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Microstructure and formation mechanism of twins of laths of austenite with high nitrogen

Science China(Technological Sciences) 2007年第6期50卷 755-764页

作者： WU CuiLan1,2 & LUO ChengPing2 1 center for high resolution electron microscopy, College of Materials Science and Engineering, Hunan University, Changsha 410082, China 2 College of Mechanical Engineering, South China University of Technology, Guangzhou 510641, China center for high resolution electron microscopy College of Materials Science and Engineering Hunan University Changsha China College of Mechanical Engineering South China University of Technology Guangzhou China

The microstructure of composite diffusion layer of the nitrided and chromized 0.2% carbon steel is investigated using TEM and EDS. It is found that laths of austenite with high nitrogen (γ N) precipitate from α-ferrite matrix in the deeper zone of the diffusion layer. These γ N laths are all twins, with their {111} twinning planes parallel to the lath axis, thus forming a characteristic "back-to-back" morphology. There are two types of γN lath. The first is a genuinely {111} twin, and γ N and α keep the accurate K-S relationship, and each γ N and α form a sharp and smooth γ N/α inter- face of {335}γN//{341}α, namely habit plane {335}fcc. The second is a pseudo-twin, with micro-twins {111} or faults formed within the two twin components. Localized lattice deformation (relaxation) seems to have occurred at the interfaces of the second type of γ N due to the formation of micro-twins or faults within the twin components. These micro-twins or faults make the orientation relationship (OR) between each of the γN and the α-matrix deviate from the accurate K-S OR, and the OR between two γ N twin components deviate from the genuine {111} twin relation- ship. In addition, the γ N/α interface of the second type of γ N is not as sharp or smooth as that of the first one.

关键词： austenite containing nitrogen, twins, steel 20, nitriding, composite chromizing

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Cu/Mo2C synthesized through Anderson-type polyoxometalates modulate interfacial water structure to achieve hydrogen evolution at high current density

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Nano Research 2024年第4期17卷 2546-2554页

作者： Dunyuan Jin Fen Qiao Yan Zhou Junfeng Wang Kecheng Cao Jing Yang Jikang Zhao Lei Zhou Haitao Li School of Energy and Power Engineering Jiangsu UniversityZhenjiang 212013China School of Physical Science and Technology and Shanghai Key Laboratory of high-resolution electron microscopy ShanghaiTech UniversityShanghai 201210China Institute for Energy Research Jiangsu UniversityZhenjiang 212013China

The development of efficient non-precious metal catalysts is important for the large-scale application of alkaline hydrogen evolution reaction(HER).Here,we synthesized a composite catalyst of Cu and Mo_(2)C(Cu/Mo_(2)C)using Anderson-type polyoxometalates(POMs)synthesized by the facile soaking method as precursors.The electronic interaction between Cu and Mo_(2)C drives the positive charge of Cu,alleviating the strong adsorption of hydrogen at the Mo site by modulating the d-band center of Mo_(2)C.By studying the interfacial water structure using in situ attenuated total reflection surface-enhanced infrared absorption spectroscopy(ATR-SEIRAS),we determined that the positively charged Cu crystals have the function of activating water molecules and optimizing the interfacial water structure.The interfacial water of Cu/Mo_(2)C contains a large amount of free water,which could facilitate the transport of reaction intermediates.Due to activated water molecules and optimized interfacial water structure and hydrogen adsorption energy,the overpotential of Cu/Mo_(2)C is 24 mV at a current density of 10 mA·cm^(-2) and 178 mV at a current density of 1000 mA·cm^(-2).This work improves catalyst performance in terms of interfacial water structure optimization and deepens the understanding of water-mediated catalysis.

