基于密度泛函理论的第一性原理计算,本文对单层1T-CoI_(2)的原子、电子结构和磁性进行了理论研究.使用广义布洛赫条件结合自旋螺旋方法计算了单层1T-CoI_(2)自旋螺旋的能量色散关系E(q),计算结果表明单层1T-CoI_(2)的基态呈现螺旋反铁磁...基于密度泛函理论的第一性原理计算,本文对单层1T-CoI_(2)的原子、电子结构和磁性进行了理论研究.使用广义布洛赫条件结合自旋螺旋方法计算了单层1T-CoI_(2)自旋螺旋的能量色散关系E(q),计算结果表明单层1T-CoI_(2)的基态呈现螺旋反铁磁,体系中含有键相关的各向异性作用,即Kitaev作用.计算了含有自旋-轨道耦合作用(spin orbital coupling,SOC)和不含有SOC的色散关系,分别将色散关系映射到HeisenbergKitaev模型,成功分解了多近邻海森伯作用参数J、Kitaev作用的K和非对角项Γ.单层1T-CoI_(2)以Heisenberg作用为主导,同时存在着较强的Kitaev相互作用,其中Γ_(1)达到了1.09 meV.可预测Kitaev作用在具有1T结构过渡金属三角格子中具有普遍适用性,表明单层1T-CoI_(2)是Kitaev的备选材料,并且为探索其他二维磁性材料的Kitaev作用奠定了理论基础.展开更多
Controlled synthesis of transition metal dichalcogenide (TMD) monolayers with unusual crystal phases has attracted increasing attention due to their promising applications in electrocatalysis.However,the facile and la...Controlled synthesis of transition metal dichalcogenide (TMD) monolayers with unusual crystal phases has attracted increasing attention due to their promising applications in electrocatalysis.However,the facile and large-scale preparation of TMD monolayers with high-concentration unusual crystal phase still remains a challenge.Herein,we report the synthesis of MoX2 (X =Se or S) monolayers with high-concentration semimetallic 1T'phase by using the 4H/face-centered cubic (fcc)-Au nanorod as template to form the 4H/fcc-Au@MoX2 nanocomposite.The concentrations of 1T'phase in the prepared MoSe2 and MoS2 monolayers are up to 86% and 81%,respectively.As a proof-of-concept application,the obtained Au@MoS2 nanocomposite is used for the electrocatalytic hydrogen evolution reaction (HER) in acid medium,exhibiting excellent performance with a low overpotential of 178 mV at the current density of 10 mNcm^2,a small Tafel slope of 43.3 mV/dec,and excellent HER stability.This work paves a way for direct synthesis of TMD monolayers with high-concentration of unusual crystal phase for the electrocatalytic application.展开更多
The isostructural and isoelectronic transition-metal-dichalcogenides 1T-TaS2 and 1T-TaSe2 are layered materials with intricate electronic structures.Combining the molecular beam epitaxy growth,scanning tunneling micro...The isostructural and isoelectronic transition-metal-dichalcogenides 1T-TaS2 and 1T-TaSe2 are layered materials with intricate electronic structures.Combining the molecular beam epitaxy growth,scanning tunneling microscopy measurements and first-principles calculations,we prepare monolayer 1T-TaS2 and TaSe2 and explore their electronic structures at the atomic scale.Both two-dimensional(2D)compounds exhibit commensurate charge density wave phase at low temperature.The conductance mapping identifies the contributions from different Ta atoms to the local density of states with spatial and energy resolution.Both 1T-TaS2 and 1T-TaSe2 monolayer are shown to be insulators,while the former has a Mott gap and the latter is a regular band insulator.展开更多
MXene is a variety of new two-dimensional(2D)materials with early transition metal carbides,nitrides,and carbonitrides.Quantum chemical studies have been carried out on the geometries,electronic structures,stability a...MXene is a variety of new two-dimensional(2D)materials with early transition metal carbides,nitrides,and carbonitrides.Quantum chemical studies have been carried out on the geometries,electronic structures,stability and catalytic properties of a non-noble metal single-atom catalyst(SAC)with single Co atom anchored on MXene materials of Mo_(2)CS_(2).The Co adatom anchored on top of the Mo atom of this MXene is found to be rather stable,and this SAC is appropriate for CO oxidation.The charge transfers