MXenes,the most recent addition to the 2D material family,have attracted significant attention owing to their distinctive characteristics,including high surface area,conductivity,surface characteristics,mechanical str...MXenes,the most recent addition to the 2D material family,have attracted significant attention owing to their distinctive characteristics,including high surface area,conductivity,surface characteristics,mechanical strength,etc.This review begins by presenting MXenes,providing insights into their structural characteristics,synthesis methods,and surface functional groups.The review covers a thorough analysis of MXene surface properties,including surface chemistry and termination group impacts.The properties of MXenes are influenced by their synthesis,which can be fluorine-based or fluorinedependent.Fluorine-based synthesis techniques involve etching with fluorine-based reagents,mainly including HF or LiF/HCl,while fluorine-free methods include electrochemical etching,chemical vapor deposition(CVD),alkaline etching,Lewis acid-based etching,etc.These techniques result in the emergence of functional groups such as-F,-O,-OH,-Cl,etc.on the MXenes surface,depending on the synthesis method used.Properties of MXenes,such as electrical conductivity,electronic properties,catalytic activity,magnetic properties,mechanical strength,and chemical and thermal stability,are examined,and the role of functional groups in determining these properties is explored.The review delves into the diverse applications of MXenes,encompassing supercapacitors,battery materials,hydrogen storage,fuel cells,electromagnetic interference(EMI) shielding,pollutant removal,water purification,flexible electronics,sensors,additive manufacturing,catalysis,biomedical and healthcare fields,etc.Finally,this article outlines the challenges and opportunities in the current and future development of MXenes research,addressing various aspects such as synthesis scalability,etching challenges,and multifunctionality,and exploring novel applications.The review concludes with future prospects and conclusions envisioning the impact of MXenes on future technologies and innovation.展开更多
Transition metal carbides and nitrides(MXenes)are crystal nanomaterials with a number of surface functional groups such as fluorine,hydroxyl,and oxygen,which can be used as carriers for proteins and drugs.MXenes have ...Transition metal carbides and nitrides(MXenes)are crystal nanomaterials with a number of surface functional groups such as fluorine,hydroxyl,and oxygen,which can be used as carriers for proteins and drugs.MXenes have excellent biocompatibility,electrical conductivity,surface hydrophilicity,mechanical properties and easy surface modification.However,at present,the stability of most MXenes needs to be improved,and more synthesis methods need to be explored.MXenes are good substrates for nerve cell regeneration and nerve reconstruction,which have broad application prospects in the repair of nervous system injury.Regarding the application of MXenes in neuroscience,mainly at the cellular level,the long-term in vivo biosafety and effects also need to be further explored.This review focuses on the progress of using MXenes in nerve regeneration over the last few years;discussing preparation of MXenes and their biocompatibility with different cells as well as the regulation by MXenes of nerve cell regeneration in two-dimensional and three-dimensional environments in vitro.MXenes have great potential in regulating the proliferation,differentiation,and maturation of nerve cells and in promoting regeneration and recovery after nerve injury.In addition,this review also presents the main challenges during optimization processes,such as the preparation of stable MXenes and long-term in vivo biosafety,and further discusses future directions in neural tissue engineering.展开更多
MXenes are under the spotlight due to their versatile physicochemical characteristics. Since their discovery in 2011, significant advancements have been achieved in their synthesis and application sectors. However, th...MXenes are under the spotlight due to their versatile physicochemical characteristics. Since their discovery in 2011, significant advancements have been achieved in their synthesis and application sectors. However, the spontaneous oxidation of MXenes, which is critical to its processing and product lifespan, has gotten less attention due to its chemical complexity and poorly understood oxidation mechanism. This perspective focuses on the oxidation stability of MXenes and addresses the most recent advancements in understanding and the possible countermeasures to limit the spontaneous oxidation of MXenes. A section is dedicated to the presently accessible methods for monitoring oxidation, with a discussion on the debatable oxidation mechanism and coherently operating factors that contribute to the complexity of MXenes oxidation. The current potential solutions for mitigating MXenes oxidation and the existing challenges are also discussed with prospects to prolong MXene's shelf-life storage and expand their application scope.展开更多
