TiO_(2) nanobelts and Co_(3)O_(4)/TiO_(2) catalytic materials were prepared using the hydrothermal method.The cat-alyst was characterized by X-ray diffraction,scanning electron microscopy,transmission electron microsc...TiO_(2) nanobelts and Co_(3)O_(4)/TiO_(2) catalytic materials were prepared using the hydrothermal method.The cat-alyst was characterized by X-ray diffraction,scanning electron microscopy,transmission electron microscopy,X-ray electron spectroscopy,and fluorescence spectroscopy.At room temperature,with a relative humidity of 50.0%,the total gas flow rate of 1.0 L·min-1,the space velocity of 1.05×10^(4) h^(-1),and toluene volume concentration of 25.0µL·L^(-1),two 6 W vacuum ultraviolet lamps were used as light sources to catalyze,degrade,and mineralize toluene.The results show that the prepared catalyst is in the shape of nano-ribbons.The loading of Co_(3)O_(4) inhibits the recombina-tion of photogenerated electrons and holes and can effectively improve the catalytic performance.The Co_(3)O_(4)/TiO_(2) with a load of 6.0%Co_(3)O_(4) has the best catalytic effect.When N2 was used as a carrier gas,the degradation rate of tol-uene was only 34.7%.The toluene degradation is mainly due to the photolysis of vacuum ultraviolet light.When air was used as a carrier gas,O_(3) was produced.The Co_(3)O_(4)/TiO_(2) with a load of 6.0%and vacuum ultraviolet synergistical-ly promote toluene degradation.The highest degradation rate of toluene was 91.7%and the mineralization rate was 74.6%.The degradation rate of toluene was 2.6 times that of nitrogen as a carrier gas.展开更多
With the continuous improvement of solar energy production capacity,how to effectively use the electricity generated by renewable solar energy for electrochemical conversion of biomass is a hot topic.Electrochemical c...With the continuous improvement of solar energy production capacity,how to effectively use the electricity generated by renewable solar energy for electrochemical conversion of biomass is a hot topic.Electrochemical conversion of 5-hydroxymethylfurfural(HMF)to biofuels and value-added oxygenated commodity chemicals provides a promising and alternative pathway to convert re-newable electricity into chemicals.Although nickel-based eletrocatalysts are well-known for HMF oxidation,their relatively low intrinsic activity,poor conductivity and stability still limit the poten-tial applications.Here,we report the fabrication of a freestanding nickel-based electrode,in which Ni(OH)_(2) species were in-situ constructed on Ni foam(NF)support using a facile ac-id-corrosion-induced strategy.The Ni(OH)2/NF electrocatalyst exhibits stable and efficient electro-chemical HMF oxidation into 2,5-furandicarboxylic acid(FDCA)with HMF conversion close to 100% with high Faraday efficiency.In-situ formation strategy results in a compact interface between Ni(OH)_(2) and NF,which contributes to good conductivity and stability during electrochemical reac-tions.The superior performance benefits from dynamic cyclic evolution of Ni(OH)_(2) to NiOOH,which acts as the reactive species for HMF oxidation to FDCA.A scaled-up device based on a continu-ous-flow electrolytic cell was also established,giving stable operation with a high FDCA production rate of 27 mg h^(-1)cm^(−2).This job offers a straightforward,economical,and scalable design strategy to design efficient and durable catalysts for electrochemical conversion of valuable chemicals.展开更多
This study explores the controllable synthesis of CuAlO_(2) using copper hydroxide and pseudo-boehmite powders as raw materials via a simple solid-phase ball milling method,along with its catalytic performance investi...This study explores the controllable synthesis of CuAlO_(2) using copper hydroxide and pseudo-boehmite powders as raw materials via a simple solid-phase ball milling method,along with its catalytic performance investigation in methanol steam reforming(MSR).Various catalysts were prepared under different conditions,such as calcination temperature,calcination atmosphere,and heating rate.Characterization techniques including BET,XRD,XPS,SEM and H2-TPR were employed to analyze the samples.The results revealed significant effects of calcination temperature on the phase compositions,specific surface area,reduction performance,and surface properties of the CA-T catalysts.Based on the findings,a synthesis route of CuAlO_(2) via the solid-phase method was proposed,highlighting the importance of high calcination temperature,nitrogen atmosphere,and low heating rate for CuAlO_(2) formation.Catalytic evaluation data demonstrated that CuAlO_(2) could catalyze MSR without pre-reduction,with the catalytic performance of CA-T catalysts being notably influenced by calcination temperature.Among the prepared catalysts,the CA-1100 catalyst exhibited the highest catalytic activity and stability.The findings of this study might be useful for the further study of the catalytic material for sustained release catalysis,including the synthesis of catalytic materials and the regulation of sustained release catalytic performance.展开更多
