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学者姓名：郑坤
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摘要 ：
The main aspects of material research: material synthesis, material structure, and material properties, are interrelated. Acquiring atomic structure information of electron beam sensitive materials by electron microscope, such as porous zeolites, organic-inorganic hybrid perovskites, metal-organic frameworks, is an important and challenging task. The difficulties in characterization of the structures will inevitably limit the optimization of their synthesis methods and further improve their performance. The emergence of integrated differential phase contrast scanning transmission electron microscopy (iDPC-STEM), a STEM characterization technique capable of obtaining images with high signal-to-noise ratio under lower doses, has made great breakthroughs in the atomic structure characterization of these materials. This article reviews the developments and applications of iDPC-STEM in electron beam sensitive materials, and provides an outlook on its capabilities and development.
关键词 ：
low dose low dose electron microscopic characterization electron microscopic characterization electron beam sensitive materials electron beam sensitive materials iDPC-STEM iDPC-STEM
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| GB/T 7714 | Wang, Hongyi , Liu, Linlin , Wang, Jiaxing et al. The Development of iDPC-STEM and Its Application in Electron Beam Sensitive Materials [J]. | MOLECULES , 2022 , 27 (12) . |
| MLA | Wang, Hongyi et al. "The Development of iDPC-STEM and Its Application in Electron Beam Sensitive Materials" . | MOLECULES 27 . 12 (2022) . |
| APA | Wang, Hongyi , Liu, Linlin , Wang, Jiaxing , Li, Chen , Hou, Jixiang , Zheng, Kun . The Development of iDPC-STEM and Its Application in Electron Beam Sensitive Materials . | MOLECULES , 2022 , 27 (12) . |
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摘要 ：
Phase transition is a physical phenomenon that attracts great interest of researchers. Although the theory of second-order phase transitions is well-established, their atomic-scale dynamics in polycrystalline materials remains elusive. In this work, second-order phase transitions in polycrystalline Cu2Se at the transition temperature are directly observed by in situ aberration-corrected transmission electron microscopy. Phase transitions in microcrystalline Cu2Se start at the grain boundaries and extend inside the grains. This phenomenon is more pronounced in nanosized grains. Analysis of phase transitions in nanocrystalline Cu2Se with different grain boundaries demonstrates that grain boundary energy dominates unsynchronized phase transition behavior. This suggests that the energy of grain boundaries is the key factor influencing the energetic barrier for initiation of phase transition. The findings advance atomic-scale understanding of second-order phase transitions, which is crucial for the control of this process in polycrystalline materials.
关键词 ：
Se-2 Se-2 unsynchronized phase transition unsynchronized phase transition atomic-scale atomic-scale in situ transmission electron microscopy in situ transmission electron microscopy Cu Cu
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| GB/T 7714 | Yuan, Hua-Lei , Wang, Kaiwen , Hu, Hanwen et al. Atomic-Scale Observation of Grain Boundary Dominated Unsynchronized Phase Transition in Polycrystalline Cu2Se [J]. | ADVANCED MATERIALS , 2022 , 34 (40) . |
| MLA | Yuan, Hua-Lei et al. "Atomic-Scale Observation of Grain Boundary Dominated Unsynchronized Phase Transition in Polycrystalline Cu2Se" . | ADVANCED MATERIALS 34 . 40 (2022) . |
| APA | Yuan, Hua-Lei , Wang, Kaiwen , Hu, Hanwen , Yang, Lei , Chen, Jie , Zheng, Kun . Atomic-Scale Observation of Grain Boundary Dominated Unsynchronized Phase Transition in Polycrystalline Cu2Se . | ADVANCED MATERIALS , 2022 , 34 (40) . |
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摘要 ：
Defect engineering modified graphite carbon nitride (g-C3N4) has been widely used in various photocatalytic systems due to the enhanced catalytic activity of multiple defect sites (such as vacancies or functional groups). However, the key mechanism of action in each defect site in the corresponding photocatalytic surface reactions is still unclear. Here, the -C N groups and N vacancies were sequentially introduced into g-C3N4 (Nv-C N-CN) for photocatalytic production of high-value and multifunctional H2O2, and the effect of dual defect sites on the overall photocatalytic conversion process was systematically analyzed. The modification of the dual defect sites forms an electron-rich structure and leads to a more localized charge density distribution, which not only enhances the light absorption and carrier separation capabilities, but also significantly improves the selectivity and activity of H2O2 generation. Importantly, detailed experimental characterizations and theoretical calculations clearly revealed the key role of each defect site in the photocataLytic H2O2 surface reaction mechanism: the N vacancies can effectively adsorb and activate O-2, and the -C N groups facilitate the adsorption of H+, which synergistically promote H2O2 generation. The Nv-C N-CN reached a H2O2 generation rate of 3093 mu moL g(-1)h(-1) and achieved an apparent quantum efficiency of 36.2% at 400 nm, significantly surpassing the previously reported g-C3N4-based photocatalysts. Meanwhile, a solar-to-chemical conversion efficiency of 0.23% was achieved in pure water. Constructing defects and understanding their crucial role provides significant insights into the rational use of defect engineering to design and synthesize highly active catalytic materials for energy conversion and environmental remediation.
