This study reports the synthesis of three sets of high-performance manganese(Mn)-doped Co_(3)O_(4)porous nanocrystals(PNCs)(5%Mn@Co_(3)O_(4),10%Mn@Co_(3)O_(4),and 15%Mn@Co_(3)O_(4))using a simple chemical co-precipita...This study reports the synthesis of three sets of high-performance manganese(Mn)-doped Co_(3)O_(4)porous nanocrystals(PNCs)(5%Mn@Co_(3)O_(4),10%Mn@Co_(3)O_(4),and 15%Mn@Co_(3)O_(4))using a simple chemical co-precipitation method.These catalysts were then used for the catalytic oxidation of carbon monoxide(CO).This investigation focused on the effects of Co^(2+)or Co^(3+)substitution by Mn^(2+)or Mn^(3+)within the Co_(3)O_(4)matrix on various properties of the PNCs,including their physicochemical characteristics,morphology,microstructure,reducibility,thermal stability,and their impact on the catalytic performance.Comprehensive characterization using techniques such as X-ray diffraction(XRD),scanning electron microscopy(SEM),Brunauer-Emmett-Teller(BET)analysis,X-ray photoelectron spectroscopy(XPS),Hydrogen-Temperature Programmed Reduction and(H_(2)-TPR),was employed to elucidate the factors responsible for effective CO oxidation.Compared to pure Mn3 O4 and Co_(3)O_(4),the Mn@Co_(3)O_(4)PNCs catalysts exhibited a more controllable microstructure and better dispersion of the active phase.The 5%Mn@Co_(3)O_(4)catalyst demonstrated the highest activity,achieving 90%CO oxidation at 197°C.This superior performance is attributed to its large specific surface area,excellent reduction capacity,and abundant oxygen species and vacancies.H_(2)-TPR and XPS analyses provided further insights into the reaction mechanism.Density functional theory calculations showed that the formation of bulk oxygen vacancies is more favorable when Mn^(3+)is substituted at the Co^(2+)sites.Overall,the chemical coprecipitation method offers a straightforward and cost-effective approach for producing Mn@Co_(3)O_(4)catalysts suitable for CO abatement in exhaust and flue gases.展开更多
In this study,Mn_(3)O_(4) spherical particles(SPs)were synthesized by the sol-gel process,after which they were thermally annealed at 400℃,and comprehensively characterized.X-ray Diffraction(XRD)revealed that Mn_(3)O...In this study,Mn_(3)O_(4) spherical particles(SPs)were synthesized by the sol-gel process,after which they were thermally annealed at 400℃,and comprehensively characterized.X-ray Diffraction(XRD)revealed that Mn_(3)O_(4) exhibited a tetragonal spinel structure,and Fourier transformed infrared(FTIR)spectroscopy identified surfaceadsorbed functional groups.Scanning electron microscopy(SEM)and the specific surface area analyses by Brunauer−Emmett−Teller(BET)revealed a porous,homogeneous surface composed of strongly agglomerated spherical grains with an estimated average particle size of∼35 nm,which corresponded to a large specific surface area of∼81.5 m^(2)/g.X-ray photoelectron spectroscopy(XPS)analysis indicated that Mn_(3)O_(4) was composed of metallic cations(Mn^(4+),Mn^(3)+,and Mn^(2+))and oxygen species(O_(2)−,OH−and CO_(3)^(2−)).The optical bandgap energy is∼2.55 eV.Assessment of the catalytic performance of the Mn_(3)O_(4) SPs indicated T90 conversion of CH4 to CO_(2) and H_(2)O at 398℃ for gas hourly space velocity(GHSV)of 72000 mL^(3) g^(−1) h^(−1).This observed performance can be attributed to the cooperative effects of the smallest spherical grain size with a mesoporous structure,which is responsible for the larger specific surface area and available surface-active oxygenated species.The cooperative effect of the good reducibility,higher ratio of active species(OLat/OAds),and results of density functional theory(DFT)calculations suggested that the total oxidation of CH_(4) over the mesoporous Mn_(3)O_(4) SPs might take place via a two-term process in which both the Langmuir−Hinshelwood and Mars−van Krevelen mechanisms are cooperatively involved.展开更多
基金the Center for Computational Sciences and Simulation(CCSS)at Universität Duisburg-Essen and provided the supercomputer magnitude(DFG grants INST 20876/209-1 FUGG and INST 20876/243-1 FUGG)at the Zentrum fur Informations-und Mediendienste(ZIM).