关键词： electrocatalytic hydrogen production interfacial water charge transport d band center in situ attenuated total reflection surface-enhanced infrared absorption spectroscopy(ATR-SEIRAS)

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Optimizing high-coordination shell of Co-based single-atom catalysts for efficient ORR and zinc-air batteries

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Journal of Energy Chemistry 2024年第8期95卷 306-314页

作者： Yugang Qi Qing Liang Kexin Song Xinyan Zhou Meiqi Liu Wenwen Li Fuxi Liu Zhou Jiang Xu Zou Zhongjun Chen Wei Zhang Weitao Zheng Key Laboratory of Automobile Materials MOE School of Materials Science & Engineering Electron Microscopy Center and International Center of Future Science Jilin Provincial International Cooperation Key Laboratory of High-Efficiency Clean Energy Materials Jilin University Institute of high Energy Physics Chinese Academy of Sciences

Atom-level modulation of the coordination environment for single-atom catalysts(SACs) is considered as an effective strategy for elevating the catalytic performance. For the MNxsite, breaking the symmetrical geometry and charge distribution by introducing relatively weak electronegative atoms into the first/second shell is an efficient way, but it remains challenging for elucidating the underlying mechanism of interaction. Herein, a practical strategy was reported to rationally design single cobalt atoms coordinated with both phosphorus and nitrogen atoms in a hierarchically porous carbon derived from metal-organic frameworks. X-ray absorption spectrum reveals that atomically dispersed Co sites are coordinated with four N atoms in the first shell and varying numbers of P atoms in the second shell(denoted as Co-N/P-C).The prepared catalyst exhibits excellent oxygen reduction reaction(ORR) activity as well as zinc-air battery performance. The introduction of P atoms in the Co-SACs weakens the interaction between Co and N,significantly promoting the adsorption process of *OOH, resulting in the acceleration of reaction kinetics and reduction of thermodynamic barrier, responsible for the increased intrinsic activity. Our discovery provides insights into an ultimate design of single-atom catalysts with adjustable electrocatalytic activities for efficient electrochemical energy conversion.

关键词： Electrocatalytic Oxygen reduction reaction Shell coordination optimization Single atom catalyst

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Efficient optimization of electron transfer pathway by constructing phosphide/ceria interface boosts seawater hydrogen production

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Journal of Energy Chemistry 2024年第8期95卷 490-498页

作者： Yifan Zhao Lingfeng Yang Youyu Long Min Xi Anran Chen Hua Zhang School of Materials and Energy Yunnan University electron microscopy Centre of Yunnan University Yunnan University

Developing efficient and durable hydrogen evolution reaction（HER） electrocatalysts is one of the most important issues for the commercialization of seawater electrolysis,but it remains challenging.Here,we report a CeO2-CoP nanoneedle array catalyst loaded on Ti mesh（CeO2-CoP/TM） with workfunction-induced directional charge transport properties.The CeO2-CoP/TM catalyst showed superior HER catalytic activity and stability,with over potentials of 41 and 60 mV to attain 10 mA cm-2,in 1 M KOH and 1 M KOH+seawater electrolyte,respectively.Experimental results and theoretical calculations reveal that the work function drives the charge transfer from CeO2to CoP,which effectively balances the electronic density of CoP and CeO2,optimizes the d-band center,and accelerates the water activation kinetics,thus enhancing the HER activity.The solar-driven water electrolysis device displays a high and stable solar-to-hydrogen conversion efficiency of 19.6%.This study offers a work function-induced directional charge transport strategy to design efficient and durable catalysts for hydrogen production.

关键词： Charge transport Heterostructure Seawater splitting Solar-to-hydrogen Work function

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high-efficiency sodium storage of Co_(0.85)Se/WSe_(2) encapsulated in N-doped carbon polyhedron via vacancy and heterojunction engineering

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Carbon Energy 2024年第1期6卷 94-107页

作者： Ya Ru Pei Hong Yu Zhou Ming Zhao Jian Chen Li Xin Ge Wei Zhang Chun Cheng Yang Qing Jiang Key Laboratory of Automobile Materials(Jilin University) Ministry of EducationSchool of Materials Science and EngineeringJilin UniversityChangchunChina Jilin Provincial International Cooperation Key Laboratory of high-Efficiency Clean Energy Materials Electron Microscopy CenterJilin UniversityChangchunChina