Developing Cu single-atom catalysts(SACs)with well-defined active sites is highly desirable for producing CH4 in the electrochemical CO_(2) reduction reaction and understanding the structure-property relationship.Here...Developing Cu single-atom catalysts(SACs)with well-defined active sites is highly desirable for producing CH4 in the electrochemical CO_(2) reduction reaction and understanding the structure-property relationship.Herein,a new graphdiyne analogue with uniformly distributed N_(2)-bidentate(note that N_(2)-bidentate site=N^N-bidentate site;N_(2)≠dinitrogen gas in this work)sites are synthesized.Due to the strong interaction between Cu and the N_(2)-bidentate site,a Cu SAC with isolated undercoordinated Cu-N_(2) sites(Cu1.0/N_(2)-GDY)is obtained,with the Cu loading of 1.0 wt%.Cu1.0/N_(2)-GDY exhibits the highest Faradaic efficiency(FE)of 80.6% for CH_(4) in electrocatalytic reduction of CO_(2) at-0.96 V vs.RHE,and the partial current density of CH_(4) is 160 mA cm^(-2).The selectivity for CH_(4) is maintained above 70% when the total current density is 100 to 300 mA cm^(-2).More remarkably,the Cu1.0/N_(2)-GDY achieves a mass activity of 53.2 A/mgCu toward CH4 under-1.18 V vs.RHE.In situ electrochemical spectroscopic studies reveal that undercoordinated Cu-N_(2) sites are more favorable in generating key ^(*)COOH and ^(*)CHO intermediate than Cu nanoparticle counterparts.This work provides an effective pathway to produce SACs with undercoordinated Metal-N_(2) sites toward efficient electrocatalysis.展开更多
Three-dimensional(3D)ordered mesoporous MnO2 was prepared using KIT-6 mesoporous molecular sieves as a hard template.The material was used for catalytic oxidation of HCHO.The material has high surface areas and the ...Three-dimensional(3D)ordered mesoporous MnO2 was prepared using KIT-6 mesoporous molecular sieves as a hard template.The material was used for catalytic oxidation of HCHO.The material has high surface areas and the mesoporous characteristics of the template,with cubic symmetry(ia3d).It consists of a β-MnO2 crystalline phase corresponding to pyrolusite,with a rutile structure.Transmission electron microscopy and X-ray photoelectron spectroscopy showed that the 3D-MnO2 catalyst has a large number of exposed Mn4+ ions on the(110)crystal plane surfaces,with a lattice spacing of 0.311 nm; this enhances oxidation of HCHO.Complete conversion of HCHO to CO2 and H2O was achieved at 130 °C on 3D-MnO2; the same conversions on α-MnO2 and β-MnO2 nanorods were obtained at 140 and 180 °C,respectively,under the same conditions.The specific mesoporous structure,high specific surface area,and large number of surface Mn4+ ions are responsible for the catalytic activity of 3D-MnO2 in HCHO oxidation.展开更多
Formaldehyde(HCHO)is carcinogenic and teratogenic,and is therefore a serious danger to human health.It also adversely affects air quality.Catalytic oxidation is an efficient technique for removing HCHO.The developme...Formaldehyde(HCHO)is carcinogenic and teratogenic,and is therefore a serious danger to human health.It also adversely affects air quality.Catalytic oxidation is an efficient technique for removing HCHO.The development of highly efficient and stable catalysts that can completely convert HCHO at low temperatures,even room temperature,is important.Supported Pt and Pd catalysts can completely convert HCHO at room temperature,but their industrial applications are limited because they are expensive.The catalytic activities in HCHO oxidation of transition-metal oxide catalysts such as manganese and cobalt oxides with unusual morphologies are better than those of traditional MnO2,Co3O4,or other metal oxides.This is attributed to their specific structures,high specific surface areas,and other factors such as active phase,reducibility,and amount of surface active oxygens.Such catalysts with various morphologies have great potential and can also be used as catalyst supports.The loading of relatively cheap Ag or Au on transition-metal oxides with special morphologies potentially improves the catalytic activity in HCHO removal at room temperature.The preparation and development of new nanocatalysts with various morphologies and structures is important for HCHO removal.In this paper,research progress on precious-metal and transition-metal oxide catalyst systems for HCHO oxidation is reviewed; topics such as oxidation properties,structure–activity relationships,and factors influencing the catalytic activity and reaction mechanism are discussed.Future prospects and directions for the development of such catalysts are also covered.展开更多
The effect of calcination temperature on the catalytic activity for the dimethyl ether (DME) carbonylation into methyl acetate (MA) was investigated over mordenite supported copper (Cu/HMOR) prepared by ion-exch...The effect of calcination temperature on the catalytic activity for the dimethyl ether (DME) carbonylation into methyl acetate (MA) was investigated over mordenite supported copper (Cu/HMOR) prepared by ion-exchange process. The results showed that the catalytic activity was obviously affected by the calcination temperature. The maximal DME conversion of 97.2% and the MA selectivity of 97.9% were obtained over the Cu/HMOR calcined at 430 ℃ under conditions of 210 ℃, 1.5 MPa, and GSHV of 4883 h^-1. The obtained Cu/HMOR catalysts were characterized by powder X-ray diffraction, N2 absorption, NH3 temperature program desorption, CO temperature program desorption, and Raman techniques. Proper calcination temperature was effective to promote copper ions migration and diffusion, and led the support HMOR to possess more acid activity sites, which exhibited the complete decomposing of copper nitrate, large surface area and optimum micropore structure, more amount of CO adsorption site and proper amount of weak acid centers.展开更多
