BrCF2CF2CH=CHCH2X(x=Cl, OAc, OH) reacted smoothly with alkynes in the presence of BrCo(dmgh)2Py/Zn, giving 4,4,5,5-tetrafluorocyclopentene derivatives in moderate yields.
At low temperature of 723 K, methane can be easily activated in the presence of ethylene in the feed, and converted to higher hydrocarbons (C2-C4) and aromatics (C6-C10), through its reaction over rare metals modi...At low temperature of 723 K, methane can be easily activated in the presence of ethylene in the feed, and converted to higher hydrocarbons (C2-C4) and aromatics (C6-C10), through its reaction over rare metals modified Zn/HZSM-5 zeolite catalysts without undesirable carbon oxides formation. Methane can get 37.3% conversion over the above catalysts under low temperature, and the catalysts show a longer lifetime than usual metal supported HZSM-5 zeolite catalysts without adding any rare earth metals. The effects of methane activation over various rare earth metal promoted Zn/HZSM-5 catalysts on the products and influences of several reaction conditions such as temperature, catalyst lifetime and molar ratio of CH4/C2H4 have been discussed.展开更多
In the present investigation, we fabricated strontium (Sr2+) incorporated CsPbI2Br-based inorganic perovskite solar cells in ambient conditions. The morphology, crystallinity, absorption, elemental composition and pho...In the present investigation, we fabricated strontium (Sr2+) incorporated CsPbI2Br-based inorganic perovskite solar cells in ambient conditions. The morphology, crystallinity, absorption, elemental composition and photoluminescence analysis of the bare CsPbI2Br and CsPb1-xSrxI2Br perovskite thin films were studied systematically to investigate the role of Sr2+ incorporation. It is observed that the surface morphology of the CsPbI2Br perovskite thin film has been improved by partial substitution of Pb2+ by Sr2+ which facilitates photoactive black phase-stabilization and defect passivation. The champion device having CsPb0.98Sr0.02I2Br composition exhibited a power conversion efficiency (PCE) of 16.61% which is much higher than the bare device (13.65%). Furthermore, our CsPb0.98Sr0.02I2Br-based devices maintain > 85% of its initial efficiency over 100 h in ambient conditions.展开更多
Carbon dioxide(CO_(2) ) capture and conversion is the key route for the mitigation of the greenhouse effect and utilization of carbon sources to obtain value-added products or fuels.Much attention is paid to the devel...Carbon dioxide(CO_(2) ) capture and conversion is the key route for the mitigation of the greenhouse effect and utilization of carbon sources to obtain value-added products or fuels.Much attention is paid to the development of novel materials with high CO_(2) adsorption capacity and conversion rate.MXene is the graphene-like two-dimensional metal carbide/nitride/carbonitride owning favorable structure,morphology,high surface-bulk ratio,and physicochemical properties.Here,we review the CO_(2) capture,sensing,and conversion by MXene and MXene-based materials.Furthermore,the underlying mechanism involved the capture,sensing,and conversion of CO_(2) is summarized.This review would open a new horizon for CO_(2) valorization with high efficiency and promising widespread applications.展开更多
The alkali-metal Na adsorption on Si(100)2×1 surface and its promoted oxidation and Si oxide growth have been investigated by means of thermal desorption,work function,Auger electron spectroscopy and photoemissio...The alkali-metal Na adsorption on Si(100)2×1 surface and its promoted oxidation and Si oxide growth have been investigated by means of thermal desorption,work function,Auger electron spectroscopy and photoemission electron spectroscopy.The experimental data showed that there was a new state,interface electron state,near the Fermi level after the deposition of Na atoms.It was found that the presence of Na always caused an increase of the oxygen initial uptake whereas the promotion of Si oxide growth was observed only at the coverage of Na greater than 0.5 ML.A new mechanism of Na-promoted Si oxide growth is suggested in this paper.展开更多
The effect of molecular nitrogen exposure on the surfaces of InP(100)modified by potassium overlayers is investigated by core-level and valence-band photoemission spectroscopy using Synchrotron radiation.In comparison...The effect of molecular nitrogen exposure on the surfaces of InP(100)modified by potassium overlayers is investigated by core-level and valence-band photoemission spectroscopy using Synchrotron radiation.In comparison with InP(110)surface,we found the promotion is much stronger for InP(100)surface due to the central role of surface defects in the promotion;furthermore,in contrast with K-promoted oxidation of InP(100)where the bonding is observed between indium and oxygen,indium atoms did not react directly with nitrogen atoms during the K-promoted nitridation of InP(100).展开更多
