Carbon supported gold-iridium composite(Au Ir/C) was synthesized by a facile one-step process and was investigated as the bifunctional catalyst for oxygen reduction reaction(ORR) and oxygen evolution reaction(OER). Th...Carbon supported gold-iridium composite(Au Ir/C) was synthesized by a facile one-step process and was investigated as the bifunctional catalyst for oxygen reduction reaction(ORR) and oxygen evolution reaction(OER). The physical properties of the Au Ir/C composite were characterized by transmission electron microscopy(TEM), X-ray diffraction(XRD) and X-ray photoelectron spectroscopy(XPS). Although the Au and Ir in the Au Ir/C did not form alloy, it is clear that the introduction of Ir decreases the average Au particle size to 4.2 nm compared to that in the Au/C(10.1 nm). By systematical analysis on chemical state of metal surface via XPS and the electrochemical results, it was found that the Au surface for the Au/C can be activated by potential cycling from 0.12 V to 1.72 V, resulting in the increased surface roughness of Au,thus improving the ORR activity. By the same potential cycling, the Ir surface of the Ir/C was irreversibly oxidized, leading to degraded ORR activity but uninfluenced OER activity. For the Au Ir/C, Ir protects Au against being oxidized due to the lower electronegativity of Ir. Combining the advantages of Au and Ir in catalyzing ORR and OER, the Au Ir/C catalyst displays an enhanced catalytic activity to the ORR and a comparable OER activity. In the 50-cycle accelerated aging test for the ORR and OER, the Au Ir/C displayed a satisfied stability, suggesting that the Au Ir/C catalyst is a potential bifunctional catalyst for the oxygen electrode.展开更多
To discuss the potential role of iridium(Ir)nanoparticles loaded under atmospheric and high pressures,we prepared a series of cata-lysts with the same active phase but different contents of 10wt%,20wt%,and 30wt%on gam...To discuss the potential role of iridium(Ir)nanoparticles loaded under atmospheric and high pressures,we prepared a series of cata-lysts with the same active phase but different contents of 10wt%,20wt%,and 30wt%on gamma-alumina for decomposition of hydrazine.Un-der atmospheric pressure,the performance of the catalyst was better when 30wt%of the Ir nanoparticles was used with chelating agent that had greater selectivity of approximately 27%.The increase in the reaction rate from 175 to 220 h^(−1)at higher Ir loading(30wt%)was due to a good dispersion of high-number active phases rather than an agglomeration surface.As a satisfactory result of this investigation at high pressure,Ir catalysts with different weight percentages showed the same stability against crushing and activity with a characteristic velocity of approxim-ately 1300 m/s.展开更多
The novel Fe-N co-doped ordered mesoporous carbon with high catalytic activity in m-cresol removal was prepared by urea-assisted impregnation and simple pyrolysis method.During the preparation of the Fe-NC catalyst,th...The novel Fe-N co-doped ordered mesoporous carbon with high catalytic activity in m-cresol removal was prepared by urea-assisted impregnation and simple pyrolysis method.During the preparation of the Fe-NC catalyst,the complexation of N elements in urea could anchor Fe,and the formation of C3N4during urea pyrolysis could also prevent migration and aggregation of Fe species,which jointly improve the dispersion and stability of Fe.The FeN4sites and highly dispersed Fe nanoparticles synergistically trigger the dual-site peroxymonosulfate (PMS) activation for highly efficient m-cresol degradation,while the ordered mesoporous structure of the catalyst could improve the mass transfer rate of the catalytic process,which together promote catalytic degradation of m-cresol by PMS activation.Reactive oxygen species (ROS) analytic experiments demonstrate that the system degrades m-cresol by free radical pathway mainly based on SO_(4)^(-)·and·OH,and partially based on·OH as the active components,and a possible PMS activation mechanism by 5Fe-50 for m-cresol degradation was proposed.This study can provide theoretical guidance for the preparation of efficient and stable catalysts for the degradation of organic pollutants by activated PMS.展开更多
