Herein, we reported the synthesis of well-defined Co_3O_4 nanoarrays(NAs) supported on a monolithic three-dimensional macroporous nickel(Ni) foam substrate for use in highefficiency CO oxidation. The monolithic Co_3O_...Herein, we reported the synthesis of well-defined Co_3O_4 nanoarrays(NAs) supported on a monolithic three-dimensional macroporous nickel(Ni) foam substrate for use in highefficiency CO oxidation. The monolithic Co_3O_4 NAs catalysts were obtained through a generic hydrothermal synthesis route with subsequent calcination. By controlling the reaction time,solvent polarity and deposition agent, these Co_3O_4 NAs catalysts exhibited various novel morphologies(single or hybrid arrays), whose physicochemical properties were further characterized by using several analytical techniques. Based on the catalytic and characterization analyses, it was found that the Co_3O_4 NAs-6 catalyst with nanobrush and nanomace arrays displayed enhanced catalytic activity for CO oxidation, achieving an efficient 100% CO oxidation conversion at a gas hourly space velocity(GHSV) 10,000 hr^(-1) and 150°C with longterm stability. Compared with the other Co_3O_4 NAs catalysts, it had the highest abundance of surface-adsorbed oxygen species, excellent low-temperature reducibility and was rich in surface-active sites(Co^(3+)/Co^(2+)= 1.26).展开更多
A modified Hummer＇s method was adopted for the synthesis of graphene oxide（GO） and reduced graphene oxide（rGO）. It was revealed that the modified method is effective for the production of GO and rGO from graphite...A modified Hummer＇s method was adopted for the synthesis of graphene oxide（GO） and reduced graphene oxide（rGO）. It was revealed that the modified method is effective for the production of GO and rGO from graphite. Transmission electron microscopy（TEM） images of GO and rGO showed a sheet-like morphology. Because of the presence of oxygenated functional groups on the carbon surface, the interlayer spacing of the prepared GO was higher than that of rGO. The presence of ／OH and CO groups in the Fourier transform infrared spectra（FTIR） spectrum and G-mode and 2D-mode in Raman spectra confirmed the synthesis of GO and rGO. rGO（292.6 m2/g） showed higher surface area than that of GO（236.4 m2/g）. The prepared rGO was used as an adsorbent for benzene and toluene（model pollutants of volatile organic compounds（VOCs）） under dynamic adsorption/desorption conditions. rGO showed higher adsorption capacity and breakthrough times than GO. The adsorption capacity of rGO for benzene and toluene was 276.4 and 304.4 mg/g, respectively.Desorption experiments showed that the spent rGO can be successfully regenerated by heating at 150.0℃. Its excellent adsorption/desorption performance for benzene and toluene makes rGO a potential adsorbent for VOC adsorption.展开更多
Anatase TiO2 nanosheets（-ns-） with dominant exposed {001} facets were used as support to load copper,and the synthesized Cu/TiO2-ns catalysts were evaluated for CO2 hydrogenation to methanol. Under the reaction cond...Anatase TiO2 nanosheets（-ns-） with dominant exposed {001} facets were used as support to load copper,and the synthesized Cu/TiO2-ns catalysts were evaluated for CO2 hydrogenation to methanol. Under the reaction conditions, P = 3.0 MPa, T = 260 ℃, V（N2）：V（H2）：V（CO2） = 8：69：23 and gas hourly space velocity（GHSV） = 3600 mL g-1h-1, the methanol yield reached an appealing high value, 5.6%. Copper-loading amount, calcination temperature and reduction atmosphere have been investigated in this work, which significantly influence the particle sizes of copper and/or the defect concentration in TiO2, then leading to different catalytic performance. Characterizations of XRD, EPR, CO2-TPD and FTIR demonstrate that higher specific surface area of Cu is good for the hydrogenation of CO2 and adequate amount of Ti3＋ plays important roles in CO2 activation. Both of them facilitate high turnover frequency（TOF） of methanol formation.展开更多
Characteristics of toluene decomposition and formation of nitrogen oxide（NOx） by-products were investigated in a dielectric barrier discharge（DBD） reactor with/without catalyst at room temperature and atmospheric ...Characteristics of toluene decomposition and formation of nitrogen oxide（NOx） by-products were investigated in a dielectric barrier discharge（DBD） reactor with/without catalyst at room temperature and atmospheric pressure. Four kinds of metal oxides, i.e., manganese oxide（Mn Ox）, iron oxide（Fe Ox）, cobalt oxide（Co Ox） and copper oxide（Cu O）, supported on Al2O3/nickel foam, were used as catalysts. It was found that introducing catalysts could improve toluene removal efficiency, promote decomposition of by-product ozone and enhance CO2 selectivity. In addition, NOx was suppressed with the decrease of specific energy density（SED） and the increase of humidity, gas flow rate and toluene concentration, or catalyst introduction. Among the four kinds of catalysts, the Cu O catalyst showed the best performance in NOx suppression. The Mn Ox catalyst exhibited the lowest concentration of O3 and highest CO2 selectivity but the highest concentration of NOx. A possible pathway for NOx production in DBD was discussed. The contributions of oxygen active species and hydroxyl radicals are dominant in NOx suppression.展开更多
Herein,a bottom-down design is presented to successfully fabricate ZIF-derived Co3O4,grown in situ on a one-dimensional(1D)α-MnO2 material,denoted as α-MnO2@Co3O4.The synergistic effect derived from the coupled inte...Herein,a bottom-down design is presented to successfully fabricate ZIF-derived Co3O4,grown in situ on a one-dimensional(1D)α-MnO2 material,denoted as α-MnO2@Co3O4.The synergistic effect derived from the coupled interface constructed betweenα-MnO2 and Co3O4 is responsible for the enhanced catalytic activity.The resultantα-MnO2@Co3O4 catalyst exhibits excellent catalytic activity at a T90%(temperature required to achieve a toluene conversion of 90%)of approximately 229℃,which is 47 and 28℃ lower than those of the pureα-MnO2 nanowire and Co3O4-b obtained via pyrolysis of ZIF-67,respectively.This activity is attributed to the increase in the number of surface-adsorbed oxygen species,which accelerate the oxygen mobility and enhance the redox pairs of Mn^4+/Mn^3+ and Co^2+/Co^3+.Moreover,the result of in situ diffuse reflectance infrared Fourier transform spectroscopy suggests that the gaseous oxygen could be more easily activated to adsorbed oxygen species on the surface of α-MnO2@Co3O4 than on that of α-MnO2.The catalytic reaction route of toluene oxidation over theα-MnO2@Co3O4 catalyst is as follows:toluene→benzoate species→alkanes containing oxygen functional group→CO2 and H2O.In addition,the α-MnO2@Co3O4 catalyst shows excellent stability and good water resistance for toluene oxidation.Furthermore,the preparation method can be extended to other 1D MnO2 materials.A new strategy for the development of high-performance catalysts of practical significance is provided.展开更多
