A series of CeO_(2)-TiO_(2)mixed oxides supports with various Ce/Ti molar ratio were synthesized by modified coprecipitation method. The corresponding Pt loaded(0.5 wt% Pt) catalysts were prepared by electronless depo...A series of CeO_(2)-TiO_(2)mixed oxides supports with various Ce/Ti molar ratio were synthesized by modified coprecipitation method. The corresponding Pt loaded(0.5 wt% Pt) catalysts were prepared by electronless deposition method and evaluated for the deep oxidation of n-hexane as a model VOCs. The results show that the CeO_(2)and TiOxnanoparticles can highly disperse into each other and form Ce_(2)Ti_(2)O_(7)solid solution with appropriate Ce/Ti molar ratio, which significantly improves their redox ability by enhancing the interaction between CeO_(2)and TiO_(x). The dispersibility of Pt species can also be adjusted by altering the Ce/Ti molar ratio, and Pt/CeTi-2/1 catalyst with Ce/Ti molar ratio of 2:1 exhibits the best Pt dispersibility that Pt species mainly exist as Pt single atoms. The high dispersion of Pt species in the Pt/CeO_(2)-TiO_(2)catalysts would promote the catalytic activity of VOCs oxidation with low T90% values(1000 ppm, GHSV = 15,000 h^(-1)), such as for n-hexane degradation with T90% of 139℃. The characterizations reveal that the superior activity is mainly related to possessing the more Pt2+species,adsorbed oxygen species and higher low-temperature reducibility owing to the strong interaction between highly dispersed Pt species and CeO_(2)-TiO_(2)as well as the promoted migration of lattice oxygen by the formation of more Ce_(2)Ti_(2)O_(7)species. Furthermore, the Pt/CeTi-2/1 catalyst also exhibits excellent stability for chlorinated and other non-chlorinated VOCs oxidation, making it very promising for real application under various operating conditions.展开更多
Autoreduction of Pt2+ ions during calcination of ets-Pt (NH3):Cl2/Kβ was found directly by CO adsorbed FTIR. Reoxidation of the reduced sample could decrease the extent of Pt agglomeration caused by autoreduction. T...Autoreduction of Pt2+ ions during calcination of ets-Pt (NH3):Cl2/Kβ was found directly by CO adsorbed FTIR. Reoxidation of the reduced sample could decrease the extent of Pt agglomeration caused by autoreduction. The unique effect of Ba2+ ions on Pt dispersion was also studied.展开更多
We report a high performance supported Pt catalyst, in which a perfluorosulfonic acid (Nation) functionalized carbon black is used as support. The catalyst is characterized by infrared spectroscopy (IR), transmiss...We report a high performance supported Pt catalyst, in which a perfluorosulfonic acid (Nation) functionalized carbon black is used as support. The catalyst is characterized by infrared spectroscopy (IR), transmission electron microscopy (TEM) and X-ray diffraction (XRD). The TEM image shows that the active Pt component is in nanoparticles and highly dispersed on the carbon black with an average particle size of 1.9 nm. The catalyst shows improved activity towards the methanol anodic oxidation and oxygen reduction reaction (ORR), resulting from the high dispersion of active Pt component. It leads to increases in electrochemically accessible surface areas and ion channels, as well as easier charge- transfer at polymer/electrolyte interfaces. The high platinum utilization and high performance of Pt/Nafion-C catalyst make it a promising electrocatalyst for fuel cell application.展开更多
Metal alloys have been widely applied for heterogeneous catalysis,especially alkane dehydrogenation.However,the catalysts always suffer from sintering and coke deposition due to the rigorous reaction conditions.Herein...Metal alloys have been widely applied for heterogeneous catalysis,especially alkane dehydrogenation.However,the catalysts always suffer from sintering and coke deposition due to the rigorous reaction conditions.Herein,we described an original approach to prepare a catalyst where highly dispersed Pt clusters alloying with copper were encapsulated in silicalite-1(S-1)zeolite for propane dehydrogenation(PDH).The introduction of Cu species significantly enhances the catalytic activity and prolongs the lifetime of the catalyst.0.1Pt0.4CuK@S-1 exhibits a propane conversion of 24.8%with 98.2%selectivity of propene,and the specific activity of propylene formation is up to 32 mol·gPt^(−1)·h^(−1)at 500℃.No obvious deactivation is observed even after 73 h on stream,affording an extremely low deactivation constant of 0.00032 h^(−1).The excellent activity and stability are ascribed to the confinement of zeolites and the stabilization of Cu species for Pt clusters.展开更多
