Background:Around the world,there is a high incidence of gastric ulcers.YS,an extract from the Chinese herb Albizzia chinensis(Osbeck)Merr,has potential therapeutic applications for gastrointestinal diseases.Here we e...Background:Around the world,there is a high incidence of gastric ulcers.YS,an extract from the Chinese herb Albizzia chinensis(Osbeck)Merr,has potential therapeutic applications for gastrointestinal diseases.Here we elucidated the protective effect and underlying mechanism of action of YS on gastric ulcer in rats injured by ethanol.Methods:The ethanol-i nduced gastric ulcer rat model was used to assess the protective effect of YS.A pathological examination of gastric tissue was performed by H&E staining.GES-1 cells damaged by hydrogen peroxide were used to simulate oxidative damage in gastric mucosal epithelial cells.Endogenous NRF2 was knocked down using small interfering RNA.Immunoprecipitation was used to detect ubiquitination of NRF2.Co-i mmunoprecipitation was used to detect the NRF2-Keap1 interaction.Results:YS(10 and 30 mg/kg,i.g.)significantly reduced the ulcer index,decreased MDA level,and increased SOD and GSH levels in gastric tissues damaged by ethanol.YS promoted NRF2 translocation from cytoplasm to nucleus and enhanced the NQO1 and HO-1 expression levels in injured rat gastric tissue.In addition,YS regulated NQO1 and HO-1 via NRF2 in H_(2)O_(2)-i nduced oxidative injured GES-1 cells.Further studies on the underlying mechanism indicated that YS reduced the interaction between NRF2 and Keap1 and decreased ubiquitylation of NRF2,thereby increasing its stability and expression of downstream factors.NRF2 knockdown abolished the effect of YS on MDA and SOD in GES-1 cells treated with H_(2)O_(2).Conclusion:YS reduced the NRF2-Keap1 interaction,promoting NRF2 translocation into the nucleus,which increasing the transcription and translation of NQO1 and HO-1 and improved the antioxidant capacity of rat stomach.展开更多
结合储层CO_(2)埋存技术,自主搭建了地层温度压力条件下CO_(2)埋存实验装置,开展了多介质辅助CO_(2)埋存实验研究。研究结果表明,乙醇-KOH体系能够有效进行CO_(2)矿化埋存,其中96%乙醇+3 g KOH 500 mL溶液捕集CO_(2)能力最强,是最佳的CO...结合储层CO_(2)埋存技术,自主搭建了地层温度压力条件下CO_(2)埋存实验装置,开展了多介质辅助CO_(2)埋存实验研究。研究结果表明,乙醇-KOH体系能够有效进行CO_(2)矿化埋存,其中96%乙醇+3 g KOH 500 mL溶液捕集CO_(2)能力最强,是最佳的CO_(2)矿化埋存溶液配比。经CO_(2)矿化埋存后,低渗透岩心孔隙度平均降低7.07%,孔隙度变化率与孔隙度呈正相关关系,渗透率平均降低16.01%。因此,96%乙醇+3 g KOH能够加速CO_(2)在储层中的CO_(2)沉淀过程,缩短CO_(2)在储层中的矿化埋存时间。该研究可重复性、准确性和可扩展性较强,能够激发学生自主设计实验的积极性及创新意识,培养学生的独立思考能力,有利于学生将理论知识与实际工程问题相结合,实现科研能力与创新能力的相互促进。展开更多
A large number of studies have shown that propolis has positive effects in the treatment of type 2 diabetes mellitus(T2DM).However,there are have only been a few reports that are based on an ultra-high performance liq...A large number of studies have shown that propolis has positive effects in the treatment of type 2 diabetes mellitus(T2DM).However,there are have only been a few reports that are based on an ultra-high performance liquid chromatography-quadrupole-time-of-flight-mass spectrometry(UPLC-Q-TOF-MS)analysis of the fecal metabolomics of ethanol extract of propolis(EEP)in the treatment of T2DM.The present investigation was designed to screen potential biomarkers of T2DM by the metabonomic method and to explain the possible anti-diabetes mechanism of EEP according to the changes in the biomarkers.The results showed that EEP improved the body weight(BW)of T2DM mice,lowered blood sugar levels,and