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| GB/T 7714 | Zhang, Xu , Ma, Peijie , Wang, Cong et al. Unraveling the dual defect sites in graphite carbon nitride for ultra-high photocatalytic H2O2 evolution [J]. | ENERGY & ENVIRONMENTAL SCIENCE , 2022 , 15 (2) : 830-842 . |
| MLA | Zhang, Xu et al. "Unraveling the dual defect sites in graphite carbon nitride for ultra-high photocatalytic H2O2 evolution" . | ENERGY & ENVIRONMENTAL SCIENCE 15 . 2 (2022) : 830-842 . |
| APA | Zhang, Xu , Ma, Peijie , Wang, Cong , Gan, Liyong , Chen, Xianjie , Zhang, Peng et al. Unraveling the dual defect sites in graphite carbon nitride for ultra-high photocatalytic H2O2 evolution . | ENERGY & ENVIRONMENTAL SCIENCE , 2022 , 15 (2) , 830-842 . |
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摘要 ：
Polymeric carbon nitride (C3N4) is a very attractive candidate to produce photocatalytic hydrogen peroxide (H2O2) due to its low-cost, metal-free characteristics. However, the low efficiency would limit its development to higher yields because of insufficient light absorption and electron-hole separation. Here, we developed a simple method to anchor CN quantum dots (QDs) onto g-C3N4 nanosheets to form a homojunction structure (HJ-C3N4), which could improve photocatalytic performance largely without introducing metal elements. Its superior efficiency is a result of the band alignment by the homojunction structure providing excellent electron-hole separation and QDs providing suppressed recombination. Simultaneously, the light responsiveness of QDs endows a wide spectrum-responsive adsorption and enhances the adsorption intensity. The H2O2 yield of the HJ-C3N4 reached 115 mu mol L-1 h(-1) in pure water by visible light, which has an 8.6x higher production than g-C3N4 nanosheets. The material design of 0D/2D homojunction could be extended to other materials with specific band alignment.
关键词 ：
Band alignment Band alignment Carbon nitride Carbon nitride Quantum dots Quantum dots H2O2 H2O2 Homojunction Homojunction
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| GB/T 7714 | Ma, Peijie , Zhang, Xu , Wang, Cong et al. Band alignment of homojunction by anchoring CN quantum dots on g-C3N4 (0D/2D) enhance photocatalytic hydrogen peroxide evolution [J]. | APPLIED CATALYSIS B-ENVIRONMENTAL , 2022 , 300 . |
| MLA | Ma, Peijie et al. "Band alignment of homojunction by anchoring CN quantum dots on g-C3N4 (0D/2D) enhance photocatalytic hydrogen peroxide evolution" . | APPLIED CATALYSIS B-ENVIRONMENTAL 300 (2022) . |
| APA | Ma, Peijie , Zhang, Xu , Wang, Cong , Wang, Zhiwei , Wang, Kaiwen , Feng, Yibo et al. Band alignment of homojunction by anchoring CN quantum dots on g-C3N4 (0D/2D) enhance photocatalytic hydrogen peroxide evolution . | APPLIED CATALYSIS B-ENVIRONMENTAL , 2022 , 300 . |
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摘要 ：
Band alignment modulation and defect passivation for organic-inorganic halide perovskite solar cells (PSCs) through interface engineering are some of the most effective methods to improve the performance. In the present work, we systematically studied the effect of formamidinium bromide (FABr) treatment on perovskite films. Transmission electron microscopy (TEM), Kelvin probe force microscopy (KPFM), and photoluminescence (PL) results validate that nonhomogeneously distributed Br- incorporation was formed in a FABr-treated perovskite layer, and an absorber with gradient band alignment was achieved. This effectively promotes the transport of photogenerated carriers and inhibits the carrier recombination in PSCs. As a result, the power conversion efficiency (PCE) is significantly increased after FABr treatment, and the enhancement is mainly due to the increased open-circuit voltage (V-OC). This approach highlights a promising strate o obtain and characterize the gradient band alignment, and thus further optimizes the performance of PSCs.
