An atomically dispersed FeCo-NC material with the 3D flower-like morphology was used as a unique substrate for the controllable deposition of ultrasmall NiFe layered double hydroxide nanodots(termed as NiFe-NDs)to sim...An atomically dispersed FeCo-NC material with the 3D flower-like morphology was used as a unique substrate for the controllable deposition of ultrasmall NiFe layered double hydroxide nanodots(termed as NiFe-NDs)to simultaneously promote the sluggish kinetics of oxygen reduction reaction(ORR)and oxygen evolution reaction(OER).The size-limiting growth of NiFe-NDs(~4.0 nm in diameter)was realized via the confinement of the 3D flower-like mesoporous structure and the rich N/O functionality of FeCo-NC.Benefiting from the distinctive structure with the simultaneously maximum exposure of both OER and ORR active sites,the NiFe-ND/FeCo-NC composite showed an ORR halfwave potential of 0.85 V and an OER potential of 1.66 V in0.1 mol L-1KOH at 10.0 mA cm-2.In-situ Raman analysis suggested the activity of OER was derived from the Ni sites on NiFe-ND/FeCo-NC.Moreover,the NiFe-ND/FeCo-NC-assembled Zn-air battery(ZAB)exhibited a very small discharge-charge voltage gap of 0.87 V at 20 mA cm-2and robust cycling stability.Furthermore,the NiFe-ND/FeCo-NC composite was also applicable for fabricating all-solid-state ZAB to power wearable electronics with superior cycling stability under deformation.Our work could enlighten a new applicable branch of atomically dispersed metal-nitrogen-carbon materials as unique substrates for fabricating multifunctional electrocatalysts.展开更多
Developing robust oxygen electrocatalyst with high-performance is very significant for practical rechargeable Zn-air battery.We report herein the preparation of three-dimensional continuous nanocarbon network composed...Developing robust oxygen electrocatalyst with high-performance is very significant for practical rechargeable Zn-air battery.We report herein the preparation of three-dimensional continuous nanocarbon network composed of interconnected nitrogen-doped carbon nanotubes and its application as oxygen electrocatalysis in rechargeable Zn-air battery.Except the excellent electrochemical bifunctionality,this carbon nanotube matrix also delivers an impressive battery performance.Specifically,an opencircuit voltage of 1.50 V as well as a high power density of 220 m W cm^(-2) with remarkable cycling stability for 1600 h is achieved in the rechargeable Zn-air battery.The study not only provides an efficient bifunctional oxygen electrocatalyst but more importantly may pave significant concepts in designing robust electrode for long-life rechargeable Zn-air battery and other energy technologies.展开更多
The optimum Mo/[H^+] ratio per unit cell of the active precursors in Mo/HZSM-5 catalysts for methane dehydro-aromatization, measured by1H MAS NMR, was found to be about 1 when adjusting the acid sites by altering eith...The optimum Mo/[H^+] ratio per unit cell of the active precursors in Mo/HZSM-5 catalysts for methane dehydro-aromatization, measured by1H MAS NMR, was found to be about 1 when adjusting the acid sites by altering either the SiO2/Al2O3 ratios or the Mo loading. This implies that a concerted interaction between the Mo species and the Bronsted acid sites probably features the bifunctionality of the Mo/HZSM-5 catalyst. On the other hand, it was found that the driving force for Mo species to move into the HSZM-5 zeolite channels and the interaction between the Mo species and the Bronsted acid sites are closely and proportionably related with the amount of Bronsted acid sites per unit cell.展开更多