significantly restored blood biochemical indicators related to T2DM,such as fasting insulin(FINS),homeostasis model assessment of insulin resistance(HOMA-IR),aspartate transaminase(AST),and alanine aminotransferase(ALT).Liver pathology showed that EEP reversed liver damage caused by T2DM.Metabolomics data identified 27 potential biomarkers in fecal samples.EEP effectively regulated the dysfunction in the metabolic pathways of glycerophospholipids,sphingolipids,riboflavins,and sterol lipids caused by T2DM.In summary,our research results revealed positive effects of EEP in the treatment of T2DM and provided potential candidate markers for further research and in the clinical treatment of T2DM.展开更多
The higher capacity of CO_(2)adsorption on the surface of magnesium oxide(MgO)with low-coordination O^(2-)sites would effectively enhance the catalytic reduction of CO_(2).Herein,a series of copper oxide(CuO)and MgO c...The higher capacity of CO_(2)adsorption on the surface of magnesium oxide(MgO)with low-coordination O^(2-)sites would effectively enhance the catalytic reduction of CO_(2).Herein,a series of copper oxide(CuO)and MgO composites with different mass ratios have been prepared by hydrothermal method and used for photothermal synergistic catalytic reduction of CO_(2)to ethanol.The catalyst with CuO mass ratio of 1.6% shows the best yield(15.17μmol·g^(-1)·h^(-1))under 3 h Xenon lamp illumination.The improved performance is attributable to the loose nano-sheet structure,uniform dispersion of active sites,the increased specific surface area,medium-strength basicity,the high separation efficiency of electrons and holes,and the formation of Mg-O-Cu species.The synthesized CuO and MgO composites with loose nano-sheet structure facilitate the diffusion of reactants CO_(2),so an excellent CO_(2)adsorption performance can be obtained.Meanwhile,the introduction of CuO in the form of bivalence provides higher specific surface area and porosity,thus obtaining more active sites.More importantly,the Mg-O-Cu species make the donation of electrons from MgO to CO_(2)easier,resulting in the breaking of the old Mg-O bond and the formation of C-O bond,thus promoting the adsorption and conversion of CO_(2)to ethanol.展开更多
Adolescent binge drinking leads to long-lasting disorders of the adult central nervous system,particularly aberrant hippocampal neurogenesis.In this study,we applied in vivo fluorescent tracing using NestinCreERT2::Ro...Adolescent binge drinking leads to long-lasting disorders of the adult central nervous system,particularly aberrant hippocampal neurogenesis.In this study,we applied in vivo fluorescent tracing using NestinCreERT2::Rosa26-tdTomato mice and analyzed the endogenous neurogenesis lineage progression of neural stem cells(NSCs)and dendritic spine formation of newborn neurons in the subgranular zone of the dentate gyrus.We found abnormal orientation of tamoxifen-induced tdTomato+(tdTom^(+))NSCs in adult mice 2 months after treatment with EtOH(5.0 g/kg,i.p.)for 7 consecutive days.EtOH markedly inhibited tdTom^(+)NSCs activation and hippocampal neurogenesis in mouse dentate gyrus from adolescence to adulthood.EtOH(100 mM)also significantly inhibited the proliferation to 39.2%and differentiation of primary NSCs in vitro.Adult mice exposed to EtOH also exhibited marked inhibitions in dendritic spine growth and newborn neuron maturation in the dentate gyrus,which was partially reversed by voluntary running or inhibition of the mammalian target of rapamycinenhancer of zeste homolog 2 pathway.In vivo tracing revealed that EtOH induced abnormal orientation of tdTom+NSCs and spatial misposition defects of newborn neurons,thus causing the disturbance of hippocampal neurogenesis and dendritic spine remodeling in mice.展开更多
