A series of Co3O4-CeO2 binary oxides with various Co/(Ce+Co)molar ratios were synthesized using a citric acid method,and their catalytic properties toward the total oxidation of propane were examined.The activities of...A series of Co3O4-CeO2 binary oxides with various Co/(Ce+Co)molar ratios were synthesized using a citric acid method,and their catalytic properties toward the total oxidation of propane were examined.The activities of the catalysts decrease in the order CoCeOx-70>CoCeOx-90>Co3O4>CoCeOx-50>CoCeOx-20>CeO2.CoCeOx-70(Co/(Ce+Co)=70% molar ratio)exhibits the highest catalytic activity toward the total oxidation of propane,of which the T90 is 310℃(GHSV=120000 mL h^-1 g^-1],which is 25℃ lower than that of pure Co3 O4.The enhancement of the catalytic performance of CoCeOx-70 is attributed to the strong interaction between CeO2 and Co3O4,the improvement of the low-temperature reducibility,and the increase in the number of active oxygen species.In-situ DRIFTS and reaction kinetics measurement reveal that Ce addition does not change the reaction mechanism,but promotes the adsorption and activation of propane on the catalyst surface.The addition of water vapor and CO2 in reactant gas has a negative effect on the propane conversion,and the catalyst is more sensitive to water vapor than to CO2.In addition,CoCeOx-70 exhibits excellent stability and reusability in water vapor and CO2 atmosphere.展开更多
As one of the most active rare earths,CeO2 has caused extensive concern due to its multifunctional properties.CeO2-based compound oxide of M2O3-CeO2(M=La,Fe,and Al)were prepared by coprecipitation and impregnation met...As one of the most active rare earths,CeO2 has caused extensive concern due to its multifunctional properties.CeO2-based compound oxide of M2O3-CeO2(M=La,Fe,and Al)were prepared by coprecipitation and impregnation methods.The photocatalytic performance of the samples for the degradation methylene blue was studied under UV and visible light irradiation.The effects of constituents on the properties of the CeO2-based catalysts were investigated by XRD,TEM,BET,and UV-Vis spectrophotometer.The highest degradation of methylene blue under 230W UV light was almost 100%at 50 min by La2O3/Fe2O3-CeO2/γ-Al2O3 catalyst and 99.42%at 50 min by Fe2O3-CeO2/γ-Al2O3 catalyst.The methylene blue removal efficiency under indoor natural light reaches 93.81%by La2O3/Fe2O3-CeO2/γ-Al2O3 catalyst and 92.34%by Fe2O3-CeO2/γ-Al2O3 catalyst at 50 min.The order of catalytic degradation activity is La2O3/Fe2O3-CeO2/γ-Al2O3>Fe2O3-CeO2/γ-Al2O3>La2O3-CeO2/γ-Al2O3>Al2O3,owing to their structural features.The doping of La^3+or Fe3+onto CeO2/γ-Al2O produced much more oxygen vacancies under light irradiation and reduced the energy laps of CeO2 with value of 2.86 ev,which improved the photocatalytic redox performance of the composite oxide.展开更多
Although most transition metals have been tested as the promoter to Pt for electrocatalysis toward fuel cell reactions,semi-conductor elements,such as Si,have hitherto not been examined.Here we report a simple synthes...Although most transition metals have been tested as the promoter to Pt for electrocatalysis toward fuel cell reactions,semi-conductor elements,such as Si,have hitherto not been examined.Here we report a simple synthesis of intermetallic Pt2Si electrode using magnetron sputtering and the electrocatalysis toward ethanol oxidation reaction（EOR）.In comparison to Pt,the intermetallic Pt2Si surface turns out to be much more active in catalyzing the EOR：the onset potential shifts negatively by 150 mV,and the current density at 0.6 V increases by a magnitude of one order.Such an enormous enhancement in EOR catalysis is ascribed to the promotion effects of Si,which can not only provide active surface oxygenated species to accelerate the removal of COads,but also strongly alter the electronic property of Pt,as clearly indicated by the core-level shift in XPS spectrum.展开更多
