Investigati on sonsimultaneous determination of silver and mercury in catalytic－ligandsub stitution reaction with stopped－flow technique calibrated by synergistic effect

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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.

In Situ Coupling of Highly Dispersed Ni/Fe Metal-NC Sites and N-Doped 3D Carbon Fibers Toward Free-Standing Bifunctional Cathode for Flexible Zinc-Air Battery

Designing flexible free-standing air-electrode with efficient OER/ORR performance is of vital importance for the application of Zinc-air batteries in flexible electronics.Herein,a flexible free-standing electrode(Ni/Fe-NC/NCF/CC)is synthesized by in-situ coupling of binary Ni/Fe-NC nanocubes and N-doped carbon nanofibers(NCF)rooted on carbon cloth.The highly dispersed binary Ni/Fe-NC sites ensure excellent ORR activity and create efficient OER active sites relative to Ni-NC and Fe-NC.The in-situ coupling of Ni/Fe-NC and NCF constructs a 3D interconnected network structure that not only provides abundant and stabilized reactive sites but also guarantees fast electron transfer and gas transportation,thus achieving efficient and fast operation of ORR/OER.Therefore,Ni/Fe-NC/NCF/CC displays a much positive potential(0.952 V)at 4.0 mA cm^(-2)for ORR and a low OER overpotential(310 mV)at 50 mA cm^(-2).The Zinc-air battery with Ni/Fe-NC/NCF/CC air-electrode exhibits excellent battery performance with outstanding discharge/charge durability for 2150 cycles.The flexible Zn-air batteries with foldable mechanical properties display a high power density of 105.0 mW cm^(-2).This work widened the way to prepare flexible bifunctional air-electrode by designing composition/structure and in-situ coupling.

Synergistic effect of various elements in Fe_(41)Co_(7)Cr_(15)Mo_(14)C_(15)B_(6)Y_(2) amorphous alloy hollow ball on catalytic degradation of methylene blue

Metallic glasses have recently attracted great attention in terms of degrading dyes and other organic pollutants as an environmentally friendly material for wastewater remediation.Herein,we report a new type of amorphous catalyst Fe_(41)Co_(7)Cr_(15)Mo_(14)C_(15)B_(6)Y_(2) hollow balls.Results demonstrate that the catalyst can still completely decolorize the 20 mg/L methylene blue(MB)solution after reused for 50 times under conditions of pH=5,catalyst content 0.5 g/L,and temperature 80°C.The catalyst is easily broken during degradation,so the inner surface also provides additional active sites.The Fe_(41)Co_(7)Cr_(15)Mo_(14)C_(15)B_(6)Y_(2) amorphous alloy hollow balls were characterized by energy dispersive X-ray specroscopy(EDS),scanning electron microscopy(SEM)and X-ray photoelectron spectroscopy(XPS),respectively.The elements in the catalytic system have a synergistic catalytic effect.Redox cycle Fe^(2+)/Fe^(3+),Co^(2+)/Co^(3+)and Mo^(4+)/Mo^(6+) promote mutual conversion and accelerate the catalytic process of their reaction with H_(2)O_(2),forming a self-stable redox cycle process.Among them,Fe^(2+)promotes the conversion of Co^(3+)to Co^(2+),and Mo^(4+) promotes the conversion of Fe^(3+)to Fe^(2+),mainly Fe^(2+)and Co^(2+)react with H_(2)O_(2) to generate•OH.Mo and Cr elements form MoO_(2) and Cr_(2)O_(3) plasma compounds on the surface,which act as a protective film to make the catalyst more stable and be repeated used more frequently.

Synergistic catalytic removals of NO,CO and HC over CeO_2 modified Mn-Mo-W-O_x/TiO_2-SiO_2 catalyst

A series of Mn-Mo-W-O_x/TiO_2-SiO_2 catalysts was modified with CeO_2 using an extrusion molding method. The catalytic activities of the obtained catalysts were tested for the synergistic catalytic removals of CO, NO and C_3H_8. The ratio of catalyst composition on catalytic activities for NH_3-SCR was optimized, which reveals that the molar ratio of Ti/Si was 9：1 and the catalyst containing 1.5 wt% CeO_2 and 12 wt% Mn-Mo-W-O_x exhibits the best catalytic performances. These samples were characterized by XRD, N_2-BET, Py-IR, NH_3-TPD, SEM/element mapping, H_2-TPR and XPS, respectively. Results show that the optimal catalyst exhibits more than 99% NO conversion, 86% CO conversion and 100% C_3H_8 conversion under GHSV of 5000 h^（-1）. In addition, the GHSV has little influence on removal of NO when it is less than 15,000 h^（-1）. Furthermore, the addition of CeO_2 will enhance the surface acidity, increase Mn^（4＋）concentration and inhibit the grain growth, which are favorable for the excellent catalytic performance.Anyway,the 1.5 wt% CeO_2-12 wt% Mn-Mo-W-O_x/TiO_2-SiO_2 possesses outstanding redox properties,abundant acid sites and high Mn^（4＋） concentration, which provide a guarantee for synergistic catalytic removal of CO, NO and HC.