Nonaqueous amine-based system is an attractive solution to overcome high-energy-intensive CO_(2) capture process using the conventional aqueous amines.Advanced nonaqueous absorbent of 2-(butylamino)ethanol(BAE)with 2-...Nonaqueous amine-based system is an attractive solution to overcome high-energy-intensive CO_(2) capture process using the conventional aqueous amines.Advanced nonaqueous absorbent of 2-(butylamino)ethanol(BAE)with 2-butoxyethanol(2-BE)has been recently proposed for low-energyconsumption CO_(2) capture.In this work,Henry’s law constants of CO_(2) in the BAE/2-BE blend were obtained by N_(2)O/CO_(2) analogy,and correlated in the temperature range of(283–333)K.Vapor-liquid equilibrium(VLE)data for the BAE+CO_(2)+2-BE system at 65.4%(mass)BAE were also determined in a stirred equilibrium cell at temperatures of(313–393)K and CO_(2) partial pressures up to 275 kPa.A single apparent equilibrium constant KCO_(2);app was proposed for this system and correlated as a function of temperature,carbonated degree of amine and CO_(2) loading.Solubility data were well represented by the modified Kent-Eisenberg model with an average absolute relative deviation(AARD)of 13%.展开更多
Product selectivity and reaction pathway are highly dependent on surface structure of heterogeneous catalysts.For vapor-phase hydrogenation of dimethyl oxalate(DMO),"EG route"(DMO→methyl glycolate(MG)ethyle...Product selectivity and reaction pathway are highly dependent on surface structure of heterogeneous catalysts.For vapor-phase hydrogenation of dimethyl oxalate(DMO),"EG route"(DMO→methyl glycolate(MG)ethylene glycol(EG)→ethanol(ET))and"MA route"(DMO→MG→methyl acetate(MA))were proposed over traditional Cu based catalysts and Mo-based or Fe-based catalysts,respectively.Herein,tunable yield of ET(93.7%)and MA(72.1%)were obtained through different reaction routes over WO_(x) modified Cu/SiO_(2) catalysts,and the corresponding reaction route was further proved by kinetic study and in-situ DRIFTS technology.Mechanistic studies demonstrated that H_(2) activation ability,acid density and Cu-WO_(x) interaction on the catalysts were tuned by regulating the surface W density,which resulted in the different reaction pathway and product selectivity.What's more,high yield of MA produced from DMO hydrogenation was firstly reported with the H_(2) pressure as low as 0.5 MPa.展开更多
二氧化碳(CO_(2))虽然被视为破坏生态环境的温室气体,但也是储量最丰富的碳资源,对其进行转化和利用将对社会环境和能源结构产生深远影响.电化学还原CO_(2)(CO_(2)RR)不仅转化效率高,而且成本较低,有望实现规模化生产.在众多催化剂中,...二氧化碳(CO_(2))虽然被视为破坏生态环境的温室气体,但也是储量最丰富的碳资源,对其进行转化和利用将对社会环境和能源结构产生深远影响.电化学还原CO_(2)(CO_(2)RR)不仅转化效率高,而且成本较低,有望实现规模化生产.在众多催化剂中,廉价易得的铜基催化剂被认为是电化学催化还原CO_(2)生成高附加值产物的理想催化剂之一,其中铜氧化物的存在是CO_(2)RR生成高附加值产物的关键.然而,CO_(2)RR过程是在负电位下进行的,当施加电位低于‒0.1 VRHE时,铜氧化物很容易被还原为金属态铜.因此,催化剂稳定氧化态铜的能力在保持连续、高效和稳定的CO_(2)RR产多碳产物性能中至关重要.本文将简单的O_(2)等离子体处理技术与静电纺丝技术相结合,合成了多孔碳纳米纤维负载的Cu/Cu_(x)O异质结催化剂,并考察了其催化CO_(2)RR的性能.在静电纺丝过程中,Cu-ZIF-8前驱体的加入使得热处理后的原丝纤维中形成了丰富的网络贯穿多孔结构,该结构有效地实现了铜纳米颗粒的均匀分散;随后,通过O_(2)等离子体处理技术,在碳纳米纤维中构建了大量的开放介孔,为CO_(2)的吸附和反应提供了有利环境,并使Cu/Cu_(x)O异质结位点暴露于反应界面.