氧化铋在膨胀阻燃聚丙烯体系中的催化协效作用

将聚磷酸铵(APP)和双季戊四醇(DPER)膨胀型阻燃剂应用于聚丙烯(PP)的阻燃,并加入少量氧化铋(Bi2O3)。采用极限氧指数、烟密度和热分析等表征其阻燃性能。结果表明,加入少量的Bi2O3(0.1%质量分数,下同),可以提高体系的氧指数,降低体系的烟密度。热失重分析表明,Bi2O3加入可以使APP生成更多的固相残留物,催化膨胀阻燃剂交联成炭,高温时残炭增加,阻燃体系的最大热失重速率对应温度后移。同时热老化实验表明,Bi2O3的加入没有加快体系热老化的现象。

Ni/SiO2催化成碳协效膨胀阻燃PP的研究

采用过渡金属盐磷酸镍负载二氧化硅制备了一种新型催化协效剂Ni/SiO2。采用燃烧性能测试、热失重分析、微型量热分析及碳层SEM形貌分析等手段研究了催化协效剂与膨胀型阻燃剂在聚丙烯复合材料中协同阻燃效果。结果表明,Ni/SiO2的引入使材料垂直燃烧性能提升至V-0级,极限氧指数(LOI)从27.5%提高至34.0%,材料热释放速率、总热释放量明显降低,降低了火灾危险性。该催化协效剂对膨胀型阻燃剂分解成炭反应有催化促进作用,是提高材料阻燃性能的主要原因,热分解残炭率有明显提升,形成了微观结构连续致密的类蜂窝形发泡炭层,阻隔了热量向基体的传导。

Synergistic effect of heterogeneous single atoms and clusters for improved catalytic performance

Electrocatalytic water splitting provides an efficient method for the production of hydrogen.In electrocatalytic water splitting,the oxygen evolution reaction(OER)involves a kinetically sluggish four-electron transfer process,which limits the efficiency of electrocatalytic water splitting.Therefore,it is urgent to develop highly active OER catalysts to accelerate reaction kinetics.Coupling single atoms and clusters in one system is an innovative approach for developing efficient catalysts that can synergistically optimize the adsorption and configuration of intermediates and improve catalytic activity.However,research in this area is still scarce.Herein,we constructed a heterogeneous single-atom cluster system by anchoring Ir single atoms and Co clusters on the surface of Ni(OH)_(2)nanosheets.Ir single atoms and Co clusters synergistically improved the catalytic activity toward the OER.Specifically,Co_(n)Ir_(1)/Ni(OH)_(2)required an overpotential of 255 mV at a current density of 10 mA·cm^(−2),which was 60 mV and 67 mV lower than those of Co_(n)/Ni(OH)_(2)and Ir1/Ni(OH)_(2),respectively.The turnover frequency of Co_(n)Ir_(1)/Ni(OH)_(2)was 0.49 s^(−1),which was 4.9 times greater than that of Co_(n)/Ni(OH)_(2)at an overpotential of 300 mV.

Hydrogenation and Ammoniation of SrTiO3 for an Enhanced Visible-light Photocatalysis

Hydrogenation and ammoniation of SrTiOa （STO）, a normal ultraviolet photocatalyst, were performed by annealing STO（100） in Hz：N2=5%：95% and NH3, respectively, at various temperatures T. It was found that hydrogenation at T≥900℃ remarkably enhanced the UV photocatalytic ability of STO, but the visible-light photocatalysis was still unavailable, while ammoniation at T≥800℃ introduced the N doping, resulting in visible-light photocat- alytie activity. Furthermore, when a hydrogenated STO was subjected to ammoniation, the visible-light photocatalytie ability was nearly the same as that of the ammoniated one; but the hydrogenation of an ammoniated one significantly enhanced visible-light photoeatalysis, indicating a synergetic effect of hydrogenation and ammoniation. Discussions and identifications have been made to analyze these results.

