摘要：
Exploring two-dimensional (2D) tetragonal carbon nitride materials is significant for unlocking new physical properties beyond those offered by traditional hexagonal lattices. In this work, we propose three theoretically stable 2D carbon nitride monolayers with tetragonal lattices, namely T-C3N, P-C3N, and PH-C5N4. Electronic structure calculations indicate that all three monolayers exhibit semiconducting characteristics, with T-C3N showing interesting flat band features. Additionally, these three carbon nitrides exhibit anisotropic and high carrier mobilities and excellent light absorption capabilities in the visible-light and near-infrared regions. Meanwhile, the calculated thermal conductivity ( kappa p) of PH-C5N4 is 63.9 W m-1K-1 at room temperature, significantly outperforming T-C3N (12.2 W m-1 K-1) and P-C3N (18.9 W m-1 K-1). Phonon scattering rates and Gr & uuml;neisen parameters confirm the origin for the relatively high kappa p in PH-C5N4. Our study proposes three tetragonal carbon nitride structures with novel physical properties, which lays a theoretical foundation for the multifunctional applications of 2D carbon nitride materials.
摘要：
Improving the efficiency and product selectivity of CO2 reduction on catalysts is of great importance. In this work, the CO2 reduction performance on Cu-x@SnS2 (x = 1-6) was systematically investigated by density functional theory (DFT). Although the CO2 adsorption strength can only be slightly enhanced, the activity of the two-electron reduction can be effectively governed by the cluster size. Cu-x@SnS2 with x being even exhibits a lower energy barrier for the formation of both CO and HCOOH than that in the odd case. Particularly, Cu-4@SnS2 has the lowest energy barrier for the formation of CO, while Cu-2@SnS2 has a preference for the formation of HCOOH, showing product selectivity. This unique behavior is determined by the splitting of energy levels and orbital symmetry between the interacted frontier orbitals of Cu-d(z)(/xz/yz)(2) and intermediates. Our findings show that including the Cu-x cluster is a promising way of designing CO2 electrocatalysts with high activity and product selectivity.
摘要：
Solar cells are a promising and potentially sustainable energy technology due to their cost-effectiveness, eco-friendliness, and capacity for integration into pliable apparatuses. Developing new photovoltaic materials to achieve higher photovoltaic conversion efficiency is a hot topic in the field of solar cells. In this work, the electronic structures and optical properties of two-dimensional (MoSe2)x(MoSTe)1-x mosaic heterostructures have been studied by density functional theory. Our results show that the mosaic heterostructures retain semiconductors with tunable band gap of 1.14–1.53 eV. With the augmentation of MoSe2 concentration in the mosaic heterostructures, the band gap of the materials has gradually increased. Besides, the mosaic heterostructures exhibit excellent optical absorption in the visible light region. Furthermore, the maximum theoretical photoelectric conversion efficiency of (MoSe2)0.80(MoSTe)0.20 mosaic heterostructure can reach 32.36 %. The tunable band gap, excellent light absorption, and ultra-high photoelectric conversion efficiency of (MoSe2)x(MoSTe)1-x mosaic heterostructures make them candidates for new nanocrystalline thin-film solar cells.
期刊：
PHYSICAL CHEMISTRY CHEMICAL PHYSICS,2024年26(21):15666-15671 ISSN：1463-9076
通讯作者：
Cao, LM
作者机构：
[Liu, Xiang; Yang, Jingying] Hengyang Normal Univ, Coll Phys & Elect Engn, Hengyang 421002, Peoples R China.;[Tang, Zhenkun; Deng, Xiaohui; Cao, Liemao; Cao, LM] Univ Hunan Prov, Hengyang Normal Univ, Coll Phys & Elect Engn, Key Lab Micronano Energy Mat & Applicat Technol, Hengyang 421002, Peoples R China.
通讯机构：
[Cao, LM ] U;Univ Hunan Prov, Hengyang Normal Univ, Coll Phys & Elect Engn, Key Lab Micronano Energy Mat & Applicat Technol, Hengyang 421002, Peoples R China.