Co3O4 catalysts prepared with different precipitants(NH3·H2O,KOH,NH4HCO3,K2CO3 and KHCO3)were investigated for the oxidation of formaldehyde(HCHO).Among these,KHCO3-precipitated Co3O4(KHCO3-Co) was the most...Co3O4 catalysts prepared with different precipitants(NH3·H2O,KOH,NH4HCO3,K2CO3 and KHCO3)were investigated for the oxidation of formaldehyde(HCHO).Among these,KHCO3-precipitated Co3O4(KHCO3-Co) was the most active low-temperature catalyst,and was able to completely oxidize HCHO at the 100-ppm level to CO2 at 90℃.In situ diffuse reflectance infrared spectroscopy demonstrated that hydroxyl groups on the catalyst surface were regenerated by K~+ and CO3^(2-),thus promoting the oxidation of HCHO.Moreover,H2-temperature programmed reduction and X-ray photoelectron spectroscopy showed that employing KHCO3 as the precipitant increased the Co^3+/Co^2+molar ratio on the surface of the Co3O4 catalyst,thus further promoting oxidation.Structural characterization revealed that catalysts precipitated with carbonate or bicarbonate reagents exhibited greater specific surface areas and pore volumes.Overall,these data suggest that the high activity observed during the Co3O4 catalyzed oxidation of HCHO can be primarily attributed to the presence of K~+ and CO3^(2-) on the Co3O4 surface and the favorable Co^3+/Co^2+ ratio.展开更多
The mechanism and kinetics of electrocatalytic oxidation of formic acid at Pt electrodes is discussed in detail based on previous electrochemical in-situ ATR-FTIRS data [Langmuir 22, 10399 (2006)and Angewa. Chem. In...The mechanism and kinetics of electrocatalytic oxidation of formic acid at Pt electrodes is discussed in detail based on previous electrochemical in-situ ATR-FTIRS data [Langmuir 22, 10399 (2006)and Angewa. Chem. Int. Ed. 50, 1159 (2011)]. A kinetic model with formic acid adsorption (and probably the simultaneous C-H bond activation) as the rate determining step, which contributes to the majority of reaction current for formic acid oxi- dation, was proposed for the direct pathway. The model simulates well the IR spectroscopic results obtained under conditions where the poisoning effect of carbon monoxide (CO) is negligible and formic acid concentration is below 0.1 mol/L. The kinetic simulation predicts that in the direct pathway formic acid oxidation probably only needs one Pt atom as active site, formate is the site blocking species instead of being the active intermediate. We review in detail the conclusion that formate pathway (with either 1st or 2nd order reaction kinetics) is the direct pathway, possible origins for the discrepancies are pointed out.展开更多
CaTiO 3-Fex was characterized by X-ray diffractometry, scanning electron microscopy equipped with an energy dispersive spectrometry system, Fourier transform infrared spectra, and UV-visible spectra. Effects of Fe con...CaTiO 3-Fex was characterized by X-ray diffractometry, scanning electron microscopy equipped with an energy dispersive spectrometry system, Fourier transform infrared spectra, and UV-visible spectra. Effects of Fe content on photocatalytic activity of CaTiO3-Fex were investigated through measuring photocatalytic degradation rate of methylene blue. The results show that chemical compositions of CaTiO3-Fex remained unchanged with increasing Fe content from 0 to 4.745%. However, the light absorption ability of CaTiO3-Fex exhibited a significant increase with increasing Fe content. Photocatalytic degradation of methylene blue over CaTiO3-Fex followed the first-order reaction kinetics. Based on changes of the concentration of methylene blue and its degradation kinetics, CaTiO3-Fe0.474% has shown to have optimal photocatalytic activity. The degradation rate of methylene blue over CaTiO3-Fe0.474% was almost 100% under UV-visible light irradiation for 3.0 h. The kobs of methylene blue over CaTiO 3-Fe0.474% was 1.33 h-1 and was 7 times that over CaTiO3-Fe0.展开更多
Dimethyl ether carbonylation to methyl acetate was comparatively investigated over mor- denite supported copper (Cu/HMOR) catalysts prepared by different methods including evaporation, urea hydrolysis, incipient wet...Dimethyl ether carbonylation to methyl acetate was comparatively investigated over mor- denite supported copper (Cu/HMOR) catalysts prepared by different methods including evaporation, urea hydrolysis, incipient wetness impregnation and ion-exchange. The results showed that Cu/HMOR prepared via iron-exchange method exhibited the highest catalytic activity due to the synergistic effect of active-site metal and acidic molecular sieve support. Conversion of 95.3% and methyl acetate selectivity of 94.9% were achieved under conditions of 210℃, 1.5 MPa, and GSHV of 4883 h-1. The catalysts were characterized by nitrogen absorption, X-ray diffraction, NH3 temperature program desorption, and CO temperature program desorption techniques. It was found that Cu/HMOR prepared by ion-exchange method possessed high surface area, moderate strong acid centers, and CO adsorption centers, which improved catalytic performance for the reaction of CO insertion to dimethyl ether.展开更多