Ag-Ni alloy nanoparticles for electrocatalytic reduction of benzyl chloride

Ag-based nanocatalysts exhibit good catalytic activity for the electrochemical reduction of organic halides. Ag-Ni alloy nanoparticles（NPs） were facilely prepared by chemical reduction, and the as-prepared nanocatalysts were characterized by X-ray diffraction, ultraviolet-visible spectroscopy, transmission electron microscopy and energy-dispersive X-ray spectroscopy. The electrocatalytic activity of Ag-Ni NPs for benzyl chloride reduction was studied in organic medium using cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy. The results show that the addition of Ni element can obviously decrease the size of Ag-Ni NPs, shift the reduction peak potential（φp） of benzyl chloride positively, and increase the catalytic activity of Ag-Ni NPs. However, when the Ni content reaches a certain value, the catalytic activity of Ag-Ni NPs decreases. Meanwhile, the synergistic catalytic effect of Ag-Ni NPs was also discussed.

Synergistic effects in N‐K_2Ti_4O_9/UiO‐66‐NH_2 composites and their photocatalysis degradation of cationic dyes

N-K2Ti4O9/UiO-66-NH2 composites synthesized by a facile solvothermal method have a core-shell structure with UiO-66-NH2 forming the shell around a N-K2Ti4O9 core.Their photocatalytic activities in the degradation of dyes under visible light irradiation were investigated.The N-K2Ti4O9/UiO-66-NH2 composites exhibited higher photocatalytic activity than the pure components.This synergistic effect was due to the high adsorption capacity of UiO-66-NH2 and that the two components together induced an enhanced separation efficiency of photogenerated electron-hole pairs.The mass ratio of N-K2Ti4O9 to ZrCl4 of 3：7 in the composite exhibited the highest photocatalytic activity.Due to the electrostatic attraction between the negatively charged backbone of UiO-66-NH2with the positively charged groups of cationic dyes,the composites were more photocatalytically active for cationic dyes than for anionic dyes.

MgO and Au nanoparticle Co-modified g-C_(3)N_(4)photocatalysts for enhanced photoreduction of CO_(2)with H_(2)O

The photoreduction of CO_(2)to achieve high-value-added hydrocarbons under simulated sunlight irradiation is advantageous,but challenging.In this study,a series of MgO and Au nanoparticle-co-modified g-C_(3)N_(4)photocatalysts were synthesized and subsequently applied for the photocatalytic reduction of CO_(2)with H2O under simulated solar irradiation.The best photocatalytic performance was demonstrated by the Au and 3%MgO-co-modified g-C_(3)N_(4)photocatalysts with CO,CH_(4),CH3OH,and CH3CHO yields of 423.9,83.2,47.2,and 130.4μmol/g,respectively,in a 3-h reaction.We investigated the effects of MgO and Au as cocatalysts on photocatalytic behaviors,respectively.The characterizations and experimental results showed that the enhanced photocatalytic activity was due to the synergistic effect among the components of the ternary photocatalyst.The cocatalyst MgO can activate CO_(2)(adsorbed at the interface between the MgO and Au particles),and the Mg-N bonds formed in the MgO-CN nanosheets played an important role in the charge transfer.Meanwhile,the Au particles that were modified into MgO/g-C_(3)N_(4)can increase the absorption of visible light via the surface plasmon resonance effect and further reduce the activation energies of the photoreduction of CO_(2)using H2O.This study provided an effective method for the modification of traditional primary photocatalysts with promising performance for photocatalytic CO_(2)reduction.

Enhanced photocatalytic H_(2) production performance of CdS hollow spheres using C and Pt as bi-cocatalysts

