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Ti_(3)C_(2)T_(x) MXene/carbon composites for advanced supercapacitors:Synthesis,progress,and perspectives

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Carbon Energy 2024年第2期6卷 113-142页

作者： Yanqing Cai Xinggang Chen Ying Xu Yalin Zhang huijun liu Hongjuan Zhang Jing Tang College of Materials Science and Engineering North China University of Science and TechnologyTangshanChina Hebei Iron and Steel Laboratory North China University of Science and TechnologyTangshanChina Songshan Lake Materials Laboratory DongguanChina Shanghai Key Laboratory of Green Chemistry and Chemical Processes School of Chemistry and Molecular EngineeringEast China Normal UniversityShanghaiChina State Key Laboratory of Petroleum Molecular and Process Engineering(SKLPMPE) Sinopec Research Institute of Petroleum Processing Co.Ltd.BeijingChina Institute of Eco-Chongming ShanghaiChina

MXenes are a family of two-dimensional(2D)layered transition metal carbides/nitrides that show promising potential for energy storage applications due to their high-specific surface areas,excellent electron conductivity,good hydrophilicity,and tunable terminations.Among various types of MXenes,Ti_(3)C_(2)T_(x) is the most widely studied for use in capacitive energy storage applications,especially in supercapacitors(SCs).However,the stacking and oxidation of MXene sheets inevitably lead to a significant loss of electrochemically active sites.To overcome such challenges,carbon materials are frequently incorporated into MXenes to enhance their electrochemical properties.This review introduces the common strategies used for synthesizing Ti_(3)C_(2)T_(x),followed by a comprehensive overview of recent developments in Ti_(3)C_(2)T_(x)/carbon composites as electrode materials for SCs.Ti_(3)C_(2)T_(x)/carbon composites are categorized based on the dimensions of carbons,including 0D carbon dots,1D carbon nanotubes and fibers,2D graphene,and 3D carbon materials(activated carbon,polymer-derived carbon,etc.).Finally,this review also provides a perspective on developing novel MXenes/carbon composites as electrodes for application in SCs.

关键词： electrochemical performance MXene/carbon composites supercapacitors

Effects of electron-phonon coupling on the phonon transport properties of the Weyl semimetals NbAs and TaAs:A comparative study

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Journal of Materiomics 2023年第3期9卷 520-526页

作者： Shihao Han Qinghang Tang Hongmei Yuan Yufeng Luo huijun liu Key Laboratory of Artificial Micro-and Nano-Structures of Ministry of Education and School of Physics and Technology Wuhan UniversityWuhan430072China

It has now become recognized that the electron-phonon coupling(EPC)may play an important role in governing the phonon transport,especially for metallic and semiconducting systems at high carrier concentration.Here we focus on the Weyl semimetals TaAs and NbAs and give a comparative study on their phonon transport properties by explicitly including the EPC in first-principles calculations.It is found that the lattice thermal conductivities of both systems are significantly reduced by the EPC,which is more pronounced for the TaAs compared with the NbAs at the same carrier concentration.Detailed analysis indicates that the TaAs exhibits smaller EPC phonon relaxation time,as characterized by stronger EPC strength which is associated with larger deformation potential constant and Born effective charge.Moreover,we see that the TaAs exhibits obviously larger overlap between the EPC relaxation time and that from intrinsic phonon-phonon scattering,which could further reduce the lattice thermal conduc-tivity.Our work not only highlights the vital importance of EPC in accurately predicting the phonon transport behaviors,but also offers a simple alternative to evaluate the EPC strength of various material systems.

关键词： Electron-phonon coupling Phonon transport Weyl semimetals First-principles Lattice thermal conductivity

Single-phase bimetal sulfide or metal sulfide heterojunction:Which one is better for reversible oxygen electrocatalyst?

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Journal of Energy Chemistry 2022年第11期31卷 420-428,I0012页

作者： Jingjing Cai huijun liu Yulin Luo Yuqing Xiong Lizhu Zhang Sheng Wang Kang Xiao Zhao-Qing liu School of Chemistry and Chemical Engineering/Institute of Clean Energy and Materials/Key Laboratory for Clean Energy and Materials Guangzhou UniversityGuangzhou 510006GuangdongChina Department of Materials Science and Engineering Northwestern UniversityEvanstonIL 60208USA