Recent developments in nanochemistry offer precise morphology control of nanomaterials, which has significant impacts in the field of heterogeneous catalysis. Rational design of bifunctional catalysts can influence va...Recent developments in nanochemistry offer precise morphology control of nanomaterials, which has significant impacts in the field of heterogeneous catalysis. Rational design of bifunctional catalysts can influence various aspects of catalytic properties. In this review, a new class of bifunctional catalysts with a metal@silica yolk-shell nanostructure is introduced. This structure has many advantages as a heterogeneous catalyst since it ensures a homogeneous environment around each metal core, and particle sintering is effectively eliminated during high temperature reactions. The catalysts exhibit high activity and recyclability in gas- and solution-phase reactions. It is anticipated that appropriate selection of bifunctional components and optimal structural control will significantly further enhance the catalytic properties, and enable target reaction-oriented development of new catalysts.展开更多
The development of advanced bifunctional oxygen electrocatalysts for oxygen reduction and evolution reactions(ORR and OER) is critical to the practical application of zinc-air batteries(ZABs). Herein, a silica-assiste...The development of advanced bifunctional oxygen electrocatalysts for oxygen reduction and evolution reactions(ORR and OER) is critical to the practical application of zinc-air batteries(ZABs). Herein, a silica-assisted method is reported to integrate numerous accessible edge Fe-Nx sites into porous graphitic carbon(named Fe-N-G) for achieving highly active and robust oxygen electrocatalysis. Silica facilitates the formation of edge Fe-Nx sites and dense graphitic domains in carbon by inhibiting iron aggregation.The purification process creates a well-developed mass transfer channel for Fe-N-G. Consequently,Fe-N-G delivers a half-wave potential of 0.859 V in ORR and an overpotential of 344 m V at10 m A cm^(-2)in OER. During long-term operation, the graphitic layers protect edge Fe-Nx sites from demetallation in ORR and synergize with Fe OOH species endowing Fe-N-G with enhanced OER activity.Density functional theory calculations reveal that the edge Fe-Nx site is superior to the in-plane Fe-Nx site in terms of OH* dissociation in ORR and OOH* formation in OER. The constructed ZAB based on Fe-N-G cathode shows a higher peak power density of 133 m W cm^(-2)and more stable cycling performance than Pt/C + RuO2counterparts. This work provides a novel strategy to obtain high-efficiency bifunctional oxygen electrocatalysts through space mediation.展开更多
Alcohol-assisted low-temperature methanol synthesis was conducted over Cu/ZnO;catalysts while varying the copper content（X）. Unlike conventional methanol synthesis, ethanol acted as both solvent and reaction interme...Alcohol-assisted low-temperature methanol synthesis was conducted over Cu/ZnO;catalysts while varying the copper content（X）. Unlike conventional methanol synthesis, ethanol acted as both solvent and reaction intermediate in this reaction, creating a different reaction pathway. The formation of crystalline phases and characteristic morphology of the co-precipitated precursors during the co-precipitation step were important factors in obtaining an efficient Cu/ZnO catalyst with a high dispersion of metallic copper,which is one of the main active sites for methanol synthesis. The acidic properties of the Cu/ZnO catalyst were also revealed as important factors, since alcohol esterification is considered the rate-limiting step in alcohol-assisted low-temperature methanol synthesis. As a consequence, bifunctionality of the Cu/ZnO catalyst such as metallic copper and acidic properties was required for this reaction. In this respect, the copper content（X） strongly affected the catalytic activity of the Cu/ZnO;catalysts, and accordingly, the Cu/ZnO;.5 catalyst with a high copper dispersion and sufficient acid sites exhibited the best catalytic performance in this reaction.展开更多