Photocatalytic H2 production from water splitting is an effective method to solve energy crisis and environmental pollution simultaneously.Herein,carbon@CdS composite hollow spheres(C@CdS-HS)are fabricated via a facile hydrothermal method using porous carbon hollow spheres(C-HS)as the template.The C@CdS-HS shows an excellent photocatalytic H2-generation rate of 20.9 mmol h^(−1) g^(−1)(apparent quantum efficiency of 15.3%at 420 nm),with 1.0 wt%Pt as a cocatalyst under simulated sunlight irradiation;this rate is 69.7,13.9,and 3.9 times higher than that obtained with pure CdS hollow spheres(CdS-HS),C@CdS-HS,and CdS-HS/Pt,respectively.The enhanced photocatalytic H_(2)-evolution activity of C@CdS-HS/Pt is due to the synergistic effect of C and Pt as the bi-cocatalyst.The C-HS serves not only as an active site provider but also as an electron transporter and reservoir.Moreover,C-HS has a strong photothermal effect that is induced by near infrared light,which kinetically accelerates the H_(2)-production reaction.Additionally,the underlying charge transfer pathway and process from CdS to C−HS is revealed.This work highlights the potential application of C-HS-based nanocomposites in solar-to-chemical energy conversion.

SiO_2-supported Au-Ni bimetallic catalyst for the selective hydrogenation of acetylene

Supported Au catalysts have been reported to exhibit high ethylene selectivity in the hydrogenation of acetylene,but the conversion is relatively low.Adding a second metal to Au has proven to be a promising approach to enhance its catalytic performance in acetylene hydrogenation.In this work,SiO2‐supported Au‐Ni bimetallic catalysts were synthesized and investigated in the selective hydrogenation of acetylene.The Au‐Ni bimetallic catalysts exhibited much higher catalytic performance than that of the corresponding monometallic Au or Ni catalysts.By tuning the reduction temperature and/or Ni loading,we obtained an Au‐Ni/SiO2catalyst with optimal performance.The results of transmission electron microscopy imaging revealed that the Au‐Ni bimetallic particles were highly dispersed on the SiO2support.Meanwhile,analysis of the bimetallic catalyst by energy‐dispersive X‐ray spectroscopy,high‐resolution transmission electron microscopy,and in situ diffuse reflectance infrared Fourier transform spectroscopy demonstrated the formation of Au‐Ni alloy,which contributed to the synergistic effect between Au and Ni in the hydrogenation of acetylene.

Elimination of 1,2-dichloroethane over(Ce,Cr)_x O_2/Nb_2O_5 catalysts: synergistic performance between oxidizing ability and acidity

A series of(Ce,Cr)xO2/Nb2O5 catalysts with different(Ce,Cr)xO2 to Nb2O5 mass ratios were synthesized by the deposition-precipitation method for use in deep catalytic oxidation of 1,2-dichloroethane(DCE), which is one of the typical chlorinated volatile organic compound pollutants. The textural properties were characterized by X-ray diffraction, N2 adsorption/desorption isotherms, UV-Raman spectroscopy, and scanning electron microscopy. The surface acidity and the redox properties were characterized by ammonia temperature-programmed desorption and H2 temperature-programmed reduction, respectively. The results show that the addition of a proper amount of(Ce,Cr)xO2 over Nb2O5 significantly improves the intrinsic catalytic activity towards the deep oxidation of DCE, and only a very small amount of C2H3Cl is detected as the byproduct of the oxidation process. Further study reveals the existence of an obvious synergistic effect between Nb2O5, with abundant strong acid sites, and(Ce,Cr)xO2, with strong oxidation sites, as the strong acid sites of Nb2O5 promote the adsorption and dehydrochlorination of DCE, while the strong oxidation sites of(Ce,Cr)xO2 contribute to the deep oxidation of the reactant, intermediates, and byproducts.

Synergetic photocatalytic and thermocatalytic reforming of methanol for hydrogen production based on Pt@TiO_(2) catalyst

