This study investigated the positive effect of surface modification with ozone on the photocatalytic performance of anatase TiO2 with dominated (001) facets for toluene degradation. The performance of photocatalyst wa...This study investigated the positive effect of surface modification with ozone on the photocatalytic performance of anatase TiO2 with dominated (001) facets for toluene degradation. The performance of photocatalyst was tested on a home-made volatile organic compounds degradation system. The ozone modification, toluene adsorption and degradation mecha-nism were established by a combination of various characterization methods, in situ diuse reectance infrared fourier transform spectroscopy, and density functional theory calculation. The surface modtication with ozone can signiticantly enhance the photocatalytic degradation performance for toluene. The abundant unsaturated coordinated 5c-Ti sites on (001) facets act as the adsorption sites for ozone. The formed Ti-O bonds reacted with H2O to generate a large amount of isolated Ti5c-OH which act as the adsorption sites for toluene, and thus signi- cantly increase the adsorption capacity for toluene. The outstanding photo- catalytic performance of ozone-modified TiO2 is due to its high adsorption ability for toluene and the abundant surface hydroxyl groups, which produce very reactive OH· radicals under irradiation. Furthermore, the O2 generated via ozone dissociation could combine with the photogenerated electrons to form superoxide radicals which are also conductive to the toluene degradation.展开更多
The adsorption of plasma proteins onto biomaterials can be characterized by either the amount of adsorbed protein or the conformation of the adsorbed proteins. The adsorption characteristics of biomaterials are import...The adsorption of plasma proteins onto biomaterials can be characterized by either the amount of adsorbed protein or the conformation of the adsorbed proteins. The adsorption characteristics of biomaterials are important for hemocompatibility evaluation. In this investigation, the amount of adsorbed human fibrinogen (HFG) and the conformation of the adsorbed HFG on different surfaces were measured simultaneously using transmission FTIR. The surface materials included CaF 2, polymethyl methacrylate (PMMA), type II polyurethane made by Chengdu University of Science & Technology, pellethane 2363 55D and pellethane 2363 80A. The results indicate that both the amount of adsorbed protein and the conformation of the adsorbed protein can be measured simultaneously using a single transmission FTIR technique. The result also suggests that a single parameter, either the adsorbed amount or the conformation of the adsorbed HFG, can not provide complete information about the hemocompatibility of the biomaterials.展开更多
The relationship between the viscosity and structure of CaF_(2)-CaO-Al_(2)O_(3)-MgO-TiO_(2)slag with different CaF_(2)contents and CaO/Al_(2)O_(3)ratios was studied using the rotating cylinder method,Fourier transform...The relationship between the viscosity and structure of CaF_(2)-CaO-Al_(2)O_(3)-MgO-TiO_(2)slag with different CaF_(2)contents and CaO/Al_(2)O_(3)ratios was studied using the rotating cylinder method,Fourier transform infrared spectroscopy,and Raman spectrometry.The activity coefficients of CaF_(2)and the CaO/Al_(2)O_(3)ratio were determined to understand the correlation between viscosity and structure of the slag.The results suggest that the slag viscosity reduces gradually with an increase in CaF_(2)content from 14.1 to 28.1 wt.%or CaO/Al_(2)O_(3)ratio from 0.9 to 1.5,and correspondingly apparent activation energy for viscous flow reductions.The addition of CaF_(2)does not change the structure of the molten slag;however,the relaxation effect of the anionic species and the hindrance effect of the cationic species are promoted by substituting part of the non-bridging oxygens(NBO)with F−ions from CaF_(2),which is attributed to the formation of NBO-Ca^(2+)-F−and NBO-Ca^(2+)-NBO,respectively.However,as the CaO/Al_(2)O_(3)ratio increases,some of the Q4 units in the aluminate structure are depolymerized into Q2 units,so that the relative strength of the Al-O-Al linkage decreases,and the relative fraction of Ti2O64−chains increases,whereas that of O-Ti-O chains decreases slightly,resulting in depolymerization on the slag structure.Additionally,the effect of the CaO/Al_(2)O_(3)ratio on the structure was greater than that of CaF_(2)because of the greater depolymerization effect.The variation in the activity can indirectly explain the relationship between the viscosity and structure of the aluminate structural units based on thermodynamic analysis.展开更多
CuCeZrO_x and KCuCeZrO_x catalysts were synthesized and coated on the blank diesel particulate filter(DPF)substrate and a particulate matter(PM)loading apparatus was used for soot loading.The catalytic performances of...CuCeZrO_x and KCuCeZrO_x catalysts were synthesized and coated on the blank diesel particulate filter(DPF)substrate and a particulate matter(PM)loading apparatus was used for soot loading.The catalytic performances of soot oxidation were evaluated by temperature programmed combustion(TPC)test and characterization tests were conducted to investigate the physicochemical properties of the catalysts.The reaction mechanism in the oxidation process was analyzed with diffuse reflectance infrared Fourier transform spectroscopy.The results demonstrated that CuCeZrO_x catalyst exhibited high activities of soot oxidation at low temperature and the best results have been attained with Cu_(0.9)Ce_(0.05)Zr_(0.05)O_x over which the maximum soot oxidation rate decreased to 410~?C.Characterization tests have shown that catalysts containing 90%Cu have uniformly distributed grains and small particle sizes,which provide excellent oxidation activity by providing more active sites and forming a good bond between the catalyst and the soot.The low-temperature oxidation activity of soot could be further optimized due to the excellent elevated NO’s conversion rate by partially substituting Cu with K.The maximum particle oxidation rate can be easily realized at such a low temperature as 347~?C.展开更多