Electrocatalysts are one of the essential components for the devices of high-efficiency green energy storage and conversion,such as metal-air cells,fuel cells,and water electrolysis systems.While catalysts made from n...Electrocatalysts are one of the essential components for the devices of high-efficiency green energy storage and conversion,such as metal-air cells,fuel cells,and water electrolysis systems.While catalysts made from noble metals possess high catalytic performance in both oxygen reduction reaction(ORR)and oxygen evolution reaction(OER),their scarcity and expensiveness significantly limit large-scale applications.In this regard,metal-free/non-noble metal carbon-based catalysts have become competitive alternatives to replace catalysts made of noble metals.Nevertheless,low catalytic ORR/OER performance is the challenge of carbon-based catalysts for the commercial applications of metal-air batteries.To solve the problem of poor catalytic performance,two strategies have been proposed:(1)controlling the microstructure of the catalysts to expose more active sites as the channels of rapid mass and electron transfer;and(2)reducing the reaction energy barrier by optimizing the electronic structures of the catalysts via surface engineering.Here,we review different types of bifunctional ORR/OER electrocatalysts with the activated surface sites.We focus on how the challenge can be overcome with different methods of material synthesis,structural and surface characterization,performance validation/optimization,to outline the principles of surface modifications behind catalyst designs.In particular,we provide critical analysis in the challenges that we are facing in structural design and surface engineering of bifunctional ORR/OER catalysts and indicate the possible solution for these problems,providing the society with clearer ideas on the practical prospects of noble-metal-free electrocatalysts for their future applications.展开更多
In this work,six novel axially unfixed biaryl-based water-compatible bifunctional organocatalysts were de-signed and synthesized for the organocatalytic access to a variety of 3-alkyl-3-hydroxy-2-oxindole derivatives ...In this work,six novel axially unfixed biaryl-based water-compatible bifunctional organocatalysts were de-signed and synthesized for the organocatalytic access to a variety of 3-alkyl-3-hydroxy-2-oxindole derivatives via aldol reactions in water.Organocatalyzed by 5a,the direct aldol reactions of isatins with enolisable ketones under-went readily in water,furnishing the structurally diverse 3-alkyl-3-hydroxy-2-oxindoles in various stereoselectivi-ties(up to>99%dr and>99%ee).Moreover,a plausible transition state of the conducted aldol reactions was hy-pothesized to shed light on the observed stereoselectivities of the obtained 3-alkyl-3-hydroxy-2-oxindoles.展开更多
随着人类社会的高速发展,在保证环境不被破坏的情况下维持众多机械和电气设备的正常运转急需清洁的能源方式。氢被认为是在未来最有前景的清洁能源之一。近期,电化学水分解已被认为是获取氢能的最有效的方法之一,它的燃料产物只是无污...随着人类社会的高速发展,在保证环境不被破坏的情况下维持众多机械和电气设备的正常运转急需清洁的能源方式。氢被认为是在未来最有前景的清洁能源之一。近期,电化学水分解已被认为是获取氢能的最有效的方法之一,它的燃料产物只是无污染的水;然而,迟缓的析氧反应严重制约了水分解效率,导致驱动水分解的电压相对较高。探求热力学有利的阳极反应以取代缓慢的氧析出和开发高活性双功能型电催化剂用于这种阳极反应和析氢对于实现可应用于工业的节能型产氢至关重要。当前,普遍认为用其他有用的且利于热力学的反应取代析氧反应可以减小分解电压从而实现节能产氢。本文报道了一种用于甲醇氧化和析氢的双功能型嵌入镍纳米粒子的碳棱柱状微米棒电催化剂(命名为镍碳微米棒),该催化剂是由74号金属有机框架结构经碳化处理获得。这种由镍和碳构成的界面材料结构通过原位碳化实现,由于碳的分隔作用,分散的镍纳米颗粒不会轻易团聚,这有利于暴露更多的镍活性位点与电解液相接触,为更快的催化剂和电解液间电荷转移和电化学动力学提供保障。在此阳极的甲醇氧化中,产物分别为二氧化碳和甲酸,两者在1.55 V电压下的法拉第效率分别为36.2%和62.5%;同时该镍碳微米棒催化剂表现出优异的甲醇氧化活性和耐久性(12 h持续性催化,电流仅衰退2.7%)。值得注意的是,该双功能催化剂不仅具有甲醇氧化活性,在室温下含有0.5mol·L^(-1)甲醇的1.0mol·L^(-1)氢氧化钾电解液中的析氢过电位也较低(仅155 m V的过电位即可驱动10 m A·cm^(-2)的电流),保证了产氢效率。更重要的是,采用这种双功能型电极构造的双电极电解槽仅需1.6 V电压即可驱动10 m A·cm^(-2)的电流,与析氧反应作为阳极反应的电解槽相比驱动电压减小了240 mV。展开更多
通过探究催化转移氢化(catalytic transfer hydrogenation,CTH)使高含氧量生物质加氢脱氧为高值平台分子的新策略,以实现生物质的资源化与利用和达成生产净零碳排放燃料的目标。文中以Zr/Hf金属氧化物非均相催化体系设计、构筑及性能调...通过探究催化转移氢化(catalytic transfer hydrogenation,CTH)使高含氧量生物质加氢脱氧为高值平台分子的新策略,以实现生物质的资源化与利用和达成生产净零碳排放燃料的目标。文中以Zr/Hf金属氧化物非均相催化体系设计、构筑及性能调控为基本思路,以乙酰丙酸、糠醛、5-羟甲基糠醛及γ-戊内酯等重要生物质平台分子的可控定向转化为主线,重点评估了催化剂结构对应的酸碱活性位点在Meerwein-Ponndorf-Verley(MPV)反应中的关键作用,探讨并展望了Zr/Hf酸碱双功能催化剂在生物质平台分子转化为高值化学品领域的发展前景。本研究不仅对催化剂活性位点(Lewis/Br?nsted酸和碱)在相应生物质转化过程中的反应机理做出了归纳和总结,并且提出了兼顾经济效益和环境影响的新型固体酸催化剂的设计思路和策略。展开更多