关键词 ：
component gradient component gradient energy band alignment energy band alignment interface engineering FABr interface engineering FABr perovskite solar cells perovskite solar cells
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| GB/T 7714 | Xuan, Zhipeng , Hao, Xia , Qu, Xianlin et al. Efficient Perovskite Solar Cells with a Gradient Light Absorption Layer and Low V-OC Loss Obtained by Interface Engineering [J]. | ACS APPLIED ENERGY MATERIALS , 2021 , 4 (4) : 3584-3592 . |
| MLA | Xuan, Zhipeng et al. "Efficient Perovskite Solar Cells with a Gradient Light Absorption Layer and Low V-OC Loss Obtained by Interface Engineering" . | ACS APPLIED ENERGY MATERIALS 4 . 4 (2021) : 3584-3592 . |
| APA | Xuan, Zhipeng , Hao, Xia , Qu, Xianlin , Wang, Yunfan , Lai, Huagui , Chen, Tingting et al. Efficient Perovskite Solar Cells with a Gradient Light Absorption Layer and Low V-OC Loss Obtained by Interface Engineering . | ACS APPLIED ENERGY MATERIALS , 2021 , 4 (4) , 3584-3592 . |
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摘要 ：
Silicon heterojunction solar cells are expected to increase their market share in the near future. Qu et al. identify an embedded nanotwin structure at the crystalline silicon/hydrogenated amorphous silicon interface of silicon heterojunction cells that limits the device performance and devise an approach to suppress its formation. The interface of high-quality crystalline silicon/hydrogenated amorphous silicon (c-Si/a-Si:H) is indispensable for achieving the ideal conversion efficiency of Si heterojunction solar cells. Therefore, it is extremely desirable to characterize and control the interface at the atomic scale. Here, we employ spherical aberration-corrected transmission electron microscopy to investigate the atomic structure of the c-Si/a-Si:H interface in high-efficiency Si heterojunction solar cells. Their structural evolution during in situ annealing is visualized at the atomic scale. High-density embedded nanotwins, detrimental to the device performance, are identified in the thin epitaxial layer between c-Si and a-Si:H. The nucleation and formation of these nanotwins are revealed via ex situ and in situ high-resolution transmission electron microscopy. Si heterojunction solar cells with low-density nanotwins are fabricated by introducing an ultra-thin intrinsic a-Si:H buffer layer and show better performance, indicating that the strategy to restrain embedded nanotwins can further enhance the conversion efficiency of Si heterojunction solar cells.
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| GB/T 7714 | Qu, Xianlin , He, Yongcai , Qu, Minghao et al. Identification of embedded nanotwins at c-Si/a-Si:H interface limiting the performance of high-efficiency silicon heterojunction solar cells [J]. | NATURE ENERGY , 2021 , 6 (2) : 194-202 . |
| MLA | Qu, Xianlin et al. "Identification of embedded nanotwins at c-Si/a-Si:H interface limiting the performance of high-efficiency silicon heterojunction solar cells" . | NATURE ENERGY 6 . 2 (2021) : 194-202 . |
| APA | Qu, Xianlin , He, Yongcai , Qu, Minghao , Ruan, Tianyu , Chu, Feihong , Zheng, Zilong et al. Identification of embedded nanotwins at c-Si/a-Si:H interface limiting the performance of high-efficiency silicon heterojunction solar cells . | NATURE ENERGY , 2021 , 6 (2) , 194-202 . |
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摘要 ：
Te-free Bi2S3-based thermoelectric materials show great potential for eco-friendly and industrial scale-up applications because of their high-abundance, low-cost, low-toxicity, and low-thermal-conductivity features. However, their low figure of merit, ZT limits their further applications. In this work, we report a high ZT of similar to 0.8 at similar to 760 K in n-type polycrystalline Bi2S3 by a combination of hierarchical structure manipulation and carrier density optimization. A step-by-step fabrication by using mechanical alloying, high-pressure and high-temperature treatment, spark plasma sintering, and annealing leads to unique micro/nanostructures in polycrystalline Bi2S3 including refined grains, high-density Bi-rich nanoprecipitates, significant lattice distortions, and nanopores that confirmed by comprehensive characterizations, which contribute to significantly suppressed lattice thermal conductivity of 0.41 W m(-1) K-1 at similar to 760 K. A further 0.5 mol% CuCl2-doping triggers impurity band in the electronic structure of Bi2S3 and narrows the bandgap for optimizing the carrier concentration at similar to 1 x 10(20) cm(-3), confirmed by both experimental results and first-principles density functional theory calculations. The optimized carrier concentration and maintained low lattice thermal conductivity give rise to a high power factor of similar to 5.3 mu W cm(-1) K-2 and high ZT that ranks as a top value. This work provides a new route to achieve high thermoelectric performance in n-type polycrystalline Bi2S3.