A vacuum heating operation at 623 K on the surfaces of SiO_2-supported promoted ca- talysts makes it possible to reveal the electron transfer from Co and Fe additives to Rh atoms: a Rh catalyst containing 1 % Eh under...A vacuum heating operation at 623 K on the surfaces of SiO_2-supported promoted ca- talysts makes it possible to reveal the electron transfer from Co and Fe additives to Rh atoms: a Rh catalyst containing 1 % Eh under CO exhibits geminal CO IR bands only, while the presence of Co and Fe in promoted Rh catalysts results in linear and bridged CO chemisorp- tions on Rh in connection with their promotion in the selective hydroformylation of propy- lene.展开更多
The anhydrous NdCl_a-LiNp (LiNp=Lithium uaphthalide) system has been fouud to cause a novel cyclodimerization of α, β-unsaturated ketoues to give cycio- -pentauol derivatives (1 and 2). A possible reaction mechanism...The anhydrous NdCl_a-LiNp (LiNp=Lithium uaphthalide) system has been fouud to cause a novel cyclodimerization of α, β-unsaturated ketoues to give cycio- -pentauol derivatives (1 and 2). A possible reaction mechanism was proposed.展开更多
Sm2O3-LaF3 and BaF2 promoted Sm2O3W3 catalysts shown good catalytic performance for the Oxidative Dehydrogenation of Ethane(ODE). XRD and XPS characterizations of the catalysts show the structure defects, which may be...Sm2O3-LaF3 and BaF2 promoted Sm2O3W3 catalysts shown good catalytic performance for the Oxidative Dehydrogenation of Ethane(ODE). XRD and XPS characterizations of the catalysts show the structure defects, which may be produced by the partial exchange of anions and cations,enhance the electron donating ability and increase the surface absorbed oxygen concentration thus should be favorable to improve the catalytic activity. However, the higher concentration of surface adsorbed oxygen is unfavorable for the ethene selectivity.展开更多
In our study on the chemistry of ZrCl_4-NaBH_4,we have found that aldehydes and ketones can be regenerated from acetals and ketals at 30℃ in Et_2O in high yield The reaction mechanism was discussed.
The electronic modification effect of various metal oxides over Pt-Al;O;catalyst andthe relationships between the polarizing force of cations(PFC)and the electrophiliccharacter(EC)and catalytic performances(CP)o...The electronic modification effect of various metal oxides over Pt-Al;O;catalyst andthe relationships between the polarizing force of cations(PFC)and the electrophiliccharacter(EC)and catalytic performances(CP)of promoted Pt catalyst have been studiecby competitive hydrogenation reaction method(CHRM)and test reaction,i.e.hydrogena-tion of benzene and hydrogenolysis of cyclopentane.展开更多
Sensory inputs,including visual,auditory,and somatosensory inputs from the environment,play a crucial role in infant brain development.Vision(light),the most important perception of mammals,has been identified for pro...Sensory inputs,including visual,auditory,and somatosensory inputs from the environment,play a crucial role in infant brain development.Vision(light),the most important perception of mammals,has been identified for promoting synaptogenesis,one of the hallmarks of brain development,in multiple brain areas.However,the neural mechanism regulating this phenomenon and the lifelong effects on cognition and learning ability remains unknown.展开更多
A series of novel carbon nanofibers(CNFs)based Cu-ZrO2 catalysts were synthesized by deposition precipitation method.To investigate the influence of promoter,catalysts were loaded with 1,2,3 and 4 wt%ZnO and character...A series of novel carbon nanofibers(CNFs)based Cu-ZrO2 catalysts were synthesized by deposition precipitation method.To investigate the influence of promoter,catalysts were loaded with 1,2,3 and 4 wt%ZnO and characterized by ICP-OES,HRTEM,BET,N2O chemisorption,TPR,XPS and CO2-TPD techniques.The results revealed that physicochemical properties of the catalysts were strongly influenced by incorporation of ZnO to the parent catalyst.Copper surface area(SCu)and dispersion(DCu)were slightly decreased by incorporation of ZnO promoter.Nevertheless,SCuand DCuwere remarkably decreased when ZnO content was exceeded beyond 3 wt%.The catalytic performance was evaluated by using autoclave slurry reactor at a pressure and temperature of 30 bar and 180℃,respectively.The promotion of CuZrO2/CNFs catalyst with 3 wt%of ZnO enhanced methanol synthesis rate from 32 to 45 g kg^-1 h^-1.Notably,with the ZnO promotion the selectivity to methanol was enhanced to 92%compared to 78%of the un-promoted Cu-ZrO2/CNFs catalyst at the expense of a lowered CO2 conversion.In addition,the catalytic activity of this novel catalyst system for CO2 hydrogenation to methanol was compared with the recent literature data.展开更多