The metal complex 5-(4-aminophenyl)-10,15,20-triphenylporphyrin copper (CuAPTPP) was covalently linked on the surface of TiO2 microspheres by using toluene disocyanate (TDI) as a bridging bond unit. The hydroxyl...The metal complex 5-(4-aminophenyl)-10,15,20-triphenylporphyrin copper (CuAPTPP) was covalently linked on the surface of TiO2 microspheres by using toluene disocyanate (TDI) as a bridging bond unit. The hydroxyl group (-OH) of TiO2 microspheres surface and the amino group (-NH2) of CuAPTPP reacted respectively with the active -NCO groups of TDI to form a surface conjugated microsphere CuAPTPP-TDI-TiO2 that was confirmed by FT-IR spectra. The CuAPTPP-TDI-TiO2 microspheres were characterized with UV-visible, elemental analysis, XRD, SEM, and UV-Vis diffuse reflectance spectra. The effect of amounts of linked TDI on the performance of photocatalytic microspheres was discussed, and the optimal molar ratio of TDI:TiO2 was established. The photocatalytic activity of CuAPTPP- TDI-TiO2 was evaluated using the photocatalytic degradation of methylene blue (MB) under visible-light irradiation. The results showed that, TDI, as a bond unit, was used to form a steady chemical brigdging bond linking CuAPTPP and the surface of TiO2 microspheres, and the prepared catalyst exhibited higher photocatalytic activity under visible-light irradiation for MB degradation. The degradation rate of 20 mg/L MB could reach 98.7% under Xe- lamp (150 W) irradiation in 120 rain. The degradation of MB followed the first-order reaction model under visible light irradiation, and the rate constant of 5.1× 10^-2 min-1 and the half- life of 11.3 min were achieved. And the new photocatalyst can be recycled for 4 times, remaining 90.0% MB degradation rate.展开更多
Direct methanol fuel cells (DMFCs) are promising for use in portable devices because of advantages such as high fuel energy density, low working temperature and low emission of pollutants. Nanotechnology has been us...Direct methanol fuel cells (DMFCs) are promising for use in portable devices because of advantages such as high fuel energy density, low working temperature and low emission of pollutants. Nanotechnology has been used to improve the performance of DMFCs. Catalytic materials composed of small, metallic particles with unique nanostructure supparted on carbons or metal oxides have been widely investigated for use in DMFCs. Despite our increased understanding of this type of fuel cell, many challenges still remain. This paper reviews the current developments of nanostructured elec- trocatalytic materials and porous electrodes for use in DMFCs. In particular, this review focuses on the synthesis and characterization of nanostructured catalysts and supporting materials. Both computational and experimental approaches to optimize mass transportation in porous electrodes of DMFCs, such as theoretical modeling of internal transfer processes and preparation of functional structures in membrane electrode assemblies, are introduced.展开更多
Three-dimensionally ordered macro-/mesoporous alumina(3DOM Al2O3)-supported cobalt oxide and platinum nanocatalysts(xPt/yCo3O4/3DOM Al2O3,Pt mass fraction(x%)= 0-1.4%,Co3O4 mass fraction(y%) = 0-9.2%) were pre...Three-dimensionally ordered macro-/mesoporous alumina(3DOM Al2O3)-supported cobalt oxide and platinum nanocatalysts(xPt/yCo3O4/3DOM Al2O3,Pt mass fraction(x%)= 0-1.4%,Co3O4 mass fraction(y%) = 0-9.2%) were prepared using poly(methyl methacrylate) templating,incipient wetness impregnation and polyvinyl alcohol-protected reduction.The resulting xPt/yCo3O4/3DOM Al2O3 samples displayed a high-quality 3DOM architecture with macropores(180-200 nm in diameter) and mesopores(4-6 nm in diameter) together with surface areas in the range of 94 to 102m^2/g.Using these techniques,Co3O4 nanoparticles(NPs,18.3 nm) were loaded on the 3DOM Al2O3 surface,after which Pt NPs(2.3-2.5 nm) were uniformly dispersed on theyCo3O4/3DOM Al2O3.The1.3Pt/8.9Co3O4/3DOM Al2O3 exhibited the best performance for toluene oxidation,with a T(90%) value(the temperature required to achieve 90%toluene conversion) of 160 ℃ at a space velocity of20000 mL g^(-1) h^(-1).It is concluded that the excellent catalytic performance of the 1.3Pt/8.9Co3O4/3DOM Al2O3 is owing to well-dispersed Pt NPs,the high concentration of adsorbed oxygen species,good low-temperature reducibility,and strong interaction between the Pt and Co3O4 NPs,as well as the unique bimodal porous structure of the support.展开更多
Platinum nanoparticles supported on carbons(Pt/C,60%,mass fraction) electrocatalysts for direct methanol fuel cell(DMFC) were prepared by citrate-stabilized method with different reductants and carbon supports.The...Platinum nanoparticles supported on carbons(Pt/C,60%,mass fraction) electrocatalysts for direct methanol fuel cell(DMFC) were prepared by citrate-stabilized method with different reductants and carbon supports.The catalysts were characterized by X-ray diffraction(XRD),transmission electron microscopy(TEM) and cyclic voltammetry(CV).It is found that the size of Pt nanoparticles on carbon is controllable by citrate addition and reductant optimization,and the form of carbon support has a great influence on electrocatalytic activity of catalysts.The citrate-stabilized Pt nanoparticles supported on BP2000 carbon,which was reduced by formaldehyde,exhibit the best performance with about 2 nm in diameter and 66.46 m2/g(Pt) in electrocatalytic active surface(EAS) area.Test on single DMFC with 60%(mass fraction) Pt/BP2000 as cathode electrocatalyst showed maximum power density at 78.8 mW/cm2.展开更多
A novel WO3-x/TiO2 film as photoanode was synthesized for photoelectrocatalytic(PEC) reduction of CO2 into formic acid(HCOOH). The films prepared by doctor blade method were characterized with X-ray diffractometer...A novel WO3-x/TiO2 film as photoanode was synthesized for photoelectrocatalytic(PEC) reduction of CO2 into formic acid(HCOOH). The films prepared by doctor blade method were characterized with X-ray diffractometer(XRD), scanning electron microscope(SEM) and transmission electron microscope(TEM). The existence of oxygen vacancies in the WO3-x was confirmed with an X-ray photoelectron spectroscopy(XPS), and the accurate oxygen index was determined by a modified potentiometric titrimetry method. After 3h of photoelectrocatalytic reduction, the formic acid yield of the WO3-x/TiO2 film is 872 nmol/cm^2, which is 1.83 times that of the WO3/TiO2 film. The results of PEC performance demonstrate that the introduction of WO3-x nanoparticles can improve the charge transfer performance so as to enhance the performance of PEC reduction of CO2 into formic acid.展开更多