A facile hydrothermal method was applied to gain stably and highly efficient CuO-CeO_(2)(denoted as Cu1Ce2)catalyst for toluene oxidation.The changes of surface and inter properties on Cu1Ce2 were investigated compari...A facile hydrothermal method was applied to gain stably and highly efficient CuO-CeO_(2)(denoted as Cu1Ce2)catalyst for toluene oxidation.The changes of surface and inter properties on Cu1Ce2 were investigated comparing with pure CeO_(2)and pure CuO.The formation of Cu-Ce interface promotes the electron transfer between Cu and Ce through Cu^(2+)+Ce^(3+)↔Cu^(+)+Ce^(4+)and leads to high redox properties and mobility of oxygen species.Thus,the Cu1Ce2 catalyst makes up the shortcoming of CeO_(2)and CuO and achieved high catalytic performance with T_(50)=234°C and T_(99)=250°C(the temperature at which 50%and 90%C_(7)H_(8)conversion is obtained,respectively)for toluene oxidation.Different reaction steps and intermediates for toluene oxidation over Cu1Ce2,CeO_(2)and CuO were detected by in situ DRIFTS,the fast benzyl species conversion and preferential transformation of benzoates into carbonates through C=C breaking over Cu1Ce2 should accelerate the reaction.展开更多
Metal organic frameworks(MOFs)derivatives represented by quasi-MOFs have excellent physical and chemical properties and can be applied for the catalytic combustion of volatile organic compounds(VOCs).In this work,Pd/q...Metal organic frameworks(MOFs)derivatives represented by quasi-MOFs have excellent physical and chemical properties and can be applied for the catalytic combustion of volatile organic compounds(VOCs).In this work,Pd/quasi-Ce-BTC synthesized by simple one-step Npyrolysis was applied to the oxidation of toluene,showing excellent toluene catalytic activity(T_(90)=175℃,30000 mL/(g·h)).Microscopic analyses indicate the formation and interaction of a carbon matrix composite quasi-MOF structure interface.The results show that the amorphous carbon matrix formed during the partial pyrolysis of Ce-BTC significantly improves the adsorption and activation capacity of toluene in the reaction,and constructs a reductive system to maintain high concentrations of Ce^(3+)and Pd^(0),which can facilitate the activation and utilization of oxygen in reaction.Quasi in-situ XPS proves that carbon matrix is indirectly involved in the activation and storage of oxygen,and Pd^(0)is the crucial active site for the activation of oxygen.Stability and water resistance tests display good stability of Pd/quasi-Ce-BTC.This work provides a potential method for designing quasi-MOF catalysts towards VOCs effective abatement.展开更多
The temperature of waste gas in refuse transfer station,airport smoking area,and RTO terminal is low,which needs deep oxidation.Catalytic ozonation is one of the most effective treatment techniques in these scenarios....The temperature of waste gas in refuse transfer station,airport smoking area,and RTO terminal is low,which needs deep oxidation.Catalytic ozonation is one of the most effective treatment techniques in these scenarios.In this study,we reported that catalysts were modified under the condition of mag-netic field to simulate the low temperature dynamic conditions of low concentration toluene for catalytic ozonation.This paper aims to explore the relationship between oxygen vacancy and active oxygen species,and the specific pathways of toluene oxidation.The study found that citric acid can enhance the syner-gistic effect between Mn and Ce,and promote the generation of oxygen vacancies.The surface molecule adsorption oxygen is more conducive to catalytic oxidation than subsurface atom adsorption oxygen.Fi-nally,we proposed the main pathways of toluene in this reaction system,which runs through the whole process of the reaction.展开更多
In an insulating system including solid and gas dielectrics, discharge type has a strong impact on charge accumulation at the interface between two dielectrics, and hence charge decay. In order to clarify the influenc...In an insulating system including solid and gas dielectrics, discharge type has a strong impact on charge accumulation at the interface between two dielectrics, and hence charge decay. In order to clarify the influence, a surface charge measurement system was constructed, and three types of discharge, i.e. surface discharge, and low intensity and high intensity coronas, were introduced to cause surface charge accumulation. The decay behavior of surface charges after different types of discharge was obtained at various temperatures. It was found that total surface charges monotonically decreased with time, and the decay rate became larger as temperature increased. However, after a surface discharge or a high intensity corona, surface charge density in the local area appeared to fluctuate during the decay process. Compared with this, the fluctuation of surface charge density was not observed after a low intensity corona. The mechanisms of surface charge accumulation and decay were analysed. Moreover, a microscopic physical model involving charge production, accumulation, and decay was proposed so that the experimental results could be explained.展开更多