from the surface to the adsorbed CO and O2 play a significant role in the activation of these molecules on Co_(1)/Mo_(2)CS_(2).With this catalyst,the Eley-Rideal(ER),Langmuir-Hinshelwood(LH),and Termolecular Eley-Rideal(TER)mechanisms are explored for CO oxidation.We find that,while all the three mechanisms are feasible at low temperature,Co_(1)/Mo_(2)CS_(2) possesses higher catalytic activity for CO oxidation through the TER mechanism that features an intriguing OC(OO)CO intermediate(IM)adsorbed on Co single atom.The calculated activation energy barriers of the rate-limiting step are 0.67 eV(TER),0.78 eV(LH)and 0.88 eV(ER),respectively.The present study illustrates that it is promising to develop and design low-cost,non-noble metal SACs using MXene types of 2D materials.展开更多
Finding transition metal catalysts for effective catalytic conversion of CO to CO_(2)has attracted much attention.MXene as a new 2D layered material of early transition metal carbides,nitrides,and carbo-nitrides is a ...Finding transition metal catalysts for effective catalytic conversion of CO to CO_(2)has attracted much attention.MXene as a new 2D layered material of early transition metal carbides,nitrides,and carbo-nitrides is a robust support for achoring metal atoms.In this study,the electronic structure,geometries,thermodynamic stability,and catalytic activity of MXene (Mo_(2)CS_(2)) supported single noble metal atoms (NM=Ru,Rh,Pd,Ir,Pt and Au) have been systematically examined using first-principles calculations and ab initio molecular dynamic (AIMD) simulations.First,AIMD simulations and phonon spectra demonstrate the dynamic and thermal stabilities of Mo_(2)CS_(2)monolayer.Three likely reaction pathways,LangmuirHinshelwood (LH),Eley-Rideal (ER),and Termolecular Eley–Rideal (TER) for CO oxidation on the Ru1-and Ir_(1)@Mo_(2)CS_(2)SACs,have been studied in detail.It is found that CO oxidation mainly proceeds via the TER mechanism under mild reaction conditions.The corresponding rate-determining steps are the dissociation of the intermediate (OCO-Ru_(1)-OCO) and formation of OCO-Ir_(1)-OCO intermediate.The downshift d-band center of Ru1-and Ir_(1)@Mo_(2)CS_(2)help to enhance activity and improve catalytst stability.Moreover,a microkinetic study predicts a maximum CO oxidation rate of 4.01×10^(2)s^(-1)and 4.15×10^(3)s^(-1)(298.15K) following the TER pathway for the Ru_(1)-and Ir_(1)@Mo_(2)CS_(2)catalysts,respectively.This work provides guideline for fabricating and designing highly efficient SACs with superb catalyts using MXene materials.展开更多
Main observation and conclusion Inspired by the nitrogen fixation process on MoFe nitrogenase,asymmetrical coordinated Fe grafted onto 1T MoS_(2) were successfully synthesized.The unique electron-rich structure with a...Main observation and conclusion Inspired by the nitrogen fixation process on MoFe nitrogenase,asymmetrical coordinated Fe grafted onto 1T MoS_(2) were successfully synthesized.The unique electron-rich structure with asymmetrical coordination made the 1T Fe_(0.1)Mo_(0.9)S_(2) layered material actively react with water and dinitrogen at room temperature and atmosphere pressure.展开更多
文摘基于密度泛函理论的第一性原理计算,本文对单层1T-CoI_(2)的原子、电子结构和磁性进行了理论研究.使用广义布洛赫条件结合自旋螺旋方法计算了单层1T-CoI_(2)自旋螺旋的能量色散关系E(q),计算结果表明单层1T-CoI_(2)的基态呈现螺旋反铁磁,体系中含有键相关的各向异性作用,即Kitaev作用.计算了含有自旋-轨道耦合作用(spin orbital coupling,SOC)和不含有SOC的色散关系,分别将色散关系映射到HeisenbergKitaev模型,成功分解了多近邻海森伯作用参数J、Kitaev作用的K和非对角项Γ.单层1T-CoI_(2)以Heisenberg作用为主导,同时存在着较强的Kitaev相互作用,其中Γ_(1)达到了1.09 meV.可预测Kitaev作用在具有1T结构过渡金属三角格子中具有普遍适用性,表明单层1T-CoI_(2)是Kitaev的备选材料,并且为探索其他二维磁性材料的Kitaev作用奠定了理论基础.