电化学性能测试结果表明,在400 mA cm^(‒2)电流密度下,独特的Cu/Cu_(x)O异质结活性位点电催化还原CO_(2)生成乙醇的法拉第效率可达70.7%,该性能优于未经O_(2)等离子体处理的多孔铜纳米纤维.此外,高暴露的Cu/Cu_(x)O异质结活性位点显著地增加实际参与反应的活性位点数量,经计算Cu/Cu_(x)O异质结CO_(2)RR产乙醇的质量活性高达8.4 A mg^(‒1),是目前报道生产乙醇的较高质量活性.多孔碳纳米纤维衬底不仅具有协同电子输运能力,而且在CO_(2)RR测试中施加的负电压有助于维持Cu/Cu_(x)O异质结构的稳定性,使其在高电流密度下能够保持长时间的催化稳定性.此外,本文利用原位拉曼光谱和红外光谱、有限元模拟及密度泛函理论计算等方法深入研究了Cu/Cu_(x)O异质结的催化机理.原位拉曼光谱和红外光谱表征结果证实了在CO_(2)RR过程中Cu_(x)O的动态稳定状态以及关键信号*CO和C‒C键的存在;理论计算表明,Cu/Cu_(x)O异质结的存在促进了关键中间体*CO的溢流,降低了C‒C耦合过程的反应能垒,从而提高了还原产物乙醇的产率.综上,本文成功地在多孔铜纳米纤维中引入氧化物物种,并优化了纤维孔结构.其表现出了较好的电催化还原CO_(2)性能,可高选择性生成乙醇,其独特的多孔碳纤维结构充分暴露了活性位点,实现了较高的质量活性.本文所采用的催化剂组分和微观结构的调控策略为提升电催化中催化剂稳定性和催化活性提供了有益的借鉴.展开更多
Pt/Ni catalysts modified with CeO2 nanoparticles were prepared by simple composite electrodeposition of Ni and CeO2,and spontaneous Ni partial replacement by Pt processes.The as-prepared CeO2-modified Pt/Ni catalysts ...Pt/Ni catalysts modified with CeO2 nanoparticles were prepared by simple composite electrodeposition of Ni and CeO2,and spontaneous Ni partial replacement by Pt processes.The as-prepared CeO2-modified Pt/Ni catalysts showed enhanced catalytic performance for ethanol electro-oxidation compared with pure Pt/Ni,and acetate species were proposed to be the main products of the oxidation when using these catalysts.The content of CeO2 in the as-prepared catalysts influenced their catalytic activity,with Pt/NiCe2（obtained from an electrolyte containing 100 mg/L CeO2 nanoparticles） exhibiting higher activity and relatively better stability in ethanol electro-oxidation.This was mainly due to the oxygen storage capacity of CeO2,the interaction between Pt and CeO2/Ni,and the relatively small contact and charge transfer resistances.The results of this work thus suggest that electrocatalysts with low price and high activity can be rationally designed and produced by a simple route for use in direct ethanol fuel cells.展开更多
KIT‐6 mesoporous silica aged at 40,100,and 150°C were used as hard templates to prepare different mesoporous MnO2 catalysts,marked as Mn‐40,Mn‐100,and Mn‐150,respectively.The catalytic activities of these cat...KIT‐6 mesoporous silica aged at 40,100,and 150°C were used as hard templates to prepare different mesoporous MnO2 catalysts,marked as Mn‐40,Mn‐100,and Mn‐150,respectively.The catalytic activities of these catalysts and the effect of pore sizes on ethanol catalytic oxidation were investigated.Mn‐40,Mn‐100,and Mn‐150 have triple,double,and single pore systems,respectively.On decreasing the aging temperature of KIT‐6,the pore sizes of KIT‐6 decrease and that of mesoporous MnO2 catalysts increase.The pore sizes and catalytic activities increase in the order:Mn‐40>Mn‐100>Mn‐150.Mn‐40 catalyst has a higher TOF(0.11 s–1 at 120°C)and the best catalytic activity for ethanol oxidation because of a bigger pore size with three pore systems with maximum distribution at 1.9,3.4,and 6.6 nm,decrease in symmetry and degree of order,more surface lattice oxygen species,oxygen vacancies resulting from more Mn3+ions,and better low‐temperature reducibility.展开更多
基金Yunnan Key Laboratory of Southern Medicinal Utilization,Yunnan University,Grant/Award Number:202105AG070012。