The recharged zinc-air battery(ZAB) has drawn significant attention owing to increasing requirement for energy conversion and storage devices.Fabricating the efficient bifunctional oxygen catalyst using a convenient s...The recharged zinc-air battery(ZAB) has drawn significant attention owing to increasing requirement for energy conversion and storage devices.Fabricating the efficient bifunctional oxygen catalyst using a convenient strategy is vitally important for the rechargeable ZAB.In this study,the bimetallic ZIFs-containing electrospun(ES) carbon nanofibers membrane with hierarchically porous structure was prepared by coaxial electrospinning and carbonization process,which was expected to be a bifunctional electrocatalyst for ZABs.Owing to the formed dual single-atomic sites of Co-N_(4) and Zn-N_(4),the obtained ES-Co/ZnCNZIFexhibited the preferable performance toward oxygen reduction reaction(ORR) with E1/2of 0.857 V and JLof 5.52 mA cm^(-2),which were more than Pt/C.Meanwhile,it exhibited a marked oxygen evolution reaction(OER) property with overpotential of 462 mV due to the agglomerated metallic Co nanoparticles.Furthermore,the ZAB based on the ES-Co/Zn-CNZIFcarbon nanofibers membranes delivered peak power density of 215 mW cm^(-2),specific capacity of 802.6 mA h g^(-1),and exceptional cycling stability,far larger than Pt/C+RuO_(2)-based ZABs.A solid-state ZAB based on ES-Co/Zn-CNZIFshowed better flexibility and stability with different bending angles.展开更多
Nitrene transfer reactions are powerful tools in synthetic organic chemistry.In recent years,transitionmetal catalyzed nitrene transfer reactions with carbamates as the nitrene precursors have been widely pursued.Such...Nitrene transfer reactions are powerful tools in synthetic organic chemistry.In recent years,transitionmetal catalyzed nitrene transfer reactions with carbamates as the nitrene precursors have been widely pursued.Such species undergoes facile C-H amination,aziridination,and bifunctionalization of alkenes under the catalysis of different transition metals including Rh,Fe,Ru and others,enabling the efficient construction of various nitrogen-containing molecules.In this review,the recent developments in nitrene transfer reactions with carbamates via N-O bond cleavage were introduced based on different types of reaction,and the key mechanistic information and synthetic applications of the methodologies were discussed.展开更多
Mesoporous silicas have a very attractive ability of sorption and enrichment of metal ions due to their huge surface area and facile functionalization by organic ligands. In this work, phosphonate-amino hifunctionaliz...Mesoporous silicas have a very attractive ability of sorption and enrichment of metal ions due to their huge surface area and facile functionalization by organic ligands. In this work, phosphonate-amino hifunctionalized mesoporous silica SBA-15 （PA-SBA-15） as U（VI） sorbent was fabricated through post-grafting method. The obtained mesoporous silica was character- ized by SEM, XRD, NMR and nitrogen sorption/desorption experiments, which revealed the existence of ordered mesoporous structure with uniform pore diameter and large surface area. The adsorptivity of PA-SBA-15 for U（VI） from aqueous solution was investigated using batch sorption technique under different experimental conditions. The preliminary results show that the U（VI） sorption by PA-SBA-15 is very quick with equilibrium time of less than 1 h, and the U（VI） uptake is as large as 373 mg/g at pH 5.5 under 95℃. The sorption isotherm has been successfully modeled by the Langmuir isotherm, suggesting a monolayer homogeneous sorption of U（VI） in PA-SBA-15. The sorption is pH-dependent due to the pH-dependent charge of sorbent in the aqueous solution. The thermodynamics research shows that the sorption is a feasible and endothermic process. Based on these results, PA-SBA-15 could be a promising solid phase sorbent for highly-efficient removal of U（VI） ions from waste water and enrichment of U（VI） from a solution at a very low level.展开更多