摘要：
The Schottky barrier between a metal and a semiconductor plays an important role in determining the transport efficiency of carriers and improving the performance of devices. In this work, we systematically studied the structure and electronic properties of heterostructures of blue phosphorene (BP) in contact with Mo(2)B based on density functional theory. The semiconductor properties of BP are destroyed owing to strong interaction with bare Mo(2)B. The effect of modifying Mo(2)B with O and OH on the contact properties was investigated. A p-type Schottky contact can be obtained in BP/Mo(2)BO(2). The height of the Schottky barrier can be modulated by interlayer distance to realize a transition from a p-type Schottky contact to a p-type Ohmic contact in BP/Mo(2)BO(2). The BP/Mo(2)B(OH)(2) forms robust Ohmic contacts, which are insensitive to interlayer distance and external electric fields due to the Fermi level pinning effect. Our work provides important clues for contact engineering and improvement of device performance based on BP.
期刊：
Journal of Applied Physics,2024年135(12):125103 ISSN：0021-8979
通讯作者：
Ouyang, YL;Chen, J
作者机构：
[Tang, Zhenkun; Tan, Rui; Yuan, Guotao; Yao, Yongsheng; Ouyang, YL; Ouyang, Yulou] Hengyang Normal Univ, Coll Phys & Elect Engn, Hengyang 421002, Peoples R China.;[Zeng, Yujia] Hunan Univ Sci & Technol, Sch Mat Sci & Engn, Xiangtan 411201, Peoples R China.;[Zeng, Yujia] Hunan Univ Sci & Technol, Hunan Prov Key Lab Adv Mat New Energy Storage & Co, Xiangtan 411201, Peoples R China.;[Zhang, Zhongwei; Chen, Jie] Tongji Univ, Ctr Phonon & Thermal Energy Sci, Sch Phys Sci & Engn, China EU Joint Lab Nanophonon,MOE,Key Lab Adv Micr, Shanghai 200092, Peoples R China.
通讯机构：
[Ouyang, YL ] H;[Chen, J ] T;Hengyang Normal Univ, Coll Phys & Elect Engn, Hengyang 421002, Peoples R China.;Tongji Univ, Ctr Phonon & Thermal Energy Sci, Sch Phys Sci & Engn, China EU Joint Lab Nanophonon,MOE,Key Lab Adv Micr, Shanghai 200092, Peoples R China.
关键词：
Antimony compounds;Boltzmann equation;Chemical bonds;Monolayers;Phonon scattering;Selenium compounds;Thermal conductivity;Asymmetric geometry;Atomic mass;Boltzmann's transport equations;Comparatives studies;High-κ;Learning potential;Machine-learning;Phonon scattering process;Thermal transport properties;Three-phonon scattering;Phonons
摘要：
Owing to the unique asymmetric geometry, Janus monolayer compounds exhibit various exotic thermal properties and have promising applications in thermal management. In this study, we combine machine learning potentials and the phonon Boltzmann transport equation to perform a comparative study of the thermal transport properties in Janus XBAlY (X = Se, S, Te; Y = S, Se, O; X not equal Y) monolayers. Our findings unveil a thermal conductivity (kappa(p)) ranking as SeBAlS > TeBAlO > SBAlSe, contradicting the conventional expectation that a higher kappa(p) is typically observed when the average atomic mass is smaller. At room temperature, the kappa(p) of SeBAlS is 174 Wm(-1) K-1, which is 4.8 times that of SBAlSe when considering three-phonon scattering processes. Moreover, the consideration of four-phonon scatterings does not alter such ranking. The anomalous kappa(p) phenomenon was explained through a detailed analysis of the phonon-phonon scattering mechanism, phonon bandgap, phonon anharmonicity, and chemical bond strength. This study highlights the intricate relationship between atomic mass, bonding characteristics, and thermal properties, offering insights for designing Janus materials with tailored thermal conductivity. (c) 2024 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).