文摘Controlled synthesis of transition metal dichalcogenide (TMD) monolayers with unusual crystal phases has attracted increasing attention due to their promising applications in electrocatalysis.However,the facile and large-scale preparation of TMD monolayers with high-concentration unusual crystal phase still remains a challenge.Herein,we report the synthesis of MoX2 (X =Se or S) monolayers with high-concentration semimetallic 1T'phase by using the 4H/face-centered cubic (fcc)-Au nanorod as template to form the 4H/fcc-Au@MoX2 nanocomposite.The concentrations of 1T'phase in the prepared MoSe2 and MoS2 monolayers are up to 86% and 81%,respectively.As a proof-of-concept application,the obtained Au@MoS2 nanocomposite is used for the electrocatalytic hydrogen evolution reaction (HER) in acid medium,exhibiting excellent performance with a low overpotential of 178 mV at the current density of 10 mNcm^2,a small Tafel slope of 43.3 mV/dec,and excellent HER stability.This work paves a way for direct synthesis of TMD monolayers with high-concentration of unusual crystal phase for the electrocatalytic application.
基金supported by the National Natural Science Foundation of China(Nos.11874233,11622433,and 11574175)the Ministry of Science and Technology of China(Nos.2016YFA0301002 and 2018YFA0305603).
文摘The isostructural and isoelectronic transition-metal-dichalcogenides 1T-TaS2 and 1T-TaSe2 are layered materials with intricate electronic structures.Combining the molecular beam epitaxy growth,scanning tunneling microscopy measurements and first-principles calculations,we prepare monolayer 1T-TaS2 and TaSe2 and explore their electronic structures at the atomic scale.Both two-dimensional(2D)compounds exhibit commensurate charge density wave phase at low temperature.The conductance mapping identifies the contributions from different Ta atoms to the local density of states with spatial and energy resolution.Both 1T-TaS2 and 1T-TaSe2 monolayer are shown to be insulators,while the former has a Mott gap and the latter is a regular band insulator.
基金the National Natural Science Foundation of China(21590792,91426302,and 21433005)Guangdong Provincial Key Laboratory of Catalysis(2020B121201002)+1 种基金the National Science Basic Research Program of Shaanxi Province(2019JM-226)the financial and technical support from the Research Center for Advanced Materials Science(RCAMS)at King Khalid University through the Grant(RCAMS/KKU/014-20)。
文摘MXene is a variety of new two-dimensional(2D)materials with early transition metal carbides,nitrides,and carbonitrides.Quantum chemical studies have been carried out on the geometries,electronic structures,stability and catalytic properties of a non-noble metal single-atom catalyst(SAC)with single Co atom anchored on MXene materials of Mo_(2)CS_(2).The Co adatom anchored on top of the Mo atom of this MXene is found to be rather stable,and this SAC is appropriate for CO oxidation.The charge transfers from the surface to the adsorbed CO and O2 play a significant role in the activation of these molecules on Co_(1)/Mo_(2)CS_(2).With this catalyst,the Eley-Rideal(ER),Langmuir-Hinshelwood(LH),and Termolecular Eley-Rideal(TER)mechanisms are explored for CO oxidation.We find that,while all the three mechanisms are feasible at low temperature,Co_(1)/Mo_(2)CS_(2) possesses higher catalytic activity for CO oxidation through the TER mechanism that features an intriguing OC(OO)CO intermediate(IM)adsorbed on Co single atom.The calculated activation energy barriers of the rate-limiting step are 0.67 eV(TER),0.78 eV(LH)and 0.88 eV(ER),respectively.The present study illustrates that it is promising to develop and design low-cost,non-noble metal SACs using MXene types of 2D materials.