With the advantage of fast charge transfer,heterojunction engineering is identified as a viable method to reinforce the anodes'sodium storage performance.Also,vacancies can effectively strengthen the Na+adsorption ability and provide extra active sites for Na+adsorption.However,their synchronous engineering is rarely reported.Herein,a hybrid of Co_(0.85)Se/WSe_(2) heterostructure with Se vacancies and N-doped carbon polyhedron(CoWSe/NCP)has been fabricated for the first time via a hydrothermal and subsequent selenization strategy.Spherical aberration-corrected transmission electron microscopy confirms the phase interface of the Co_(0.85)Se/WSe_(2) heterostructure and the existence of Se vacancies.Density functional theory simulations reveal the accelerated charge transfer and enhanced Na+adsorption ability,which are contributed by the Co_(0.85)Se/WSe_(2) heterostructure and Se vacancies,respectively.As expected,the CoWSe/NCP anode in sodium-ion battery achieves outstanding rate capability(339.6 mAh g^(−1) at 20 A g^(−1)),outperforming almost all Co/W-based selenides.

关键词： Co_(0.85)Se/WSe_(2)heterostructure density functional theory simulations N-doped carbon polyhedron Se vacancies sodium-ion batteries

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Hierarchical FeO_(χ)H_(y)@Ni_(3)B hybrid for efficient alkaline oxygen evolution at high current density

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Journal of Energy Chemistry 2024年第7期94卷 599-607页

作者： Fuxi Liu Qing Liang Zhenyu Li Meiqi Liu Naiin Yue Zizhun Wang Xu Zou Wei Zhang Key Laboratory of Automobile Materials Ministry of Education School of Materials Science&EngineeringElectron Microscopy CenterInternational Center of Future ScienceJilin Provincial International Cooperation Key Laboratory of High-Eficiency Clean Energy MaterialsJilin UniversityChangchun 130012JilinChina

Electrocatalysts with high activity and long-term durability are vital toward large-scale hydrogen pro-duction from electrocatalytic water splitting.Here,the self-supported electrode(FeO_(χ)H_(y)@Ni_(3)B/NF)with hierarchical heterostructure was simply prepared by using NigB chunks grown on nickel foam as sub-strate to in situ form vertical FeO_(χ)H_(y)nanosheets.Such hybrid shows efficient oxygen evolution reaction activity with overpotentials as low as 267 and 249 mV at 100 mA cm^(-2)in 1 M K0H solution and 30 wt%KOH solution,respectively.Meanwhile,it also exhibits excellent catalytic stability,sustaining catalysis at 500 mA cm^(-2)in 1 M K0H solution for 200 h,and even for 200 h at 1000 mA cm^(-2)in 30 wt%K0H solution.Further experimental results reveal that the FeO_(χ)H_(y)@Ni_(3)B/NF is endowed with superhydrophilic and superaerophobic surface properties,which not only provide more mass transport channels,as well as facilitated the diffusion of reaction intermediates and gas bubbles.Also,it holds faster reaction kinetics,more accessible active sites and accelerated electron transfer rates due to strong synergistic interactions attheheterogeneous interface.

关键词： FeO_(χ)H_(y)@Ni_(3)B/NF hybrid Heterostructure Oxygen evolution reaction Electrocatalytic

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Kinetically and thermodynamically expediting elementary steps via high-valence Cr-incorporated of nickel selenide for water electrolysis

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Nano Research 2024年第3期17卷 1199-1208页

作者： Huafeng Fan Dongxu Jiao Jinchang Fan Dewen Wang Bilal Zaman Wei Zhang Lei Zhang Weitao Zheng Xiaoqiang Cui State Key Laboratory of Automotive Simulation and Control School of Materials Science and EngineeringKey Laboratory of Automobile Materials of MOEJilin Provincial International Cooperation Key Laboratory of High-Efficiency Clean Energy MaterialsElectron Microscopy CenterJilin UniversityChangchun 130012China College of Chemistry Jilin UniversityChangchun 130012China