文摘Background:Around the world,there is a high incidence of gastric ulcers.YS,an extract from the Chinese herb Albizzia chinensis(Osbeck)Merr,has potential therapeutic applications for gastrointestinal diseases.Here we elucidated the protective effect and underlying mechanism of action of YS on gastric ulcer in rats injured by ethanol.Methods:The ethanol-i nduced gastric ulcer rat model was used to assess the protective effect of YS.A pathological examination of gastric tissue was performed by H&E staining.GES-1 cells damaged by hydrogen peroxide were used to simulate oxidative damage in gastric mucosal epithelial cells.Endogenous NRF2 was knocked down using small interfering RNA.Immunoprecipitation was used to detect ubiquitination of NRF2.Co-i mmunoprecipitation was used to detect the NRF2-Keap1 interaction.Results:YS(10 and 30 mg/kg,i.g.)significantly reduced the ulcer index,decreased MDA level,and increased SOD and GSH levels in gastric tissues damaged by ethanol.YS promoted NRF2 translocation from cytoplasm to nucleus and enhanced the NQO1 and HO-1 expression levels in injured rat gastric tissue.In addition,YS regulated NQO1 and HO-1 via NRF2 in H_(2)O_(2)-i nduced oxidative injured GES-1 cells.Further studies on the underlying mechanism indicated that YS reduced the interaction between NRF2 and Keap1 and decreased ubiquitylation of NRF2,thereby increasing its stability and expression of downstream factors.NRF2 knockdown abolished the effect of YS on MDA and SOD in GES-1 cells treated with H_(2)O_(2).Conclusion:YS reduced the NRF2-Keap1 interaction,promoting NRF2 translocation into the nucleus,which increasing the transcription and translation of NQO1 and HO-1 and improved the antioxidant capacity of rat stomach.
文摘结合储层CO_(2)埋存技术,自主搭建了地层温度压力条件下CO_(2)埋存实验装置,开展了多介质辅助CO_(2)埋存实验研究。研究结果表明,乙醇-KOH体系能够有效进行CO_(2)矿化埋存,其中96%乙醇+3 g KOH 500 mL溶液捕集CO_(2)能力最强,是最佳的CO_(2)矿化埋存溶液配比。经CO_(2)矿化埋存后,低渗透岩心孔隙度平均降低7.07%,孔隙度变化率与孔隙度呈正相关关系,渗透率平均降低16.01%。因此,96%乙醇+3 g KOH能够加速CO_(2)在储层中的CO_(2)沉淀过程,缩短CO_(2)在储层中的矿化埋存时间。该研究可重复性、准确性和可扩展性较强,能够激发学生自主设计实验的积极性及创新意识,培养学生的独立思考能力,有利于学生将理论知识与实际工程问题相结合,实现科研能力与创新能力的相互促进。
基金supported by the Shanxi Proxince Higher Education Revitalization Plan “1331 Project” (J201811301)
文摘A large number of studies have shown that propolis has positive effects in the treatment of type 2 diabetes mellitus(T2DM).However,there are have only been a few reports that are based on an ultra-high performance liquid chromatography-quadrupole-time-of-flight-mass spectrometry(UPLC-Q-TOF-MS)analysis of the fecal metabolomics of ethanol extract of propolis(EEP)in the treatment of T2DM.The present investigation was designed to screen potential biomarkers of T2DM by the metabonomic method and to explain the possible anti-diabetes mechanism of EEP according to the changes in the biomarkers.The results showed that EEP improved the body weight(BW)of T2DM mice,lowered blood sugar levels,and significantly restored blood biochemical indicators related to T2DM,such as fasting insulin(FINS),homeostasis model assessment of insulin resistance(HOMA-IR),aspartate transaminase(AST),and alanine aminotransferase(ALT).Liver pathology showed that EEP reversed liver damage caused by T2DM.Metabolomics data identified 27 potential biomarkers in fecal samples.EEP effectively regulated the dysfunction in the metabolic pathways of glycerophospholipids,sphingolipids,riboflavins,and sterol lipids caused by T2DM.In summary,our research results revealed positive effects of EEP in the treatment of T2DM and provided potential candidate markers for further research and in the clinical treatment of T2DM.