Since the discovery in 2011,MXenes have become the rising star in the field of two-dimensional materials.Benefiting from the metallic-level conductivity,large and adjustable gallery spacing,low ion diffusion barrier,r...Since the discovery in 2011,MXenes have become the rising star in the field of two-dimensional materials.Benefiting from the metallic-level conductivity,large and adjustable gallery spacing,low ion diffusion barrier,rich surface chemistry,superior mechanical strength,MXenes exhibit great application prospects in energy storage and conversion,sensors,optoelectronics,electromagnetic interference shielding and biomedicine.Nevertheless,two issues seriously deteriorate the further development of MXenes.One is the high experimental risk of common preparation methods such as HF etching,and the other is the difficulty in obtaining MXenes with controllable surface groups.Recently,Lewis acidic etching,as a brand-new preparation strategy for MXenes,has attracted intensive attention due to its high safety and the ability to endow MXenes with uniform terminations.However,a comprehensive review of Lewis acidic etching method has not been reported yet.Herein,we first introduce the Lewis acidic etching from the following four aspects:etching mechanism,terminations regulation,in-situ formed metals and delamination of multi-layered MXenes.Further,the applications of MXenes and MXene-based hybrids obtained by Lewis acidic etching route in energy storage and conversion,sensors and microwave absorption are carefully summarized.Finally,some challenges and opportunities of Lewis acidic etching strategy are also presented.展开更多
With an excellent power conversion efficiency of 25.7%,closer to the Shockley–Queisser limit,perovskite solar cells(PSCs)have become a strong candidate for a next-generation energy harvester.However,the lack of stabi...With an excellent power conversion efficiency of 25.7%,closer to the Shockley–Queisser limit,perovskite solar cells(PSCs)have become a strong candidate for a next-generation energy harvester.However,the lack of stability and reliability in PSCs remained challenging for commercialization.Strategies,such as interfacial and structural engineering,have a more critical influence on enhanced performance.MXenes,two-dimensional materials,have emerged as promising materials in solar cell applications due to their metallic electrical conductivity,high carrier mobility,excellent optical transparency,wide tunable work function,and superior mechanical properties.Owing to different choices of transition elements and surface-terminating functional groups,MXenes possess the feature of tuning the work function,which is an essential metric for band energy alignment between the absorber layer and the charge transport layers for charge carrier extraction and collection in PSCs.Furthermore,adopting MXenes to their respective components helps reduce the interfacial recombination resistance and provides smooth charge transfer paths,leading to enhanced conductivity and operational stability of PSCs.This review paper aims to provide an overview of the applications of MXenes as components,classified according to their roles as additives(into the perovskite absorber layer,charge transport layers,and electrodes)and themselves alone or as interfacial layers,and their significant importance in PSCs in terms of device performance and stability.Lastly,we discuss the present research status and future directions toward its use in PSCs.展开更多
Perovskite solar cells(PSCs)have been developed over the past decade as the forefront of the state-of-theart photovoltaic technologies owing to their high efficiency and low cost,where nanostructured functional materi...Perovskite solar cells(PSCs)have been developed over the past decade as the forefront of the state-of-theart photovoltaic technologies owing to their high efficiency and low cost,where nanostructured functional materials play key roles in performance optimization.As a versatile class of two-dimensional(2D)materials,transition metal carbides/nitrides MXenes have gained enormous attentions in PSCs since 2018 due to their superior properties such as excellent metallic conductivity,abundant