关键词 ：
Thermoelectric Thermoelectric Bi2S3 Bi2S3 Calculation Calculation Doping Doping Structure Structure
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| GB/T 7714 | Ji, Wenting , Shi, Xiao-Lei , Liu, Wei-Di et al. Boosting the thermoelectric performance of n-type Bi2S3 by hierarchical structure manipulation and carrier density optimization [J]. | NANO ENERGY , 2021 , 87 . |
| MLA | Ji, Wenting et al. "Boosting the thermoelectric performance of n-type Bi2S3 by hierarchical structure manipulation and carrier density optimization" . | NANO ENERGY 87 (2021) . |
| APA | Ji, Wenting , Shi, Xiao-Lei , Liu, Wei-Di , Yuan, Hualei , Zheng, Kun , Wan, Biao et al. Boosting the thermoelectric performance of n-type Bi2S3 by hierarchical structure manipulation and carrier density optimization . | NANO ENERGY , 2021 , 87 . |
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摘要 ：
Discovering high-performance near-room-temperature thermoelectric materials is extremely imperative to widen the practical application in thermoelectric power generation and refrigeration. Here, ternary Ag2Se1-xTex (x = 0.1, 0.2, 0.3, 0.4, and 0.5) materials are prepared via the wet-mechanical alloying and spark plasma sintering process to investigate their near-room-temperature thermoelectric properties. From density functional theory calculation and single-parabolic-band modeling study, we found that the reduced contribution of Se 4p orbitals to the total density of states decreases the carrier effective mass with increasing Te content, which should enhance the theoretically maximum zT. These calculation results are also verified by the experimental results. Meanwhile, complex microstructures including dislocations, nanograins, high-density boundaries, Te-Se substitution, lattice distortions, and localized strain have been observed in ternary Ag2Se1-xTex. These complex microstructures strengthen phonon scattering and in turn lead to ultralow lattice thermal conductivity in the range of 0.21-0.31 W m(-1) K-1 in ternary Ag2Se1-xTex at 300 K. Although the increased deformation potential suppresses the carrier mobility, benefiting from the engineered band structures and ultralow lattice thermal conductivity, a high zT of >1 can be potentially obtained in the ternary Ag2Se1-xTex with appropriate carrier concentration. This study indicates that ternary Ag2Se1-xTex is a promising candidate for near-room-temperature thermoelectric applications.
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| GB/T 7714 | Chen, Jie , Yuan, Hualei , Zhu, Yu-Ke et al. Ternary Ag2Se1-xTex: A Near-Room-Temperature Thermoelectric Material with a Potentially High Figure of Merit [J]. | INORGANIC CHEMISTRY , 2021 , 60 (18) : 14165-14173 . |
| MLA | Chen, Jie et al. "Ternary Ag2Se1-xTex: A Near-Room-Temperature Thermoelectric Material with a Potentially High Figure of Merit" . | INORGANIC CHEMISTRY 60 . 18 (2021) : 14165-14173 . |
| APA | Chen, Jie , Yuan, Hualei , Zhu, Yu-Ke , Zheng, Kun , Ge, Zhen-Hua , Tang, Jun et al. Ternary Ag2Se1-xTex: A Near-Room-Temperature Thermoelectric Material with a Potentially High Figure of Merit . | INORGANIC CHEMISTRY , 2021 , 60 (18) , 14165-14173 . |
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摘要 ：
The platinum single-atom-catalyst is verified as a very successful route to approach the size limit of Pt catalysts, while how to further improve the catalytic efficiency of Pt is a fundamental scientific question and is challenging because the size issue of Pt is approached at the ultimate ceiling as single atoms. Here, a new route for further improving Pt catalytic efficiency by cobalt (Co) and Pt dual-single-atoms on titanium dioxide (TiO2 ) surfaces, which contains a fraction of nonbonding oxygen-coordinated Co-O-Pt dimers, is reported. These Co-Pt dimer sites originate from loading high-density Pt single-atoms and Co single-atoms, with them anchoring randomly on the TiO2 substrate. This dual-single-atom catalyst yields 13.4% dimer sites and exhibits an ultrahigh and stable photocatalytic activity with a rate of 43.467 mmol g-1 h-1 and external quantum efficiency of ≈83.4% at 365 nm. This activity far exceeds those of equal amounts of Pt single-atom and typical Pt clustered catalysts by 1.92 and 1.64 times, respectively. The enhancement mechanism relies on the oxygen-coordinated Co-O-Pt dimer coupling, which can mutually optimize the electronic states of both Pt and Co sites to weaken H* binding. Namely, the "mute" Co single-atom is activated by Pt single-atom and the activity of the Pt atom is further enhanced through the dimer interaction. This strategy of nonbonding interactive dimer sites and the oxygen-mediated catalytic mechanisms provide emerging rich opportunities for greatly improving the catalytic efficiency and developing novel catalysts with creating new electronic states.