基金Financial supports by National Natural Science Foundation of China(21908052)the Key Program of Natural Science Foundation of Hebei Province(B2020209017)+1 种基金the Project of Science and Technology Innovation Team,Tang shan(20130203D)Youth Program of Natural Science of Hebei Province(B2020209065)。
文摘The higher capacity of CO_(2)adsorption on the surface of magnesium oxide(MgO)with low-coordination O^(2-)sites would effectively enhance the catalytic reduction of CO_(2).Herein,a series of copper oxide(CuO)and MgO composites with different mass ratios have been prepared by hydrothermal method and used for photothermal synergistic catalytic reduction of CO_(2)to ethanol.The catalyst with CuO mass ratio of 1.6% shows the best yield(15.17μmol·g^(-1)·h^(-1))under 3 h Xenon lamp illumination.The improved performance is attributable to the loose nano-sheet structure,uniform dispersion of active sites,the increased specific surface area,medium-strength basicity,the high separation efficiency of electrons and holes,and the formation of Mg-O-Cu species.The synthesized CuO and MgO composites with loose nano-sheet structure facilitate the diffusion of reactants CO_(2),so an excellent CO_(2)adsorption performance can be obtained.Meanwhile,the introduction of CuO in the form of bivalence provides higher specific surface area and porosity,thus obtaining more active sites.More importantly,the Mg-O-Cu species make the donation of electrons from MgO to CO_(2)easier,resulting in the breaking of the old Mg-O bond and the formation of C-O bond,thus promoting the adsorption and conversion of CO_(2)to ethanol.
基金supported by the National Natural Science Foundation of China,Nos.31601175(to YL),81803508(to KZ),82074056(to JY)the Natural Science Foundation of Liaoning Province of China,No.20180550335(to YL)the Scientific Research Project of Educational Commission of Liaoning Province of China,No.201610163L22(to YL)。
文摘Adolescent binge drinking leads to long-lasting disorders of the adult central nervous system,particularly aberrant hippocampal neurogenesis.In this study,we applied in vivo fluorescent tracing using NestinCreERT2::Rosa26-tdTomato mice and analyzed the endogenous neurogenesis lineage progression of neural stem cells(NSCs)and dendritic spine formation of newborn neurons in the subgranular zone of the dentate gyrus.We found abnormal orientation of tamoxifen-induced tdTomato+(tdTom^(+))NSCs in adult mice 2 months after treatment with EtOH(5.0 g/kg,i.p.)for 7 consecutive days.EtOH markedly inhibited tdTom^(+)NSCs activation and hippocampal neurogenesis in mouse dentate gyrus from adolescence to adulthood.EtOH(100 mM)also significantly inhibited the proliferation to 39.2%and differentiation of primary NSCs in vitro.Adult mice exposed to EtOH also exhibited marked inhibitions in dendritic spine growth and newborn neuron maturation in the dentate gyrus,which was partially reversed by voluntary running or inhibition of the mammalian target of rapamycinenhancer of zeste homolog 2 pathway.In vivo tracing revealed that EtOH induced abnormal orientation of tdTom+NSCs and spatial misposition defects of newborn neurons,thus causing the disturbance of hippocampal neurogenesis and dendritic spine remodeling in mice.
基金supported by Natural Science Foundation of Hebei Province(B2018208154)Department of Education of Hebei Province,P.R.China(SLRC2019051)Key Foundation of Hebei Provincial Department of Science and Technology,P.R.China(21373703D).