A termetallic catalyst of Pt-Ir-Au/Al2O3 for NOx decomposition was prepared by loading the metallic colloids in C2H5OH-H2O solution and a surfactant of polyvinyl pyrrolidone.Compared with an impregnated Pt/Al2O3 catal...A termetallic catalyst of Pt-Ir-Au/Al2O3 for NOx decomposition was prepared by loading the metallic colloids in C2H5OH-H2O solution and a surfactant of polyvinyl pyrrolidone.Compared with an impregnated Pt/Al2O3 catalyst,the termetallic catalyst of PtIrAu811/Al2O3,with a Pt：Ir：Au atomic ratio of 8：1：1,exhibited higher NO decomposition and selectivity to N2.Transmission electron microscopy and X-ray diffraction were conducted to clarify the state of the supported metals and indicate three precious metals alloyed on the catalyst.In the study of NO-temperature programmed desorption,oxygen desorption on the PtIrAu811 catalyst shifted to the low temperature side compared to that on Pt/Al2O3,which correlated well with its higher catalytic performance in NO decomposition.展开更多
N2O is a promising green propellant and exhibits great potential for satellite propulsion systems. It is difficult for catalytic decomposition, which is an important way to initiate the propulsion process, to occur at...N2O is a promising green propellant and exhibits great potential for satellite propulsion systems. It is difficult for catalytic decomposition, which is an important way to initiate the propulsion process, to occur at temperatures below 600 °C due to the high activation energy of N2O. In this work, we report an Ir supported on rutile TiO2（Ir/r-TiO2） catalyst which exhibits a fairly high activity for high-concentration N2O decomposition. HAADF-STEM, H2-TPR, and XPS results indicate that highly dispersed Ir particles and improved oxygen mobility on the Ir/r-TiO2 could facilitate the decompo-sition of N2O and desorption of the adsorbed oxygen. Bridge-bonded peroxide intermediates were observed with in-situ DRIFT and herein, a detailed decomposition route is proposed.展开更多
Understanding the relationship between structure and properties is critical to the development of solidstate luminescence materials with desired characteristics and performance optimization. In this work, we elaborate...Understanding the relationship between structure and properties is critical to the development of solidstate luminescence materials with desired characteristics and performance optimization. In this work, we elaborately designed and synthesized a pair of mononuclear iridium(Ⅲ) complexes with similar structures but different degrees of cationization. [Ir2-f][2PF_(6)] with two counterions is obtained by simple Nmethylation of the ancillary ligand of [Ir1-f][PF_(6)] which is a classic cationic iridium(Ⅲ) complex. Such a tiny modification results in tremendously different optical properties in dilute solutions and powders.[Ir1-f][PF_(6)] exhibits weak light in solution but enhanced emission in solid-state as well as poly(methyl methacrylate) matrix, indicative of its aggregation-induced emission(AIE) activity. On the sharp contrary, [Ir2-f][2PF_(6)] is an aggregation-caused quenching(ACQ) emitter showing strong emission in the isolated state but nearly nonemissive in aggregation states. Benefiting from the appealing characteristics of mechanochromic luminescence and AIE behavior, [Ir1-f][PF_(6)] has been successfully applied in reversible re-writable data recording and cell imaging. These results might provide deep insights into AIE and ACQ phenomenon of iridium(Ⅲ) complexes and facilitate the development of phosphorescent materials with promising properties.展开更多
Asymmetric hydrogenation of dialkyl imines to chiral amines is difficult because the two alkyls of imines are so similar in spatial and electronic structure that chiral catalysts are difficult to distinguish between t...Asymmetric hydrogenation of dialkyl imines to chiral amines is difficult because the two alkyls of imines are so similar in spatial and electronic structure that chiral catalysts are difficult to distinguish between them.In this study,we described an asymmetric hydrogenation of dialkyl imines by a chiral iridium catalyst containing spiro phosphine-amine-phosphine ligand.By precisely adjusting the chiral pocket of catalyst,a highly efficient catalyst was developed.Using this catalyst,a variety of dialkyl imines were hydrogenated to chiral amines with high yield and enantioselectivity.展开更多