This study was focused on the influence of active oxygen on the performance of Pt/CeO2 catalysts for CO oxidation. A series of CeO2 supports with different contents of active oxygen were obtained by adding surfactant ...This study was focused on the influence of active oxygen on the performance of Pt/CeO2 catalysts for CO oxidation. A series of CeO2 supports with different contents of active oxygen were obtained by adding surfactant at different synthesis steps. 0.25 wt% Pt was loaded on these CeO2 supports by incipientwetness impregnation methods. The catalysts were characterized by N2 adsorption, X-ray diffraction(XRD), high-resolution transmission electron microscopy(HRTEM), H2 temperature-programmed reduction(H2-TPR), dynamic oxygen storage capacity(DOSC) and in-situ DRIFTS technologies. For S-f supports, the surfactant was added into the solution before spray-drying in the synthesis process, which facilitates more active oxygen formation on the surface of CeO2. After loading Pt, the more active oxygen on CeO2 contributes to dispersing Pt species and enhancing the CO oxidation activity. As for the aged samples,Pt-R-h shows the highest activity above 190 ℃ because of the presence of more partly oxidized Pt^(δ+) species. Thus the activity is also influenced by the states of Pt and the Pt^(δ+) species may contribute to the high activity at elevated temperature.展开更多
Rational design and performance promotion are eternal topics and ultimate goals in catalyst preparation.In contrast,trial–and–error is still the common method people take.Therefore,it is important to develop methods...Rational design and performance promotion are eternal topics and ultimate goals in catalyst preparation.In contrast,trial–and–error is still the common method people take.Therefore,it is important to develop methods to intrinsically enhance the performance of catalysts.The most effective solutions are the one from a kinetic perspective based on clear knowledge of the reaction mechanism.This paper describes rate-determining step cognition and modulation to promote CO oxidation on highly dispersed Pt on CeO_(2).The different degrees of metal–support interactions due to variation of hydroxyl density of support could alter the structure of active species and the ability of oxygen activation apparently,further shift the rate-determining step from oxygen activation to oxygen reverse spillover kinetically.The transformation of rate-determining step could enhance the intrinsic activity significantly,and decrease the T_(50) approximately 140℃.The findings of this research exemplify the universal and effective method of performance elevation by rate-determining step modulation,which is promising for application in different systems.展开更多
基金supported by a grant from the National Key Research and Development Program of China (2016YFC0204300)the National Nature Science Foundation of China (21477109)。
文摘A series of CeO_(2)-TiO_(2)mixed oxides supports with various Ce/Ti molar ratio were synthesized by modified coprecipitation method. The corresponding Pt loaded(0.5 wt% Pt) catalysts were prepared by electronless deposition method and evaluated for the deep oxidation of n-hexane as a model VOCs. The results show that the CeO_(2)and TiOxnanoparticles can highly disperse into each other and form Ce_(2)Ti_(2)O_(7)solid solution with appropriate Ce/Ti molar ratio, which significantly improves their redox ability by enhancing the interaction between CeO_(2)and TiO_(x). The dispersibility of Pt species can also be adjusted by altering the Ce/Ti molar ratio, and Pt/CeTi-2/1 catalyst with Ce/Ti molar ratio of 2:1 exhibits the best Pt dispersibility that Pt species mainly exist as Pt single atoms. The high dispersion of Pt species in the Pt/CeO_(2)-TiO_(2)catalysts would promote the catalytic activity of VOCs oxidation with low T90% values(1000 ppm, GHSV = 15,000 h^(-1)), such as for n-hexane degradation with T90% of 139℃. The characterizations reveal that the superior activity is mainly related to possessing the more Pt2+species,adsorbed oxygen species and higher low-temperature reducibility owing to the strong interaction between highly dispersed Pt species and CeO_(2)-TiO_(2)as well as the promoted migration of lattice oxygen by the formation of more Ce_(2)Ti_(2)O_(7)species. Furthermore, the Pt/CeTi-2/1 catalyst also exhibits excellent stability for chlorinated and other non-chlorinated VOCs oxidation, making it very promising for real application under various operating conditions.
文摘Autoreduction of Pt2+ ions during calcination of ets-Pt (NH3):Cl2/Kβ was found directly by CO adsorbed FTIR. Reoxidation of the reduced sample could decrease the extent of Pt agglomeration caused by autoreduction. The unique effect of Ba2+ ions on Pt dispersion was also studied.