Bimetallic sulfides,integrating the merits of individual components,are ideal structures for efficient electrocatalysis.However,for bimetallic sulfides including metal sulfide heterojunctions(MSH)and singlephase bimetallic sulfides(SBS),it is still unclear about which one has better catalytic activity toward reversible oxygen catalysis and its difference on catalytic mechanism.In this work,we demonstrate a bimetallic sulfide electrocatalyst that could transform from metal sulfide heterojunction(CoS/FeS)to single-phase bimetallic sulfide(CoFeS_(2))through a facile temperature control strategy.The single-phase bimetallic sulfide(CoFeS_(2))affords high intrinsic activity,fast reaction kinetics and superior durability toward oxygen evolution reaction(OER)and oxygen reduction reaction(ORR).Density functional theory(DFT)simulations reveal that the(CoFeS_(2))has homogeneous electron distribution of the CoFeS_(2)structure,improves the central energy level of d band,and optimizes the O*and OOH*intermediate and efficiently reduces the energy barrier of the reaction rate-determining step(RDS).The assembled rechargeable zincair battery is more stable than the Pt/C and IrO_(2) assemblies due to the excellent electrocatalytic activity and stability of CoFeS_(2)/NC,suggesting that it has potential for use in practical applications.

关键词： Metal sulfide Sulfide heterojunction OER ORR Zinc-air batteries

A Two-Phase Paradigm for Joint Entity-Relation Extraction

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Computers, Materials & Continua 2023年第1期74卷 1303-1318页

作者： Bin Ji Hao Xu Jie Yu Shasha Li JunMa Yuke Ji huijun liu College of Computer National University of Defense TechnologyChangsha410073China The Affiliated Eye Hospital of Nanjing Medical University Nanjing210029China

An exhaustive study has been conducted to investigate span-based models for the joint entity and relation extraction task.However,these models sample a large number of negative entities and negative relations during the model training,which are essential but result in grossly imbalanced data distributions and in turn cause suboptimal model performance.In order to address the above issues,we propose a two-phase paradigm for the span-based joint entity and relation extraction,which involves classifying the entities and relations in the first phase,and predicting the types of these entities and relations in the second phase.The two-phase paradigm enables our model to significantly reduce the data distribution gap,including the gap between negative entities and other entities,aswell as the gap between negative relations and other relations.In addition,we make the first attempt at combining entity type and entity distance as global features,which has proven effective,especially for the relation extraction.Experimental results on several datasets demonstrate that the span-based joint extraction model augmented with the two-phase paradigm and the global features consistently outperforms previous state-ofthe-art span-based models for the joint extraction task,establishing a new standard benchmark.Qualitative and quantitative analyses further validate the effectiveness the proposed paradigm and the global features.

关键词： Joint extraction span-based named entity recognition relation extraction data distribution global features

Effect of substrate COD/N ratio on performance and microbial community structure of a membrane aerated biofilm reactor

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Journal of Environmental Sciences 2010年第4期22卷 540-546页

作者： huijun liu Fenglin Yang Shuyi Shi Xincheng liu China Agriculture University Yantai 264670 China. School of Environmental and Biological Science and Technology Dalian University of Technology Dalian 116024 China

Two parallel carbon-membrane aerated biofilm reactors were operated at well-defined conditions to investigate the effect of substrate COD/N ratios on the performance and microbial community structure of the bioreactor. Results showed that at substrate COD/N of 5, organic and nitrogen could be eliminated simultaneously, and COD removal degree, nitrification and denitrification efficiency reached 85%, 93% and 92%, respectively. With increasing substrate COD/N ratios, the specific oxygen utilization rates of nitrifying bacteria in biofilm were found to decrease, indicating that nitrifying population became less dominant. At substrate COD/N ratio of 6, excessive heterotrophs inhibited the activity of nitrifying bacteria greatly and thus led to poor nitrification process. With the help of fluorescence in situ hybridization （FISH）, Nitrosomonas and Nitrosospira were identified as dominant ammonia-oxidizing bacteria in the biofilm at substrate COD/N of 0, whereas only Nitrosospira were detected in the biofilm at COD/N ratio of 5. Nitrospira were present as dominant nitrite-oxidizing bacteria in our study. Confocal laser scanning microscopy images revealed that at substrate COD/N ratio of 0 nitrifying bacteria existed throughout the biofilm and that at COD/N ratio of 5 they were mainly distributed in the inner layer of biofilm.

关键词： substrate COD/N ratio simultaneous organic and nitrogen removal biofilm activity fluorescence in situ hybridization

Synthesis and characterization of nanosized Ti3AlC2 ceramic powder by elemental powders of Ti, Al and C in molten salt

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Journal of Materials Science & Technology 2020年第2期37卷 77-84页

作者： huijun liu Ying Wang Lingxu Yang Ruijia liu Chaoliu Zeng Laboratory for Corrosion and Protection Institute of Metal ResearchChinese Academy of SciencesShenyang 110016China School of Materials Science and Engineering University of Science and Technology of ChinaHefei 230026China