基金supported by the National Natural Science Foundation of China (Nos. 11874141 and 22033005)the Henan Overseas Expertise Introduction Center for Discipline Innovation (No. CXJD2019005)+1 种基金the Guangdong Provincial Key Laboratory of Catalysis (No. 2020B121201002)funding support from the Researchers Supporting Project number (No. RSP-2021/399), King Saud University, Riyadh, Saudi Arabia。
文摘Finding transition metal catalysts for effective catalytic conversion of CO to CO_(2)has attracted much attention.MXene as a new 2D layered material of early transition metal carbides,nitrides,and carbo-nitrides is a robust support for achoring metal atoms.In this study,the electronic structure,geometries,thermodynamic stability,and catalytic activity of MXene (Mo_(2)CS_(2)) supported single noble metal atoms (NM=Ru,Rh,Pd,Ir,Pt and Au) have been systematically examined using first-principles calculations and ab initio molecular dynamic (AIMD) simulations.First,AIMD simulations and phonon spectra demonstrate the dynamic and thermal stabilities of Mo_(2)CS_(2)monolayer.Three likely reaction pathways,LangmuirHinshelwood (LH),Eley-Rideal (ER),and Termolecular Eley–Rideal (TER) for CO oxidation on the Ru1-and Ir_(1)@Mo_(2)CS_(2)SACs,have been studied in detail.It is found that CO oxidation mainly proceeds via the TER mechanism under mild reaction conditions.The corresponding rate-determining steps are the dissociation of the intermediate (OCO-Ru_(1)-OCO) and formation of OCO-Ir_(1)-OCO intermediate.The downshift d-band center of Ru1-and Ir_(1)@Mo_(2)CS_(2)help to enhance activity and improve catalytst stability.Moreover,a microkinetic study predicts a maximum CO oxidation rate of 4.01×10^(2)s^(-1)and 4.15×10^(3)s^(-1)(298.15K) following the TER pathway for the Ru_(1)-and Ir_(1)@Mo_(2)CS_(2)catalysts,respectively.This work provides guideline for fabricating and designing highly efficient SACs with superb catalyts using MXene materials.
基金The work was supported by the Science and Technology Commission of National Natural Science Foundation of China(Nos.21901156,21975148 and 21771124)the Shanghai Municipality(Nos.19JC1412600,18QA1402400 and 18230743400)+4 种基金Z.Feng thanks the startup funding from Oregon State University.The XAS measurements were done at 9-BM of Advanced Photon Source,which is a U.S.Department of Energy(DOE)Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No.DE-AC02-06CH11357.T.Cheng and H.Yang thanks the Natural Science Foundation of Jiangsu Province(Grant No.SBK20190810)the Jiangsu Province High-Level Talents(JNHB-106)the China Postdoctoral Science Foundation(No.2019M660128)the Collaborative Innova-tion Center of Suzhou Nano Science&Technology,the Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD)the 111 Project.
文摘Main observation and conclusion Inspired by the nitrogen fixation process on MoFe nitrogenase,asymmetrical coordinated Fe grafted onto 1T MoS_(2) were successfully synthesized.The unique electron-rich structure with asymmetrical coordination made the 1T Fe_(0.1)Mo_(0.9)S_(2) layered material actively react with water and dinitrogen at room temperature and atmosphere pressure.
基金supported by the National Key Research and Development Program of China(2018YFA0306800,2021YFA1400400,2018YFA0306200,and 2021YFA1202901)the National Natural Science Foundation of China(92165205,11790311,12004172,51861145201,52072168,21733001,and 91750101)+2 种基金the Innovation Program for Quantum Science and Technology for China(2021ZD0302803)the Jiangsu Planned Projects for Postdoctoral Research Funds(2020Z172)the Program of High-Level Entrepreneurial and Innovative Talents Introduction of Jiangsu Province,China。
