染料污染是水污染中最严重的问题之一,吸引了很多科学家的关注.人们尝试了很多方法去解决该问题,如化学氧化法、物理吸附法、光催化降解法和生物降解法等.与其他几种方法相比,光催化法有着低能耗、环保以及高效等优势.三氧化钨是常见的...染料污染是水污染中最严重的问题之一,吸引了很多科学家的关注.人们尝试了很多方法去解决该问题,如化学氧化法、物理吸附法、光催化降解法和生物降解法等.与其他几种方法相比,光催化法有着低能耗、环保以及高效等优势.三氧化钨是常见的半导体材料,具有独特的光学性能,近年来受到了广泛的研究.本文以钨酸钠和硫脲为前驱体,通过水热法制备了三氧化钨/氧化银(WO_3/Ag_2O)复合材料,并用光催化降解亚甲基蓝来分析其光催化性能.通过X射线光电子能谱、X射线衍射、透射电子显微镜、扫描电子显微镜、紫外可见吸收光谱等表征手段对样品的形貌、晶格结构和光催化的性能进行表征.氧化银的带宽为1.2 e V,对可见光很敏感,三氧化钨和氧化银的复合使材料在可见光下的光催化活性显著增强,在可见光下对亚甲基蓝染料的光降解率可以达到98%.实验结果表明,复合材料中的三氧化钨纳米棒为六方相,其平均直径约为200 nm,平均长度约为4μm.而复合材料中的氧化银纳米颗粒为六方相,附着在氧化钨纳米棒的表面,平均晶粒尺寸为20 nm.氧化银的存在为复合材料提供了更多的反应活性位点.相较于单一组分,复合材料在可见光下的光吸收度更高,这说明三氧化钨和氧化银的复合改变了材料的能带结构.研究发现,三氧化钨和氧化银之间形成的异质结构是其优良光催化性能的来源.此外,三氧化钨和氧化银复合材料还具有良好的催化稳定性和化学稳定性.本文结果表明,可以通过给宽带隙的半导体材料复合一些带隙合适的金属氧化物以提升其光催化活性.展开更多
开发经济高效的析氧反应电催化剂对于推进可充电金属-空气电池和电解水技术的发展至关重要.一般来说,具有完整蜂窝结构的石墨碳基面是电化学惰性的,需要依赖缺陷或者掺杂结构诱导的电荷极化效应来提升催化活性.相比于基面,边缘位点具有...开发经济高效的析氧反应电催化剂对于推进可充电金属-空气电池和电解水技术的发展至关重要.一般来说,具有完整蜂窝结构的石墨碳基面是电化学惰性的,需要依赖缺陷或者掺杂结构诱导的电荷极化效应来提升催化活性.相比于基面,边缘位点具有特殊的局域电子态,为提升石墨碳电极的本征催化活性开辟了新的思路,然而其结构精准构筑目前仍面临极大挑战.本文以“人字形”多壁碳纳米管(H-MWCNTs)作为研究切入点,利用高温熔盐介质主导的插层剥离和截断效应,实现“边缘-平面位点”结构可控构筑,为实现高效电解水析氧反应(OER)提供了重要的结构基础.通过熔盐辅助热解方法可控制备了具有完全暴露的内外边缘平面的目标催化剂H-MWCNTs-MS,并研究其OER催化性能.在碱性介质中10 mA cm^(-2)电流密度所需过电位仅为236 mV,是目前报道的较好的非金属电催化剂.同时,H-MWCNTs-MS在10,50和100 mA cm^(-2)电流密度下均表现出较好的电化学稳定性.利用原位衰减全反射-表面增强红外吸收光谱(ATR-SEIRAS)技术研究了“边缘-平面位点”在OER过程中的结构重构过程,与理论计算分析的高能“边缘态”结果一致,并确定酮氧官能化位点为真实催化活性中心.理论计算结果表明,氧官能团修饰结构能够显著促进电荷的再分配,增强层间耦合作用,降低关键含氧中间体*OOH的形成能垒,加速OER反应动力学.此外,H-MWCNTs-MS的开放式结构极大程度提高了“边缘-平面位点”的利用率,减小的纳米管壁厚促进了层间电荷迁移,也是增强OER活性的关键要素.综上,精准构筑“边缘-平面位点”为开发高效石墨碳电极开辟了新的思路,通过原位谱学技术揭示边缘位点催化结构重构,能够进一步丰富研究者对于电催化协同效应的科学认识.展开更多
本文利用原子级扫描透射电子显微术(scanning transmission electron microscopy,STEM)研究了PtS_(2)在连续Ar等离子体作用下其表面S原子不断缺失并导致相转变的过程。实验发现随着S原子占比的减小,层状1T相PtS_(2)以逐层非晶化的方式...本文利用原子级扫描透射电子显微术(scanning transmission electron microscopy,STEM)研究了PtS_(2)在连续Ar等离子体作用下其表面S原子不断缺失并导致相转变的过程。实验发现随着S原子占比的减小,层状1T相PtS_(2)以逐层非晶化的方式转变为无定形非晶相PtS_(x)(x<2),并且基于径向分布函数(radial distribution function,RDF)分析定量提取了最邻近Pt-Pt、Pt-S、S-S原子对的分布概率。随着S原子占比的继续减小,表面非晶相PtSx最终转变为单晶Pt,结合电子能量损失谱(electron energy loss spectroscopy,EELS)与STEM原子序数衬度图像分析表明,Pt原子以(111)面心立方密堆的方式堆垛,形成少层甚至单层Pt晶畴。展开更多
Titanium dioxide(TiO2) has gained burgeoning attention for potassium-ion storage because of its large theoretical capacity,wide availability,and environmental benignity.Nevertheless,the inherently poor conductivity gi...Titanium dioxide(TiO2) has gained burgeoning attention for potassium-ion storage because of its large theoretical capacity,wide availability,and environmental benignity.Nevertheless,the inherently poor conductivity gives rise to its sluggish reaction kinetics and inferior rate capability.Here,we report the direct graphene growth over TiO2 nanotubes by virtue of chemical vapor deposition.Such conformal graphene coatings effectively enhance the conductive environment and well accommodate the volume change of TiO2 upon potassiation/depotassiation.When paired with an activated carbon cathode,the graphene-armored TiO2 nanotubes allow the potassium-ion hybrid capacitor full cells to harvest an energy/power density of 81.2 Wh kg-1/3746.6 W kg-1.We further employ in situ transmis sion electron microscopy and ope rando X-ray diffraction to probe the potassium-ion storage behavior.This work offers a viable and versatile solution to the anode design and in situ probing of potassium storage technologies that is readily promising for practical applications.展开更多