Achieving regioselectivity in radical cyclization reactions is of central importance,yet extremely challenging.Although Baldwin’s rules provided guidance on the addition of radical species with alkenes/alkynes,the or...Achieving regioselectivity in radical cyclization reactions is of central importance,yet extremely challenging.Although Baldwin’s rules provided guidance on the addition of radical species with alkenes/alkynes,the ortho-/ipso-selectivity of the cyclic reaction between radical species(especially alkyl and alkenyl radical)and aryl groups is still ambiguous.Herein,we develop an electrochemically enabled regioselective ortho-(4+2)/ipso-(3+2)cyclization of alkyl/alkenyl radicals with aryl groups,which provides a series of tetrahydronaphthalene and spirocarbocycle derivatives,exhibiting a broad substrate scope and functional group tolerance.Alkyl/alkenyl radicals are generated by Cp2Fe-mediated electrochemical oxidative radical addition of benzylic malonates with alkenes and alkynes.The method avoids the use of chemical oxidant/base/noble metal,the pre-functionalization of substrates,and the over-oxidation of compounds.Theoretical studies reveal that the dominant factor promoting the alkene-preferred ortho-addition is the favorable interaction energy;the alkyne-preferred ipso-addition regioselectivity is controlled by the distortion energy.Notably,this strategy is regarded as an important supplement to Baldwin’s rules for radical cyclization.展开更多
The comparison of degradation of Acid Yellow 61 as a model dye compound in both oxidation processes of H 2O 2/UV and O 3 has been studied. When the decolorization rate of Acid Yellow 61 in both reactions presented ...The comparison of degradation of Acid Yellow 61 as a model dye compound in both oxidation processes of H 2O 2/UV and O 3 has been studied. When the decolorization rate of Acid Yellow 61 in both reactions presented similar, it was found there are some differences from the results of AOX removal and production of inorganic ions and organic acids. The results reveal that the H 2O 2/UV has beneficial effect on mineralization than O 3 only for degradation of Acid Yellow 61 solution and it is possible for enhancement of method efficiency by taking longer reaction time and addition of high concentration of oxidants.展开更多
The octahedral molecular sieve(OMS-2)-supported Fe( xFe/OMS-2: x = 1, 3, 5, and 10) catalysts were prepared using the pre-incorporation method. Physicochemical properties of the as-synthesized materials were character...The octahedral molecular sieve(OMS-2)-supported Fe( xFe/OMS-2: x = 1, 3, 5, and 10) catalysts were prepared using the pre-incorporation method. Physicochemical properties of the as-synthesized materials were characterized by means of various techniques, and their catalytic activities for CO, ethyl acetate, and toluene oxidation were evaluated. Among all of the samples, performed the best, with the reaction temperature required to achieve 90% conversion( T 90%) being 160 ℃ for CO oxidation, 210 ℃ for ethyl acetate oxidation, and 285 ℃ for toluene oxidation. Such a good catalytic performance of 5Fe/OMS-2 was associated with its high(Mn^(3+) + Mn^(2+)) content and adsorbed oxygen species concentration, and good lowtemperature reducibility and lattice oxygen mobility as well as strong interaction between Fe and OMS-2. In addition, catalytic mechanisms of the oxidation of three pollutants over the 5Fe/OMS-2 catalyst were also studied. It was found that CO, ethyl acetate or toluene was first adsorbed, then the related intermediates were formed, and finally the formed intermediates were completely converted into CO_(2) and H_(2)O.展开更多