基金financially supported by the National Natural Science Foundation of China(21701101)the National Key Research and Development Project,Key Projects of Intergovernmental International Innovation Cooperation(2018YFE0118200 and 2016YFF0204402)+4 种基金the Fundamental Research Funds for the Central Universities(18CX06063A)the Key Research and Development Project of Shandong Province(2019JZZY010506)the Scientific Research Awards Foundation for Outstanding Young Scientists of Shandong Province(ZR2018JL010)the Joint Fund of Outstanding Young Talents of Shandong Province(ZR2017BB018)the Program of Qingdao Scientific and Technological Innovation High-level Talents Project(172-1-1-zhc)。
文摘An atomically dispersed FeCo-NC material with the 3D flower-like morphology was used as a unique substrate for the controllable deposition of ultrasmall NiFe layered double hydroxide nanodots(termed as NiFe-NDs)to simultaneously promote the sluggish kinetics of oxygen reduction reaction(ORR)and oxygen evolution reaction(OER).The size-limiting growth of NiFe-NDs(~4.0 nm in diameter)was realized via the confinement of the 3D flower-like mesoporous structure and the rich N/O functionality of FeCo-NC.Benefiting from the distinctive structure with the simultaneously maximum exposure of both OER and ORR active sites,the NiFe-ND/FeCo-NC composite showed an ORR halfwave potential of 0.85 V and an OER potential of 1.66 V in0.1 mol L-1KOH at 10.0 mA cm-2.In-situ Raman analysis suggested the activity of OER was derived from the Ni sites on NiFe-ND/FeCo-NC.Moreover,the NiFe-ND/FeCo-NC-assembled Zn-air battery(ZAB)exhibited a very small discharge-charge voltage gap of 0.87 V at 20 mA cm-2and robust cycling stability.Furthermore,the NiFe-ND/FeCo-NC composite was also applicable for fabricating all-solid-state ZAB to power wearable electronics with superior cycling stability under deformation.Our work could enlighten a new applicable branch of atomically dispersed metal-nitrogen-carbon materials as unique substrates for fabricating multifunctional electrocatalysts.
基金financially supported by the National Natural Science Foundation of China(21802048,21805103,21805104)the Fundamental Research Funds for the Central Universities(2018KFYXKJC044,2018KFYYXJJ121,2017KFXKJC002,2017KFYXJJ164)the National 1000 Young Talents Program of China。
文摘Developing robust oxygen electrocatalyst with high-performance is very significant for practical rechargeable Zn-air battery.We report herein the preparation of three-dimensional continuous nanocarbon network composed of interconnected nitrogen-doped carbon nanotubes and its application as oxygen electrocatalysis in rechargeable Zn-air battery.Except the excellent electrochemical bifunctionality,this carbon nanotube matrix also delivers an impressive battery performance.Specifically,an opencircuit voltage of 1.50 V as well as a high power density of 220 m W cm^(-2) with remarkable cycling stability for 1600 h is achieved in the rechargeable Zn-air battery.The study not only provides an efficient bifunctional oxygen electrocatalyst but more importantly may pave significant concepts in designing robust electrode for long-life rechargeable Zn-air battery and other energy technologies.
文摘The optimum Mo/[H^+] ratio per unit cell of the active precursors in Mo/HZSM-5 catalysts for methane dehydro-aromatization, measured by1H MAS NMR, was found to be about 1 when adjusting the acid sites by altering either the SiO2/Al2O3 ratios or the Mo loading. This implies that a concerted interaction between the Mo species and the Bronsted acid sites probably features the bifunctionality of the Mo/HZSM-5 catalyst. On the other hand, it was found that the driving force for Mo species to move into the HSZM-5 zeolite channels and the interaction between the Mo species and the Bronsted acid sites are closely and proportionably related with the amount of Bronsted acid sites per unit cell.