Selective catalytic NH_(3)-to-N_(2) oxidation(NH_(3)-SCO)is highly promising for abating NH_(3) emissions slipped from stationary flue gas after-treatment devices.Its practical application,however,is limited by the no...Selective catalytic NH_(3)-to-N_(2) oxidation(NH_(3)-SCO)is highly promising for abating NH_(3) emissions slipped from stationary flue gas after-treatment devices.Its practical application,however,is limited by the non-availability of low-cost catalysts with high activity and N_(2) selectivity.Here,using defect-rich nitrogen-doped carbon nanotubes(NCNT-AW)as the support,we developed a highly active and durable copper-based NH_(3)-SCO catalyst with a high abundance of cuprous(Cu^(+))sites.The obtained Cu/NCNT-AW catalyst demonstrated outstanding activity with a T_(50)(i.e.the temperature to reach 50% NH_(3) conversion)of 174℃ in the NH_(3)-SCO reaction,which outperformed not only the Cu catalyst supported on N-free O-functionalized CNTs(OCNTs)or NCNT with less surface defects,but also those most active Cu catalysts in open literature.Reaction kinetics measurements and temperature-programmed surface reactions using NH_(3)as a probe molecule revealed that the NH_(3)-SCO reaction on Cu/NCNT-AW follows an internal selective catalytic reaction(i-SCR)route involving nitric oxide(NO)as a key intermediate.According to mechanistic investigations by X-ray photoelectron spectroscopy,Raman spectroscopy,and X-ray absorption spectroscopy,the superior NH_(3)-SCO performance of Cu/NCNT-AW originated from a synergy of surface defects and N-dopants.Specifically,surface defects promoted the anchoring of Cu O nanoparticles on N-containing sites and,thereby,enabled efficient electron transfer from N to Cu O,increasing significantly the fraction of SCR-active Cu^(+)sites in the catalyst.This study puts forward a new idea for manipulating and utilizing the interplay of defects and N-dopants on carbon surfaces to fabricate Cu^(+)-rich Cu catalysts for efficient abatement of slip NH_(3)emissions via selective oxidation.展开更多
Palladium-exchanged chabazite(Pd-CHA) zeolites as passive NO_x adsorbers(PNAs) enable efficient purification of nitrogen oxides(NO_x) in cold-start diesel exhausts. Their commercial application, however,is limited by ...Palladium-exchanged chabazite(Pd-CHA) zeolites as passive NO_x adsorbers(PNAs) enable efficient purification of nitrogen oxides(NO_x) in cold-start diesel exhausts. Their commercial application, however,is limited by the lack of facile preparation method. Here, high-performance CHA-type Pd-SAPO-34 zeolite was synthesized by a modified solid-state ion exchange(SSIE) method using PdO as Pd precursor,and demonstrated superior PNA performance as compared to Pd-SAPO-34 prepared by conventional wetchemistry strategies. Structural characterization using Raman spectroscopy and X-ray diffraction revealed that the SSIE method avoided water-induced damage to the zeolite framework during Pd loading. Mechanistic investigations on the SSIE process by in situ infrared spectroscopy and X-ray photoelectron spectroscopy disclosed that, while PdO precursor was mainly converted to Pd^(2+) cations coordinated to the zeolite framework by consuming the-OH groups of the zeolite, a portion of PdO could also undergo thermal decomposition to form highly dispersed Pd~0 clusters in the pore channels. This simplified and scalable SSIE method paves a new way for the cost-effective synthesis of defect-free high-performance Pd-SAPO-34 zeolites as PNA catalysts.展开更多
SF_(6) has excellent insulation performance and arc extinguishing ability,and is widely used in the power industry.However,its global warming potential is about 23,500 times that of C0_(2),it can exist stably in the a...SF_(6) has excellent insulation performance and arc extinguishing ability,and is widely used in the power industry.However,its global warming potential is about 23,500 times that of C0_(2),it can exist stably in the atmosphere,it is not easily degradable and is of great potential harm to the environment.Based on pulsed dielectric barrier discharge plasma technology,the effects of H_(2)O and 0_(2) on the degradation of SF_(6) were studied.Studies have shown that H_(2)O can effectively promote the decomposition of SF_(6) and improve its degradation rate and energy efficiency of degradation.Under the action of a pulse input voltage and input frequency of 15 kV and 15 kHz,respectively,when H_(2)O is added alone the effect of 1% H_(2)O is the best,and the rate and energy efficiency of degradation of SF_(6) reach their maximum values,which are 91.9% and 8.25 g kWh^(-1),respectively.The synergistic effect of H_(2)O and O_(2) on the degradation of SF_(6) was similar to that of H_(2)O.When the concentration of H_(2)O and O_(2) was 1%,the system obtained the best rate and energy efficiency of degradation,namely 89.7% and 8.05 g kWh~(-1),respectively.At the same time,different external gases exhibit different capabilities to regulate decomposition products.The addition of H_(2)O can effectively improve the selectivity of S0_(2).Under the synergistic effect of H_(2)O and O_(2),with increase in O_(2) concentration the degradation products gradually transformed into SO_(2)F_(2).From the perspective of harmless treatment of the degradation products of SF_(6),the addition of O_(2) during the SF_(6) degradation process should be avoided.展开更多
Herein,a facile glycol reduction route is successful employed to synthesize bimetallic Pt Ag alloys with homogeneous distribution of sizes and elements.Experimental studies reveal that the ultrafine Pt Ag alloys with ...Herein,a facile glycol reduction route is successful employed to synthesize bimetallic Pt Ag alloys with homogeneous distribution of sizes and elements.Experimental studies reveal that the ultrafine Pt Ag alloys with well-defined sizes from around 3.3 nm to 5.8 nm are immobilized onto MnO_(2)microsphere,which remarkably enhances the catalytic performances for CO oxidation.Importantly,quasi in-situ X-ray photoelectron spectroscopy(XPS)result reveals that both Mn and Pt ions on the surface of catalysts would realize alternating reduction-oxidation by CO and O_(2)molecules,and the oxygen vacancy sites could be replenished and excited by gas-phase O_(2).展开更多
Ceria is widely used as a catalyst for soot combustion,but effects of Zr substitution on the reaction mechanism is ambiguous.The present work elucidates effects of Zr substitution on soot combustion over cubic fluorit...Ceria is widely used as a catalyst for soot combustion,but effects of Zr substitution on the reaction mechanism is ambiguous.The present work elucidates effects of Zr substitution on soot combustion over cubic fluorite-structured nanoceria.The nanostructured CeO_(2),Ce_(0.92)Zr_(0.08)O_(2),and Ce_(0.84)Zr_(0.16)O_(2)composed of 5-6 nm crystallites display T_(m-CO2)(the temperature at maximum CO_2 yield)at 383,355,and 375℃under 10 vol.%O_(2)/N_(2),respectively.The size of agglomerate decreases from 165.5 to 51.9-57.3 nm,which is beneficial for the sootceria contact.Moreover,Zr increases the amount of surface oxygen vacancies,generating more active oxygen(O_(2)^-and O^(-))for soot oxidation.Thus,the activities of Ce_(0.92)Zr_(0.08)O_(2)and Ce_(0.84)Zr_(0.16)O_(2)in soot combustion are better than that of CeO_(2).Although oxygen vacancies promote the migration of lattice O~(2-),the enriched surface Zr also inhibits the mobility of lattice O^(2-).Therefore,the T_(m-CO2)of Ce_(0.84)Zr_(0.1)6 O_(2)is higher than that of Ce_(0.92)Zr_(0.08)O_(2).Based on reaction kinetic study,soot in direct contact with ceria preferentially decomposes with low activation energy,while the oxidation of isolated soot occurs through diffusion with high activation energy.The obtained findings provide new understanding on the soot combustion over nanoceria.展开更多