Mechanical strain can induce noteworthy structural and electronic changes in vanadium dioxide, imparting substantial scientific importance to both the exploration of phase transitions and the development of potential ...Mechanical strain can induce noteworthy structural and electronic changes in vanadium dioxide, imparting substantial scientific importance to both the exploration of phase transitions and the development of potential technological applications. Unlike the traditional rutile(R) phase, bronze-phase vanadium dioxide [VO_(2)(B)] exhibits an in-plane anisotropic structure. When subjected to stretching along distinct crystallographic axes, VO_(2)(B) may further manifest the axial dependence in lattice–electron interactions, which is beneficial for gaining insights into the anisotropy of electronic transport.Here, we report an anisotropic room-temperature metal–insulator transition in single-crystal VO_(2)(B) by applying in-situ uniaxial tensile strain. This material exhibits significantly different electromechanical responses along two anisotropic axes.We reveal that such an anisotropic electromechanical response mainly arises from the preferential arrangement of a straininduced unidirectional stripe state in the conductive channel. This insulating stripe state could be attributed to the in-plane dimerization within the distorted zigzag chains of vanadium atoms, evidenced by strain-modulated Raman spectra. Our work may open up a promising avenue for exploiting the anisotropy of metal–insulator transition in vanadium dioxide for potential technological applications.展开更多
Detecting tiny deformations or vibrations, particularly those associated with strains below 1%, is essential in various technological applications. Traditional intrinsic materials, including metals and semiconductors,...Detecting tiny deformations or vibrations, particularly those associated with strains below 1%, is essential in various technological applications. Traditional intrinsic materials, including metals and semiconductors, face challenges in simultaneously achieving initial metallic state and strain-induced insulating state, hindering the development of highly sensitive mechanical sensors. Here we report an ultrasensitive mechanical sensor based on a strain-induced tunable ordered array of metallic and insulating states in the single-crystal bronze-phase vanadium dioxide [VO_(2)(B)] quantum material. It is shown that the initial metallic state in the VO_(2)(B) flake can be tuned to the insulating state by applying a weak uniaxial