Black phosphorus quantum dots as multifunctional nanozymes for tumor photothermal/catalytic synergistic therapy

Nanozymes are nanomaterials with enzyme-like properties that have attracted significant interest owing to their high stability,easy preparation,and tunable catalytic properties,especially in the field of cancer therapy.However,the unfavorable catalytic effects of nanozymes in the acidic tumor microenvironment have limited their applications.Herein,we developed a biomimetic erythrocyte membrane-camouflaged ultrasmall black phosphorus quantum dots(BPQDs)nanozymes that simultaneously exhibited an exceptional near-infrared(NIR)photothermal property and dramatically photothermal-enhanced glucose oxidase(GOx)-like activity in the acidic tumor microenvironment.We demonstrated the engineered BPQDs gave a photothermal conversion efficiency of 28.9%that could rapidly heat the tumor up to 50℃ while effectively localized into tumors via homing peptide iRGD leading after intravenously injection.Meanwhile,the significantly enhanced GOx-like activity of BPQDs under NIR irradiation was capable of catalytical generating massive toxic reactive oxygen species via using cellular glucose.By combining the intrinsic photothermal property and the unique photothermal-enhanced GOx-like catalytic activity,the developed BPQDs were demonstrated to be an effective therapeutic strategy for inhibiting tumor growth in vivo.We believe that this work will provide a novel perspective for the development of nanozymes in tumor catalytic therapy.

Fabrication of HRP/Bi_(2)WO_(6) photoenzyme-coupled artificial catalytic system for efficiently degrading bisphenol A

A novel photoenzyme-coupled artificial catalytic system is fabricated by immobilizing horseradish peroxidase(HRP)on the Bi_(2)WO_(6)hollow nanospheres via a facile electrostatic self-assembly process.The obtained Bi_(2)WO_(6)/HRP sample not only improves the visible light harvest ability but also promotes the high-efficiency separation of charge carriers.More importantly,the photogenerated electrons and produced H2O2 on Bi_(2)WO_(6)directly take part in redox cycle reactions of HRP to induce photoenzyme synergic catalytic effect.In consequence,the degradation activity of Bi_(2)WO_(6)/HRP is significantly improved relative to Bi_(2)WO_(6)and HRP for removing bisphenol A(BPA)under the visible light irradiation.This work launches a feasible design strategy for exploiting photoenzyme-coupled artificial catalytic system with special structure to degrade organic pollutants in water efficiently.

Catalytic effect of MOF-derived transition metal catalyst FeCoS@C on hydrogen storage of magnesium

The introduction of the heterogeneous catalysts with high activity can significantly improve hydrogen storage performance of MgH_(2),therefore,in this paper,we synthesize a carbon-supported transition metal compound,FeCoS@C derivative from ZIF-67,by utilizing the in situ formed C dispersive multiphase Mg_(2)Co,α-Fe,Co_(3)Fe_(7),and MgS to implement catalysis to MgH_(2).Noteworthily,MgH_(2)-FeCoS@C rapidly ab-sorbs 6.78 wt%H_(2)within 60 s at 573 K and can also absorb 4.56 wt%H_(2)in 900 s at 473 K.Besides,the addition of FeCoS@C results in decreasing of the initial dehydrogenation temperatures of MgH_(2)from 620 to 550 K.The dehydrogenation activation energy of MgH_(2)decreases from 160.7 to 91.9 kJ mol^(-1).Studies show that the Mg_(2)Co,α-Fe,and Co_(3)Fe_(7)act as“hydrogen channels”to accelerate hydrogen transfer due to the presence of transition metals,and MgS with excellent catalytic effect formed from MgH_(2)-FeCoS@C provides a strong and stable catalytic effect.Besides,the carbon skeleton obtained by the carbonization of ZIF-67 not only serves as a dispersion for the multiphase catalytic system,but also provides more active sites for the catalysts.Our study shows that the multiphase and multiscale catalytic system provides an effective strategy for improving the hydrogen storage performance of MgH_(2).

Synergetic catalytic removal of chlorobenzene and NOχfrom waste incineration exhaust over MnNb0.4Ce0.2Oχcatalysts:Performance and mechanism study