The authors regret“In the whole text,ppm and mg/L was confusing.As in aqueous phase,1 ppm=1 mg/L,but in gaseous phase,1 ppm=0.001%o.In this paper,in text and figures,the concentration units were ppm,but when calculat...The authors regret“In the whole text,ppm and mg/L was confusing.As in aqueous phase,1 ppm=1 mg/L,but in gaseous phase,1 ppm=0.001%o.In this paper,in text and figures,the concentration units were ppm,but when calculating the adsorption ca-pacity,the concentration units ppm were mistakenly used as mg/L.As for benzene,1 ppm=3.4871 x 10^-3 mg/L,as for toluene。展开更多
This paper investigates elastomer-toughened polypropylene(PP)insulation to meet the application requirements for green noncrosslinked PP cables in high-voltage direct current(HVDC)transmission.It focuses on the format...This paper investigates elastomer-toughened polypropylene(PP)insulation to meet the application requirements for green noncrosslinked PP cables in high-voltage direct current(HVDC)transmission.It focuses on the formation ofβ-crystals in isotactic polypropylene(iPP)by adding aβ-nucleator.It examines how varying concentrations ofβ-nucleator and elastomer(POE)impact the aggregation structure of PP insulation and its conductivity and breakdown characteristics in the DC field.The results indicated that at aβ-nucleator agent content of 0.1 wt%,the samples with various POE contents achieved the highest crystallinity,the maximum proportion ofβ-crystals and the most uniform elastomer distribution.The nucleating agent facilitates the formation ofβ-crystals in PP and enhances the order degree of the elastomer molecular chains,thereby improving their crystallization capabilities.Evaluations of DC performances and trap characteristics reveal that when the amount of theβ-nucleator is set at 0.1 wt%,the sample demonstrates the lowest trap density,an exceptional and lower electric field coefficient of conductivity at elevated electric fields and a superior DC field breakdown strength at 90°C.Compared to samples withoutβ-nucleator,the reduction of DC field breakdown strength for PPBx-0.1 from 25°C to 90°C is approximately 4.86%lower.This improvement is attributed to the ability of theβ-nucleator to improve the aggregation structure between PP and POE while optimising the stability of the two-phase interface.Thus,although DC electrical characteristics are maintained at normal temperatures,the DC characteristics are significantly improved at elevated temperatures.展开更多
In modern power transmission systems,AC cables are increasingly integrated with overhead lines,forming hybrid networks.These cables are frequently exposed to repeated impulse voltages from the overhead lines.While sur...In modern power transmission systems,AC cables are increasingly integrated with overhead lines,forming hybrid networks.These cables are frequently exposed to repeated impulse voltages from the overhead lines.While surge arresters offer partial protection,the long-term effects of these impulses on polypropylene(PP)insulation remain unclear.This study systematically investigates the cumulative degradation of the electrical breakdown properties of PP insulation under repeated impulse voltage stress.The 50%impulse breakdown voltage(U_(50))was first determined,and a series of impulse tests were conducted at varying voltage levels to assess the number of impulses required for elec-trical breakdown,leading to the construction of an amplitude of impulse voltage(U)and the number of times required for breakdown(N),which is U-N curve.To evaluate the cumulative degradation,impulse voltage at 0.8 U_(50)was applied for 50,100,and 200 cycles,with the electrical conductivity current measured before and after each series of impulses.The results indicate significant degradation in the insulating properties of PP under repeated impulse stress.Mechanisms of cumulative degradation under impulse stress were further explored using isothermal relaxation current and space charge measurements.These findings provide critical insights into the performance of PP in hybrid transmission systems and offer valuable data to inform improved insulation design and protection strategies.展开更多
基金supported by Science and Technology Planning Project of Guangdong Province China (No.2015B0202236002)the National Natural Science Foundation of China (Nos.21401200,51108187,51672273,B5151050)+2 种基金the National Key R & D Plan (No.2017YFC0211503)the Open Research Fund of State Key Laboratory of Multi-phase Complex Systems (No.MPCS-2017-D-06)the Guangdong Natural Science Foundation (No.2016A030311003)
文摘Herein, we reported the synthesis of well-defined Co_3O_4 nanoarrays(NAs) supported on a monolithic three-dimensional macroporous nickel(Ni) foam substrate for use in highefficiency CO oxidation. The monolithic Co_3O_4 NAs catalysts were obtained through a generic hydrothermal synthesis route with subsequent calcination. By controlling the reaction time,solvent polarity and deposition agent, these Co_3O_4 NAs catalysts exhibited various novel morphologies(single or hybrid arrays), whose physicochemical properties were further characterized by using several analytical techniques. Based on the catalytic and characterization analyses, it was found that the Co_3O_4 NAs-6 catalyst with nanobrush and nanomace arrays displayed enhanced catalytic activity for CO oxidation, achieving an efficient 100% CO oxidation conversion at a gas hourly space velocity(GHSV) 10,000 hr^(-1) and 150°C with longterm stability. Compared with the other Co_3O_4 NAs catalysts, it had the highest abundance of surface-adsorbed oxygen species, excellent low-temperature reducibility and was rich in surface-active sites(Co^(3+)/Co^(2+)= 1.26).