Well-defined surface structures and uniformity are key factors in exploring structure–activity relationships in heterogeneous catalysts.A modified atomic layer deposition method and three well-defined CeO_(2) nanosha...Well-defined surface structures and uniformity are key factors in exploring structure–activity relationships in heterogeneous catalysts.A modified atomic layer deposition method and three well-defined CeO_(2) nanoshapes,octahedra with(111)surfaces,cubes exposing(100)facets,and rods with(100)and(110)surface facet terminations,were utilized to synthesize ultra-low loading Pt/CeO_(2) catalysts and allow investigations on the influence of ceria surface facet on isolated Pt species under reducing conditions.A mild reduction temperature(150℃)reduces the initial platinum ions present on the surfaces of the ceria support but preserves the isolated Pt atoms on all ceria surface facets.In contrast,a reduction temperature of 350°C,reveals very different interactions between the initial single Pt atoms and the various ceria surface facets,leading to dissimilar and nonuniform Pt ensembles on the three ceria shapes.To isolate facet dependent Pt–CeO_(2) interactions and avoid variations between Pt species,the Pt1/CeO_(2) catalysts after reduction at 150°C were subjected to CO oxidation conditions.The isolated Pt atoms on the CeO_(2) octahedra and cubes are less active in the CO oxidation reaction,compared with Pt on CeO_(2) rods.In the case of Pt on the CeO_(2) octahedra this is due to strongly bound CO blocking active sites together with a stable CeO_(2)(111)surface limiting the oxygen supply from the support.On the CeO_(2) cubes,some Pt is not available for reaction and CO is bound strongly on the available Pt species.In addition,the Pt catalysts supported on the CeO_(2) cubes are not stable with time on stream.The isolated Pt atoms on the CeO_(2) rods are considerably more active under these conditions and this is due to a weaker Pt–CO bond strength and more facile reverse oxygen spillover from the defect-rich(110)surfaces of the rods due to the lower energy of oxygen vacancy formation on this CeO_(2) surface.The Pt supported on the CeO_(2) rods is also remarkably stable with time on stream.This work demonstrates the importance of using ultra-low loadings of active metal and well-defined oxide supports to isolate interactions between single metal atoms and oxide supports and determine the effects of the oxide support surface facet on the active metal at the atomic level.展开更多
基金the National Natural Science Foundation of China (U1632273, 21673214,U1732272, U1832165).
文摘This study investigated the positive effect of surface modification with ozone on the photocatalytic performance of anatase TiO2 with dominated (001) facets for toluene degradation. The performance of photocatalyst was tested on a home-made volatile organic compounds degradation system. The ozone modification, toluene adsorption and degradation mecha-nism were established by a combination of various characterization methods, in situ diuse reectance infrared fourier transform spectroscopy, and density functional theory calculation. The surface modtication with ozone can signiticantly enhance the photocatalytic degradation performance for toluene. The abundant unsaturated coordinated 5c-Ti sites on (001) facets act as the adsorption sites for ozone. The formed Ti-O bonds reacted with H2O to generate a large amount of isolated Ti5c-OH which act as the adsorption sites for toluene, and thus signi- cantly increase the adsorption capacity for toluene. The outstanding photo- catalytic performance of ozone-modified TiO2 is due to its high adsorption ability for toluene and the abundant surface hydroxyl groups, which produce very reactive OH· radicals under irradiation. Furthermore, the O2 generated via ozone dissociation could combine with the photogenerated electrons to form superoxide radicals which are also conductive to the toluene degradation.
文摘The adsorption of plasma proteins onto biomaterials can be characterized by either the amount of adsorbed protein or the conformation of the adsorbed proteins. The adsorption characteristics of biomaterials are important for hemocompatibility evaluation. In this investigation, the amount of adsorbed human fibrinogen (HFG) and the conformation of the adsorbed HFG on different surfaces were measured simultaneously using transmission FTIR. The surface materials included CaF 2, polymethyl methacrylate (PMMA), type II polyurethane made by Chengdu University of Science & Technology, pellethane 2363 55D and pellethane 2363 80A. The results indicate that both the amount of adsorbed protein and the conformation of the adsorbed protein can be measured simultaneously using a single transmission FTIR technique. The result also suggests that a single parameter, either the adsorbed amount or the conformation of the adsorbed HFG, can not provide complete information about the hemocompatibility of the biomaterials.
基金This study was funded by the National Natural Science Foundation of China(No.51774225).