作者机构：
[Zhou, Zhong-Peng; Deng, Xiao-Hui; Zhang, Qian-Kui; Tang, Zhen-Kun] Hengyang Normal Univ, Coll Phys & Elect Engn, Hengyang 421002, Peoples R China.;[Zhou, Zhong-Peng; Tong, Chuan-Jia; Hao, Ning-Jing] Cent South Univ, Sch Phys & Elect, Hunan Key Lab Nanophoton & Devices, Hunan Key Lab Super Microstructure & Ultrafast Pro, Changsha 410083, Peoples R China.;[Zhang, Hui] Shenyang Univ, Normal Sch, Shenyang 110044, Peoples R China.
通讯机构：
[Zhen-Kun Tang] C;[Chuan-Jia Tong] H;Hunan Key Laboratory of Nanophotonics and Devices, Hunan Key Laboratory of Super-Microstructure and Ultrafast Process, School of Physics and Electronics, Central South University, Changsha 410083, China<&wdkj&>College of Physics and Electronics Engineering, Hengyang Normal University, Hengyang 421002, China
期刊：
Physica E-Low-Dimensional Systems & Nanostructures,2023年152:115748 ISSN：1386-9477
通讯作者：
Xiaohui Deng
作者机构：
[Xiaohui Deng; Liemao Cao; Jing Zeng; Zhenkun Tang] College of Physics and Electronic Engineering, Hengyang Normal University, Hengyang, Hunan, 421002, China
通讯机构：
[Xiaohui Deng] C;College of Physics and Electronic Engineering, Hengyang Normal University, Hengyang, Hunan, 421002, China
摘要：
A suitable band gap together with high carrier mobility are very important for modern electronic device. Phosphide has being an ideal candidate since black phosphor was successfully fabricated in experiment. Here, we had successfully predicted a new class of MX2 (M = Ca, Sr, X = P, As) monolayers that had ideal band gaps as well as high carrier mobility comparable with black phosphor. Furthermore，these monolayers exhibit excellent absorption ability for visible light. This work provided another possibility to acquire new materials as high-speed electronic devices or optoelectronic devices.
作者机构：
[Tang, Zhenkun; Deng, Xiaohui] Hengyang Normal Univ, Coll Phys & Elect Engn, Hengyang 421002, Hunan, Peoples R China.
通讯机构：
[Deng, X.] C;College of Physics and Electronic Engineering, China
摘要：
<jats:title>Abstract</jats:title>
<jats:p>The ultra-wide single spin states are of importance for ideal magnetic storage materials and spin injection sources. Here, a new type of CrOX (X=Cr, Br, I) monolayer has been revealed. We find that the basic constructive units for such new monolayers are four-coordinated, almost never being reported until now. More interestingly, they are half-metals and have an ultra-wide single spin channel in their electronic band structures. Monte Carlo simulations show that the Curie temperatures of three monolayers are relatively low, however they can be enhanced to exceed the liquid nitrogen temperature under strain or hole doping. The four-coordinated Cr compounds predicted here may open a new windows for exploring high spin-polarized half-metals.</jats:p>
通讯机构：
[Liemao Cao] C;[Yee Sin Ang] S;College of Physics and Electronic Engineering, Hengyang Normal University , Hengyang 421002, China<&wdkj&>Science, Mathematics and Technology (SMT), Singapore University of Technology and Design (SUTD) , 8 Somapah Road, Singapore 487372
摘要：
The substantial capacity gap between available anode and cathode materials for commercial Li-ion batteries (LiBs) remains, as of today, an unsolved problem. Oxygen vacancies (OVs) can promote Li-ion diffusion, reduce the charge transfer resistance, and improve the capacity and rate performance of LiBs. However, OVs can also lead to accelerated degradation of the cathode material structure, and from there, of the battery performance. Understanding the role of OVs for the performance of layered lithium transition metal oxides holds great promise and potential for the development of next generation cathode materials. This review summarises some of the most recent and exciting progress made on the understanding and control of OVs in cathode materials for Li-ion battery, focusing primarily on Li-rich layered oxides. Recent successes and residual unsolved challenges are presented and discussed to stimulate further interest and research in harnessing OVs towards next generation oxide-based cathode materials.