Designing high-performance electrocatalysts toward hydrogen evolution reaction(HER)and oxygen evolution reaction(OER)is essential to reduce the activation barrier and optimize free adsorption energy of reactive intermediates.Herein,we report that incorporating high-valence Cr into NiSe_(2)(Cr_(x)Ni_(1-x)Se_(2))kinetically and thermodynamically expedites elementary steps of both HER and OER.The as-prepared Cr_(0.05)Ni_(0.95)Se_(2) catalyst displays excellent HER and OER activities,with low overpotentials of 89 and 272 mV at the current density of 10 mA·cm^(-2)(j10),respectively,and remains stable during operation for 30 h.A low cell voltage of only 1.59 V is required to drive j10 in alkaline media.In situ Raman spectroscopy reveals that Cr incorporation facilitates the formation of NiOOH active species during the OER process.Meanwhile,theoretical explorations demonstrate that high-valence Cr incorporation efficiently accelerates water dissociation kinetics and improves H*adsorption during HER process,lowering the activation barrier of OER and optimizing the adsorption energy of oxygen-based intermediate,thus kinetically and thermodynamically enhancing the intrinsic performance of NiSe_(2) for over water splitting.This strategy provides a new horizon to design transition metal based electrocatalysts in the clean energy field.

关键词： nickel selenide electrocatalytic water splitting high-valence Cr density functional theory(DFT)calculation

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Pressure-Tuned Intrinsic Anomalous Hall Conductivity in Kagome Magnets RV_(6)Sn_(6)(R=Gd,Tb)

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Chinese Physics Letters 2024年第4期41卷 139-151页

作者：孔祥明陶咨成张蕊夏威陈旭裴翠颖应天平齐彦鹏郭艳峰杨小帆李世燕 State Key Laboratory of Surface Physics Department of PhysicsFudan UniversityShanghai 200438China Shanghai Research center for Quantum Sciences Shanghai 201315China School of Physical Science and Technology ShanghaiTech UniversityShanghai 201210China ShanghaiTech Laboratory for Topological Physics Shanghai 201210China Northwest Institute for Non-Ferrous Metal Research Xi'an 710016China Beijing National Laboratory for Condensed Matter Physics and Institute of PhysicsChinese Academy of SciencesBeijing 100190China Shanghai Key Laboratory of high-resolution electron microscopy Shanghai 201210China Collaborative Innovation center of Advanced Microstructures Nanjing 210093China

Exploration of exotic phenomena in magnetic topological systems is at the frontier of condensed matter physics,holding a significant promise for applications in topological spintronics.However,complex magnetic structures carrying nontrivial topological properties hinder its progresses.Here,we investigate the pressure effect on the novel topological kagome magnets GdV_(6)Sn_(6) and TbV_(6)Sn_(6) to dig out the interplay between magnetic Gd/Tb layers and nonmagnetic V-based kagome sublattice.The pressure-tuned magnetic transition temperature Tm in both the compounds exhibit a turning point at the critical pressure P_(c),accompanied with a sign reversal in anomalous Hall effect(AHE).The separation of intrinsic and extrinsic contributions using the Tian-Ye-Jin scaling model suggests that the intrinsic mechanism originating from the electronic Berry curvature holds the priority in the competition with extrinsic mechanism in AHE.The above-mentioned findings can be attributed to the combined effect of pressure-tuned band topology and magnetic interaction in segregated layers.Our results provide a practical route to design and manipulate the intrinsic AHE in magnetic topological materials.