文摘目的建立山甲催乳颗粒的定性与定量检测方法,并制定质量标准。方法采用薄层色谱(TLC)法对山甲催乳颗粒中的当归、丹参、穿山甲进行定性鉴别;采用高效液相色谱(HPLC)法对该制剂中的主要有效成分黄芪甲苷进行含量测定,色谱柱为Agilent Extend C18(4.6 mm×250.0 mm,5μm),流动相为乙腈-水(36∶64),流速1.0 m L/min,柱温30℃,采用ELSD检测器(Alltech Model 3300),漂移管温度90℃,氮气流速1.7 L/min,进样量10μL。结果当归、丹参、穿山甲的TLC斑点清晰、专属性强,阴性无干扰;黄芪甲苷的回归方程为Y=1.514X+13.702,r=0.9995,表明黄芪甲苷在0.1071~4.2840μg范围内线性关系良好;平均加样回收率为96.60%,RSD为0.85%。结论所制定的山甲催乳颗粒的定性与定量检测方法结果准确,专属性强、重复性好,能有效控制该制剂的质量。
文摘TiO_(2) nanobelts and Co_(3)O_(4)/TiO_(2) catalytic materials were prepared using the hydrothermal method.The cat-alyst was characterized by X-ray diffraction,scanning electron microscopy,transmission electron microscopy,X-ray electron spectroscopy,and fluorescence spectroscopy.At room temperature,with a relative humidity of 50.0%,the total gas flow rate of 1.0 L·min-1,the space velocity of 1.05×10^(4) h^(-1),and toluene volume concentration of 25.0µL·L^(-1),two 6 W vacuum ultraviolet lamps were used as light sources to catalyze,degrade,and mineralize toluene.The results show that the prepared catalyst is in the shape of nano-ribbons.The loading of Co_(3)O_(4) inhibits the recombina-tion of photogenerated electrons and holes and can effectively improve the catalytic performance.The Co_(3)O_(4)/TiO_(2) with a load of 6.0%Co_(3)O_(4) has the best catalytic effect.When N2 was used as a carrier gas,the degradation rate of tol-uene was only 34.7%.The toluene degradation is mainly due to the photolysis of vacuum ultraviolet light.When air was used as a carrier gas,O_(3) was produced.The Co_(3)O_(4)/TiO_(2) with a load of 6.0%and vacuum ultraviolet synergistical-ly promote toluene degradation.The highest degradation rate of toluene was 91.7%and the mineralization rate was 74.6%.The degradation rate of toluene was 2.6 times that of nitrogen as a carrier gas.
文摘With the continuous improvement of solar energy production capacity,how to effectively use the electricity generated by renewable solar energy for electrochemical conversion of biomass is a hot topic.Electrochemical conversion of 5-hydroxymethylfurfural(HMF)to biofuels and value-added oxygenated commodity chemicals provides a promising and alternative pathway to convert re-newable electricity into chemicals.Although nickel-based eletrocatalysts are well-known for HMF oxidation,their relatively low intrinsic activity,poor conductivity and stability still limit the poten-tial applications.Here,we report the fabrication of a freestanding nickel-based electrode,in which Ni(OH)_(2) species were in-situ constructed on Ni foam(NF)support using a facile ac-id-corrosion-induced strategy.The Ni(OH)2/NF electrocatalyst exhibits stable and efficient electro-chemical HMF oxidation into 2,5-furandicarboxylic acid(FDCA)with HMF conversion close to 100% with high Faraday efficiency.In-situ formation strategy results in a compact interface between Ni(OH)_(2) and NF,which contributes to good conductivity and stability during electrochemical reac-tions.The superior performance benefits from dynamic cyclic evolution of Ni(OH)_(2) to NiOOH,which acts as the reactive species for HMF oxidation to FDCA.A scaled-up device based on a continu-ous-flow electrolytic cell was also established,giving stable operation with a high FDCA production rate of 27 mg h^(-1)cm^(−2).This job offers a straightforward,economical,and scalable design strategy to design efficient and durable catalysts for electrochemical conversion of valuable chemicals.
基金supported by the Scientific Research Foundation for High-level Talents of Anhui University of Science and Technology(2023yjrc51)the National Natural Science Foundation of China(22172184)+2 种基金the Foundation of State Key Laboratory of Coal Conversion(J24-25-603)the Fundamental Research Project of ICC-CAS(SCJC-DT-2023-01)Weiqiao-UCAS Special Projects on Low-Carbon Technology Development(GYY-DTFZ-2022-015)。
文摘This study explores the controllable synthesis of CuAlO_(2) using copper hydroxide and pseudo-boehmite powders as raw materials via a simple solid-phase ball milling method,along with its catalytic performance investigation in methanol steam reforming(MSR).Various catalysts were prepared under different conditions,such as calcination temperature,calcination atmosphere,and heating rate.Characterization techniques including BET,XRD,XPS,SEM and H2-TPR were employed to analyze the samples.The results revealed significant effects of calcination temperature on the phase compositions,specific surface area,reduction performance,and surface properties of the CA-T catalysts.Based on the findings,a synthesis route of CuAlO_(2) via the solid-phase method was proposed,highlighting the importance of high calcination temperature,nitrogen atmosphere,and low heating rate for CuAlO_(2) formation.Catalytic evaluation data demonstrated that CuAlO_(2) could catalyze MSR without pre-reduction,with the catalytic performance of CA-T catalysts being notably influenced by calcination temperature.Among the prepared catalysts,the CA-1100 catalyst exhibited the highest catalytic activity and stability.The findings of this study might be useful for the further study of the catalytic material for sustained release catalysis,including the synthesis of catalytic materials and the regulation of sustained release catalytic performance.
