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Pb induced dislocation defects of PtCo systems: strain-triggered oxygen reduction reaction for PEMFC

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Nano Research 2024年第4期17卷 2462-2472页

作者： Chun Jin Qiheng Wang Jingjun Liu Beijing Key Laboratory of Electrochemical Process and Technology for Materials Beijing 100029China Beijing University of Chemical Technology Beijing 100029China

Design and development of advanced electrocatalysts with high performance and low Pt consumption are crucial for reducing the kinetic energy barrier of the cathode oxygen reduction reaction(ORR)and improving the efficiency of proton exchange membrane fuel cells(PEMFC).In this study,we demonstrate a Pb-modulated PtCo system for efficient ORR,in which the inclusion of Pb in ternary alloys induces dislocation defects due to the significant difference in atomic radius.Dislocation-PtCoPb was confirmed to exhibit significantly higher ORR activity and stability in acidic ORR.In practical PEMFC applications,it outperforms the corresponding commercial Pt/C with a mass activity of 0.58 A·mgPt^(-1),making it a promising alternative to state-of-the-art Pt-based catalysts.The combination of experimental results and density functional theory(DFT)calculations offers valuable atomic-level insights into the dislocation structures.Pb with a larger atomic radius is located in the lattice stretching region below the dislocation slip plane,forming a structure similar to a Cottrell atmosphere,which reduces the dislocation energy and puts the system in a lower energy state.The Cottrell atmosphere pins the dislocation structure and stabilizes the ternary alloy.By adjusting the amount of added Pb,a moderate level of dislocation density induces a tuned strain effect,thereby enhancing the electrocatalytic mechanism by optimizing the electronic structure of the alloy surface and the adsorption and desorption of oxygen species.This work provides valuable insights into the design and development of lattice dislocation defect structures to trigger strain effects for improving ORR performance.

关键词： dislocation defect strain effect Pb-modulated oxygen reduction reaction

Atomscopic of ripple origins for two-dimensional monolayer transition metal dichalcogenides

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Nano Research 2024年第3期17卷 2136-2144页

作者： Haitao Yu Mingzi Sun Xiao Wu Cheuk Hei Chan Bolong Huang Zhong Lin Wang CAS Center for Excellence in Nanoscience Beijing Institute of Nanoenergy and NanosystemsChinese Academy of SciencesBeijing 100083China School of Nanoscience and Technology University of Chinese Academy of SciencesBeijing 100049China Department of Applied Biology and Chemical Technology The Hong Kong Polytechnic UniversityKowloon 999077Hong KongChina Research Centre for Carbon-Strategic Catalysis The Hong Kong Polytechnic UniversityKowloon 999077Hong KongChina School of Materials Science and Engineering Georgia Institute of TechnologyAtlantaGeorgia 30332USA

During the development of ultrathin two-dimensional(2D)materials,the appearance of ripples has been widely observed.However,the formation mechanisms and their influences are still rarely investigated,especially their contributions to the electronic structures and optical properties.To compensate for the knowledge gap,we have carried out comprehensive theoretical studies on the monolayer WSe_(2) with a series of ripple structures from 0 to 12Åin different lattice sizes.The sensitivity of the formation energy,band structures,electronic structures,and optical properties to the ripple structures have been performed systematically for the first time.The formation of ripples in Armchair and zigzag simultaneously are more energetically favorable,leading to more flexible optimizations of the optoelectronic properties.The improved charge-locking effect and extension of absorption ranges indicate the significant role of ripple structures.The spontaneous formation of ripples is associated with orbital rearrangements and structural distortions.This leads to the unique charge carrier correlate inversion between W-5d and Se-4p orbitals,resulting in the pinning of the Fermi level.This work has supplied significant references to understand ultrathin 2D structures and benefit their future developments and applications in high-performance optoelectronic devices.

关键词： two-dimensional(2D)materials ripples strain effect charge carrier correlation inversion optoelectronic properties

Anomalous strain effect on the thermal conductivity of low-buckled two-dimensional silicene

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National Science Review 2021年第9期8卷 23-31页

作者： Bin Ding Xiaoyan Li Wuxing Zhou Gang Zhang Huajian Gao Institute of High Performance Computing A*STAR Centre for Advanced Mechanics and Materials Applied Mechanics Laboratory Department of Engineering Mechanics Tsinghua University School of Materials Science and Engineering & Hunan Provincial Key Laboratory of Advanced Materials for New Energy Storage and Conversion Hunan University of Science and Technology School of Mechanical and Aerospace Engineering College of Engineering Nanyang Technological University

The thermal conductivity of two-dimensional materials, such as graphene, typically decreases when tensile strain is applied, which softens their phonon modes. Here, we report an anomalous strain effect on the thermal conductivity of monolayer silicene, a representative low-buckled two-dimensional (LB-2D)material. Reax FF-based molecular dynamics simulations are performed to show that biaxially stretched monolayer silicene exhibits a remarkable increase in thermal conductivity, by as much as 10 times the freestanding value, with increasing applied strain in the range of [0, 0.1], which is attributed to increased contributions from long-wavelength phonons. A further increase in strain in the range of [0.11, 0.18] results in a plateau of the thermal conductivity in an oscillatory manner, governed by a unique dynamic bonding behavior under extreme loading. This anomalous effect reveals new physical insights into the thermal properties of LB-2D materials and may provide some guidelines for designing heat management and energy conversion devices based on such materials.