Rare earth gangue, which mainly consists of mixtures of light rare earths such as lanthana, ceria, neodymium oxide and praseodymium oxide, was used as the promoter of fused iron catalysts for ammonia synthesis. The re...Rare earth gangue, which mainly consists of mixtures of light rare earths such as lanthana, ceria, neodymium oxide and praseodymium oxide, was used as the promoter of fused iron catalysts for ammonia synthesis. The result showed that the activity of the catalyst promoted with rare earth gangue was comparable with those of commercial iron catalysts with high amount of cobalt. The role of rare earths was owed to their advantages for favoring the deep reduction of the main composite in catalyst, i.e., iron oxide. This fmding indicated that the use of rare earth gangue could decrease the content of cobalt or even completely replace cobalt, which was used to be regarded as unsub- stitutable promoters for high performance ammonia catalyst; therefore, the cost of fused iron catalysts would decrease significantly.展开更多
Rare-earth (La, Ce, Yb) promoted Ni/γ-Al2O3 catalysts were prepared by impregnation method. Activity and carbon formation resistance of the prepared catalysts were evaluated under various reaction conditions. Catal...Rare-earth (La, Ce, Yb) promoted Ni/γ-Al2O3 catalysts were prepared by impregnation method. Activity and carbon formation resistance of the prepared catalysts were evaluated under various reaction conditions. Catalyst characterizations with TG, TPR and H2 chemisorption were carried out to investigate the promoting mechanism. Experimental results show that rare-earth promoters, especially Yb promoter, obviously improve the activity and carbon formation resistance of Ni/γ-Al2O3 catalyst, and Yb-Ni catalyst shows even higher performance than several commercial catalysts. According to the characterization results, Yb promoter enhances the interaction between the active metal and support, thus increasing the active metal's dispersion and improving its performance. Furthermore, the obvious difference in diesel conversion between Yb-Ni catalyst and others was shown in the temperature range of 450-550 °C, which would be the reason for its excellent carbon resistance.展开更多
A series of Ce-promoted Mn-Na2WO4/SiO2 catalysts were prepared by incipient wetness impregnation method, and their catalytic performance for oxidative coupling of methane (OCM) was investigated at atmospheric pressu...A series of Ce-promoted Mn-Na2WO4/SiO2 catalysts were prepared by incipient wetness impregnation method, and their catalytic performance for oxidative coupling of methane (OCM) was investigated at atmospheric pressure in a micro-quartz-tube reactor. The catalysts were characterized by X-ray diffraction (XRD), temperature program reduction (TPR) and BET surface area. Ce promoter increased surface area and Na2WO4 species dispersion, which enriched the amount of the surface species. In addition, Ce promoter increased the Na/W species reduction, but the reduction peak shifted to higher temperature. Stability test of 5wt%Ce catalyst indicated suitable performance and stability. The selectivity and yield of C^2+ hydrocarbons after 50 h operation reached 65.5% and 19.6%, respectively, at 840 ℃ over 5wt%Ce-2wt%Mn5wt%Na2WO4/SiO2 catalyst.展开更多
it was found by XPS and XRD that cerium existed as CeO_2 in iron based catalyst for dehydrogenation of ethylbenzene to styrene. and CeO_2 can be partly reduced under the reaction conditions to create Ce(3+)/Ce(4+) red...it was found by XPS and XRD that cerium existed as CeO_2 in iron based catalyst for dehydrogenation of ethylbenzene to styrene. and CeO_2 can be partly reduced under the reaction conditions to create Ce(3+)/Ce(4+) redox couples in the catalyst. The experiment of XPS and TPR-GC showed that there is an interaction between Ce oxide and Fe oxide, resulting in the shift of negative charge from iron to cerium and in the difficulty of Fe_2O_3 reduction to Fe_3O_4 in Fe_2O_3-CeO_2 system.The role of cerium promoter in the catalytic process was supposed to enhance the electron transfer among neighboring Fe active-sites of the catalyst and to improve the redox process of ethylbenzene dehydrogenation in the presence of steam by transferring oxygen from water to the active phase of the catalyst.展开更多
文摘BrCF2CF2CH=CHCH2X(x=Cl, OAc, OH) reacted smoothly with alkynes in the presence of BrCo(dmgh)2Py/Zn, giving 4,4,5,5-tetrafluorocyclopentene derivatives in moderate yields.