文摘Recent developments in nanochemistry offer precise morphology control of nanomaterials, which has significant impacts in the field of heterogeneous catalysis. Rational design of bifunctional catalysts can influence various aspects of catalytic properties. In this review, a new class of bifunctional catalysts with a metal@silica yolk-shell nanostructure is introduced. This structure has many advantages as a heterogeneous catalyst since it ensures a homogeneous environment around each metal core, and particle sintering is effectively eliminated during high temperature reactions. The catalysts exhibit high activity and recyclability in gas- and solution-phase reactions. It is anticipated that appropriate selection of bifunctional components and optimal structural control will significantly further enhance the catalytic properties, and enable target reaction-oriented development of new catalysts.
基金financial support from the National Key Research and Development Project (2017YFB0308200)the CAS Key Laboratory of Carbon Materials (KLCMKFJJ2011)。
文摘The development of advanced bifunctional oxygen electrocatalysts for oxygen reduction and evolution reactions(ORR and OER) is critical to the practical application of zinc-air batteries(ZABs). Herein, a silica-assisted method is reported to integrate numerous accessible edge Fe-Nx sites into porous graphitic carbon(named Fe-N-G) for achieving highly active and robust oxygen electrocatalysis. Silica facilitates the formation of edge Fe-Nx sites and dense graphitic domains in carbon by inhibiting iron aggregation.The purification process creates a well-developed mass transfer channel for Fe-N-G. Consequently,Fe-N-G delivers a half-wave potential of 0.859 V in ORR and an overpotential of 344 m V at10 m A cm^(-2)in OER. During long-term operation, the graphitic layers protect edge Fe-Nx sites from demetallation in ORR and synergize with Fe OOH species endowing Fe-N-G with enhanced OER activity.Density functional theory calculations reveal that the edge Fe-Nx site is superior to the in-plane Fe-Nx site in terms of OH* dissociation in ORR and OOH* formation in OER. The constructed ZAB based on Fe-N-G cathode shows a higher peak power density of 133 m W cm^(-2)and more stable cycling performance than Pt/C + RuO2counterparts. This work provides a novel strategy to obtain high-efficiency bifunctional oxygen electrocatalysts through space mediation.
基金supported by C1 Gas Refinery Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Science,ICT & Future Planning (2015M3D3A1A01064908)
文摘Alcohol-assisted low-temperature methanol synthesis was conducted over Cu/ZnO;catalysts while varying the copper content（X）. Unlike conventional methanol synthesis, ethanol acted as both solvent and reaction intermediate in this reaction, creating a different reaction pathway. The formation of crystalline phases and characteristic morphology of the co-precipitated precursors during the co-precipitation step were important factors in obtaining an efficient Cu/ZnO catalyst with a high dispersion of metallic copper,which is one of the main active sites for methanol synthesis. The acidic properties of the Cu/ZnO catalyst were also revealed as important factors, since alcohol esterification is considered the rate-limiting step in alcohol-assisted low-temperature methanol synthesis. As a consequence, bifunctionality of the Cu/ZnO catalyst such as metallic copper and acidic properties was required for this reaction. In this respect, the copper content（X） strongly affected the catalytic activity of the Cu/ZnO;catalysts, and accordingly, the Cu/ZnO;.5 catalyst with a high copper dispersion and sufficient acid sites exhibited the best catalytic performance in this reaction.
基金financially supported by the National Natural Science Foundation of China(51572166)the project funded by China Postdoctoral Science Foundation(2021 M702073)support from the Program for Professors with Special Appointments(Eastern Scholar:TP2014041)at Shanghai Institutions of Higher Learning。
文摘Electrocatalysts are one of the essential components for the devices of high-efficiency green energy storage and conversion,such as metal-air cells,fuel cells,and water electrolysis systems.While catalysts made from noble metals possess high catalytic performance in both oxygen reduction reaction(ORR)and oxygen evolution reaction(OER),their scarcity and expensiveness significantly limit large-scale applications.In this regard,metal-free/non-noble metal carbon-based catalysts have become competitive alternatives to replace catalysts made of noble metals.Nevertheless,low catalytic ORR/OER performance is the challenge of carbon-based catalysts for the commercial applications of metal-air batteries.To solve the problem of poor catalytic performance,two strategies have been proposed:(1)controlling the microstructure of the catalysts to expose more active sites as the channels of rapid mass and electron transfer;and(2)reducing the reaction energy barrier by optimizing the electronic structures of the catalysts via surface engineering.Here,we review different types of bifunctional ORR/OER electrocatalysts with the activated surface sites.We focus on how the challenge can be overcome with different methods of material synthesis,structural and surface characterization,performance validation/optimization,to outline the principles of surface modifications behind catalyst designs.In particular,we provide critical analysis in the challenges that we are facing in structural design and surface engineering of bifunctional ORR/OER catalysts and indicate the possible solution for these problems,providing the society with clearer ideas on the practical prospects of noble-metal-free electrocatalysts for their future applications.