关键词： low-buckled two-dimensional materials strain effect thermal conductivity bonding dynamics

strain effect of Manganin Transverse Piezoresistive Gauge and Measurement of Dynamic Transverse Stresses

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Journal of Beijing Institute of Technology 2010年第3期19卷 253-258页

作者：段卓平欧卓成蔡绍佳黄风雷 State Key Laboratory of Explosion Science and Technology Beijing Institute of Technology

Manganin piezoresistive gauges have been extensively used in dynamic stress measurement for decades.It is noted,however,that when used to measure transverse stresses,considerable strain effect is caused as the consequence of change of electrical resistance resulted from bending of wires in the longitudinal-strain-experiencing sensing element of the gauge,a phenomenon discussed in this paper theoretically as well as experimentally.This effect yields unwanted signals to blend with output piezoresistive signals and is not negligible,hence decreases measurement accuracy sizably if not properly handled.To overcome this drawback,a new type of manganin transverse piezoresistive gauge has been developed by authors of this paper,which can reduce the resistance increment to acceptable low level so as to effectively bring the adverse effect under control.

关键词： engineering mechanics transverse stress dynamic measurement manganin piezoresistive stress gauge strain effect

Revealing the A1g-type strain effect on superconductivity and nematicity in FeSe thin flake

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Chinese Physics B 2021年第9期30卷 56-61页

作者：程朝晖雷彬罗习刚应剑俊王震宇吴涛陈仙辉 CAS Key Laboratory of Strongly-coupled Quantum Matter Physics Department of PhysicsUniversity of Science and Technology of ChinaHefei 230026China Hefei National Laboratory for Physical Sciences at the Microscale University of Science and Technology of ChinaHefei 230026China CAS Center for Excellence in Superconducting Electronics(CENSE) Shanghai 200050China CAS Center for Excellence in Quantum Information and Quantum Physics Hefei 230026China Collaborative Innovation Center of Advanced Microstructures Nanjing UniversityNanjing 210093China

The driving mechanism of nematicity and its twist with superconductivity in iron-based superconductors are still under debate.Recently,a dominant B1g-type strain effect on superconductivity is observed in underdoped iron-pnictides superconductors Ba(Fe_(1-x)Co_(x))_(2)As_(2),suggesting a strong interplay between nematicity and superconductivity.Since the long-range spin order is absent in FeSe superconductor,whether a similar strain effect could be also observed or not is an interesting question.Here,by utilizing a flexible film as substrate,we successfully achieve a wide-range-strain tuning of FeSe thin flake,in which both the tensile and compressive strain could reach up to~0.7%,and systematically study the strain effect on both superconducting and nematic transition(T_(c)and Ts)in the FeSe thin flake.Our results reveal a predominant A1g-type strain effect on T_(c).Meanwhile,Ts exhibits a monotonic anti-correlation with T_(c)and the maximum T_(c)reaches to 12 K when Ts is strongly suppressed under the maximum compressive strain.Finally,in comparison with the results in the underdoped Ba(Fe_(1-x)Co_(x))_(2)As_(2),the absence of B1g-type strain effect in FeSe further supports the role of stripe-type spin fluctuations on superconductivity.In addition,our work also supports that the orbital degree of freedom plays a key role to drive the nematic transition in FeSe.

关键词： iron-based superconductors superconductivity electronic nematicity strain effect

effect of strain on charge density wave order inα-U

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Chinese Physics B 2022年第6期31卷 643-649页

作者：谢刘桦袁宏宽邱睿智 School of Physical Science and Technology Southwest UniversityChongqing 400715China Institute of Materials China Academy of Engineering PhysicsMianyang 621907China

The effect of strain on charge density wave(CDW)order inα-U is investigated within the framework of relativistic density-functional theory.The energetical stability ofα-U with CDW distortion is enhanced by the tensile strain along a and b axes,which is similar to the case of negative pressure and normal.However,the tensile strain along c axis suppresses the energetical stability of CDW phase.This abnormal effect could be understood from the emergence of a new onedimensional atomic chain along c axis inα-U.Furthermore,this effect is supported by the calculations of Fermi surface and phonon mode,in which the topological objects and the dynamical instability show opposite behaviors between strains along a/b and c axes.