Electrochemical oxidation is an effective method to degrade persistent organic pollutants.However,due to the limited catalytic activity of traditional thin film electrodes,the anodic oxidation process is slow and usua...Electrochemical oxidation is an effective method to degrade persistent organic pollutants.However,due to the limited catalytic activity of traditional thin film electrodes,the anodic oxidation process is slow and usually requires high energy consumption.Herein,Ti/SnO_(2)-Sb electrode with regulated surface structure was reported to enhance the performance for electrochemical oxidation of persistent organic pollutants.The electrode deposited with SnO_(2)-Sb nanoneedles(Ti/N-SnO_(2)-Sb)showed higher oxidation activity.Its kinetic constant for perfluorooctanoic acid(PFOA)oxidation was 2.0 h^(-1)and the total organic carbon removal rate was 81.7%(4 h)at a relatively low current density of 6 mA/cm^2.Compared with Ti/SnO_(2)-Sb thin film and nanoparticles,Ti/N-SnO_(2)-Sb significantly improved the electrochemical active area and·OH yield,and simultaneously reduced the electron transfer resistance,which enabled it to oxidize PFOA more rapidly even at a lower potential.This work provides a new strategy for promoting the electrochemical oxidation performance.展开更多
The technology of photothermal catalytic degradation of acetone and conversion of nitrogen monoxide(NO)not only reduces energy consumption compared to traditional thermal catalytic oxidation technology but also improv...The technology of photothermal catalytic degradation of acetone and conversion of nitrogen monoxide(NO)not only reduces energy consumption compared to traditional thermal catalytic oxidation technology but also improves degradation efficiency,effectively overcoming the limitations of single photocatalytic or thermal catalytic technology.This paper aims to control the lattice oxygen activity and oxygen vacancy concentration of the catalyst by optimizing the manganese-cobalt(Mn-Co)molar ratio and modifying the catalyst with Ce doping,thereby enhancing its photocatalytic and thermal catalytic performance for the degradation of acetone and NO.At 240℃,when the Mn-Co molar ratio is 4:2,the CoO_(x)/MnO_(x)@Fe_(2)O_(3)-2 catalyst exhibits good catalytic activity for both acetone and NO,with conversion rates of 52%and 63.8%for acetone and NO,respectively.Based on the optimization of the Mn-Co molar ratio,Ce was doped into the CoO_(x)/MnO_(x)@Fe_(2)O_(3)-2 sample using the co-precipitation method to synthesize samples with different Ce doping amounts.The sample of CeO_(2)/CoO_(x)/MnO_(x)@Fe_(2)O_(3)-2-0.25(nMn-Co:nCe=1:0.25)shows the highest catalytic performance compared with the other samples,with the conversion of acetone and NO reaching 60%and 70%,respectively,at 240℃.Additionally,the intrinsic mechanism under photothermal synergy is based on the Mars-van Krevelen redox cycle theory.展开更多
基金supported by the National Key R&D Program of China(2016YFB0600305)~~
文摘A series of Co3O4-CeO2 binary oxides with various Co/(Ce+Co)molar ratios were synthesized using a citric acid method,and their catalytic properties toward the total oxidation of propane were examined.The activities of the catalysts decrease in the order CoCeOx-70>CoCeOx-90>Co3O4>CoCeOx-50>CoCeOx-20>CeO2.CoCeOx-70(Co/(Ce+Co)=70% molar ratio)exhibits the highest catalytic activity toward the total oxidation of propane,of which the T90 is 310℃(GHSV=120000 mL h^-1 g^-1],which is 25℃ lower than that of pure Co3 O4.The enhancement of the catalytic performance of CoCeOx-70 is attributed to the strong interaction between CeO2 and Co3O4,the improvement of the low-temperature reducibility,and the increase in the number of active oxygen species.In-situ DRIFTS and reaction kinetics measurement reveal that Ce addition does not change the reaction mechanism,but promotes the adsorption and activation of propane on the catalyst surface.The addition of water vapor and CO2 in reactant gas has a negative effect on the propane conversion,and the catalyst is more sensitive to water vapor than to CO2.In addition,CoCeOx-70 exhibits excellent stability and reusability in water vapor and CO2 atmosphere.