surface functional groups,tunable work functions,high optical transparency,and mechanical robustness.The explorations of MXenes are of significance in performance promotion and commercialization expansion of devices.As such,this review focuses on the diversified advantages of MXenes,comprehensively summarizing their applications and developments in PSCs as additives,electron/hole transporting layers,interfacial engineering layers,and electrodes in sequence and explaining the relevant mechanisms behind.Simultaneously,the problems emerged from the related studies are considered and the corresponding suggestions like opening up the type of MXenes usage,taking further insight of the modulation of surface termination groups on Fermi levels,understanding the effect on energy level structures of perovskite or other functional layers,and realizing commercialization,etc.are provided for the future in-depth explorations.This review is intended to provide overall perspective of the current status of MXenes and highlight the direction for the future advancements in MXenes design and processes towards efficient,stable,large-area,and low-cost PSCs.展开更多
The artificial nitrogen(N_(2)) reduction reaction(NRR) via electrocatalysis is a newly developed methodology to produce ammonia(NH3) at ambient conditions,but faces the challenges in N_(2)activation and poor reaction ...The artificial nitrogen(N_(2)) reduction reaction(NRR) via electrocatalysis is a newly developed methodology to produce ammonia(NH3) at ambient conditions,but faces the challenges in N_(2)activation and poor reaction selectivity.Herein,Nb-based MXenes are developed to remarkably enhance the NRR activity through the engineering of the stretched 3D structure and oxygen vacancies(VO).The theoretical studies indicate that N_(2)could be initially adsorbed on VOwith an end-on configuration,and the potential determining step might be the first hydrogenation step.The catalysts achieve an NH3production rate of 29.1 μg h^(-1)mg_(cat)^(-1)and excellent Faradic efficiency of 11.5%,surpassing other Nbbased catalysts.The selectivity of NRR is assigned to the unique structure of the catalysts,including(1) the layered graphitic structure for fast electron transfer and active site distribution,(2) the reactive VOfor N_(2)adsorption and activation,and(3) the expanded interlayer space for mass transfer.展开更多
基金supported by the National Research Foundation of Korea(NRF)grant funded by the Korean government(MSIT)(NRF-2020R1A6A1A03043435 and 2020R1A2C1099862)supported by the Korea Institute for Advancement of Technology(KIAT)grant funded by the Korean Government(MOTIE)(P0012451,The Competency Development Program for Industry Specialist)。
文摘MXenes,the most recent addition to the 2D material family,have attracted significant attention owing to their distinctive characteristics,including high surface area,conductivity,surface characteristics,mechanical strength,etc.This review begins by presenting MXenes,providing insights into their structural characteristics,synthesis methods,and surface functional groups.The review covers a thorough analysis of MXene surface properties,including surface chemistry and termination group impacts.The properties of MXenes are influenced by their synthesis,which can be fluorine-based or fluorinedependent.Fluorine-based synthesis techniques involve etching with fluorine-based reagents,mainly including HF or LiF/HCl,while fluorine-free methods include electrochemical etching,chemical vapor deposition(CVD),alkaline etching,Lewis acid-based etching,etc.These techniques result in the emergence of functional groups such as-F,-O,-OH,-Cl,etc.on the MXenes surface,depending on the synthesis method used.Properties of MXenes,such as electrical conductivity,electronic properties,catalytic activity,magnetic properties,mechanical strength,and chemical and thermal stability,are examined,and the role of functional groups in determining these properties is explored.The review delves into the diverse applications of MXenes,encompassing supercapacitors,battery materials,hydrogen storage,fuel cells,electromagnetic interference(EMI) shielding,pollutant removal,water purification,flexible electronics,sensors,additive manufacturing,catalysis,biomedical and healthcare fields,etc.Finally,this article outlines the challenges and opportunities in the current and future development of MXenes research,addressing various aspects such as synthesis scalability,etching challenges,and multifunctionality,and exploring novel applications.The review concludes with future prospects and conclusions envisioning the impact of MXenes on future technologies and innovation.