A simple method to synthesize high-content ternary carbide Ti3AlC2 nanoparticles from Ti,Al,and C starting elemental powders without ball milling in NaCl–KCl molten salt was reported.The effects of mass ratio of the salt to starting materials,temperature,reaction time,and Al molar ratio on preparation of Ti3AlC2 were investigated.The Ti3AlC2 formation is dramatically influenced by temperature and mass ratio of the salt to raw materials:a higher temperature and higher mass ratio of the salt to raw materials are more preferable for Ti3AlC2 powder formation.Homogenous Ti3AlC2 powder with particle size of■nm is synthesized by 3Ti/Al/2C starting elemental powders in NaCl–KCl molten salt at 900℃for 10 h,950℃for 5h,or 1000℃for 2h,respectively,when the mass ratio of the salt to 3Ti/Al/2C starting materials is 10:1.

关键词： Nanosized Ti3AlC2 Ternary carbide Powder Molten salt

High-throughput prediction of the carrier relaxation time via data-driven descriptor

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npj Computational Materials 2020年第1期6卷 435-440页

作者： Zizhen Zhou Guohua Cao Jianghui liu huijun liu Key Laboratory of Artificial Micro-and Nano-Structures of Ministry of Education and School of Physics and Technology Wuhan UniversityWuhan 430072China Center for Quantum Materials and Devices College of PhysicsChongqing UniversityChongqing 401331China International Center for Quantum Design of Functional Materials(ICQD) Hefei National Laboratory for Physical Sciences at the Microscaleand Synergetic Innovation Center of Quantum Information and Quantum PhysicsUniversity of Science and Technology of ChinaHefeiAnhui 230026China

It has been demonstrated that many promising thermoelectric materials,such as tetradymite compounds are also threedimensional topological insulators.In both cases,a fundamental question is the evaluation of carrier relaxation time,which is usually a rough task due to the complicated scattering mechanisms.Previous works using the simple deformation potential theory or considering complete electron-phonon coupling are,however,restricted to small systems.By adopting a data-driven method named SISSO(Sure Independence Screening and Sparsifying Operator)with the training data obtained via deformation potential theory,we propose an efficient and physically interpretable descriptor to evaluate the relaxation time,using tetradymites as prototypical examples.Without any input from first-principles calculations,the descriptor contains only several elemental properties of the constituent atoms,and could be utilized to quickly and reliably predict the carrier relaxation time of a substantial number of tetradymites with arbitrary stoichiometry.

关键词： relaxation arbitrary utilized

“电报战”之久与“军事战”之迅:五四前后直皖易势的舆论驱动

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历史教学问题 2024年第1期 69-75,206页

作者：刘会军张恒吉林大学文学院 130012

五四运动前后的中国社会急剧变革,作为集中反映民意的舆论推动乃至左右着政局变迁,直皖力量随之此长彼消。五四前,直系迎合民意抨击皖系的对外媚日和对内主战,由此打破了北洋集团内部的政治平衡;五四后,直系积极顺从舆情,利用电报“为... 详细信息

五四运动前后的中国社会急剧变革,作为集中反映民意的舆论推动乃至左右着政局变迁,直皖力量随之此长彼消。五四前,直系迎合民意抨击皖系的对外媚日和对内主战,由此打破了北洋集团内部的政治平衡;五四后,直系积极顺从舆情,利用电报“为民发声”,在收获民心的同时基本掌控政治话语权,取得压倒皖系的政治优势。直皖开战前夕,直系高举“民意”旗帜而颇得舆论声援,皖系的“整饬纲纪”却备受舆论抨击,以致双方的“军事战”稍动而胜败即定。持久的“电报战”与急迅的“军事战”背后是左右政局的舆论及其反映的民意。这种新的政治动能不仅促动直皖力量长消和易势,而且猛烈冲击并持续瓦解着窳败不堪的军阀政治。

关键词：舆论民意直皖易势驱动

Predicting lattice thermal conductivity via machine learning: a mini review

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npj Computational Materials 2023年第1期9卷 2322-2332页

作者： Yufeng Luo Mengke Li Hongmei Yuan huijun liu Ying Fang Key Laboratory of Artificial Micro-and Nano-Structures of Ministry of Education and School of Physics and Technology Wuhan UniversityWuhan 430072China School of Computer Science Wuhan UniversityWuhan 430072China

Over the past few decades,molecular dynamics simulations and first-principles calculations have become two major approaches to predict the lattice thermal conductivity(κ_(L)),which are however limited by insufficient accuracy and high computational cost,respectively.To overcome such inherent disadvantages,machine learning(ML)has been successfully used to accurately predictκL in a high-throughput style.In this review,we give some introductions of recent ML works on the direct and indirect prediction ofκL,where the derivations and applications of data-driven models are discussed in details.A brief summary of current works and future perspectives are given in the end.

关键词： conductivity lattice thermal