In order to efficiently produce H_(2),conventional methanol‐water thermocatalytic(TC)reforming requires a very high temperature due to high Gibbs free energy,while the energy conversion efficiency of methanol‐water photocatalytic(PC)reforming is far from satisfaction because of the kinetic limitation.To address these issues,herein,we incorporate PC and TC processes together in a specially designed reactor and realize simultaneous photocatalytic/thermocatalytic(PC‐TC)reforming of methanol in an aqueous phase.Such a design facilitates the synergetic effect of the PC and TC process for H_(2) production due to a lower energy barrier and faster reaction kinetics.The methanol‐water reforming based on the optimized 0.05%Pt@TiO_(2) catalyst delivers an outstanding H_(2) production rate in the PC‐TC process(5.66μmol H_(2)·g^(‒1) catalyst·s^(‒1)),which is about 3 and 7 times than those of the TC process(1.89μmol H_(2)·g^(‒1) catalyst·s^(‒1))and the PC process(0.80μmol H_(2)·g^(‒1) catalyst·s^(‒1)),respectively.Isotope tracer experiments,active intermediate trapping experiments,and theoretical calculations demonstrate that the photo‐generated holes and hydroxyl radicals could enhance the methanol dehydrogenation,water molecule splitting,and water‐gas shift reaction,while high temperature accelerates reaction kinetics.The proposed PC‐TC reforming of methanol for hydrogen production can be a promising technology to solve the energy and environmental issue in the closed‐loop hydrogen economy in the near future.

Tuning strategies and structure effects of electrocatalysts for carbon dioxide reduction reaction

Carbon dioxide emissions have increased due to the consumption of fossil fuels,making the neutralization and utilization of CO_(2) a pressing issue.As a clean and efficient energy conversion process,electrocatalytic reduction can reduce carbon dioxide into a series of alcohols and acidic organic molecules,which can effectively realize the utilization and transformation of carbon dioxide.This review focuses on the tuning strategies and structure effects of catalysts for the electrocatalytic CO_(2) reduction reaction(CO_(2)RR).The tuning strategies for the active sites of catalysts have been reviewed from intrinsic and external perspectives.The structure effects for the CO_(2)RR catalysts have also been discussed,such as tandem catalysis,synergistic effects and confinement catalysis.We expect that this review about tuning strategies and structure effects can provide guidance for designing highly efficient CO_(2)RR electrocatalysts.

Synergistic effect of metallic nickel and cobalt oxides with nitrogen-doped carbon nanospheres for highly efficient oxygen evolution

The most energy-inefficient step in the oxygen evolution reaction(OER), which involves a complicated four-electron transfer process, limits the efficiency of the electrochemical water splitting. Here, well-defined Ni/Co3O4 nanoparticles coupled with N-doped carbon hybrids(Ni/Co3O4@NC) were synthesized via a facile impregnation-calcination method as efficient electrocatalysts for OER in alkaline media. Notably, the impregnation of the polymer with Ni and Co ions in the first step ensured the homogeneous distribution of metals, thus guaranteeing the subsequent in situ calcination reaction, which produced well-dispersed Ni and Co3O4 nanoparticles. Moreover, the N-doped carbon matrix formed at high temperatures could effectively prevent the aggregation and coalescence, and regulate the electronic configuration of active species. Benefiting from the synergistic effect between the Ni, Co3O4, and NC species, the obtained Ni/Co3O4@NC hybrids exhibited enhanced OER activities and remarkable stability in an alkaline solution with a smaller overpotential of 350 m V to afford 10 m A cm-2, lower Tafel slope of 52.27 m V dec-1, smaller charge-transfer resistance, and higher double-layer capacitance of 25.53 m F cm-2 compared to those of unary Co3O4@NC or Ni@NC metal hybrids. Therefore, this paper presents a facile strategy for designing other heteroatom-doped oxides coupled with ideal carbon materials as electrocatalysts for the OER.

Synergetic effect between non-thermal plasma and photocatalytic oxidation on the degradation of gas-phase toluene: Role of ozone

In this study, a hybrid process using non‐thermal plasma (NTP) and photocatalytic oxidation (PCO) was adopted for the degradation of gas‐phase toluene using TiO2 as the photocatalyst. To discover the synergetic effect between NTP and PCO, the performances of both sole (O3, UV, NTP, and PCO) and combined (O3 + TiO2, O3 + UV, NTP + UV, O3 + PCO, and NTP + PCO) processes were investigated from different perspectives, such as the toluene removal efficiency, selectivity of COx, mineralization rate, ozone utilization, and the generation of by‐products. The toluene removal efficiency of the combined NTP + PCO process was 80.2%, which was much higher than that of a sole degradation process such as NTP (18.8%) and PCO (13.4%). The selectivity of CO2 and the ozone utilization efficiency also significantly improved. The amount of by‐products in the gas phase and the carbon‐ based intermediates adsorbed on the catalyst surface dramatically reduced. The improvement in the overall performances of the combined NTP + PCO process was mainly ascribed to the efficient utilization of ozone in the photocatalytic oxidation, and the ozone further acting as an electron acceptor and scavenger, generating more hydroxyl radicals and reducing the recombination of electron‐ hole pairs.