基金supported by grants from the National Key R&D Program of China,Nos.2021YFA1101300,2021YFA1101803,2020YFA0112503the National Natural Science Foundation of China,Nos.82030029,81970882,92149304Science and Technology Department of Sichuan Province,No.2021YFS0371(all to RC)。
文摘Transition metal carbides and nitrides(MXenes)are crystal nanomaterials with a number of surface functional groups such as fluorine,hydroxyl,and oxygen,which can be used as carriers for proteins and drugs.MXenes have excellent biocompatibility,electrical conductivity,surface hydrophilicity,mechanical properties and easy surface modification.However,at present,the stability of most MXenes needs to be improved,and more synthesis methods need to be explored.MXenes are good substrates for nerve cell regeneration and nerve reconstruction,which have broad application prospects in the repair of nervous system injury.Regarding the application of MXenes in neuroscience,mainly at the cellular level,the long-term in vivo biosafety and effects also need to be further explored.This review focuses on the progress of using MXenes in nerve regeneration over the last few years;discussing preparation of MXenes and their biocompatibility with different cells as well as the regulation by MXenes of nerve cell regeneration in two-dimensional and three-dimensional environments in vitro.MXenes have great potential in regulating the proliferation,differentiation,and maturation of nerve cells and in promoting regeneration and recovery after nerve injury.In addition,this review also presents the main challenges during optimization processes,such as the preparation of stable MXenes and long-term in vivo biosafety,and further discusses future directions in neural tissue engineering.
基金financial support by the National Natural Science Foundation of China (Grant No. U2004212 and 51802012)。
文摘MXenes are under the spotlight due to their versatile physicochemical characteristics. Since their discovery in 2011, significant advancements have been achieved in their synthesis and application sectors. However, the spontaneous oxidation of MXenes, which is critical to its processing and product lifespan, has gotten less attention due to its chemical complexity and poorly understood oxidation mechanism. This perspective focuses on the oxidation stability of MXenes and addresses the most recent advancements in understanding and the possible countermeasures to limit the spontaneous oxidation of MXenes. A section is dedicated to the presently accessible methods for monitoring oxidation, with a discussion on the debatable oxidation mechanism and coherently operating factors that contribute to the complexity of MXenes oxidation. The current potential solutions for mitigating MXenes oxidation and the existing challenges are also discussed with prospects to prolong MXene's shelf-life storage and expand their application scope.
基金supported by the Highstar Corporation HSD20210118Taihu Electric Corporation 0001。
文摘Since the discovery in 2011,MXenes have become the rising star in the field of two-dimensional materials.Benefiting from the metallic-level conductivity,large and adjustable gallery spacing,low ion diffusion barrier,rich surface chemistry,superior mechanical strength,MXenes exhibit great application prospects in energy storage and conversion,sensors,optoelectronics,electromagnetic interference shielding and biomedicine.Nevertheless,two issues seriously deteriorate the further development of MXenes.One is the high experimental risk of common preparation methods such as HF etching,and the other is the difficulty in obtaining MXenes with controllable surface groups.Recently,Lewis acidic etching,as a brand-new preparation strategy for MXenes,has attracted intensive attention due to its high safety and the ability to endow MXenes with uniform terminations.However,a comprehensive review of Lewis acidic etching method has not been reported yet.Herein,we first introduce the Lewis acidic etching from the following four aspects:etching mechanism,terminations regulation,in-situ formed metals and delamination of multi-layered MXenes.Further,the applications of MXenes and MXene-based hybrids obtained by Lewis acidic etching route in energy storage and conversion,sensors and microwave absorption are carefully summarized.Finally,some challenges and opportunities of Lewis acidic etching strategy are also presented.
基金supported by the National Research Foundation of Korea(NRF)grant funded by the Korean government(MSIT)(No.2022M3J7A1062940 and 2022033777)supported by Korea Electric Power Corporation(Grant Number:R21XO01-5)+2 种基金supported by the Technology Innovation Program(or Industrial Strategic Technology Development Program)(1415172732/20011410,Development of SPD smart film and service of aftermarket for energy saving in building and automobiles)the Ministry of Trade,Industry&Energy(MOTIE,Korea)supported by Basic Science Research Program through the National Research Foundation of Korea(NRF)funded by the Ministry of Education(2018R1A6A1A03023788 and 2021R1I1A1A01055790).