tensile strain. Such a unique property gives rise to a record-high gauge factor of above 607970, surpassing previous values by an order of magnitude, with excellent linearity and mechanical resilience as well as durability. As a proof-of-concept application, we use our proposed mechanical sensor to demonstrate precise sensing of the micro piece, gentle airflows and water droplets. We attribute the superior performance of the sensor to the strain-induced continuous metal-insulator transition in the single-crystal VO_(2)(B) flake, evidenced by experimental and simulation results. Our findings highlight the potential of exploiting correlated quantum materials for next-generation ultrasensitive flexible mechanical sensors, addressing critical limitations in traditional materials.展开更多
Poor cycling stability in lithium–sulfur(Li–S)batteries necessitates advanced electrode/electrolyte design and innovative interlayer architectures.Heterogeneous catalysis has emerged as a promising approach,leveragi...Poor cycling stability in lithium–sulfur(Li–S)batteries necessitates advanced electrode/electrolyte design and innovative interlayer architectures.Heterogeneous catalysis has emerged as a promising approach,leveraging the adsorption and catalytic performance on lithium polysulfides(LiPSs)to inhibit LiPSs shuttling and improve redox kinetics.In this study,we report an ultrathin and laminar SnO_(2)@MXene heterostructure interlayer(SnO_(2)@MX),where SnO_(2) quantum dots(QDs)are uniformly distributed across the MXene layer.The combined structure of SnO_(2) QDs and MXene,along with the creation of numerous active boundary sites with coordination electron environments,plays a critical role in manipulating the catalytic kinetics of sulfur species.The Li–S cell with the SnO_(2)@MX-modified separator not only demonstrates superior electrochemical performance compared to cells with a bare separator but also induces homogeneous Li deposition during cycling.As a result,an areal capacity of 7.6 mAh cm^(-2) under a sulfur loading of 7.5 mg cm^(-2) and a high stability over 500 cycles are achieved.Our work demonstrates a feasible strategy of utilizing a laminar separator interlayer for advanced Li–S batteries awaiting commercialization and may shed light on the understanding of heterostructure catalysis with enhanced reaction kinetics.展开更多
文摘染料污染是水污染中最严重的问题之一,吸引了很多科学家的关注.人们尝试了很多方法去解决该问题,如化学氧化法、物理吸附法、光催化降解法和生物降解法等.与其他几种方法相比,光催化法有着低能耗、环保以及高效等优势.三氧化钨是常见的半导体材料,具有独特的光学性能,近年来受到了广泛的研究.本文以钨酸钠和硫脲为前驱体,通过水热法制备了三氧化钨/氧化银(WO_3/Ag_2O)复合材料,并用光催化降解亚甲基蓝来分析其光催化性能.通过X射线光电子能谱、X射线衍射、透射电子显微镜、扫描电子显微镜、紫外可见吸收光谱等表征手段对样品的形貌、晶格结构和光催化的性能进行表征.氧化银的带宽为1.2 e V,对可见光很敏感,三氧化钨和氧化银的复合使材料在可见光下的光催化活性显著增强,在可见光下对亚甲基蓝染料的光降解率可以达到98%.实验结果表明,复合材料中的三氧化钨纳米棒为六方相,其平均直径约为200 nm,平均长度约为4μm.而复合材料中的氧化银纳米颗粒为六方相,附着在氧化钨纳米棒的表面,平均晶粒尺寸为20 nm.氧化银的存在为复合材料提供了更多的反应活性位点.相较于单一组分,复合材料在可见光下的光吸收度更高,这说明三氧化钨和氧化银的复合改变了材料的能带结构.研究发现,三氧化钨和氧化银之间形成的异质结构是其优良光催化性能的来源.此外,三氧化钨和氧化银复合材料还具有良好的催化稳定性和化学稳定性.本文结果表明,可以通过给宽带隙的半导体材料复合一些带隙合适的金属氧化物以提升其光催化活性.