关键词 ：
dual single-atoms dual single-atoms hydrogen evolution reaction hydrogen evolution reaction oxygen-coordination oxygen-coordination single-atomic-site catalysts single-atomic-site catalysts TiO2 photocatalysts TiO2 photocatalysts
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| GB/T 7714 | Wang Cong , Wang Kaiwen , Feng Yibo et al. Co and Pt Dual-Single-Atoms with Oxygen-Coordinated Co-O-Pt Dimer Sites for Ultrahigh Photocatalytic Hydrogen Evolution Efficiency. [J]. | Advanced materials , 2021 , 33 (13) : e2003327 . |
| MLA | Wang Cong et al. "Co and Pt Dual-Single-Atoms with Oxygen-Coordinated Co-O-Pt Dimer Sites for Ultrahigh Photocatalytic Hydrogen Evolution Efficiency." . | Advanced materials 33 . 13 (2021) : e2003327 . |
| APA | Wang Cong , Wang Kaiwen , Feng Yibo , Li Chong , Zhou Xiaoyuan , Gan Liyong et al. Co and Pt Dual-Single-Atoms with Oxygen-Coordinated Co-O-Pt Dimer Sites for Ultrahigh Photocatalytic Hydrogen Evolution Efficiency. . | Advanced materials , 2021 , 33 (13) , e2003327 . |
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摘要 ：
Programmable magnetic field-free manipulation of perpendicular magnetization switching is essential for the development of ultralow-power spintronic devices. However, the magnetization in a centrosymmetric single-layer ferromagnetic film cannot be switched directly by passing an electrical current in itself. Here, we demonstrate a repeatable bulk spin-orbit torque (SOT) switching of the perpendicularly magnetized CoPt alloy single-layer films by introducing a composition gradient in the thickness direction to break the inversion symmetry. Experimental results reveal that the bulk SOT-induced effective field on the domain walls leads to the domain walls motion and magnetization switching. Moreover, magnetic field-free perpendicular magnetization switching caused by SOT and its switching polarity (clockwise or counterclockwise) can be reversibly controlled in the IrMn/Co/Ru/CoPt heterojunctions based on the exchange bias and interlayer exchange coupling. This unique composition gradient approach accompanied with electrically controllable SOT magnetization switching provides a promising strategy to access energy-efficient control of memory and logic devices.
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| GB/T 7714 | Xie Xuejie , Zhao Xiaonan , Dong Yanan et al. Controllable field-free switching of perpendicular magnetization through bulk spin-orbit torque in symmetry-broken ferromagnetic films. [J]. | Nature communications , 2021 , 12 (1) : 2473 . |
| MLA | Xie Xuejie et al. "Controllable field-free switching of perpendicular magnetization through bulk spin-orbit torque in symmetry-broken ferromagnetic films." . | Nature communications 12 . 1 (2021) : 2473 . |
| APA | Xie Xuejie , Zhao Xiaonan , Dong Yanan , Qu Xianlin , Zheng Kun , Han Xiaodong et al. Controllable field-free switching of perpendicular magnetization through bulk spin-orbit torque in symmetry-broken ferromagnetic films. . | Nature communications , 2021 , 12 (1) , 2473 . |
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