基金supported by the National Natural Science Foundation of China (Grants No. 20273021)the Key Project of Shanghai Science and Technology Committee (No. 05JC14070, 06DZ05025, 0552nm042, 08JC1408600)Scientific Research Foundation of the Education Department of Heilongjiang Province (No.11544005)
文摘At low temperature of 723 K, methane can be easily activated in the presence of ethylene in the feed, and converted to higher hydrocarbons (C2-C4) and aromatics (C6-C10), through its reaction over rare metals modified Zn/HZSM-5 zeolite catalysts without undesirable carbon oxides formation. Methane can get 37.3% conversion over the above catalysts under low temperature, and the catalysts show a longer lifetime than usual metal supported HZSM-5 zeolite catalysts without adding any rare earth metals. The effects of methane activation over various rare earth metal promoted Zn/HZSM-5 catalysts on the products and influences of several reaction conditions such as temperature, catalyst lifetime and molar ratio of CH4/C2H4 have been discussed.
基金This work was supported by Priority Research Centre Program through the National Research Foundation of Korea(NRF)funded by the Ministry of Education,Science,and Technology(NRF-2018R1A6A1A03024334)Also,this work was supported by Priority Research Centre Program through the National Research Foundation of Korea(NRF)funded by the Ministry of Education,Science,and Technology(2020R1A2C2004880).
文摘In the present investigation, we fabricated strontium (Sr2+) incorporated CsPbI2Br-based inorganic perovskite solar cells in ambient conditions. The morphology, crystallinity, absorption, elemental composition and photoluminescence analysis of the bare CsPbI2Br and CsPb1-xSrxI2Br perovskite thin films were studied systematically to investigate the role of Sr2+ incorporation. It is observed that the surface morphology of the CsPbI2Br perovskite thin film has been improved by partial substitution of Pb2+ by Sr2+ which facilitates photoactive black phase-stabilization and defect passivation. The champion device having CsPb0.98Sr0.02I2Br composition exhibited a power conversion efficiency (PCE) of 16.61% which is much higher than the bare device (13.65%). Furthermore, our CsPb0.98Sr0.02I2Br-based devices maintain > 85% of its initial efficiency over 100 h in ambient conditions.
基金Natural Science Foundation of Hebei Province (B2019408018, E2020048004)the Fundamental Research Funds for the Universities in Hebei Province (JYQ201902, JYT201901)+4 种基金Program for the Top Young Talents of Higher Learning Institutions of Hebei Province (BJ2020047)College Students’ Innovation and Entrepreneurship Training Program Project Fund of Langfang Normal University (202010100001, S202010100011)National Natural Science Foundation of China (21773307)Hebei Higher Education Teaching Reform Research and Practice Project (2019GJJG357)Research Project of Langfang Teachers University (LSLB201701) for financial support。
文摘Carbon dioxide(CO_(2) ) capture and conversion is the key route for the mitigation of the greenhouse effect and utilization of carbon sources to obtain value-added products or fuels.Much attention is paid to the development of novel materials with high CO_(2) adsorption capacity and conversion rate.MXene is the graphene-like two-dimensional metal carbide/nitride/carbonitride owning favorable structure,morphology,high surface-bulk ratio,and physicochemical properties.Here,we review the CO_(2) capture,sensing,and conversion by MXene and MXene-based materials.Furthermore,the underlying mechanism involved the capture,sensing,and conversion of CO_(2) is summarized.This review would open a new horizon for CO_(2) valorization with high efficiency and promising widespread applications.