基金We thank the Beijing Municipal Commission of Education(No.JC015001200902)the Beijing Municipal Natural Science Foundation(Nos.710201,2122008)+1 种基金the Basic Research Foundation of Beijing University of Technology(No.X4015001201101)the Funding Project for Academic Human Resources Development in Institutions of Higher Learning under the Jurisdiction of Beijing Municipality(No.PHR201008025)and the Doctoral Scientific Research Start-up Foundation of Beijing University of Technology(No.52015001200701)for financial supports.
文摘In this work,six novel axially unfixed biaryl-based water-compatible bifunctional organocatalysts were de-signed and synthesized for the organocatalytic access to a variety of 3-alkyl-3-hydroxy-2-oxindole derivatives via aldol reactions in water.Organocatalyzed by 5a,the direct aldol reactions of isatins with enolisable ketones under-went readily in water,furnishing the structurally diverse 3-alkyl-3-hydroxy-2-oxindoles in various stereoselectivi-ties(up to>99%dr and>99%ee).Moreover,a plausible transition state of the conducted aldol reactions was hy-pothesized to shed light on the observed stereoselectivities of the obtained 3-alkyl-3-hydroxy-2-oxindoles.
文摘随着人类社会的高速发展,在保证环境不被破坏的情况下维持众多机械和电气设备的正常运转急需清洁的能源方式。氢被认为是在未来最有前景的清洁能源之一。近期,电化学水分解已被认为是获取氢能的最有效的方法之一,它的燃料产物只是无污染的水;然而,迟缓的析氧反应严重制约了水分解效率,导致驱动水分解的电压相对较高。探求热力学有利的阳极反应以取代缓慢的氧析出和开发高活性双功能型电催化剂用于这种阳极反应和析氢对于实现可应用于工业的节能型产氢至关重要。当前,普遍认为用其他有用的且利于热力学的反应取代析氧反应可以减小分解电压从而实现节能产氢。本文报道了一种用于甲醇氧化和析氢的双功能型嵌入镍纳米粒子的碳棱柱状微米棒电催化剂(命名为镍碳微米棒),该催化剂是由74号金属有机框架结构经碳化处理获得。这种由镍和碳构成的界面材料结构通过原位碳化实现,由于碳的分隔作用,分散的镍纳米颗粒不会轻易团聚,这有利于暴露更多的镍活性位点与电解液相接触,为更快的催化剂和电解液间电荷转移和电化学动力学提供保障。在此阳极的甲醇氧化中,产物分别为二氧化碳和甲酸,两者在1.55 V电压下的法拉第效率分别为36.2%和62.5%;同时该镍碳微米棒催化剂表现出优异的甲醇氧化活性和耐久性(12 h持续性催化,电流仅衰退2.7%)。值得注意的是,该双功能催化剂不仅具有甲醇氧化活性,在室温下含有0.5mol·L^(-1)甲醇的1.0mol·L^(-1)氢氧化钾电解液中的析氢过电位也较低(仅155 m V的过电位即可驱动10 m A·cm^(-2)的电流),保证了产氢效率。更重要的是,采用这种双功能型电极构造的双电极电解槽仅需1.6 V电压即可驱动10 m A·cm^(-2)的电流,与析氧反应作为阳极反应的电解槽相比驱动电压减小了240 mV。
文摘通过探究催化转移氢化(catalytic transfer hydrogenation,CTH)使高含氧量生物质加氢脱氧为高值平台分子的新策略,以实现生物质的资源化与利用和达成生产净零碳排放燃料的目标。文中以Zr/Hf金属氧化物非均相催化体系设计、构筑及性能调控为基本思路,以乙酰丙酸、糠醛、5-羟甲基糠醛及γ-戊内酯等重要生物质平台分子的可控定向转化为主线,重点评估了催化剂结构对应的酸碱活性位点在Meerwein-Ponndorf-Verley(MPV)反应中的关键作用,探讨并展望了Zr/Hf酸碱双功能催化剂在生物质平台分子转化为高值化学品领域的发展前景。本研究不仅对催化剂活性位点(Lewis/Br?nsted酸和碱)在相应生物质转化过程中的反应机理做出了归纳和总结,并且提出了兼顾经济效益和环境影响的新型固体酸催化剂的设计思路和策略。
基金supported by the Beijing Natural Science Foundation (2222004)。
文摘The recharged zinc-air battery(ZAB) has drawn significant attention owing to increasing requirement for energy conversion and storage devices.Fabricating the efficient bifunctional oxygen catalyst using a convenient strategy is vitally important for the rechargeable ZAB.In this study,the bimetallic ZIFs-containing electrospun(ES) carbon nanofibers membrane with hierarchically porous structure was prepared by coaxial electrospinning and carbonization process,which was expected to be a bifunctional electrocatalyst for ZABs.Owing to the formed dual single-atomic sites of Co-N_(4) and Zn-N_(4),the obtained ES-Co/ZnCNZIFexhibited the preferable performance toward oxygen