关键词： uranium charge density wave strain effect density-functional theory

effect of strain on electrochemical performance of Janus MoSSe monolayer anode material for Li-ion batteries: First-principles study

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Chinese Physics B 2021年第4期30卷 394-401页

作者：王国庆秦文静石晶 Department of Physics Jiangxi Normal UniversityNanchang 330022China Institute of Fundamental and Frontier Sciences University of Electronic Science and Technology of ChinaChengdu 610054China

First-principles calculations are performed to investigate the effect of strain on the electrochemical performance of Janus MoSSe monolayer.The calculation focuses on the specific capacity,intercalation potential,electronic structure,and migration behavior of Li-ion under various strains by using the climbing-image nudged elastic band method.The result shows that the specific capacity is nearly unchanged under strain.But interestingly,the tensile strain can cause the intercalation potential and Li-ion migration energy barrier increase in MoSSe monolayer,whereas the compressive strain can lead to the intercalation potential and energy barrier decreasing.Thus,the rate performance of the MoSSe anode is improved.By analyzing the potential energy surface of MoSSe surface and equilibrium adsorption distance of Li-ion,we explain the physical origin of the change in the intercalation potential and migration energy barrier.The increase of MoSSe potential energy surface and the decrease of adsorption distance caused by tensile strain are the main reason that hinders Li-ion migration.

关键词： Janus Mo SSe monolayer strain effect specific capacity migration behavior

Structure and strain tunings of topological anomalous Hall effect in cubic noncollinear antiferromagnet Mn3Pt epitaxial films

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Science China(Physics,Mechanics & Astronomy) 2020年第9期63卷 105-110页

作者： Ning An Meng Tang Shuai Hu HuangLin Yang WeiJia Fan ShiMing Zhou XuePeng Qiu Shanghai Key Laboratory of Special Artificial Microstructure Materials and Technology School of Physics Science and EngineeringTongji UniversityShanghai 200092China

Antiferromagnets(AFMs)with chiral noncollinear spin structure have attracted great attention in recent years.However,the existing research has mainly focused on hexagonal chiral AFMs,such as Mn3Sn,Mn3Ga,Mn3Ge with low crystalline symmetry.Here,we present our systematical study for the face-centered cubic noncollinear antiferromagnetic Mn3Pt.By varying the alloy composition(x),we have successfully fabricated antiferromagnetic Mn1-xPtx epitaxial films on MgO substrates and have observed a crystalline structure transition from L10 MnPt to L12 Mn3Pt.The Mn3Pt exhibits a large anomalous Hall effect,which is in the same order of magnitude as those of ferromagnetic materials.Moreover,a large thickness-evolved strain effect is revealed in Mn3Pt films by X-ray diffraction(XRD)analysis based on the Scherrer method.Our work explores Mn3Pt as a promising candidate for topological antiferromagnetic spintronics.

关键词： anomalous Hall effect noncollinear antiferromagnet strain effect L10 and L12 alloys

Lattice distortion releasing local surface strain on high-entropy alloys

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Nano Research 2022年第6期15卷 4775-4779页

作者： Christian M.Clausen Jack K.Pedersen Thomas A.A.Batchelor Jan Rossmeisl Department of Chemistry University of Copenhagen2100 KøbenhavnØDenmark

High-entropy alloys(HEAs)have the potential to be a paradigm-shift for rational catalyst discovery but this new type of alloy requires a completely new approach to predict the surface reactivity.In addition to the ligand effect perturbing the surface–adsorbate bond,the random configuration of elements in the surface will also induce local strain effects due to the varying radii of neighboring atoms.Accurate modelling of HEA surface reactivity requires an estimate of this effect:To what degree is the adsorption of intermediates on these lattice distorted atomic environments affected by local strain?In this study,more than 3,500 density functional theory(DFT)calculated adsorption energies of*OH and*O adsorbed on the HEAs IrPdPtRhRu and AgAuCuPdPt are statistically analyzed with respect to the lattice constants of the alloys and the surfaces of each individual binding site.It is found that the inherent distortion of the lattice structure in HEAs releases the local strain effect on the adsorption energy as the atomic environment surrounding the binding atom(s)settles into a relaxed structure.This is even observed to be true for clusters of atoms of which the sizes deviate significantly from the atomic environment in which they are embedded.This elucidates an important aspect of binding site interaction with the neighboring atoms and thus constitutes a step towards a more accurate theoretical model of estimating the reactivity of HEA surfaces.

关键词： high-entropy alloys surface reactivity strain effect surface strain electrocatalysis oxygen reduction reaction