文摘开发经济高效的析氧反应电催化剂对于推进可充电金属-空气电池和电解水技术的发展至关重要.一般来说,具有完整蜂窝结构的石墨碳基面是电化学惰性的,需要依赖缺陷或者掺杂结构诱导的电荷极化效应来提升催化活性.相比于基面,边缘位点具有特殊的局域电子态,为提升石墨碳电极的本征催化活性开辟了新的思路,然而其结构精准构筑目前仍面临极大挑战.本文以“人字形”多壁碳纳米管(H-MWCNTs)作为研究切入点,利用高温熔盐介质主导的插层剥离和截断效应,实现“边缘-平面位点”结构可控构筑,为实现高效电解水析氧反应(OER)提供了重要的结构基础.通过熔盐辅助热解方法可控制备了具有完全暴露的内外边缘平面的目标催化剂H-MWCNTs-MS,并研究其OER催化性能.在碱性介质中10 mA cm^(-2)电流密度所需过电位仅为236 mV,是目前报道的较好的非金属电催化剂.同时,H-MWCNTs-MS在10,50和100 mA cm^(-2)电流密度下均表现出较好的电化学稳定性.利用原位衰减全反射-表面增强红外吸收光谱(ATR-SEIRAS)技术研究了“边缘-平面位点”在OER过程中的结构重构过程,与理论计算分析的高能“边缘态”结果一致,并确定酮氧官能化位点为真实催化活性中心.理论计算结果表明,氧官能团修饰结构能够显著促进电荷的再分配,增强层间耦合作用,降低关键含氧中间体*OOH的形成能垒,加速OER反应动力学.此外,H-MWCNTs-MS的开放式结构极大程度提高了“边缘-平面位点”的利用率,减小的纳米管壁厚促进了层间电荷迁移,也是增强OER活性的关键要素.综上,精准构筑“边缘-平面位点”为开发高效石墨碳电极开辟了新的思路,通过原位谱学技术揭示边缘位点催化结构重构,能够进一步丰富研究者对于电催化协同效应的科学认识.
文摘本文利用原子级扫描透射电子显微术(scanning transmission electron microscopy,STEM)研究了PtS_(2)在连续Ar等离子体作用下其表面S原子不断缺失并导致相转变的过程。实验发现随着S原子占比的减小,层状1T相PtS_(2)以逐层非晶化的方式转变为无定形非晶相PtS_(x)(x<2),并且基于径向分布函数(radial distribution function,RDF)分析定量提取了最邻近Pt-Pt、Pt-S、S-S原子对的分布概率。随着S原子占比的继续减小,表面非晶相PtSx最终转变为单晶Pt,结合电子能量损失谱(electron energy loss spectroscopy,EELS)与STEM原子序数衬度图像分析表明,Pt原子以(111)面心立方密堆的方式堆垛,形成少层甚至单层Pt晶畴。
基金financially supported by the National Natural Science Foundation of China(51702225,11774051,61574034,51672007)the National Basic Research Program of China(No.2016YFA0200103)the Natural Science Foundation of Jiangsu Province(BK20170336)。
文摘Titanium dioxide(TiO2) has gained burgeoning attention for potassium-ion storage because of its large theoretical capacity,wide availability,and environmental benignity.Nevertheless,the inherently poor conductivity gives rise to its sluggish reaction kinetics and inferior rate capability.Here,we report the direct graphene growth over TiO2 nanotubes by virtue of chemical vapor deposition.Such conformal graphene coatings effectively enhance the conductive environment and well accommodate the volume change of TiO2 upon potassiation/depotassiation.When paired with an activated carbon cathode,the graphene-armored TiO2 nanotubes allow the potassium-ion hybrid capacitor full cells to harvest an energy/power density of 81.2 Wh kg-1/3746.6 W kg-1.We further employ in situ transmis sion electron microscopy and ope rando X-ray diffraction to probe the potassium-ion storage behavior.This work offers a viable and versatile solution to the anode design and in situ probing of potassium storage technologies that is readily promising for practical applications.