基金financially supported by the China Postdoctoral Science Foundation(2016M592496)National Natural Science Foundation of China(Nos.91645119,21207039,U1201231,51378218,51108187 and 50978103)+2 种基金the Fundamental Research Funds for the Central Universities(Nos.2017BQ053 and 2017BQ055)Natural Science Foundation of Guangdong Province,China(Grant No.2014A030310431)Guangzhou Science and Technology Plan(201607010095)
文摘A modified Hummer＇s method was adopted for the synthesis of graphene oxide（GO） and reduced graphene oxide（rGO）. It was revealed that the modified method is effective for the production of GO and rGO from graphite. Transmission electron microscopy（TEM） images of GO and rGO showed a sheet-like morphology. Because of the presence of oxygenated functional groups on the carbon surface, the interlayer spacing of the prepared GO was higher than that of rGO. The presence of ／OH and CO groups in the Fourier transform infrared spectra（FTIR） spectrum and G-mode and 2D-mode in Raman spectra confirmed the synthesis of GO and rGO. rGO（292.6 m2/g） showed higher surface area than that of GO（236.4 m2/g）. The prepared rGO was used as an adsorbent for benzene and toluene（model pollutants of volatile organic compounds（VOCs）） under dynamic adsorption/desorption conditions. rGO showed higher adsorption capacity and breakthrough times than GO. The adsorption capacity of rGO for benzene and toluene was 276.4 and 304.4 mg/g, respectively.Desorption experiments showed that the spent rGO can be successfully regenerated by heating at 150.0℃. Its excellent adsorption/desorption performance for benzene and toluene makes rGO a potential adsorbent for VOC adsorption.
基金financially supported by the National Natural Science Foundation of China (no. 91645119, 21207039, B5151050)the Fundamental Research Funds for the Central Universities (No.2017ZD076)+2 种基金Guangzhou science and technology plan (201607010095)the Natural Science Foundation of Guangdong Province, China (Grant no. S2011010000737)State Key Laboratory of Physical Chemistry of Solid Surfaces, Xiamen University, P.R. China (No. 201602)
文摘Anatase TiO2 nanosheets（-ns-） with dominant exposed {001} facets were used as support to load copper,and the synthesized Cu/TiO2-ns catalysts were evaluated for CO2 hydrogenation to methanol. Under the reaction conditions, P = 3.0 MPa, T = 260 ℃, V（N2）：V（H2）：V（CO2） = 8：69：23 and gas hourly space velocity（GHSV） = 3600 mL g-1h-1, the methanol yield reached an appealing high value, 5.6%. Copper-loading amount, calcination temperature and reduction atmosphere have been investigated in this work, which significantly influence the particle sizes of copper and/or the defect concentration in TiO2, then leading to different catalytic performance. Characterizations of XRD, EPR, CO2-TPD and FTIR demonstrate that higher specific surface area of Cu is good for the hydrogenation of CO2 and adequate amount of Ti3＋ plays important roles in CO2 activation. Both of them facilitate high turnover frequency（TOF） of methanol formation.
基金funded by the National Natural Science Foundation of China (Nos. 50708021, 51108187)the Research Fund Program of Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation Technology (Sun Yat-sen University, No. 2013K0007)Guangdong Provincial Key Laboratory of Atmospheric environment and Pollution Control (No. 2011A060901011)
文摘Characteristics of toluene decomposition and formation of nitrogen oxide（NOx） by-products were investigated in a dielectric barrier discharge（DBD） reactor with/without catalyst at room temperature and atmospheric pressure. Four kinds of metal oxides, i.e., manganese oxide（Mn Ox）, iron oxide（Fe Ox）, cobalt oxide（Co Ox） and copper oxide（Cu O）, supported on Al2O3/nickel foam, were used as catalysts. It was found that introducing catalysts could improve toluene removal efficiency, promote decomposition of by-product ozone and enhance CO2 selectivity. In addition, NOx was suppressed with the decrease of specific energy density（SED） and the increase of humidity, gas flow rate and toluene concentration, or catalyst introduction. Among the four kinds of catalysts, the Cu O catalyst showed the best performance in NOx suppression. The Mn Ox catalyst exhibited the lowest concentration of O3 and highest CO2 selectivity but the highest concentration of NOx. A possible pathway for NOx production in DBD was discussed. The contributions of oxygen active species and hydroxyl radicals are dominant in NOx suppression.