文摘The alkali-metal Na adsorption on Si(100)2×1 surface and its promoted oxidation and Si oxide growth have been investigated by means of thermal desorption,work function,Auger electron spectroscopy and photoemission electron spectroscopy.The experimental data showed that there was a new state,interface electron state,near the Fermi level after the deposition of Na atoms.It was found that the presence of Na always caused an increase of the oxygen initial uptake whereas the promotion of Si oxide growth was observed only at the coverage of Na greater than 0.5 ML.A new mechanism of Na-promoted Si oxide growth is suggested in this paper.
基金Supported by the National Natutal Science Foundation of Chinaby Hefei National Synchrotron Radiation Laboratory.
文摘The effect of molecular nitrogen exposure on the surfaces of InP(100)modified by potassium overlayers is investigated by core-level and valence-band photoemission spectroscopy using Synchrotron radiation.In comparison with InP(110)surface,we found the promotion is much stronger for InP(100)surface due to the central role of surface defects in the promotion;furthermore,in contrast with K-promoted oxidation of InP(100)where the bonding is observed between indium and oxygen,indium atoms did not react directly with nitrogen atoms during the K-promoted nitridation of InP(100).
文摘A vacuum heating operation at 623 K on the surfaces of SiO_2-supported promoted ca- talysts makes it possible to reveal the electron transfer from Co and Fe additives to Rh atoms: a Rh catalyst containing 1 % Eh under CO exhibits geminal CO IR bands only, while the presence of Co and Fe in promoted Rh catalysts results in linear and bridged CO chemisorp- tions on Rh in connection with their promotion in the selective hydroformylation of propy- lene.
基金Project supported by the National Science Foundation of China
文摘The anhydrous NdCl_a-LiNp (LiNp=Lithium uaphthalide) system has been fouud to cause a novel cyclodimerization of α, β-unsaturated ketoues to give cycio- -pentauol derivatives (1 and 2). A possible reaction mechanism was proposed.
文摘Sm2O3-LaF3 and BaF2 promoted Sm2O3W3 catalysts shown good catalytic performance for the Oxidative Dehydrogenation of Ethane(ODE). XRD and XPS characterizations of the catalysts show the structure defects, which may be produced by the partial exchange of anions and cations,enhance the electron donating ability and increase the surface absorbed oxygen concentration thus should be favorable to improve the catalytic activity. However, the higher concentration of surface adsorbed oxygen is unfavorable for the ethene selectivity.
文摘In our study on the chemistry of ZrCl_4-NaBH_4,we have found that aldehydes and ketones can be regenerated from acetals and ketals at 30℃ in Et_2O in high yield The reaction mechanism was discussed.
文摘The electronic modification effect of various metal oxides over Pt-Al;O;catalyst andthe relationships between the polarizing force of cations(PFC)and the electrophiliccharacter(EC)and catalytic performances(CP)of promoted Pt catalyst have been studiecby competitive hydrogenation reaction method(CHRM)and test reaction,i.e.hydrogena-tion of benzene and hydrogenolysis of cyclopentane.
文摘Sensory inputs,including visual,auditory,and somatosensory inputs from the environment,play a crucial role in infant brain development.Vision(light),the most important perception of mammals,has been identified for promoting synaptogenesis,one of the hallmarks of brain development,in multiple brain areas.However,the neural mechanism regulating this phenomenon and the lifelong effects on cognition and learning ability remains unknown.