Selective tandem hydrogenation and rearrangement of furfural to cyclopentanone over CuNi bimetallic catalyst in water

Tandem catalysis for the hydrogenation rearrangement of furfural(FA)provides an attractive solution for manufacturing cyclopentanone(CPO)from renewable biomass resources.The Cu-Ni/Al-MCM-41 catalyst was synthesized and afforded excellent catalytic performance with 99.0%conversion and 97.7%selectivity to CPO in a near-neutral solution under 2.0 MPa H2 at 160℃ for 5 h,much higher than those on other molecular sieve supports including MCM-41,SBA-15,HY,and ZSM-5.A small amount of Al highly dispersed in MCM-41 plays an anchoring role and ensures the formation of highly dispersed CuNi bimetallic nanoparticles(NPs).The remarkably improved catalytic performance may be attributed to the bimetallic synergistic and charge transfer effects.In addition,the initial FA concentration and the aqueous system pH required precise control to minimize polymerization and achieve high selectivity of CPO.Fourier transform infrared spectroscopy and mass spectra results indicated that polymerization was sensitive to pH values.Under acidic conditions,FA and intermediate furfuryl alcohol polymerize,while the intermediate 4-hydroxy-2-cyclopentenone mainly polymerizes under alkaline conditions,blocking the cascade of multiple reactions.Therefore,near-neutral conditions are most suitable for minimizing the impact of polymerization.This study provides a useful solution for the current universal problems of polymerization side reactions and low carbon balance for biomass conversion.

Metal–organic-framework-based catalysts for hydrogenation reactions

Metal-organic-framework （MOF）-based materials with novel physicochemical properties have emerged as promising catalysts for various hydrogenation reactions. In addition to metal clusters and multifunctional organic ligands, MOF-based catalysts can incorporate other functional species, and thus provide various active sites for hydrogenation processes. The structural properties of the catalysts play significant roles in enhancing the interactions among the reactants, products, and catalytic sites, which can be rationally designed. Because of the synergistic effects between the ac-tive sites and the structural properties, MOF-based catalysts can achieve higher activities and selec- tivities in hydrogenation reactions than can be obtained using traditional heterogeneous catalysts. This review provides an overview of recent developments in MOF-based catalysts in the hydro-genation of alkenes, alkynes, nitroarenes, cinnamaldehyde, furfural, benzene, and other compounds. Strategies for improving the catalytic performances of MOF-based catalysts are discussed as well as the different active sites and structural properties of the catalysts.

Cobalt/iron bimetal-organic frameworks as efficient electrocatalysts for the oxygen evolution reaction

The development of high efficiency and stable electrocatalysts for oxygen evolution is critical for energy storage and conversion systems. Herein, a series of Co/Fe bimetal-organic frameworks (MOFs) were fabricated using a facile ultrasonic method at room temperature, as electrocatalysts for the oxygen evolution reaction (OER) in alkaline solution. The Co2Fe-MOF exhibited an overpotential of 280 mV at a current density of 10 mA cm^-2, a low Tafel slope of 44.7 mV dec^-1, and long-term stability over 12000 s in 1 mol L^-1 KOH. This impressive performance was attributed to the high charge transfer rate, large specific surface area, and synergistic effects of the cobalt and iron centers.