基金financially supported by the Key Program of the Chinese Academy of Science(grant no.KGZD-EW-T08)the National Basic Research Program of China(973 Program,2012CB215500)the"Strategic Priority Research Program"of the Chinese Academy of Sciences(grant no.XDA09030104)
文摘Carbon supported gold-iridium composite(Au Ir/C) was synthesized by a facile one-step process and was investigated as the bifunctional catalyst for oxygen reduction reaction(ORR) and oxygen evolution reaction(OER). The physical properties of the Au Ir/C composite were characterized by transmission electron microscopy(TEM), X-ray diffraction(XRD) and X-ray photoelectron spectroscopy(XPS). Although the Au and Ir in the Au Ir/C did not form alloy, it is clear that the introduction of Ir decreases the average Au particle size to 4.2 nm compared to that in the Au/C(10.1 nm). By systematical analysis on chemical state of metal surface via XPS and the electrochemical results, it was found that the Au surface for the Au/C can be activated by potential cycling from 0.12 V to 1.72 V, resulting in the increased surface roughness of Au,thus improving the ORR activity. By the same potential cycling, the Ir surface of the Ir/C was irreversibly oxidized, leading to degraded ORR activity but uninfluenced OER activity. For the Au Ir/C, Ir protects Au against being oxidized due to the lower electronegativity of Ir. Combining the advantages of Au and Ir in catalyzing ORR and OER, the Au Ir/C catalyst displays an enhanced catalytic activity to the ORR and a comparable OER activity. In the 50-cycle accelerated aging test for the ORR and OER, the Au Ir/C displayed a satisfied stability, suggesting that the Au Ir/C catalyst is a potential bifunctional catalyst for the oxygen electrode.
文摘To discuss the potential role of iridium(Ir)nanoparticles loaded under atmospheric and high pressures,we prepared a series of cata-lysts with the same active phase but different contents of 10wt%,20wt%,and 30wt%on gamma-alumina for decomposition of hydrazine.Un-der atmospheric pressure,the performance of the catalyst was better when 30wt%of the Ir nanoparticles was used with chelating agent that had greater selectivity of approximately 27%.The increase in the reaction rate from 175 to 220 h^(−1)at higher Ir loading(30wt%)was due to a good dispersion of high-number active phases rather than an agglomeration surface.As a satisfactory result of this investigation at high pressure,Ir catalysts with different weight percentages showed the same stability against crushing and activity with a characteristic velocity of approxim-ately 1300 m/s.
基金gratefully acknowledge the financial support of the National Natural Science Foundation of China(22108145 and 21978143)the Shandong Province Natural Science Foundation(ZR2020QB189)+1 种基金State Key Laboratory of Heavy Oil Processing(SKLHOP202203008)the Talent Foundation funded by Province and Ministry Co-construction Collaborative Innovation Center of Eco-chemical Engineering(STHGYX2201).
文摘The novel Fe-N co-doped ordered mesoporous carbon with high catalytic activity in m-cresol removal was prepared by urea-assisted impregnation and simple pyrolysis method.During the preparation of the Fe-NC catalyst,the complexation of N elements in urea could anchor Fe,and the formation of C3N4during urea pyrolysis could also prevent migration and aggregation of Fe species,which jointly improve the dispersion and stability of Fe.The FeN4sites and highly dispersed Fe nanoparticles synergistically trigger the dual-site peroxymonosulfate (PMS) activation for highly efficient m-cresol degradation,while the ordered mesoporous structure of the catalyst could improve the mass transfer rate of the catalytic process,which together promote catalytic degradation of m-cresol by PMS activation.Reactive oxygen species (ROS) analytic experiments demonstrate that the system degrades m-cresol by free radical pathway mainly based on SO_(4)^(-)·and·OH,and partially based on·OH as the active components,and a possible PMS activation mechanism by 5Fe-50 for m-cresol degradation was proposed.This study can provide theoretical guidance for the preparation of efficient and stable catalysts for the degradation of organic pollutants by activated PMS.