基金the Ministry of Higher Education Malaysia for providing financial support to this work via FRGS No:FRGS/1/2011/SG/UTP/02/13Universiti Teknologi PETRONAS
文摘A series of novel carbon nanofibers(CNFs)based Cu-ZrO2 catalysts were synthesized by deposition precipitation method.To investigate the influence of promoter,catalysts were loaded with 1,2,3 and 4 wt%ZnO and characterized by ICP-OES,HRTEM,BET,N2O chemisorption,TPR,XPS and CO2-TPD techniques.The results revealed that physicochemical properties of the catalysts were strongly influenced by incorporation of ZnO to the parent catalyst.Copper surface area(SCu)and dispersion(DCu)were slightly decreased by incorporation of ZnO promoter.Nevertheless,SCuand DCuwere remarkably decreased when ZnO content was exceeded beyond 3 wt%.The catalytic performance was evaluated by using autoclave slurry reactor at a pressure and temperature of 30 bar and 180℃,respectively.The promotion of CuZrO2/CNFs catalyst with 3 wt%of ZnO enhanced methanol synthesis rate from 32 to 45 g kg^-1 h^-1.Notably,with the ZnO promotion the selectivity to methanol was enhanced to 92%compared to 78%of the un-promoted Cu-ZrO2/CNFs catalyst at the expense of a lowered CO2 conversion.In addition,the catalytic activity of this novel catalyst system for CO2 hydrogenation to methanol was compared with the recent literature data.
基金the National Natural Science Foundation of China (20576021)Science & Technology Priority Project of Fujian Province (2005HZ01-2)National Key Technology R&D Program of China (2007BAE08B02)
文摘Rare earth gangue, which mainly consists of mixtures of light rare earths such as lanthana, ceria, neodymium oxide and praseodymium oxide, was used as the promoter of fused iron catalysts for ammonia synthesis. The result showed that the activity of the catalyst promoted with rare earth gangue was comparable with those of commercial iron catalysts with high amount of cobalt. The role of rare earths was owed to their advantages for favoring the deep reduction of the main composite in catalyst, i.e., iron oxide. This fmding indicated that the use of rare earth gangue could decrease the content of cobalt or even completely replace cobalt, which was used to be regarded as unsub- stitutable promoters for high performance ammonia catalyst; therefore, the cost of fused iron catalysts would decrease significantly.
基金supported by the National Natural Science Foundation of China (No. 20776016 and 21006005)
文摘Rare-earth (La, Ce, Yb) promoted Ni/γ-Al2O3 catalysts were prepared by impregnation method. Activity and carbon formation resistance of the prepared catalysts were evaluated under various reaction conditions. Catalyst characterizations with TG, TPR and H2 chemisorption were carried out to investigate the promoting mechanism. Experimental results show that rare-earth promoters, especially Yb promoter, obviously improve the activity and carbon formation resistance of Ni/γ-Al2O3 catalyst, and Yb-Ni catalyst shows even higher performance than several commercial catalysts. According to the characterization results, Yb promoter enhances the interaction between the active metal and support, thus increasing the active metal's dispersion and improving its performance. Furthermore, the obvious difference in diesel conversion between Yb-Ni catalyst and others was shown in the temperature range of 450-550 °C, which would be the reason for its excellent carbon resistance.
文摘A series of Ce-promoted Mn-Na2WO4/SiO2 catalysts were prepared by incipient wetness impregnation method, and their catalytic performance for oxidative coupling of methane (OCM) was investigated at atmospheric pressure in a micro-quartz-tube reactor. The catalysts were characterized by X-ray diffraction (XRD), temperature program reduction (TPR) and BET surface area. Ce promoter increased surface area and Na2WO4 species dispersion, which enriched the amount of the surface species. In addition, Ce promoter increased the Na/W species reduction, but the reduction peak shifted to higher temperature. Stability test of 5wt%Ce catalyst indicated suitable performance and stability. The selectivity and yield of C^2+ hydrocarbons after 50 h operation reached 65.5% and 19.6%, respectively, at 840 ℃ over 5wt%Ce-2wt%Mn5wt%Na2WO4/SiO2 catalyst.
文摘it was found by XPS and XRD that cerium existed as CeO_2 in iron based catalyst for dehydrogenation of ethylbenzene to styrene. and CeO_2 can be partly reduced under the reaction conditions to create Ce(3+)/Ce(4+) redox couples in the catalyst. The experiment of XPS and TPR-GC showed that there is an interaction between Ce oxide and Fe oxide, resulting in the shift of negative charge from iron to cerium and in the difficulty of Fe_2O_3 reduction to Fe_3O_4 in Fe_2O_3-CeO_2 system.The role of cerium promoter in the catalytic process was supposed to enhance the electron transfer among neighboring Fe active-sites of the catalyst and to improve the redox process of ethylbenzene dehydrogenation in the presence of steam by transferring oxygen from water to the active phase of the catalyst.