Synergistic effect of cobalt and copper on a nickel-based modified graphite electrode during methanol electro-oxidation in NaOH solution

The electrocatalytic oxidation of methanol was studied over Ni, Co and Cu binary or ternary alloys on graphite electrodes in a NaOH solution （0.1 mol/L）. The catalysts were prepared by cycling the graphite electrode in solutions containing Ni, Cu and Co ions at cathodic potentials. The synergistic effects and catalytic activity of the modified electrodes were investigated by cyclic voltammetry （CV）, chronoamperometry CCA） and electrochemical impedance spectroscopy （EIS）. It was found that, in the presence of methanol, the modified Ni-based ternary alloy electrode （G/NiCuCo） exhibited a significantly higher response for methanol oxidation compared to the other samples. The anodic peak currents showed a linear dependency on the square root of the scan rate, which is a characteristic of a diffusion controlled process. During CA studies, the reaction exhibited Cottrellin behavior and the diffusion coefficient of methanol was determined to be 6.25× 10-6 cm2/s and the catalytic rate constant, K, for methanol oxidation was found to be 40×107 cm3/Cmol.s）. EIS was used to investigate the catalytic oxidation of methanol on the surface of the modified electrode.

Amorphous CoOx coupled carbon dots as a spongy porous bifunctional catalyst for efficient photocatalytic water oxidation and CO2 reduction

Cobalt-based oxides,with high abundance,good stability and excellent catalytic performance,are regarded as promising photocatalysts for artificial photosynthetic systems to alleviate foreseeable energy shortages and global warming.Herein,for the first time,a series of novel spongy porous CDs@CoOx materials were synthesized to act as an efficient and stable bifunctional photocatalyst for water oxidation and CO2 reduction.Notably,the preparation temperatures visibly influence the morphologies and photocatalytic performances of the CDs@CoOx.Under the optimal conditions,a maximum O2 yield of 40.4% and pretty apparent quantum efficiency(AQE)of 58.6% at 460 nm were obtained over CDs@CoOx-300 for water oxidation.Similarly,the optimized sample CDs@CoOx-300 manifests significant enhancement on the CO2-to-CO conversion with a high selectivity of 89.3% and CO generation rate of 8.1μmol/h,which is superior to most previous cobalt-based catalysts for CO2 reduction.The composite CDs@CoOx-300 not only exposes more active sites but also facilitates electron transport,which results in excellent photocatalytic activity.In addition,the boosted photocatalytic behavior is attributed to the synergistic effect between CoOx and CDs,which was verified by the photocatalytic activity control experiments and electrochemical characterization.The work offers a novel strategy to fabricate a high performance bifunctional photocatalyst for water oxidation and CO2 reduction.

An examination of active sites on Au-Ag bimetallic catalysts based on CO oxidation over Au/Ag_2O and a comparison to Ag-contaminated Au powder

There are two theories regarding the origin of the remarkable synergistic effect observed in Au‐Ag bimetallic catalysts when applied to various oxidative reactions. One is based on the importance of the contact interfaces between AgOx regions and the surface of the bulk Au as active working sites, while the other holds that charge transfer from Ag to Au in a surface Au‐Ag alloy causes the catalytic activity. One key point in examining these theories and determining the origin of the synergy in‐volves determining whether or not Ag exists as an oxide or as a metallic alloy on the Au surface. To confirm that enhanced activity results from contact between Ag2O and Au nanoparticles （NPs）, a comparative study of catalytic CO oxidation over Au/Ag2O and Ag2O was performed in the present work, using a closed recirculation reaction system. A reaction mixture consisting of a stoichiometric composition of CO and O2 （CO/O2=2/1） was supplied to both catalysts and the resulting pressure decrease rates were tracked, from which the amounts of gas consumed as well as the quantity of CO2 produced were determined. The steady state reactions of both Au/Ag2O and Ag2O did not lead to any meaningful difference in the rate of pressure decrease during the oxidation. The pressure decrease over both catalysts was attributed to the reduction of surface lattice O on Ag2O by CO. The results obtained for Au/Ag2O are in good agreement with previous data resulting from the use of Ag‐contaminated Au powder （Ag/Au‐b） having an oxidized surfaces. This finding suggests that the perimeters between AgOx zones and the bulk Au surface may not function as active sites during CO oxidation. A review of previous results obtained with Ag/Au‐b specimens having so‐called steady state surfaces indicates that AgOx species in such materials are reduced to the 0 state to form a Ag‐Au alloy that provides the active sites.