文摘Developing Cu single-atom catalysts(SACs)with well-defined active sites is highly desirable for producing CH4 in the electrochemical CO_(2) reduction reaction and understanding the structure-property relationship.Herein,a new graphdiyne analogue with uniformly distributed N_(2)-bidentate(note that N_(2)-bidentate site=N^N-bidentate site;N_(2)≠dinitrogen gas in this work)sites are synthesized.Due to the strong interaction between Cu and the N_(2)-bidentate site,a Cu SAC with isolated undercoordinated Cu-N_(2) sites(Cu1.0/N_(2)-GDY)is obtained,with the Cu loading of 1.0 wt%.Cu1.0/N_(2)-GDY exhibits the highest Faradaic efficiency(FE)of 80.6% for CH_(4) in electrocatalytic reduction of CO_(2) at-0.96 V vs.RHE,and the partial current density of CH_(4) is 160 mA cm^(-2).The selectivity for CH_(4) is maintained above 70% when the total current density is 100 to 300 mA cm^(-2).More remarkably,the Cu1.0/N_(2)-GDY achieves a mass activity of 53.2 A/mgCu toward CH4 under-1.18 V vs.RHE.In situ electrochemical spectroscopic studies reveal that undercoordinated Cu-N_(2) sites are more favorable in generating key ^(*)COOH and ^(*)CHO intermediate than Cu nanoparticle counterparts.This work provides an effective pathway to produce SACs with undercoordinated Metal-N_(2) sites toward efficient electrocatalysis.
基金supported by the National Natural Science Foundation of China(21325731,21221004 and 51478241)~~
文摘Three-dimensional(3D)ordered mesoporous MnO2 was prepared using KIT-6 mesoporous molecular sieves as a hard template.The material was used for catalytic oxidation of HCHO.The material has high surface areas and the mesoporous characteristics of the template,with cubic symmetry(ia3d).It consists of a β-MnO2 crystalline phase corresponding to pyrolusite,with a rutile structure.Transmission electron microscopy and X-ray photoelectron spectroscopy showed that the 3D-MnO2 catalyst has a large number of exposed Mn4+ ions on the(110)crystal plane surfaces,with a lattice spacing of 0.311 nm; this enhances oxidation of HCHO.Complete conversion of HCHO to CO2 and H2O was achieved at 130 °C on 3D-MnO2; the same conversions on α-MnO2 and β-MnO2 nanorods were obtained at 140 and 180 °C,respectively,under the same conditions.The specific mesoporous structure,high specific surface area,and large number of surface Mn4+ ions are responsible for the catalytic activity of 3D-MnO2 in HCHO oxidation.
基金supported by the National Natural Science Foundation of China(21325731,51478241,21221004)~~
文摘Formaldehyde(HCHO)is carcinogenic and teratogenic,and is therefore a serious danger to human health.It also adversely affects air quality.Catalytic oxidation is an efficient technique for removing HCHO.The development of highly efficient and stable catalysts that can completely convert HCHO at low temperatures,even room temperature,is important.Supported Pt and Pd catalysts can completely convert HCHO at room temperature,but their industrial applications are limited because they are expensive.The catalytic activities in HCHO oxidation of transition-metal oxide catalysts such as manganese and cobalt oxides with unusual morphologies are better than those of traditional MnO2,Co3O4,or other metal oxides.This is attributed to their specific structures,high specific surface areas,and other factors such as active phase,reducibility,and amount of surface active oxygens.Such catalysts with various morphologies have great potential and can also be used as catalyst supports.The loading of relatively cheap Ag or Au on transition-metal oxides with special morphologies potentially improves the catalytic activity in HCHO removal at room temperature.The preparation and development of new nanocatalysts with various morphologies and structures is important for HCHO removal.In this paper,research progress on precious-metal and transition-metal oxide catalyst systems for HCHO oxidation is reviewed; topics such as oxidation properties,structure–activity relationships,and factors influencing the catalytic activity and reaction mechanism are discussed.Future prospects and directions for the development of such catalysts are also covered.
基金This work was supported by the National Natural Science Foundation of China (No.51006110 and No.51276183) and the National Natural Research Foundation of China/Japan Science and Technology Agency (No.51161140331).
文摘The effect of calcination temperature on the catalytic activity for the dimethyl ether (DME) carbonylation into methyl acetate (MA) was investigated over mordenite supported copper (Cu/HMOR) prepared by ion-exchange process. The results showed that the catalytic activity was obviously affected by the calcination temperature. The maximal DME conversion of 97.2% and the MA selectivity of 97.9% were obtained over the Cu/HMOR calcined at 430 ℃ under conditions of 210 ℃, 1.5 MPa, and GSHV of 4883 h^-1. The obtained Cu/HMOR catalysts were characterized by powder X-ray diffraction, N2 absorption, NH3 temperature program desorption, CO temperature program desorption, and Raman techniques. Proper calcination temperature was effective to promote copper ions migration and diffusion, and led the support HMOR to possess more acid activity sites, which exhibited the complete decomposing of copper nitrate, large surface area and optimum micropore structure, more amount of CO adsorption site and proper amount of weak acid centers.