Nb doped MnCe0.2Ox complex oxides catalysts prepared via a homogeneous precipitation method were investigated for synergistic catalytic removal of NOx and chlorobenzene(CB)at low temperatures.The MnNb0.4Ce0.2Ox catalyst with a molar ratio of Nb/Mn=0.4 exhibits excellent activity and the NOx and CB removal efficiency reaches 94.5%and 96%at 220℃,respectively.Furthermore,the NOx and CB removal efficiency of MnNb0.4Ce0.2Ox still remains above 80%after injecting 300 ppm SO2 and 7 vol%H2 O for 36 h.In addition,the presence of CB and NOx+NH3 can improve the NOx and CB removal efficiency of MnNb0.4Ce0.2Ox,respectively.The analysis results from N2-BET,Py-IR,H2-TPR and NH3-TPD reveal that the introduction of Nb increases the average pore size,pore volume and surface area,promoted the growth of Lewis acid amount obviously,and enhances redox ability of MnCe0.2Ox at 100-250℃.Moreover,the molecular migration process of NOx,NH3,CB and SO2 in NH3-SCR and CB oxidation reaction over MnNb0.4Ce0.2Ox catalysts were systematically studied.In situ DRIFTS,FT-IR and XPS also confirm that the adsorption of sulfate species and SO2 on the surface of MnNb0.4Ce0.2Ox is inhibited effectively by the introduction of Nb in the presence of SO2 and H2 O.Moreover,Nb additives also enhance the structural stability of MnNb0.4Ce0.2Ox,due to the interactions among Mn,Nb and Ce.The NH3-TPD,H2-TPR and in situ DRIFTS results also confirm that the MnNb0.4Ce0.2Ox still retains abundant acid sites and high redox ability in the presence of SO2 and H2O.In summary,MnNb0.4Ce0.2Ox catalysts represent a promising and effective candidate for controlling NOx and CB at low temperatures.

Anchoring Pt nanoparticles and Ti_(3)C_(2)T_(x)MXene nanosheets on CdS nanospheres as efficient synergistic photocatalysts for hydrogen evolution

The development of a new-fashioned functional nanomaterial with an outstanding photocatalytic hydrogen evolution reaction(HER)activity under visible-light irradiation is a sustainable and promising strategy to cope with the increasingly serious global energy crisis.Herein,an advanced ternary photocatalytic HER catalyst,in which the Pt nanoparticles and Ti_(3)C_(2)T_(x)nanosheets are synchronously anchored on the surface of CdS nanospheres(Ti_(3)C_(2)T_(x)/Pt@CdS),is elaborately constructed via acid etching,sel-freduction,and solvothermal treatment.Therein,the synergistic promoting effect between Ti_(3)C_(2)T_(x)and Pt on the charge transfer of CdS effectively hinders the backtransfer of electrons to recombine with holes,resulting in a high-effective utilization of photoexcited charges.The obtained Ti_(3)C_(2)T_(x)/Pt@CdS possesses a superior photocatalytic HER activity compared to that of single active component catalyst.This work demonstrates the great potential of MXene materials in constructing high performance photocatalysts.

Degradation of carbamazepine by MWCNTs-promoted generation of high-valent iron-oxo species in a mild system with O-bridged iron perfluorophthalocyanine dimers

Metal phthalocyanine has been extensively studied as a catalyst for degradation of carbamazepine(CBZ).However,metal phthalocyanine tends to undergo their own dimerization or polymerization,thereby reducing their activity points and affecting their catalytic properties.In this study,a catalytic system consisting of O-bridged iron perfluorophthalocyanine dimers(FePcF16-O-FePcF16),multi-walled carbon nanotubes(MWCNTs)and H2O_(2) was proposed.The results showed MWCNTs loaded with FePcF16-O-FePcF16 can achieve excellent degradation of CBZ with smaller dosages of FePcF16-O-FePcF16 and H2O_(2),and milder reaction temperatures.In addition,the results of experiments revealed the reaction mechanism of non-hydroxyl radicals.The highly oxidized high-valent iron-oxo(Fe(IV)=O)species was the main reactive species in the FePcF16-O-FePcF16/MWCNTs/H2O_(2) system.It is noteworthy that MWCNTs can improve the dispersion of FePcF16-O-FePcF16,contributing to the production of highly oxidized Fe(IV)=O.Then,the pathway of CBZ oxidative degradation was speculated,and the study results also provide new ideas for metal phthalocyanine-loaded carbon materials to degrade emerging pollutants.

Preparation of tungsten-iron composite oxides and application in environmental catalysis for volatile organic compounds degradation

Emission of volatile organic compounds has important influence on complex air pollution and human health.In this paper,a series of tungsten-iron composite oxides with different proportions and preparation methods were synthesized and first used for catalytic combustion of chlorobenzene and toluene,as typical polluting gas sources.These WO_(3)-based solid catalytic materials were systematically characterized by modern analytical methods,and the results showed that there was strong electron interaction between W and Fe elements in the composite oxides,and the presence of a certain amount of tungsten oxide inhibited the crystallization of iron oxide,and vice versa,which were beneficial to the uniform dispersion of tungsten-iron components into each other and the improvement of redox properties.Compared with single-component oxide,the formation of tungsten-iron composite oxide affected the micro-structure,improved the specific surface area and optimized the pore structure of materials.The performance test results showed that the tungsten-iron composite oxide(FeWO_4-0.5 Fe_(2)O_(3),molar ratio of tungsten and iron was 1/2)prepared using citric acid-based sol-gel method was the optimal,and its catalytic degradation efficiency could reach 90%for chlorobenzene and 83%for toluene at 320℃,and maintain at least 60 h without obvious deactivation,with high selectivity to the formation of HCl and CO_(2).