摘要：
Two-dimensional (2D) metallic states induced by oxygen vacancies ( VOs) at oxide surfaces and interfaces provide opportunities for the development of advanced applications, but the ability to control the behavior of these states is still limited. We used angle resolved photoelectron spectroscopy combined with density-functional theory (DFT) to study the reactivity of VO-induced states at the (001) surface of anatase TiO2, where both 2D metallic and deeper lying in-gap states (IGs) are observed. The 2D and IG states exhibit remarkably different evolutions when the surface is exposed to molecular O2: while IGs are almost completely quenched, the metallic states are only weakly affected. DFT calculations indeed show that the IGs originate from surface VOs and remain localized at the surface, where they can promptly react with O2. In contrast, the metallic states originate from subsurface vacancies whose migration to the surface for recombination with O2 is kinetically hindered on anatase TiO2 (001), thus making them much less sensitive to oxygen dosing.
摘要：
Surfaces, interfaces and grain boundaries are classically known to be sinks of defects generated within the bulk lattice. Here, we report an inverse case by which the defects generated at the particle surface are continuously pumped into the bulk lattice. We show that, during operation of a rechargeable battery, oxygen vacancies produced at the surfaces of lithium-rich layered cathode particles migrate towards the inside lattice. This process is associated with a high cutoff voltage at which an anionic redox process is activated. First-principle calculations reveal that triggering of this redox process leads to a sharp decrease of both the formation energy of oxygen vacancies and the migration barrier of oxidized oxide ions, therefore enabling the migration of oxygen vacancies into the bulk lattice of the cathode. This work unveils a coupled redox dynamic that needs to be taken into account when designing high-capacity layered cathode materials for high-voltage lithium-ion batteries.
期刊：
PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS,2019年256(11):1900185- ISSN：0370-1972
通讯作者：
Tang, Zhen-Kun;Chen, Mingyang
作者机构：
[Luo, Lin-Tao; Deng, Xiao-Hui; Zhang, Deng-Yu; Tang, Zhen-Kun] Hengyang Normal Univ, Coll Phys & Elect Engn, Hengyang 421002, Peoples R China.;[Chen, Mingyang] Beijing Computat Sci Res Ctr, Beijing 100193, Peoples R China.
通讯机构：
[Tang, Zhen-Kun] H;[Chen, Mingyang] B;Hengyang Normal Univ, Coll Phys & Elect Engn, Hengyang 421002, Peoples R China.;Beijing Computat Sci Res Ctr, Beijing 100193, Peoples R China.
关键词：
density functional theory;semiconductor photocatalysts;two-dimensional heterostructures
摘要：
<jats:sec><jats:label /><jats:p>Semiconductor photocatalysts have received a lot of attention because of their wide range of applications in solving energy and environmental problems. In this work, the electronic structure and optical properties of two‐dimensional (2D) heterostructures of bismuth oxyhalides (BiOX, X = Cl, Br, I) and transition‐metal oxides (YO<jats:sub>3</jats:sub>, Y = Mo, W) are studied by density functional theory. The results reveal that the 2D BiOX–YO<jats:sub>3</jats:sub> heterostructures are semiconductors with band gaps of 0–1.41 eV. Electronic structure analyses indicate that the valence band maximum (VBM) and conduction band minimum (CBM) of BiOX–YO<jats:sub>3</jats:sub> are spatially separated and reside in the BiOX and YO<jats:sub>3</jats:sub> layers, respectively. The electron effective masses of BiOI–YO<jats:sub>3</jats:sub> (Y = Mo, W) heterostructures, especially BiOI–WO<jats:sub>3</jats:sub>, are significantly lower than those of BiOI and YO<jats:sub>3</jats:sub>. BiOI–YO<jats:sub>3</jats:sub> (Y = Mo, W) heterostructures exhibit a good absorption in the visible light region. The enhanced optoelectronic properties of BiOI–YO<jats:sub>3</jats:sub> are found to be related to the comparably large lattice mismatches between BiOI and YO<jats:sub>3</jats:sub>. The ultra‐low electron effective mass and good visible absorption of the BiOI–WO<jats:sub>3</jats:sub> heterostructure make it a promising candidate for the high‐efficient photocatalyts for water‐splitting.</jats:p></jats:sec>