基金the National Natural Science Foundation of China(No.41763008)the National Science Foundation of Hunan Province(No.2018JJ2112)+1 种基金the Qian Jiao He KY(2019114)the Talents of Qian Ke He Platform(20175727-11)。
文摘As one of the most active rare earths,CeO2 has caused extensive concern due to its multifunctional properties.CeO2-based compound oxide of M2O3-CeO2(M=La,Fe,and Al)were prepared by coprecipitation and impregnation methods.The photocatalytic performance of the samples for the degradation methylene blue was studied under UV and visible light irradiation.The effects of constituents on the properties of the CeO2-based catalysts were investigated by XRD,TEM,BET,and UV-Vis spectrophotometer.The highest degradation of methylene blue under 230W UV light was almost 100%at 50 min by La2O3/Fe2O3-CeO2/γ-Al2O3 catalyst and 99.42%at 50 min by Fe2O3-CeO2/γ-Al2O3 catalyst.The methylene blue removal efficiency under indoor natural light reaches 93.81%by La2O3/Fe2O3-CeO2/γ-Al2O3 catalyst and 92.34%by Fe2O3-CeO2/γ-Al2O3 catalyst at 50 min.The order of catalytic degradation activity is La2O3/Fe2O3-CeO2/γ-Al2O3>Fe2O3-CeO2/γ-Al2O3>La2O3-CeO2/γ-Al2O3>Al2O3,owing to their structural features.The doping of La^3+or Fe3+onto CeO2/γ-Al2O produced much more oxygen vacancies under light irradiation and reduced the energy laps of CeO2 with value of 2.86 ev,which improved the photocatalytic redox performance of the composite oxide.
基金supported by the National Basic Research Program(2012CB932800,2012CB215503)the National Science Foundation of China(21125312,21203142)the Doctoral Fund of Ministry of Education of China(20110141130002)
文摘Although most transition metals have been tested as the promoter to Pt for electrocatalysis toward fuel cell reactions,semi-conductor elements,such as Si,have hitherto not been examined.Here we report a simple synthesis of intermetallic Pt2Si electrode using magnetron sputtering and the electrocatalysis toward ethanol oxidation reaction（EOR）.In comparison to Pt,the intermetallic Pt2Si surface turns out to be much more active in catalyzing the EOR：the onset potential shifts negatively by 150 mV,and the current density at 0.6 V increases by a magnitude of one order.Such an enormous enhancement in EOR catalysis is ascribed to the promotion effects of Si,which can not only provide active surface oxygenated species to accelerate the removal of COads,but also strongly alter the electronic property of Pt,as clearly indicated by the core-level shift in XPS spectrum.
文摘Achieving regioselectivity in radical cyclization reactions is of central importance,yet extremely challenging.Although Baldwin’s rules provided guidance on the addition of radical species with alkenes/alkynes,the ortho-/ipso-selectivity of the cyclic reaction between radical species(especially alkyl and alkenyl radical)and aryl groups is still ambiguous.Herein,we develop an electrochemically enabled regioselective ortho-(4+2)/ipso-(3+2)cyclization of alkyl/alkenyl radicals with aryl groups,which provides a series of tetrahydronaphthalene and spirocarbocycle derivatives,exhibiting a broad substrate scope and functional group tolerance.Alkyl/alkenyl radicals are generated by Cp2Fe-mediated electrochemical oxidative radical addition of benzylic malonates with alkenes and alkynes.The method avoids the use of chemical oxidant/base/noble metal,the pre-functionalization of substrates,and the over-oxidation of compounds.Theoretical studies reveal that the dominant factor promoting the alkene-preferred ortho-addition is the favorable interaction energy;the alkyne-preferred ipso-addition regioselectivity is controlled by the distortion energy.Notably,this strategy is regarded as an important supplement to Baldwin’s rules for radical cyclization.
文摘The comparison of degradation of Acid Yellow 61 as a model dye compound in both oxidation processes of H 2O 2/UV and O 3 has been studied. When the decolorization rate of Acid Yellow 61 in both reactions presented similar, it was found there are some differences from the results of AOX removal and production of inorganic ions and organic acids. The results reveal that the H 2O 2/UV has beneficial effect on mineralization than O 3 only for degradation of Acid Yellow 61 solution and it is possible for enhancement of method efficiency by taking longer reaction time and addition of high concentration of oxidants.