文摘Herein,a bottom-down design is presented to successfully fabricate ZIF-derived Co3O4,grown in situ on a one-dimensional(1D)α-MnO2 material,denoted as α-MnO2@Co3O4.The synergistic effect derived from the coupled interface constructed betweenα-MnO2 and Co3O4 is responsible for the enhanced catalytic activity.The resultantα-MnO2@Co3O4 catalyst exhibits excellent catalytic activity at a T90%(temperature required to achieve a toluene conversion of 90%)of approximately 229℃,which is 47 and 28℃ lower than those of the pureα-MnO2 nanowire and Co3O4-b obtained via pyrolysis of ZIF-67,respectively.This activity is attributed to the increase in the number of surface-adsorbed oxygen species,which accelerate the oxygen mobility and enhance the redox pairs of Mn^4+/Mn^3+ and Co^2+/Co^3+.Moreover,the result of in situ diffuse reflectance infrared Fourier transform spectroscopy suggests that the gaseous oxygen could be more easily activated to adsorbed oxygen species on the surface of α-MnO2@Co3O4 than on that of α-MnO2.The catalytic reaction route of toluene oxidation over theα-MnO2@Co3O4 catalyst is as follows:toluene→benzoate species→alkanes containing oxygen functional group→CO2 and H2O.In addition,the α-MnO2@Co3O4 catalyst shows excellent stability and good water resistance for toluene oxidation.Furthermore,the preparation method can be extended to other 1D MnO2 materials.A new strategy for the development of high-performance catalysts of practical significance is provided.
基金financially supported by the China Postdoctoral Science Foundation(No.2018M643090)the National Natural Science Foundation of China(No.52000077)+3 种基金the National Key Research and Development Project of Research(No.2017YFC0212805)the National Natural Science Foundation of China(No.51878292)the Natural Science Foundation of Guangdong Province,China(No.2015B020236002)the China Postdoctoral Science Foundation(No.2020M682715).
文摘A facile hydrothermal method was applied to gain stably and highly efficient CuO-CeO_(2)(denoted as Cu1Ce2)catalyst for toluene oxidation.The changes of surface and inter properties on Cu1Ce2 were investigated comparing with pure CeO_(2)and pure CuO.The formation of Cu-Ce interface promotes the electron transfer between Cu and Ce through Cu^(2+)+Ce^(3+)↔Cu^(+)+Ce^(4+)and leads to high redox properties and mobility of oxygen species.Thus,the Cu1Ce2 catalyst makes up the shortcoming of CeO_(2)and CuO and achieved high catalytic performance with T_(50)=234°C and T_(99)=250°C(the temperature at which 50%and 90%C_(7)H_(8)conversion is obtained,respectively)for toluene oxidation.Different reaction steps and intermediates for toluene oxidation over Cu1Ce2,CeO_(2)and CuO were detected by in situ DRIFTS,the fast benzyl species conversion and preferential transformation of benzoates into carbonates through C=C breaking over Cu1Ce2 should accelerate the reaction.
基金Project supported by the National Natural Science Foundation of China(51878293)the National Key Research and Development Plan(2018YFB0605200)China Postdoctoral Science Foundation(2020M682715)。
文摘Metal organic frameworks(MOFs)derivatives represented by quasi-MOFs have excellent physical and chemical properties and can be applied for the catalytic combustion of volatile organic compounds(VOCs).In this work,Pd/quasi-Ce-BTC synthesized by simple one-step Npyrolysis was applied to the oxidation of toluene,showing excellent toluene catalytic activity(T_(90)=175℃,30000 mL/(g·h)).Microscopic analyses indicate the formation and interaction of a carbon matrix composite quasi-MOF structure interface.The results show that the amorphous carbon matrix formed during the partial pyrolysis of Ce-BTC significantly improves the adsorption and activation capacity of toluene in the reaction,and constructs a reductive system to maintain high concentrations of Ce^(3+)and Pd^(0),which can facilitate the activation and utilization of oxygen in reaction.Quasi in-situ XPS proves that carbon matrix is indirectly involved in the activation and storage of oxygen,and Pd^(0)is the crucial active site for the activation of oxygen.Stability and water resistance tests display good stability of Pd/quasi-Ce-BTC.This work provides a potential method for designing quasi-MOF catalysts towards VOCs effective abatement.
基金financially supported by the Scientific Research Project of Guangzhou City(No.201804020026)the National Nat-ural Science Foundation of China(Nos.51878293,21777047)+1 种基金the National Key Research and Development Program of China(No.2018YFB0605200)the Natural Science Foundation of Guang-dong Province(No.2017B090901049).
文摘The temperature of waste gas in refuse transfer station,airport smoking area,and RTO terminal is low,which needs deep oxidation.Catalytic ozonation is one of the most effective treatment techniques in these scenarios.In this study,we reported that catalysts were modified under the condition of mag-netic field to simulate the low temperature dynamic conditions of low concentration toluene for catalytic ozonation.This paper aims to explore the relationship between oxygen vacancy and active oxygen species,and the specific pathways of toluene oxidation.The study found that citric acid can enhance the syner-gistic effect between Mn and Ce,and promote the generation of oxygen vacancies.The surface molecule adsorption oxygen is more conducive to catalytic oxidation than subsurface atom adsorption oxygen.Fi-nally,we proposed the main pathways of toluene in this reaction system,which runs through the whole process of the reaction.
基金the financial support from National Natural Science Foundation of China (No. 51607128)Natural Science Foundation of Hubei Province (No. 2016CFB111)China Postdoctoral Science Foundation (No. 2016M602353)
文摘In an insulating system including solid and gas dielectrics, discharge type has a strong impact on charge accumulation at the interface between two dielectrics, and hence charge decay. In order to clarify the influence, a surface charge measurement system was constructed, and three types of discharge, i.e. surface discharge, and low intensity and high intensity coronas, were introduced to cause surface charge accumulation. The decay behavior of surface charges after different types of discharge was obtained at various temperatures. It was found that total surface charges monotonically decreased with time, and the decay rate became larger as temperature increased. However, after a surface discharge or a high intensity corona, surface charge density in the local area appeared to fluctuate during the decay process. Compared with this, the fluctuation of surface charge density was not observed after a low intensity corona. The mechanisms of surface charge accumulation and decay were analysed. Moreover, a microscopic physical model involving charge production, accumulation, and decay was proposed so that the experimental results could be explained.