关键词： holds frontier hinder

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面向碱性析氢反应的原子级优化Fe-Pt金属间化合物催化剂表面终结态探索

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Science Bulletin 2024年第8期69卷 1091-1099页

作者：梁庆孟繁玲李文文邹旭宋可心葛昕姜周刘玉华刘美琦李振宇董韬文陈中军张伟郑伟涛 Key Laboratory of Automobile Materials(Ministry of Education) School of Materials Science and EngineeringElectron Microscopy CenterInternational Center of Future ScienceJilin Provincial International Cooperation Key Laboratory of High-Efficiency Clean Energy MaterialsJilin UniversityChangchun 130012China Institute of high Energy Physics Chinese Academy of SciencesBeijing 100049China

Controlling the atomic arrangement of elemental atoms in intermetallic catalysts to govern their surface and subsurface properties is a crucial but challenging endeavor in electrocatalytic reactions.In hydrogen evolution reaction(HER),adjusting the d-band center of the conventional noble-metallic Pt by introducing Fe enables the optimization of catalytic performance.However,a notable gap exists in research on the effective transition from disordered Fe/Pt alloys to highly ordered intermetallic compounds(IMCs)such as FePt_(3)in the alkaline HER,hampering their broader application.In this study,a series of catalysts FePt_(3-x)H(x=5,6,7,8 and 9)supported on carbon nanotubes(CNTs)were synthesized via a simple impregnation method,along with a range of heat treatment processes,including annealing in a reductive atmosphere,to regulate the order degree of the arrangement of Fe/Pt atoms within the FePt_(3)catalyst.By using advanced microscopy and spectroscopy techniques,we systematically explored the impact of the order degree of FePt_(3)in the HER.The as-prepared FePt_(3)-8H exhibited notable HER catalytic activity with low overpotentials(η=37 mV in 1.0 mol L^(-1)KOH)at j=10 mA cm^(-2).The surface of the L1_(2)FePt_(3)-8H catalyst was demonstrated to be Pt-rich.The Pt on the surface was not easily oxidized due to the unique Fe/Pt coordination,resulting in significant enhancement of HER performance.

关键词： Intermetallic Hydrogen evolution reaction Surface Catalyst

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Ultra-thin robust CNT@GC film integrating effective electromagnetic shielding and flexible Joule heating

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Nano Research 2024年第5期17卷 3462-3471页

作者： Ding Zhang Chunhui Wang Meng Li Weixue Meng Shipeng Zhang Mengdan Yang Xinguang Huang Yingjiu Zhang Yuanyuan Shang Anyuan Cao Key Laboratory of Materials Physics(Ministry of Education) School of Physics and MicroelectronicsZhengzhou UniversityZhengzhou450052China electron microscopy center Yunnan UniversityKunming650091China School of Materials Science and Engineering Peking UniversityBeijing100871China

The demand for lightweight,thin electromagnetic interference(EMI)shielding film materials with high shielding effectiveness(SE),excellent mechanical properties,and stability in complex environments is particularly pronounced in the realm of flexible and portable electronic products.Here,we developed an ultra-thin film(CNT@GC)in which the glassy carbon(GC)layer wrapped around and welded carbon nanotubes(CNTs)to form a core-shell network structure,leading to exceptional tensile strength(327.2 MPa)and electrical conductivity(2.87×10^(5) S·m^(−1)).The CNT@GC film achieved EMI SE of 60 dB at a thickness of 2µm after post-acid treatment and high specific SE of 3.49×10^(5) dB·cm^(2)·g^(−1),with comprehensive properties surpassing those of the majority of previous shielding materials.Additionally,the CNT@GC film exhibited Joule heating capability,reaching a surface temperature of 135℃at 3 V with a fast thermal response of about 0.5 s,enabling anti-icing/de-icing functionality.This work presented a methodology for constructing a robust CNT@GC film with high EMI shielding performance and exceptional Joule heating capability,demonstrating immense potential in wearable devices,defense,and aerospace applications.

关键词： core-shell structure ultra-thin lightweight film robust film electromagnetic shielding Joule heating

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