基金supported by the National Natural Science Foundation of China (Nos. 21277008 and 20777005)National Key Research and Development Program of China (No. 2017YFC0209905)Natural Science Foundation of Beijing (No. 8082008 )。
文摘The octahedral molecular sieve(OMS-2)-supported Fe( xFe/OMS-2: x = 1, 3, 5, and 10) catalysts were prepared using the pre-incorporation method. Physicochemical properties of the as-synthesized materials were characterized by means of various techniques, and their catalytic activities for CO, ethyl acetate, and toluene oxidation were evaluated. Among all of the samples, performed the best, with the reaction temperature required to achieve 90% conversion( T 90%) being 160 ℃ for CO oxidation, 210 ℃ for ethyl acetate oxidation, and 285 ℃ for toluene oxidation. Such a good catalytic performance of 5Fe/OMS-2 was associated with its high(Mn^(3+) + Mn^(2+)) content and adsorbed oxygen species concentration, and good lowtemperature reducibility and lattice oxygen mobility as well as strong interaction between Fe and OMS-2. In addition, catalytic mechanisms of the oxidation of three pollutants over the 5Fe/OMS-2 catalyst were also studied. It was found that CO, ethyl acetate or toluene was first adsorbed, then the related intermediates were formed, and finally the formed intermediates were completely converted into CO_(2) and H_(2)O.
基金supported by Liaoning Revitalization Talents Program(No.XLYC2007069)the National Natural Science Foundation of China(Nos.22076019 and 22222601)open project of State Key Laboratory of Urban Water Resource and Environment,Harbin Institute of Technology(No.HC201705)。
文摘Electrochemical oxidation is an effective method to degrade persistent organic pollutants.However,due to the limited catalytic activity of traditional thin film electrodes,the anodic oxidation process is slow and usually requires high energy consumption.Herein,Ti/SnO_(2)-Sb electrode with regulated surface structure was reported to enhance the performance for electrochemical oxidation of persistent organic pollutants.The electrode deposited with SnO_(2)-Sb nanoneedles(Ti/N-SnO_(2)-Sb)showed higher oxidation activity.Its kinetic constant for perfluorooctanoic acid(PFOA)oxidation was 2.0 h^(-1)and the total organic carbon removal rate was 81.7%(4 h)at a relatively low current density of 6 mA/cm^2.Compared with Ti/SnO_(2)-Sb thin film and nanoparticles,Ti/N-SnO_(2)-Sb significantly improved the electrochemical active area and·OH yield,and simultaneously reduced the electron transfer resistance,which enabled it to oxidize PFOA more rapidly even at a lower potential.This work provides a new strategy for promoting the electrochemical oxidation performance.
基金supported by the Foundation of Guangxi Science and Technology of Base&Talent Special Program(AD20159067)Central Guiding Local Development of Science and Technology Plan Project in Guigang City(2023 No.2)。
文摘The technology of photothermal catalytic degradation of acetone and conversion of nitrogen monoxide(NO)not only reduces energy consumption compared to traditional thermal catalytic oxidation technology but also improves degradation efficiency,effectively overcoming the limitations of single photocatalytic or thermal catalytic technology.This paper aims to control the lattice oxygen activity and oxygen vacancy concentration of the catalyst by optimizing the manganese-cobalt(Mn-Co)molar ratio and modifying the catalyst with Ce doping,thereby enhancing its photocatalytic and thermal catalytic performance for the degradation of acetone and NO.At 240℃,when the Mn-Co molar ratio is 4:2,the CoO_(x)/MnO_(x)@Fe_(2)O_(3)-2 catalyst exhibits good catalytic activity for both acetone and NO,with conversion rates of 52%and 63.8%for acetone and NO,respectively.Based on the optimization of the Mn-Co molar ratio,Ce was doped into the CoO_(x)/MnO_(x)@Fe_(2)O_(3)-2 sample using the co-precipitation method to synthesize samples with different Ce doping amounts.The sample of CeO_(2)/CoO_(x)/MnO_(x)@Fe_(2)O_(3)-2-0.25(nMn-Co:nCe=1:0.25)shows the highest catalytic performance compared with the other samples,with the conversion of acetone and NO reaching 60%and 70%,respectively,at 240℃.Additionally,the intrinsic mechanism under photothermal synergy is based on the Mars-van Krevelen redox cycle theory.
