO2 and Ru on Ru–RuO2/C is crucial to the high hydrolysis activity of sodium borohydride and it can also be kept in repeated experiments.

In this article, a novel single-column atmospheric cryogenic air separation process is proposed to reduce energy consumption through the implementation of thermal pump technique. Different from the conventional double-column cryogenic process, the new single-column distillation includes a nitrogen compressor acting as a thermal pump, which makes use of the latent thermal energy of the streams in the distillation column. To verify the validity of the proposed separation process, four typical configurations of the single-column processes are constructed and simulated on the ASPEN PLUS platform with the operation conditions: air flow rate at 50 000 N m3, inlet temperature of the distillation column at 87 K, and various nitrogen compression temperatures. The conventional double-column cryogenic air separation process is also simulated as the base to compare the energy consumptions between the conventional and the novel processes. On the basis of such a comparison, the novel single-column cryogenic air separation process can save energy up to 23% and produce the products’ purity in industrial standard.

Understanding how the pathway of formic acid electrooxidation depends on the composition and structure of Pt or Pd atoms on the surface of Pd- or Pt-based nanoparticles is important for designing catalysts aiming toward active, selective, stable, and low-cost. This work reports new findings of the investigation of submonolayer Pt decorated PdAu/C nanocatalysts (donated as Pt-PdAu/C) for formic acid electrooxidation. The Pt-PdAu/C are synthesized via a spontaneous displacement reaction and characterized by an array of analytical techniques including transmission electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy. The electrocatalytic activity is examined using cyclic voltammetric and chronoamperometric measurements. The results show that the as-prepared Pt-PdAu/C with an optimal Pt:Pd atomic ratio of 1:100 exhibits enhanced electrocatalytic activity for formic acid electrooxidation compared with the PdAu/C and commercial the Pt/C catalysts. The oxidation potential on the Pt-PdAu/C shifts negatively by about 200 mV compared with that of the PdAu/C. The enhanced electrocatalytic activity and stability are attributed to the replacement of the Pd atom layer by Pt atoms, which significantly reduces the presence of the so-called "three neighboring site" of Pd or Pt atoms in the Pt-PdAu/C to efficiently suppress CO formation. The enhanced activity/stability and ultralow Pt loading of the Pt-PdAu/C have implications to the development of commercially-viable catalysts for application in direct formic acid fuel cells and catalysis.Highlights► Pt decorated PdAu/C via surface limited spontaneous displacement reaction. ► Pt-PdAu/C catalysts have higher activities and stability for FA oxidation. ► Significantly reduce the Pt loading and thus the cost.

The understanding of the electrocatalytic activity of bimetallic nanoparticle catalysts requires the ability to precisely control the composition and phase properties. In this report, we describe a new strategy in the preparation of a series of carbon supported platinum–gold bimetallic nanoparticles with various bimetallic compositions which were loaded onto a carbon black support and subjected subsequently by thermal treatment (Pt100−mAum/C). The Pt100−mAum/C catalysts are characterized by X-ray diffraction (XRD), transmission electron spectroscopy (TEM), and induced coupled plasma-atomic emission spectroscopy (ICP-AES). The XRD pattern for the bimetallic nanoparticles shows single-phase alloy character. This ability enabled us to establish the correlation between the bimetallic composition and the electrocatalytic activity for formic acid (FA) electrooxidation. The electrocatalytic activities of the catalysts toward FA oxidation reaction are shown to strongly depend on the bimetallic PtAu composition. Within a wide range of bimetallic composition, the Pt50Au50/C catalyst shows the highest electrocatalytic activity for the FA oxidation, with a mass activity eight times higher than that of Pt/C. The high performance of the PtAu/C catalyst can be ascribed to the increased selectivity toward the FA dehydrogenation at the decreased availability of adjacent Pt atoms.Highlights• Pt100−mAum/C catalysts with controllable bimetallic composition were synthesized. • The correlation for the effect of PtAu bimetallic composition on mass activity was established. • The Pt50Au50/C catalyst exhibits an eight-fold increase of electrocatalytic activity for the oxidation of formic acid in comparison with Pt/C. • The origin of the high activity mainly owes to its high selectivity toward the dehydrogenation of formic acid molecules on the bimetallic alloy surface.

•The Ru0.04Ni0.96/C(T) (T-reducing temperature) catalysts were synthesized.•Ru0.04Ni0.96/C(30) was with the nanostructure of Ru-on-Ni/Ni(OH)2 nanoparticles.•Ru0.04Ni0.96/C(280) was with the nanostructure of complete RuNi alloy.•Ru0.04Ni0.96/C(30) showed the highest catalytic activity in benzene hydrogenation.•Synergistic effect of Ru, Ni and Ni(OH)2 sites was present in Ru0.04Ni0.96/C(30).In this study, the Ru0.04Ni0.96/C(T) catalysts were successfully prepared by the simple methods of hydrazine-reduction and galvanic replacement, where 0.04/0.96 and T represented the Ru/Ni atomic ratio and reducing temperature of the catalyst in N2+10%H2, respectively. The nanostructures of the Ru0.04Ni0.96 nanoparticles in the Ru0.04Ni0.96/C(T) catalysts were controlled by modulating their annealing temperature in N2+10%H2 and characterized by an array of techniques, including X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), scanning transmission electron microscopy energy dispersive X-ray spectroscopy (STEM-EDS) mapping and high-sensitivity low-energy ion scattering (HS-LEIS). The Ru0.04Ni0.96/C(30) catalyst, which was composed of Ru clusters or single atoms supported on Ni/Ni(OH)2 nanoparticles, exhibited much better catalytic performance for benzene hydrogenation than the Ru0.04Ni0.96/C(T) catalysts reduced at above 30 °C, such as Ru0.04Ni0.96/C(160) with the nanostructure of partial Ru0.04Ni0.9 alloy and Ru0.04Ni0.96/C(280) with the nanostructure of complete Ru0.04Ni0.9 alloy. The reason was that the synergistic effect of multiple active sites – Ru, Ni and Ni(OH)2 sites was present in the Ru0.04Ni0.96/C(30) catalyst, where hydrogen was preferentially activated at Ru sites, benzene was probably activated at Ni(OH)2 surface and Ni acted as a “bridge” for transferring activated H∗ species to activated benzene by hydrogen spillover effect, hydrogenating and forming product – cyclohexane. This study also provided a typical example to illustrate that the synergy effect of multiple active sites can largely improve the catalytic hydrogenation performance.