基金supported by the National Natural Science Foundation of China(21577088)~~
文摘Co3O4 catalysts prepared with different precipitants(NH3·H2O,KOH,NH4HCO3,K2CO3 and KHCO3)were investigated for the oxidation of formaldehyde(HCHO).Among these,KHCO3-precipitated Co3O4(KHCO3-Co) was the most active low-temperature catalyst,and was able to completely oxidize HCHO at the 100-ppm level to CO2 at 90℃.In situ diffuse reflectance infrared spectroscopy demonstrated that hydroxyl groups on the catalyst surface were regenerated by K~+ and CO3^(2-),thus promoting the oxidation of HCHO.Moreover,H2-temperature programmed reduction and X-ray photoelectron spectroscopy showed that employing KHCO3 as the precipitant increased the Co^3+/Co^2+molar ratio on the surface of the Co3O4 catalyst,thus further promoting oxidation.Structural characterization revealed that catalysts precipitated with carbonate or bicarbonate reagents exhibited greater specific surface areas and pore volumes.Overall,these data suggest that the high activity observed during the Co3O4 catalyzed oxidation of HCHO can be primarily attributed to the presence of K~+ and CO3^(2-) on the Co3O4 surface and the favorable Co^3+/Co^2+ ratio.
基金This work was supported by one hundred Tal- ents' Program of the Chinese Academy of Science, the National Natural Science Foundation of China (No.21273215), 973 program from the Ministry of Sci- ence and Technology of China (No.2010CB923302).
文摘The mechanism and kinetics of electrocatalytic oxidation of formic acid at Pt electrodes is discussed in detail based on previous electrochemical in-situ ATR-FTIRS data [Langmuir 22, 10399 (2006)and Angewa. Chem. Int. Ed. 50, 1159 (2011)]. A kinetic model with formic acid adsorption (and probably the simultaneous C-H bond activation) as the rate determining step, which contributes to the majority of reaction current for formic acid oxi- dation, was proposed for the direct pathway. The model simulates well the IR spectroscopic results obtained under conditions where the poisoning effect of carbon monoxide (CO) is negligible and formic acid concentration is below 0.1 mol/L. The kinetic simulation predicts that in the direct pathway formic acid oxidation probably only needs one Pt atom as active site, formate is the site blocking species instead of being the active intermediate. We review in detail the conclusion that formate pathway (with either 1st or 2nd order reaction kinetics) is the direct pathway, possible origins for the discrepancies are pointed out.
基金Project(51090384)supported by the National Natural Science Foundation of ChinaProject(2012AA062304)supported by the Hi-tech Research and Development Program of China+1 种基金Project(2012CBA01205)supported by the National Basic Research Program of ChinaProject(N110502002)supported by Fundamental Research Funds for the Central Universities,China
文摘CaTiO 3-Fex was characterized by X-ray diffractometry, scanning electron microscopy equipped with an energy dispersive spectrometry system, Fourier transform infrared spectra, and UV-visible spectra. Effects of Fe content on photocatalytic activity of CaTiO3-Fex were investigated through measuring photocatalytic degradation rate of methylene blue. The results show that chemical compositions of CaTiO3-Fex remained unchanged with increasing Fe content from 0 to 4.745%. However, the light absorption ability of CaTiO3-Fex exhibited a significant increase with increasing Fe content. Photocatalytic degradation of methylene blue over CaTiO3-Fex followed the first-order reaction kinetics. Based on changes of the concentration of methylene blue and its degradation kinetics, CaTiO3-Fe0.474% has shown to have optimal photocatalytic activity. The degradation rate of methylene blue over CaTiO3-Fe0.474% was almost 100% under UV-visible light irradiation for 3.0 h. The kobs of methylene blue over CaTiO 3-Fe0.474% was 1.33 h-1 and was 7 times that over CaTiO3-Fe0.
文摘Dimethyl ether carbonylation to methyl acetate was comparatively investigated over mor- denite supported copper (Cu/HMOR) catalysts prepared by different methods including evaporation, urea hydrolysis, incipient wetness impregnation and ion-exchange. The results showed that Cu/HMOR prepared via iron-exchange method exhibited the highest catalytic activity due to the synergistic effect of active-site metal and acidic molecular sieve support. Conversion of 95.3% and methyl acetate selectivity of 94.9% were achieved under conditions of 210℃, 1.5 MPa, and GSHV of 4883 h-1. The catalysts were characterized by nitrogen absorption, X-ray diffraction, NH3 temperature program desorption, and CO temperature program desorption techniques. It was found that Cu/HMOR prepared by ion-exchange method possessed high surface area, moderate strong acid centers, and CO adsorption centers, which improved catalytic performance for the reaction of CO insertion to dimethyl ether.
基金ACKNOWLEDGMENTS This work was supported by the National Natural Science Foundation of China (No.21276208), the Doctor Fundation of Education Ministry of China (No.20096118110008), the Special Research Fund of Shaanxi Provincial Department of Education of China (No.12JK0606), and the Research Fund for Excellent Doctoral Thesis of Xi'an University of Technology (No.207-002J1304).