基金supported by the National Natural Science Foundation of China(Nos.21806039,21976058)the Natural Science Foundation of Guangdong Province(No.2023A1515011682)+2 种基金the Fundamental Research Funds for the Central Universities(No.2022ZYGXZR018)the Science and Technology Program of Guangzhou(No.202102080490).P.C.appreciates the funding from the Pearl River Talent Recruitment Program of Guangdong Province(No.2019QN01L170)the Innovation&Entrepreneurship Talent Program of Shaoguan City。
文摘Selective catalytic NH_(3)-to-N_(2) oxidation(NH_(3)-SCO)is highly promising for abating NH_(3) emissions slipped from stationary flue gas after-treatment devices.Its practical application,however,is limited by the non-availability of low-cost catalysts with high activity and N_(2) selectivity.Here,using defect-rich nitrogen-doped carbon nanotubes(NCNT-AW)as the support,we developed a highly active and durable copper-based NH_(3)-SCO catalyst with a high abundance of cuprous(Cu^(+))sites.The obtained Cu/NCNT-AW catalyst demonstrated outstanding activity with a T_(50)(i.e.the temperature to reach 50% NH_(3) conversion)of 174℃ in the NH_(3)-SCO reaction,which outperformed not only the Cu catalyst supported on N-free O-functionalized CNTs(OCNTs)or NCNT with less surface defects,but also those most active Cu catalysts in open literature.Reaction kinetics measurements and temperature-programmed surface reactions using NH_(3)as a probe molecule revealed that the NH_(3)-SCO reaction on Cu/NCNT-AW follows an internal selective catalytic reaction(i-SCR)route involving nitric oxide(NO)as a key intermediate.According to mechanistic investigations by X-ray photoelectron spectroscopy,Raman spectroscopy,and X-ray absorption spectroscopy,the superior NH_(3)-SCO performance of Cu/NCNT-AW originated from a synergy of surface defects and N-dopants.Specifically,surface defects promoted the anchoring of Cu O nanoparticles on N-containing sites and,thereby,enabled efficient electron transfer from N to Cu O,increasing significantly the fraction of SCR-active Cu^(+)sites in the catalyst.This study puts forward a new idea for manipulating and utilizing the interplay of defects and N-dopants on carbon surfaces to fabricate Cu^(+)-rich Cu catalysts for efficient abatement of slip NH_(3)emissions via selective oxidation.
基金supported by the National Natural Science Foundation of China (No.21976058)the Natural Science Foundation of Guangdong Province (No.2023A1515011682)+3 种基金the Fundamental Research Funds for the Central Universities (No.2022ZYGXZR018)the National Engineering Laboratory for Mobile Source Emission Control Technology (No.NELMS2020A10)the funding from the Pearl River Talent Recruitment Program of Guangdong Province (No.2019QN01L170)the Innovation & Entrepreneurship Talent Program of Shaoguan City。
文摘Palladium-exchanged chabazite(Pd-CHA) zeolites as passive NO_x adsorbers(PNAs) enable efficient purification of nitrogen oxides(NO_x) in cold-start diesel exhausts. Their commercial application, however,is limited by the lack of facile preparation method. Here, high-performance CHA-type Pd-SAPO-34 zeolite was synthesized by a modified solid-state ion exchange(SSIE) method using PdO as Pd precursor,and demonstrated superior PNA performance as compared to Pd-SAPO-34 prepared by conventional wetchemistry strategies. Structural characterization using Raman spectroscopy and X-ray diffraction revealed that the SSIE method avoided water-induced damage to the zeolite framework during Pd loading. Mechanistic investigations on the SSIE process by in situ infrared spectroscopy and X-ray photoelectron spectroscopy disclosed that, while PdO precursor was mainly converted to Pd^(2+) cations coordinated to the zeolite framework by consuming the-OH groups of the zeolite, a portion of PdO could also undergo thermal decomposition to form highly dispersed Pd~0 clusters in the pore channels. This simplified and scalable SSIE method paves a new way for the cost-effective synthesis of defect-free high-performance Pd-SAPO-34 zeolites as PNA catalysts.
基金supported by Guizhou Province (Ceneral), grant/award number Qian Ke He Zhi Cheng [2022] General 207, National Natural Science Foundation of China (No. 52307170)Natural Science Foundation of Hubei Province, China (No. 2023AFB382)。
文摘SF_(6) has excellent insulation performance and arc extinguishing ability,and is widely used in the power industry.However,its global warming potential is about 23,500 times that of C0_(2),it can exist stably in the atmosphere,it is not easily degradable and is of great potential harm to the environment.Based on pulsed dielectric barrier discharge plasma technology,the effects of H_(2)O and 0_(2) on the degradation of SF_(6) were studied.Studies have shown that H_(2)O can effectively promote the decomposition of SF_(6) and improve its degradation rate and energy efficiency of degradation.Under the action of a pulse input voltage and input frequency of 15 kV and 15 kHz,respectively,when H_(2)O is added alone the effect of 1% H_(2)O is the best,and the rate and energy efficiency of degradation of SF_(6) reach their maximum values,which are 91.9% and 8.25 g kWh^(-1),respectively.The synergistic effect of H_(2)O and O_(2) on the degradation of SF_(6) was similar to that of H_(2)O.When the concentration of H_(2)O and O_(2) was 1%,the system obtained the best rate and energy efficiency of degradation,namely 89.7% and 8.05 g kWh~(-1),respectively.At the same time,different external gases exhibit different capabilities to regulate decomposition products.The addition of H_(2)O can effectively improve the selectivity of S0_(2).Under the synergistic effect of H_(2)O and O_(2),with increase in O_(2) concentration the degradation products gradually transformed into SO_(2)F_(2).From the perspective of harmless treatment of the degradation products of SF_(6),the addition of O_(2) during the SF_(6) degradation process should be avoided.