基金Project supported by the National Key R&D Program of China (Grant No. 2023YFF1203600)the National Natural Science Foundation of China (Grant Nos. 62122036, 62034004, 12322407, 61921005, and 12074176)+1 种基金the Strategic Priority Research Program of the Chinese Academy of Sciences (Grant No. XDB44000000)supported by the program for Outstanding Ph D Candidates of Nanjing University。
文摘Mechanical strain can induce noteworthy structural and electronic changes in vanadium dioxide, imparting substantial scientific importance to both the exploration of phase transitions and the development of potential technological applications. Unlike the traditional rutile(R) phase, bronze-phase vanadium dioxide [VO_(2)(B)] exhibits an in-plane anisotropic structure. When subjected to stretching along distinct crystallographic axes, VO_(2)(B) may further manifest the axial dependence in lattice–electron interactions, which is beneficial for gaining insights into the anisotropy of electronic transport.Here, we report an anisotropic room-temperature metal–insulator transition in single-crystal VO_(2)(B) by applying in-situ uniaxial tensile strain. This material exhibits significantly different electromechanical responses along two anisotropic axes.We reveal that such an anisotropic electromechanical response mainly arises from the preferential arrangement of a straininduced unidirectional stripe state in the conductive channel. This insulating stripe state could be attributed to the in-plane dimerization within the distorted zigzag chains of vanadium atoms, evidenced by strain-modulated Raman spectra. Our work may open up a promising avenue for exploiting the anisotropy of metal–insulator transition in vanadium dioxide for potential technological applications.
基金supported in part by the National Key R&D Program of China (Grant Nos.2023YFF1203600 and 2023YFF0718400)the National Natural Science Foundation of China (Grant Nos.62122036,12322407,62034004,61921005,and 12074176)+2 种基金the Leading-edge Technology Program of Jiangsu Natural Science Foundation (Grant No.BK20232004)the Strategic Priority Research Program of the Chinese Academy of Sciences (Grant No.XDB44000000)support from the AIQ Foundation and the eScience Center of Collaborative Innovation Center of Advanced Microstructures。
文摘Detecting tiny deformations or vibrations, particularly those associated with strains below 1%, is essential in various technological applications. Traditional intrinsic materials, including metals and semiconductors, face challenges in simultaneously achieving initial metallic state and strain-induced insulating state, hindering the development of highly sensitive mechanical sensors. Here we report an ultrasensitive mechanical sensor based on a strain-induced tunable ordered array of metallic and insulating states in the single-crystal bronze-phase vanadium dioxide [VO_(2)(B)] quantum material. It is shown that the initial metallic state in the VO_(2)(B) flake can be tuned to the insulating state by applying a weak uniaxial tensile strain. Such a unique property gives rise to a record-high gauge factor of above 607970, surpassing previous values by an order of magnitude, with excellent linearity and mechanical resilience as well as durability. As a proof-of-concept application, we use our proposed mechanical sensor to demonstrate precise sensing of the micro piece, gentle airflows and water droplets. We attribute the superior performance of the sensor to the strain-induced continuous metal-insulator transition in the single-crystal VO_(2)(B) flake, evidenced by experimental and simulation results. Our findings highlight the potential of exploiting correlated quantum materials for next-generation ultrasensitive flexible mechanical sensors, addressing critical limitations in traditional materials.
基金financial support from the Swiss National Science Foundation via the Southeast Asia–Europe Joint Funding Scheme 2020(Grant No.IZJFZ2_202476)funding from the National Natural Science Foundation of China(Grant Nos.22209118 and 00301054A1073)the Fundamental Research Funds for the Central Universities(Grant Nos.1082204112A26,20826044D3083,and 20822041G4080)。
文摘Poor cycling stability in lithium–sulfur(Li–S)batteries necessitates advanced electrode/electrolyte design and innovative interlayer architectures.Heterogeneous catalysis has emerged as a promising approach,leveraging the adsorption and catalytic performance on lithium polysulfides(LiPSs)to inhibit LiPSs shuttling and improve redox kinetics.In this study,we report an ultrathin and laminar SnO_(2)@MXene heterostructure interlayer(SnO_(2)@MX),where SnO_(2) quantum dots(QDs)are uniformly distributed across the MXene layer.The combined structure of SnO_(2) QDs and MXene,along with the creation of numerous active boundary sites with coordination electron environments,plays a critical role in manipulating the catalytic kinetics of sulfur species.The Li–S cell with the SnO_(2)@MX-modified separator not only demonstrates superior electrochemical performance compared to cells with a bare separator but also induces homogeneous Li deposition during cycling.As a result,an areal capacity of 7.6 mAh cm^(-2) under a sulfur loading of 7.5 mg cm^(-2) and a high stability over 500 cycles are achieved.Our work demonstrates a feasible strategy of utilizing a laminar separator interlayer for advanced Li–S batteries awaiting commercialization and may shed light on the understanding of heterostructure catalysis with enhanced reaction kinetics.