文摘Nonaqueous amine-based system is an attractive solution to overcome high-energy-intensive CO_(2) capture process using the conventional aqueous amines.Advanced nonaqueous absorbent of 2-(butylamino)ethanol(BAE)with 2-butoxyethanol(2-BE)has been recently proposed for low-energyconsumption CO_(2) capture.In this work,Henry’s law constants of CO_(2) in the BAE/2-BE blend were obtained by N_(2)O/CO_(2) analogy,and correlated in the temperature range of(283–333)K.Vapor-liquid equilibrium(VLE)data for the BAE+CO_(2)+2-BE system at 65.4%(mass)BAE were also determined in a stirred equilibrium cell at temperatures of(313–393)K and CO_(2) partial pressures up to 275 kPa.A single apparent equilibrium constant KCO_(2);app was proposed for this system and correlated as a function of temperature,carbonated degree of amine and CO_(2) loading.Solubility data were well represented by the modified Kent-Eisenberg model with an average absolute relative deviation(AARD)of 13%.
基金supported by National Natural Science Foundation of China (No.22102147 and 22002151)State Key Laboratory of Chemical Engineering (No.SKL-ChE-22A02)+2 种基金Zhejiang Provincial Natural Science Foundation of China under Grant No.LQ21B030009the Strategic Priority Research Program of the Chinese Academy of Sciences (No.XDA29050300)Qinchuang Yuan high-level innovation and entrepreneurship talents implementing project (No.QCYRCXM-2022-177)。
文摘Product selectivity and reaction pathway are highly dependent on surface structure of heterogeneous catalysts.For vapor-phase hydrogenation of dimethyl oxalate(DMO),"EG route"(DMO→methyl glycolate(MG)ethylene glycol(EG)→ethanol(ET))and"MA route"(DMO→MG→methyl acetate(MA))were proposed over traditional Cu based catalysts and Mo-based or Fe-based catalysts,respectively.Herein,tunable yield of ET(93.7%)and MA(72.1%)were obtained through different reaction routes over WO_(x) modified Cu/SiO_(2) catalysts,and the corresponding reaction route was further proved by kinetic study and in-situ DRIFTS technology.Mechanistic studies demonstrated that H_(2) activation ability,acid density and Cu-WO_(x) interaction on the catalysts were tuned by regulating the surface W density,which resulted in the different reaction pathway and product selectivity.What's more,high yield of MA produced from DMO hydrogenation was firstly reported with the H_(2) pressure as low as 0.5 MPa.
文摘二氧化碳(CO_(2))虽然被视为破坏生态环境的温室气体,但也是储量最丰富的碳资源,对其进行转化和利用将对社会环境和能源结构产生深远影响.电化学还原CO_(2)(CO_(2)RR)不仅转化效率高,而且成本较低,有望实现规模化生产.在众多催化剂中,廉价易得的铜基催化剂被认为是电化学催化还原CO_(2)生成高附加值产物的理想催化剂之一,其中铜氧化物的存在是CO_(2)RR生成高附加值产物的关键.然而,CO_(2)RR过程是在负电位下进行的,当施加电位低于‒0.1 VRHE时,铜氧化物很容易被还原为金属态铜.因此,催化剂稳定氧化态铜的能力在保持连续、高效和稳定的CO_(2)RR产多碳产物性能中至关重要.本文将简单的O_(2)等离子体处理技术与静电纺丝技术相结合,合成了多孔碳纳米纤维负载的Cu/Cu_(x)O异质结催化剂,并考察了其催化CO_(2)RR的性能.在静电纺丝过程中,Cu-ZIF-8前驱体的加入使得热处理后的原丝纤维中形成了丰富的网络贯穿多孔结构,该结构有效地实现了铜纳米颗粒的均匀分散;随后,通过O_(2)等离子体处理技术,在碳纳米纤维中构建了大量的开放介孔,为CO_(2)的吸附和反应提供了有利环境,并使Cu/Cu_(x)O异质结位点暴露于反应界面.