文摘This study reports the synthesis of three sets of high-performance manganese(Mn)-doped Co_(3)O_(4)porous nanocrystals(PNCs)(5%Mn@Co_(3)O_(4),10%Mn@Co_(3)O_(4),and 15%Mn@Co_(3)O_(4))using a simple chemical co-precipitation method.These catalysts were then used for the catalytic oxidation of carbon monoxide(CO).This investigation focused on the effects of Co^(2+)or Co^(3+)substitution by Mn^(2+)or Mn^(3+)within the Co_(3)O_(4)matrix on various properties of the PNCs,including their physicochemical characteristics,morphology,microstructure,reducibility,thermal stability,and their impact on the catalytic performance.Comprehensive characterization using techniques such as X-ray diffraction(XRD),scanning electron microscopy(SEM),Brunauer-Emmett-Teller(BET)analysis,X-ray photoelectron spectroscopy(XPS),Hydrogen-Temperature Programmed Reduction and(H_(2)-TPR),was employed to elucidate the factors responsible for effective CO oxidation.Compared to pure Mn3 O4 and Co_(3)O_(4),the Mn@Co_(3)O_(4)PNCs catalysts exhibited a more controllable microstructure and better dispersion of the active phase.The 5%Mn@Co_(3)O_(4)catalyst demonstrated the highest activity,achieving 90%CO oxidation at 197°C.This superior performance is attributed to its large specific surface area,excellent reduction capacity,and abundant oxygen species and vacancies.H_(2)-TPR and XPS analyses provided further insights into the reaction mechanism.Density functional theory calculations showed that the formation of bulk oxygen vacancies is more favorable when Mn^(3+)is substituted at the Co^(2+)sites.Overall,the chemical coprecipitation method offers a straightforward and cost-effective approach for producing Mn@Co_(3)O_(4)catalysts suitable for CO abatement in exhaust and flue gases.
基金S.K.acknowledges computing time granted by the Center for Computational Sciences and Simulation(CCSS)the Universität DuisburgEssen and provided on the supercomputer magnitude(DFG grants INST 20876/209-1 FUGG,INST 20876/243-1 FUGG)the Zentrum für Informations-und Mediendienste(ZIM).S.K.gratefully acknowledges the Deutsche Forschungsgemeinschaft(DFG,German Research Foundation)for funding 388390466-TRR 247.
文摘In this study,Mn_(3)O_(4) spherical particles(SPs)were synthesized by the sol-gel process,after which they were thermally annealed at 400℃,and comprehensively characterized.X-ray Diffraction(XRD)revealed that Mn_(3)O_(4) exhibited a tetragonal spinel structure,and Fourier transformed infrared(FTIR)spectroscopy identified surfaceadsorbed functional groups.Scanning electron microscopy(SEM)and the specific surface area analyses by Brunauer−Emmett−Teller(BET)revealed a porous,homogeneous surface composed of strongly agglomerated spherical grains with an estimated average particle size of∼35 nm,which corresponded to a large specific surface area of∼81.5 m^(2)/g.X-ray photoelectron spectroscopy(XPS)analysis indicated that Mn_(3)O_(4) was composed of metallic cations(Mn^(4+),Mn^(3)+,and Mn^(2+))and oxygen species(O_(2)−,OH−and CO_(3)^(2−)).The optical bandgap energy is∼2.55 eV.Assessment of the catalytic performance of the Mn_(3)O_(4) SPs indicated T90 conversion of CH4 to CO_(2) and H_(2)O at 398℃ for gas hourly space velocity(GHSV)of 72000 mL^(3) g^(−1) h^(−1).This observed performance can be attributed to the cooperative effects of the smallest spherical grain size with a mesoporous structure,which is responsible for the larger specific surface area and available surface-active oxygenated species.The cooperative effect of the good reducibility,higher ratio of active species(OLat/OAds),and results of density functional theory(DFT)calculations suggested that the total oxidation of CH_(4) over the mesoporous Mn_(3)O_(4) SPs might take place via a two-term process in which both the Langmuir−Hinshelwood and Mars−van Krevelen mechanisms are cooperatively involved.