文摘With an excellent power conversion efficiency of 25.7%,closer to the Shockley–Queisser limit,perovskite solar cells(PSCs)have become a strong candidate for a next-generation energy harvester.However,the lack of stability and reliability in PSCs remained challenging for commercialization.Strategies,such as interfacial and structural engineering,have a more critical influence on enhanced performance.MXenes,two-dimensional materials,have emerged as promising materials in solar cell applications due to their metallic electrical conductivity,high carrier mobility,excellent optical transparency,wide tunable work function,and superior mechanical properties.Owing to different choices of transition elements and surface-terminating functional groups,MXenes possess the feature of tuning the work function,which is an essential metric for band energy alignment between the absorber layer and the charge transport layers for charge carrier extraction and collection in PSCs.Furthermore,adopting MXenes to their respective components helps reduce the interfacial recombination resistance and provides smooth charge transfer paths,leading to enhanced conductivity and operational stability of PSCs.This review paper aims to provide an overview of the applications of MXenes as components,classified according to their roles as additives(into the perovskite absorber layer,charge transport layers,and electrodes)and themselves alone or as interfacial layers,and their significant importance in PSCs in terms of device performance and stability.Lastly,we discuss the present research status and future directions toward its use in PSCs.
基金supported by the National Key R&D Program of China (2021YFA0716404)the National Natural Science Foundation of China (51872043,51732003,11974129)+1 种基金the“111”project (B13013)the Jilin Province Development and Reform Commission (2022C040-1)。
文摘Perovskite solar cells(PSCs)have been developed over the past decade as the forefront of the state-of-theart photovoltaic technologies owing to their high efficiency and low cost,where nanostructured functional materials play key roles in performance optimization.As a versatile class of two-dimensional(2D)materials,transition metal carbides/nitrides MXenes have gained enormous attentions in PSCs since 2018 due to their superior properties such as excellent metallic conductivity,abundant surface functional groups,tunable work functions,high optical transparency,and mechanical robustness.The explorations of MXenes are of significance in performance promotion and commercialization expansion of devices.As such,this review focuses on the diversified advantages of MXenes,comprehensively summarizing their applications and developments in PSCs as additives,electron/hole transporting layers,interfacial engineering layers,and electrodes in sequence and explaining the relevant mechanisms behind.Simultaneously,the problems emerged from the related studies are considered and the corresponding suggestions like opening up the type of MXenes usage,taking further insight of the modulation of surface termination groups on Fermi levels,understanding the effect on energy level structures of perovskite or other functional layers,and realizing commercialization,etc.are provided for the future in-depth explorations.This review is intended to provide overall perspective of the current status of MXenes and highlight the direction for the future advancements in MXenes design and processes towards efficient,stable,large-area,and low-cost PSCs.
基金financially supported by China Postdoctoral Science Foundation (2019M652305)Qingdao Postdoctoral Application Research Project。
文摘The artificial nitrogen(N_(2)) reduction reaction(NRR) via electrocatalysis is a newly developed methodology to produce ammonia(NH3) at ambient conditions,but faces the challenges in N_(2)activation and poor reaction selectivity.Herein,Nb-based MXenes are developed to remarkably enhance the NRR activity through the engineering of the stretched 3D structure and oxygen vacancies(VO).The theoretical studies indicate that N_(2)could be initially adsorbed on VOwith an end-on configuration,and the potential determining step might be the first hydrogenation step.The catalysts achieve an NH3production rate of 29.1 μg h^(-1)mg_(cat)^(-1)and excellent Faradic efficiency of 11.5%,surpassing other Nbbased catalysts.The selectivity of NRR is assigned to the unique structure of the catalysts,including(1) the layered graphitic structure for fast electron transfer and active site distribution,(2) the reactive VOfor N_(2)adsorption and activation,and(3) the expanded interlayer space for mass transfer.