•The PtNi/Ni(OH)2/C catalyst was successfully synthesized at room temperature.•PtNi alloy/C was obtained after PtNi/Ni(OH)2/C reduced in hydrogen at 300 °C.•Nanostructures of the PtNi catalysts were characterized by numerous techniques.•PtNi alloy/C exhibited high catalytic activity for 3-pentanone hydrogenation.In this work, we prepared the Ni/Ni(OH)2/C sample at room temperature by hydrazine hydrate reducing method. The galvanic replacement reaction method was applied to deposit platinum on the Ni/Ni(OH)2 nanoparticles, to prepare the PtNi/Ni(OH)2/C catalyst. The catalyst of platinum-nickel alloy nanoparticles supported on carbon (signed as PtNi/C) was obtained by the thermal treatment of PtNi/Ni(OH)2/C in flowing hydrogen at 300 °C for 2 h. The size, nanostructure, surface properties, Pt and Ni chemical states of the PtNi/C catalyst were analyzed using powder X-ray diffraction (XRD), transmission electron microscope (TEM) and high resolution transmission electron microscope (HRTEM), high-angle annular dark-field scanning TEM (HAADF-STEM) and elemental energy dispersive X-ray spectroscopy (EDS) line scanning, X-ray photoelectron spectroscopy (XPS) and high-sensitivity low-energy ion scattering spectroscopy (HS-LEIS) techniques. The as-synthesized PtNi/C catalyst showed enhanced catalytic performance relative to the Ni/Ni(OH)2/C, Ni/C, Pt/C and PtNi/Ni(OH)2/C catalysts for 3-pentanone hydrogenation due to electron synergistic effect between Pt and Ni species in the PtNi/C catalyst. The PtNi/C catalyst also had exceling stability, with industrial application value.

In this paper, the influence of feed concentration on the performance of nanofiltration membrane separation under high concentration (0.1–0.98 mol/L) of aqueous glucose is investigated using a commercial spiral-wound nanofiltration membrane. The results of the experiments show that the permeate volume flux and observed rejection at certain operating pressures are influenced seriously by concentration. In this work, the influence of concentration is studied generally based on the solution-diffusion model, from which the concentration polarization boundary resistance Rcp and mass transfer coefficient k as functions of concentrations are obtained for high concentrations. Using these relationships, the observed rejection Ro can be predicted in the case of high concentration. The good agreements between the predicted and experimental values indicate that the models proposed and modified in this work could be used to describe the behavior of nanofiltration membrane separation in a wider range of uncharged aqueous solution concentration.Highlights► Focus on high solution concentration membrane separation ► Established the function of concentration polarization and concentration ► Setup function of mass transfer coefficient and concentration ► Buildup function of solute transport parameter with concentration ► The CP model and CFSD model were modified with concentration term.

Improving the utilization of metals in heterogeneous catalysts with excellent catalytic performance, high selectivity and good stability represents a major challenge. Herein a new strategy is disclosed by enabling a nanoscale synergy between a transition metal and a noble metal. A novel Ru/Ni/Ni(OH)2/C catalyst, which is a hybrid of Ru nanoclusters anchored on Ni/Ni(OH)2 nanoparticles (NPs), was designed, prepared and characterized. The Ru/Ni/Ni(OH)2/C catalyst exhibited a remarkable catalytic activity for naphthalene hydrogenation in comparison with existing Ru/C, Ni/Ni(OH)2/C and Ru–Ni alloy/C catalysts. This is mainly attributed to the interfacial Ru, Ni and Ni(OH)2 sites of Ru/Ni/Ni(OH)2/C, where hydrogen is adsorbed and activated on Ru while Ni transfers the activated hydrogen species (as a “bridge”) to the activated naphthalene on Ni(OH)2 sites, producing decalin through a highly effective pathway.

Ru/Co/Co3O4/C (Ru nanoclusters-on-Co/Co3O4 nanoparticles) has an unexpected enhancement of activity for benzene hydrogenation which is about 2500 times higher than Ru–Co nanoalloy/C. Detailed nanostructure characterization of Ru/Co/Co3O4/C has revealed that the high activity originates from a synergetic multifunction of the catalytic Ru, Co and Co3O4 sites on the nanocluster/nanoparticle surfaces.

δ-MnO2 with a very high amount of Mn4+ showed high catalytic activity and stability for the catalytic wet air oxidation (CWAO) of phenol at a very low temperature of 70 °C. The abundance of Mn4+ and reactive surface oxygen species in this catalyst, its resistance to Mn leaching, and its repeatable Mn4+/Mn3+ (Mn4+/Mn2+) redox cycles contributed greatly to its remarkable catalytic performance.