电化学性能测试结果表明,在400 mA cm^(‒2)电流密度下,独特的Cu/Cu_(x)O异质结活性位点电催化还原CO_(2)生成乙醇的法拉第效率可达70.7%,该性能优于未经O_(2)等离子体处理的多孔铜纳米纤维.此外,高暴露的Cu/Cu_(x)O异质结活性位点显著地增加实际参与反应的活性位点数量,经计算Cu/Cu_(x)O异质结CO_(2)RR产乙醇的质量活性高达8.4 A mg^(‒1),是目前报道生产乙醇的较高质量活性.多孔碳纳米纤维衬底不仅具有协同电子输运能力,而且在CO_(2)RR测试中施加的负电压有助于维持Cu/Cu_(x)O异质结构的稳定性,使其在高电流密度下能够保持长时间的催化稳定性.此外,本文利用原位拉曼光谱和红外光谱、有限元模拟及密度泛函理论计算等方法深入研究了Cu/Cu_(x)O异质结的催化机理.原位拉曼光谱和红外光谱表征结果证实了在CO_(2)RR过程中Cu_(x)O的动态稳定状态以及关键信号*CO和C‒C键的存在;理论计算表明,Cu/Cu_(x)O异质结的存在促进了关键中间体*CO的溢流,降低了C‒C耦合过程的反应能垒,从而提高了还原产物乙醇的产率.综上,本文成功地在多孔铜纳米纤维中引入氧化物物种,并优化了纤维孔结构.其表现出了较好的电催化还原CO_(2)性能,可高选择性生成乙醇,其独特的多孔碳纤维结构充分暴露了活性位点,实现了较高的质量活性.本文所采用的催化剂组分和微观结构的调控策略为提升电催化中催化剂稳定性和催化活性提供了有益的借鉴.
基金supported by the National Natural Science Foundation of China (21307038 and 21577046)Key Project of Chinese Ministry of Education (212115)Physical Chemistry Experiment of Huanggang Normal University (2015CK12)~~
文摘Pt/Ni catalysts modified with CeO2 nanoparticles were prepared by simple composite electrodeposition of Ni and CeO2,and spontaneous Ni partial replacement by Pt processes.The as-prepared CeO2-modified Pt/Ni catalysts showed enhanced catalytic performance for ethanol electro-oxidation compared with pure Pt/Ni,and acetate species were proposed to be the main products of the oxidation when using these catalysts.The content of CeO2 in the as-prepared catalysts influenced their catalytic activity,with Pt/NiCe2（obtained from an electrolyte containing 100 mg/L CeO2 nanoparticles） exhibiting higher activity and relatively better stability in ethanol electro-oxidation.This was mainly due to the oxygen storage capacity of CeO2,the interaction between Pt and CeO2/Ni,and the relatively small contact and charge transfer resistances.The results of this work thus suggest that electrocatalysts with low price and high activity can be rationally designed and produced by a simple route for use in direct ethanol fuel cells.
基金supported by the National Key Research and Development Program Foundation of China(2016YFC0209203)the National Natural Science Foundation of China(21707130,21325731)~~
文摘KIT‐6 mesoporous silica aged at 40,100,and 150°C were used as hard templates to prepare different mesoporous MnO2 catalysts,marked as Mn‐40,Mn‐100,and Mn‐150,respectively.The catalytic activities of these catalysts and the effect of pore sizes on ethanol catalytic oxidation were investigated.Mn‐40,Mn‐100,and Mn‐150 have triple,double,and single pore systems,respectively.On decreasing the aging temperature of KIT‐6,the pore sizes of KIT‐6 decrease and that of mesoporous MnO2 catalysts increase.The pore sizes and catalytic activities increase in the order:Mn‐40>Mn‐100>Mn‐150.Mn‐40 catalyst has a higher TOF(0.11 s–1 at 120°C)and the best catalytic activity for ethanol oxidation because of a bigger pore size with three pore systems with maximum distribution at 1.9,3.4,and 6.6 nm,decrease in symmetry and degree of order,more surface lattice oxygen species,oxygen vacancies resulting from more Mn3+ions,and better low‐temperature reducibility.