文摘The metal complex 5-(4-aminophenyl)-10,15,20-triphenylporphyrin copper (CuAPTPP) was covalently linked on the surface of TiO2 microspheres by using toluene disocyanate (TDI) as a bridging bond unit. The hydroxyl group (-OH) of TiO2 microspheres surface and the amino group (-NH2) of CuAPTPP reacted respectively with the active -NCO groups of TDI to form a surface conjugated microsphere CuAPTPP-TDI-TiO2 that was confirmed by FT-IR spectra. The CuAPTPP-TDI-TiO2 microspheres were characterized with UV-visible, elemental analysis, XRD, SEM, and UV-Vis diffuse reflectance spectra. The effect of amounts of linked TDI on the performance of photocatalytic microspheres was discussed, and the optimal molar ratio of TDI:TiO2 was established. The photocatalytic activity of CuAPTPP- TDI-TiO2 was evaluated using the photocatalytic degradation of methylene blue (MB) under visible-light irradiation. The results showed that, TDI, as a bond unit, was used to form a steady chemical brigdging bond linking CuAPTPP and the surface of TiO2 microspheres, and the prepared catalyst exhibited higher photocatalytic activity under visible-light irradiation for MB degradation. The degradation rate of 20 mg/L MB could reach 98.7% under Xe- lamp (150 W) irradiation in 120 rain. The degradation of MB followed the first-order reaction model under visible light irradiation, and the rate constant of 5.1× 10^-2 min-1 and the half- life of 11.3 min were achieved. And the new photocatalyst can be recycled for 4 times, remaining 90.0% MB degradation rate.
基金supported by the National Natural Science Foundation of China(51274028)~~
文摘Direct methanol fuel cells (DMFCs) are promising for use in portable devices because of advantages such as high fuel energy density, low working temperature and low emission of pollutants. Nanotechnology has been used to improve the performance of DMFCs. Catalytic materials composed of small, metallic particles with unique nanostructure supparted on carbons or metal oxides have been widely investigated for use in DMFCs. Despite our increased understanding of this type of fuel cell, many challenges still remain. This paper reviews the current developments of nanostructured elec- trocatalytic materials and porous electrodes for use in DMFCs. In particular, this review focuses on the synthesis and characterization of nanostructured catalysts and supporting materials. Both computational and experimental approaches to optimize mass transportation in porous electrodes of DMFCs, such as theoretical modeling of internal transfer processes and preparation of functional structures in membrane electrode assemblies, are introduced.
基金supported by the National High Technology Research and Development Program of China(863 Program,2015AA034603)the National Natural Science Foundation of China(21377008)Foundation on the Creative Research Team Construction Promotion Project of Beijing Municipal Institutions
文摘Three-dimensionally ordered macro-/mesoporous alumina(3DOM Al2O3)-supported cobalt oxide and platinum nanocatalysts(xPt/yCo3O4/3DOM Al2O3,Pt mass fraction(x%)= 0-1.4%,Co3O4 mass fraction(y%) = 0-9.2%) were prepared using poly(methyl methacrylate) templating,incipient wetness impregnation and polyvinyl alcohol-protected reduction.The resulting xPt/yCo3O4/3DOM Al2O3 samples displayed a high-quality 3DOM architecture with macropores(180-200 nm in diameter) and mesopores(4-6 nm in diameter) together with surface areas in the range of 94 to 102m^2/g.Using these techniques,Co3O4 nanoparticles(NPs,18.3 nm) were loaded on the 3DOM Al2O3 surface,after which Pt NPs(2.3-2.5 nm) were uniformly dispersed on theyCo3O4/3DOM Al2O3.The1.3Pt/8.9Co3O4/3DOM Al2O3 exhibited the best performance for toluene oxidation,with a T(90%) value(the temperature required to achieve 90%toluene conversion) of 160 ℃ at a space velocity of20000 mL g^(-1) h^(-1).It is concluded that the excellent catalytic performance of the 1.3Pt/8.9Co3O4/3DOM Al2O3 is owing to well-dispersed Pt NPs,the high concentration of adsorbed oxygen species,good low-temperature reducibility,and strong interaction between the Pt and Co3O4 NPs,as well as the unique bimodal porous structure of the support.
基金Project(50573041)supported by the National Natural Science Foundation of China
文摘Platinum nanoparticles supported on carbons(Pt/C,60%,mass fraction) electrocatalysts for direct methanol fuel cell(DMFC) were prepared by citrate-stabilized method with different reductants and carbon supports.The catalysts were characterized by X-ray diffraction(XRD),transmission electron microscopy(TEM) and cyclic voltammetry(CV).It is found that the size of Pt nanoparticles on carbon is controllable by citrate addition and reductant optimization,and the form of carbon support has a great influence on electrocatalytic activity of catalysts.The citrate-stabilized Pt nanoparticles supported on BP2000 carbon,which was reduced by formaldehyde,exhibit the best performance with about 2 nm in diameter and 66.46 m2/g(Pt) in electrocatalytic active surface(EAS) area.Test on single DMFC with 60%(mass fraction) Pt/BP2000 as cathode electrocatalyst showed maximum power density at 78.8 mW/cm2.
基金Project(21471054)supported by the National Natural Science Foundation of China
文摘A novel WO3-x/TiO2 film as photoanode was synthesized for photoelectrocatalytic(PEC) reduction of CO2 into formic acid(HCOOH). The films prepared by doctor blade method were characterized with X-ray diffractometer(XRD), scanning electron microscope(SEM) and transmission electron microscope(TEM). The existence of oxygen vacancies in the WO3-x was confirmed with an X-ray photoelectron spectroscopy(XPS), and the accurate oxygen index was determined by a modified potentiometric titrimetry method. After 3h of photoelectrocatalytic reduction, the formic acid yield of the WO3-x/TiO2 film is 872 nmol/cm^2, which is 1.83 times that of the WO3/TiO2 film. The results of PEC performance demonstrate that the introduction of WO3-x nanoparticles can improve the charge transfer performance so as to enhance the performance of PEC reduction of CO2 into formic acid.