基金financially supported by the Research Funds of the Guilin University of Technology(No.GUTQDJJ202041)Guangxi Key Laboratory of Theory and Technology for Environmental Pollution Control(No.Guikeneng 2001K002)+2 种基金National Natural Science Foundation of China(Nos.51978189,51878292)National Key R&D Program of China(No.2017YFC0211503)China Postdoctoral Science Foundation(No.2020M683629XB)。
文摘Herein,a facile glycol reduction route is successful employed to synthesize bimetallic Pt Ag alloys with homogeneous distribution of sizes and elements.Experimental studies reveal that the ultrafine Pt Ag alloys with well-defined sizes from around 3.3 nm to 5.8 nm are immobilized onto MnO_(2)microsphere,which remarkably enhances the catalytic performances for CO oxidation.Importantly,quasi in-situ X-ray photoelectron spectroscopy(XPS)result reveals that both Mn and Pt ions on the surface of catalysts would realize alternating reduction-oxidation by CO and O_(2)molecules,and the oxygen vacancy sites could be replenished and excited by gas-phase O_(2).
基金financially supported by Guangdong Major Project of Basic and Applied Basic Research(No.2019B030302013)the Natural Science Foundation for Distinguished Young Scientists of Guangdong Province(No.2020B1515020015)+1 种基金Pearl River S&T Nova Program of Guangzhou(No.201806010069)。
文摘Ceria is widely used as a catalyst for soot combustion,but effects of Zr substitution on the reaction mechanism is ambiguous.The present work elucidates effects of Zr substitution on soot combustion over cubic fluorite-structured nanoceria.The nanostructured CeO_(2),Ce_(0.92)Zr_(0.08)O_(2),and Ce_(0.84)Zr_(0.16)O_(2)composed of 5-6 nm crystallites display T_(m-CO2)(the temperature at maximum CO_2 yield)at 383,355,and 375℃under 10 vol.%O_(2)/N_(2),respectively.The size of agglomerate decreases from 165.5 to 51.9-57.3 nm,which is beneficial for the sootceria contact.Moreover,Zr increases the amount of surface oxygen vacancies,generating more active oxygen(O_(2)^-and O^(-))for soot oxidation.Thus,the activities of Ce_(0.92)Zr_(0.08)O_(2)and Ce_(0.84)Zr_(0.16)O_(2)in soot combustion are better than that of CeO_(2).Although oxygen vacancies promote the migration of lattice O~(2-),the enriched surface Zr also inhibits the mobility of lattice O^(2-).Therefore,the T_(m-CO2)of Ce_(0.84)Zr_(0.1)6 O_(2)is higher than that of Ce_(0.92)Zr_(0.08)O_(2).Based on reaction kinetic study,soot in direct contact with ceria preferentially decomposes with low activation energy,while the oxidation of isolated soot occurs through diffusion with high activation energy.The obtained findings provide new understanding on the soot combustion over nanoceria.
文摘The authors regret“In the whole text,ppm and mg/L was confusing.As in aqueous phase,1 ppm=1 mg/L,but in gaseous phase,1 ppm=0.001%o.In this paper,in text and figures,the concentration units were ppm,but when calculating the adsorption ca-pacity,the concentration units ppm were mistakenly used as mg/L.As for benzene,1 ppm=3.4871 x 10^-3 mg/L,as for toluene。
基金supported by China Southern Power Grid Company Limited(Grant GDKJXM20222136).
文摘This paper investigates elastomer-toughened polypropylene(PP)insulation to meet the application requirements for green noncrosslinked PP cables in high-voltage direct current(HVDC)transmission.It focuses on the formation ofβ-crystals in isotactic polypropylene(iPP)by adding aβ-nucleator.It examines how varying concentrations ofβ-nucleator and elastomer(POE)impact the aggregation structure of PP insulation and its conductivity and breakdown characteristics in the DC field.The results indicated that at aβ-nucleator agent content of 0.1 wt%,the samples with various POE contents achieved the highest crystallinity,the maximum proportion ofβ-crystals and the most uniform elastomer distribution.The nucleating agent facilitates the formation ofβ-crystals in PP and enhances the order degree of the elastomer molecular chains,thereby improving their crystallization capabilities.Evaluations of DC performances and trap characteristics reveal that when the amount of theβ-nucleator is set at 0.1 wt%,the sample demonstrates the lowest trap density,an exceptional and lower electric field coefficient of conductivity at elevated electric fields and a superior DC field breakdown strength at 90°C.Compared to samples withoutβ-nucleator,the reduction of DC field breakdown strength for PPBx-0.1 from 25°C to 90°C is approximately 4.86%lower.This improvement is attributed to the ability of theβ-nucleator to improve the aggregation structure between PP and POE while optimising the stability of the two-phase interface.Thus,although DC electrical characteristics are maintained at normal temperatures,the DC characteristics are significantly improved at elevated temperatures.
基金China Southern Power Grid Company Limited,Grant/Award Number:ZBKJXM20220101National Natural Science Foundation of China,Grant/Award Number:52107019。
文摘In modern power transmission systems,AC cables are increasingly integrated with overhead lines,forming hybrid networks.These cables are frequently exposed to repeated impulse voltages from the overhead lines.While surge arresters offer partial protection,the long-term effects of these impulses on polypropylene(PP)insulation remain unclear.This study systematically investigates the cumulative degradation of the electrical breakdown properties of PP insulation under repeated impulse voltage stress.The 50%impulse breakdown voltage(U_(50))was first determined,and a series of impulse tests were conducted at varying voltage levels to assess the number of impulses required for elec-trical breakdown,leading to the construction of an amplitude of impulse voltage(U)and the number of times required for breakdown(N),which is U-N curve.To evaluate the cumulative degradation,impulse voltage at 0.8 U_(50)was applied for 50,100,and 200 cycles,with the electrical conductivity current measured before and after each series of impulses.The results indicate significant degradation in the insulating properties of PP under repeated impulse stress.Mechanisms of cumulative degradation under impulse stress were further explored using isothermal relaxation current and space charge measurements.These findings provide critical insights into the performance of PP in hybrid transmission systems and offer valuable data to inform improved insulation design and protection strategies.