文摘A termetallic catalyst of Pt-Ir-Au/Al2O3 for NOx decomposition was prepared by loading the metallic colloids in C2H5OH-H2O solution and a surfactant of polyvinyl pyrrolidone.Compared with an impregnated Pt/Al2O3 catalyst,the termetallic catalyst of PtIrAu811/Al2O3,with a Pt：Ir：Au atomic ratio of 8：1：1,exhibited higher NO decomposition and selectivity to N2.Transmission electron microscopy and X-ray diffraction were conducted to clarify the state of the supported metals and indicate three precious metals alloyed on the catalyst.In the study of NO-temperature programmed desorption,oxygen desorption on the PtIrAu811 catalyst shifted to the low temperature side compared to that on Pt/Al2O3,which correlated well with its higher catalytic performance in NO decomposition.
基金supported by the National Natural Science Foundation of China (21476229, 21376236, 21503264)~~
文摘N2O is a promising green propellant and exhibits great potential for satellite propulsion systems. It is difficult for catalytic decomposition, which is an important way to initiate the propulsion process, to occur at temperatures below 600 °C due to the high activation energy of N2O. In this work, we report an Ir supported on rutile TiO2（Ir/r-TiO2） catalyst which exhibits a fairly high activity for high-concentration N2O decomposition. HAADF-STEM, H2-TPR, and XPS results indicate that highly dispersed Ir particles and improved oxygen mobility on the Ir/r-TiO2 could facilitate the decompo-sition of N2O and desorption of the adsorbed oxygen. Bridge-bonded peroxide intermediates were observed with in-situ DRIFT and herein, a detailed decomposition route is proposed.
基金financial support from the National Natural Science Foundation of China(Nos.22175033 and 51902124).
文摘Understanding the relationship between structure and properties is critical to the development of solidstate luminescence materials with desired characteristics and performance optimization. In this work, we elaborately designed and synthesized a pair of mononuclear iridium(Ⅲ) complexes with similar structures but different degrees of cationization. [Ir2-f][2PF_(6)] with two counterions is obtained by simple Nmethylation of the ancillary ligand of [Ir1-f][PF_(6)] which is a classic cationic iridium(Ⅲ) complex. Such a tiny modification results in tremendously different optical properties in dilute solutions and powders.[Ir1-f][PF_(6)] exhibits weak light in solution but enhanced emission in solid-state as well as poly(methyl methacrylate) matrix, indicative of its aggregation-induced emission(AIE) activity. On the sharp contrary, [Ir2-f][2PF_(6)] is an aggregation-caused quenching(ACQ) emitter showing strong emission in the isolated state but nearly nonemissive in aggregation states. Benefiting from the appealing characteristics of mechanochromic luminescence and AIE behavior, [Ir1-f][PF_(6)] has been successfully applied in reversible re-writable data recording and cell imaging. These results might provide deep insights into AIE and ACQ phenomenon of iridium(Ⅲ) complexes and facilitate the development of phosphorescent materials with promising properties.
基金supported by the National Key R&D Program of China(grant no.2022YFA1504302)the National Natural Science Foundation of China(grant nos.22188101,91956000,and 92256301)the Fundamental Research Funds for the Central Universities,and the Haihe Laboratory of Sustainable Chemical Transformations.
文摘Asymmetric hydrogenation of dialkyl imines to chiral amines is difficult because the two alkyls of imines are so similar in spatial and electronic structure that chiral catalysts are difficult to distinguish between them.In this study,we described an asymmetric hydrogenation of dialkyl imines by a chiral iridium catalyst containing spiro phosphine-amine-phosphine ligand.By precisely adjusting the chiral pocket of catalyst,a highly efficient catalyst was developed.Using this catalyst,a variety of dialkyl imines were hydrogenated to chiral amines with high yield and enantioselectivity.