reduction reaction(ORR) with E1/2of 0.857 V and JLof 5.52 mA cm^(-2),which were more than Pt/C.Meanwhile,it exhibited a marked oxygen evolution reaction(OER) property with overpotential of 462 mV due to the agglomerated metallic Co nanoparticles.Furthermore,the ZAB based on the ES-Co/Zn-CNZIFcarbon nanofibers membranes delivered peak power density of 215 mW cm^(-2),specific capacity of 802.6 mA h g^(-1),and exceptional cycling stability,far larger than Pt/C+RuO_(2)-based ZABs.A solid-state ZAB based on ES-Co/Zn-CNZIFshowed better flexibility and stability with different bending angles.
基金the financial support provided by the National Natural Science Foundation of China(Nos.21572163 and 21873074)the Wenzhou Science&Technology Bureau(No.G20210032)。
文摘Nitrene transfer reactions are powerful tools in synthetic organic chemistry.In recent years,transitionmetal catalyzed nitrene transfer reactions with carbamates as the nitrene precursors have been widely pursued.Such species undergoes facile C-H amination,aziridination,and bifunctionalization of alkenes under the catalysis of different transition metals including Rh,Fe,Ru and others,enabling the efficient construction of various nitrogen-containing molecules.In this review,the recent developments in nitrene transfer reactions with carbamates via N-O bond cleavage were introduced based on different types of reaction,and the key mechanistic information and synthetic applications of the methodologies were discussed.
基金supported by the National Natural Science Foundation of China (91026007)the "Strategic Priority Research program" of the Chinese Academy of Sciences (XDA03010401,XDA03010403)
文摘Mesoporous silicas have a very attractive ability of sorption and enrichment of metal ions due to their huge surface area and facile functionalization by organic ligands. In this work, phosphonate-amino hifunctionalized mesoporous silica SBA-15 （PA-SBA-15） as U（VI） sorbent was fabricated through post-grafting method. The obtained mesoporous silica was character- ized by SEM, XRD, NMR and nitrogen sorption/desorption experiments, which revealed the existence of ordered mesoporous structure with uniform pore diameter and large surface area. The adsorptivity of PA-SBA-15 for U（VI） from aqueous solution was investigated using batch sorption technique under different experimental conditions. The preliminary results show that the U（VI） sorption by PA-SBA-15 is very quick with equilibrium time of less than 1 h, and the U（VI） uptake is as large as 373 mg/g at pH 5.5 under 95℃. The sorption isotherm has been successfully modeled by the Langmuir isotherm, suggesting a monolayer homogeneous sorption of U（VI） in PA-SBA-15. The sorption is pH-dependent due to the pH-dependent charge of sorbent in the aqueous solution. The thermodynamics research shows that the sorption is a feasible and endothermic process. Based on these results, PA-SBA-15 could be a promising solid phase sorbent for highly-efficient removal of U（VI） ions from waste water and enrichment of U（VI） from a solution at a very low level.