文摘The relationship between the viscosity and structure of CaF_(2)-CaO-Al_(2)O_(3)-MgO-TiO_(2)slag with different CaF_(2)contents and CaO/Al_(2)O_(3)ratios was studied using the rotating cylinder method,Fourier transform infrared spectroscopy,and Raman spectrometry.The activity coefficients of CaF_(2)and the CaO/Al_(2)O_(3)ratio were determined to understand the correlation between viscosity and structure of the slag.The results suggest that the slag viscosity reduces gradually with an increase in CaF_(2)content from 14.1 to 28.1 wt.%or CaO/Al_(2)O_(3)ratio from 0.9 to 1.5,and correspondingly apparent activation energy for viscous flow reductions.The addition of CaF_(2)does not change the structure of the molten slag;however,the relaxation effect of the anionic species and the hindrance effect of the cationic species are promoted by substituting part of the non-bridging oxygens(NBO)with F−ions from CaF_(2),which is attributed to the formation of NBO-Ca^(2+)-F−and NBO-Ca^(2+)-NBO,respectively.However,as the CaO/Al_(2)O_(3)ratio increases,some of the Q4 units in the aluminate structure are depolymerized into Q2 units,so that the relative strength of the Al-O-Al linkage decreases,and the relative fraction of Ti2O64−chains increases,whereas that of O-Ti-O chains decreases slightly,resulting in depolymerization on the slag structure.Additionally,the effect of the CaO/Al_(2)O_(3)ratio on the structure was greater than that of CaF_(2)because of the greater depolymerization effect.The variation in the activity can indirectly explain the relationship between the viscosity and structure of the aluminate structural units based on thermodynamic analysis.
基金the National Key R&D Program of China(Nos.2016YFC0205200 and 2016YFC0208000)the National Natural Science Foundation of China(No.51676127)
文摘CuCeZrO_x and KCuCeZrO_x catalysts were synthesized and coated on the blank diesel particulate filter(DPF)substrate and a particulate matter(PM)loading apparatus was used for soot loading.The catalytic performances of soot oxidation were evaluated by temperature programmed combustion(TPC)test and characterization tests were conducted to investigate the physicochemical properties of the catalysts.The reaction mechanism in the oxidation process was analyzed with diffuse reflectance infrared Fourier transform spectroscopy.The results demonstrated that CuCeZrO_x catalyst exhibited high activities of soot oxidation at low temperature and the best results have been attained with Cu_(0.9)Ce_(0.05)Zr_(0.05)O_x over which the maximum soot oxidation rate decreased to 410~?C.Characterization tests have shown that catalysts containing 90%Cu have uniformly distributed grains and small particle sizes,which provide excellent oxidation activity by providing more active sites and forming a good bond between the catalyst and the soot.The low-temperature oxidation activity of soot could be further optimized due to the excellent elevated NO’s conversion rate by partially substituting Cu with K.The maximum particle oxidation rate can be easily realized at such a low temperature as 347~?C.
基金supported by the National Science Foundation(NSF)(CHE-1507230 and CBET-1933723)the National High Magnetic Field Laboratory,which is supported by the NSF Cooperative Agreement(DMR-1644779)and the State of Florida.Startup funding from the University of Florida is also gratefully acknowledged.
文摘Well-defined surface structures and uniformity are key factors in exploring structure–activity relationships in heterogeneous catalysts.A modified atomic layer deposition method and three well-defined CeO_(2) nanoshapes,octahedra with(111)surfaces,cubes exposing(100)facets,and rods with(100)and(110)surface facet terminations,were utilized to synthesize ultra-low loading Pt/CeO_(2) catalysts and allow investigations on the influence of ceria surface facet on isolated Pt species under reducing conditions.A mild reduction temperature(150℃)reduces the initial platinum ions present on the surfaces of the ceria support but preserves the isolated Pt atoms on all ceria surface facets.In contrast,a reduction temperature of 350°C,reveals very different interactions between the initial single Pt atoms and the various ceria surface facets,leading to dissimilar and nonuniform Pt ensembles on the three ceria shapes.To isolate facet dependent Pt–CeO_(2) interactions and avoid variations between Pt species,the Pt1/CeO_(2) catalysts after reduction at 150°C were subjected to CO oxidation conditions.The isolated Pt atoms on the CeO_(2) octahedra and cubes are less active in the CO oxidation reaction,compared with Pt on CeO_(2) rods.In the case of Pt on the CeO_(2) octahedra this is due to strongly bound CO blocking active sites together with a stable CeO_(2)(111)surface limiting the oxygen supply from the support.On the CeO_(2) cubes,some Pt is not available for reaction and CO is bound strongly on the available Pt species.In addition,the Pt catalysts supported on the CeO_(2) cubes are not stable with time on stream.The isolated Pt atoms on the CeO_(2) rods are considerably more active under these conditions and this is due to a weaker Pt–CO bond strength and more facile reverse oxygen spillover from the defect-rich(110)surfaces of the rods due to the lower energy of oxygen vacancy formation on this CeO_(2) surface.The Pt supported on the CeO_(2) rods is also remarkably stable with time on stream.This work demonstrates the importance of using ultra-low loadings of active metal and well-defined oxide supports to isolate interactions between single metal atoms and oxide supports and determine the effects of the oxide support surface facet on the active metal at the atomic level.