文摘We report a high performance supported Pt catalyst, in which a perfluorosulfonic acid (Nation) functionalized carbon black is used as support. The catalyst is characterized by infrared spectroscopy (IR), transmission electron microscopy (TEM) and X-ray diffraction (XRD). The TEM image shows that the active Pt component is in nanoparticles and highly dispersed on the carbon black with an average particle size of 1.9 nm. The catalyst shows improved activity towards the methanol anodic oxidation and oxygen reduction reaction (ORR), resulting from the high dispersion of active Pt component. It leads to increases in electrochemically accessible surface areas and ion channels, as well as easier charge- transfer at polymer/electrolyte interfaces. The high platinum utilization and high performance of Pt/Nafion-C catalyst make it a promising electrocatalyst for fuel cell application.
基金the National Key Research and Development Program of China(No.2020YFA0210900)the Science and Technology Key Project of Guangdong Province(No.2020B010188002)+1 种基金the National Natural Science Foundation of China(Nos.21905313 and 21938001)the Local Innovative and Research Teams Project of Guangdong Pearl River Talents Program(No.2017BT01C102).
文摘Metal alloys have been widely applied for heterogeneous catalysis,especially alkane dehydrogenation.However,the catalysts always suffer from sintering and coke deposition due to the rigorous reaction conditions.Herein,we described an original approach to prepare a catalyst where highly dispersed Pt clusters alloying with copper were encapsulated in silicalite-1(S-1)zeolite for propane dehydrogenation(PDH).The introduction of Cu species significantly enhances the catalytic activity and prolongs the lifetime of the catalyst.0.1Pt0.4CuK@S-1 exhibits a propane conversion of 24.8%with 98.2%selectivity of propene,and the specific activity of propylene formation is up to 32 mol·gPt^(−1)·h^(−1)at 500℃.No obvious deactivation is observed even after 73 h on stream,affording an extremely low deactivation constant of 0.00032 h^(−1).The excellent activity and stability are ascribed to the confinement of zeolites and the stabilization of Cu species for Pt clusters.
基金Project supported by the National key research and development program(2016YFC0204901)the National Natural Science Foundation of China(21576207)+1 种基金the Introduction Of Talent and Technology Cooperation Plan Of Tianjin(14RCGFGX00849)GM Global Research&Development(GAC 1539)
文摘This study was focused on the influence of active oxygen on the performance of Pt/CeO2 catalysts for CO oxidation. A series of CeO2 supports with different contents of active oxygen were obtained by adding surfactant at different synthesis steps. 0.25 wt% Pt was loaded on these CeO2 supports by incipientwetness impregnation methods. The catalysts were characterized by N2 adsorption, X-ray diffraction(XRD), high-resolution transmission electron microscopy(HRTEM), H2 temperature-programmed reduction(H2-TPR), dynamic oxygen storage capacity(DOSC) and in-situ DRIFTS technologies. For S-f supports, the surfactant was added into the solution before spray-drying in the synthesis process, which facilitates more active oxygen formation on the surface of CeO2. After loading Pt, the more active oxygen on CeO2 contributes to dispersing Pt species and enhancing the CO oxidation activity. As for the aged samples,Pt-R-h shows the highest activity above 190 ℃ because of the presence of more partly oxidized Pt^(δ+) species. Thus the activity is also influenced by the states of Pt and the Pt^(δ+) species may contribute to the high activity at elevated temperature.
基金the National Key R&D Program of China (2021YFA1501302)the National Natural Science Foundation of China (22121004,U1862207)+1 种基金the Haihe Laboratory of Sustainable Chemical Transformations and the Program of Introducing Talents of Discipline to Universities (BP0618007) for financial supportsupported by the XPLORER PRIZE
文摘Rational design and performance promotion are eternal topics and ultimate goals in catalyst preparation.In contrast,trial–and–error is still the common method people take.Therefore,it is important to develop methods to intrinsically enhance the performance of catalysts.The most effective solutions are the one from a kinetic perspective based on clear knowledge of the reaction mechanism.This paper describes rate-determining step cognition and modulation to promote CO oxidation on highly dispersed Pt on CeO_(2).The different degrees of metal–support interactions due to variation of hydroxyl density of support could alter the structure of active species and the ability of oxygen activation apparently,further shift the rate-determining step from oxygen activation to oxygen reverse spillover kinetically.The transformation of rate-determining step could enhance the intrinsic activity significantly,and decrease the T_(50) approximately 140℃.The findings of this research exemplify the universal and effective method of performance elevation by rate-determining step modulation,which is promising for application in different systems.