34 results on '"Hedong Chen"'
Search Results
2. An InGaN/SiNx/Si Uniband Diode Photodetector
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Jiaxun Song, Xingyu Wang, Jinyou Xu, Yongjie Chen, Hedong Chen, Yingzhi Zhao, Guofu Zhou, and Richard Nötzel
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Fowler−Nordheim tunneling ,InGaN ,photodetectors ,silicon nitride ,sub-Poissonian shot noise ,uniband diodes ,Applied optics. Photonics ,TA1501-1820 ,Optics. Light ,QC350-467 - Abstract
A novel self‐powered InGaN/SiNx/Si uniband diode photodetector (PD) is introduced. The full band structure is first constructed from the transition of direct tunneling to Fowler‐Nordheim tunneling of holes through the ultrathin SiNx interlayer at forward bias in the dark. Basis is the alignment of the n‐InGaN conduction band with the p‐Si valence band at zero bias. Under illumination, the photocurrent, responsivity, and bandwidth for the self‐powered PD at zero bias indicate two distinct operation modes (i) for longer and (ii) for shorter wavelengths of incident light. The two modes involve (i) absorption in Si and electron tunneling through the SiNx interlayer and (ii) absorption in InGaN and hole transport across the SiNx interlayer. The noise is considerably larger in operation mode (i) than in operation mode (ii). This is attributed to the presence or absence of energy barriers for electron and hole transport in PD operation. Hence, noise is introduced as an independent parameter to discriminate between longer and shorter wavelength regions in dual‐wavelength photodetection.
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- 2022
- Full Text
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3. InGaN/Cu2O Heterostructure Core-Shell Nanowire Photoanode for Efficient Solar Water Splitting
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Yingzhi Zhao, Lingyun Xie, Hedong Chen, Xingyu Wang, Yongjie Chen, Guofu Zhou, and Richard Nötzel
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Cu2O ,InGaN nanowires ,core-shell ,stability ,co-catalyst ,Physics ,QC1-999 - Abstract
The heterostructuring and doping concepts have proved to obtain a novel n-InGaN/p-Cu2O nanowire (NW) photoanode by strong enhancement of the photocurrent compared to a bare InGaN NW photoanode in solar water splitting. The large photocurrent is due to the maximized photocarrier separation and hole transfer to the surface in the depletion zone of the p–n heterojunction established by the p-Cu2O layer, forming a thin, uniform shell-layer around the n-InGaN NW core by electrodeposition. For sufficiently thin Cu2O layers, the upward energy band bending in the depletion zone extends up to the surface for optimized hole transport and surface reaction. Thick Cu2O layers on top of the InGaN NWs act as common photocathodes. The functional InGaN/Cu2O heterostructure core-shell NW photoanode is chemically self-stabilized at positive applied voltage by a thin CuO surface layer. Final deposition of the earth-abundant NiOOH co-catalyst boosts the photocurrent of the InGaN/Cu2O/NiOOH complete NW photoanode into the competitive mA/cm2 range.
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- 2021
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4. Electrocatalytic activity of InN/InGaN quantum dots
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Hongjie Yin, Yinping Qian, Lingyun Xie, Changkun Song, Xingyu Wang, Hedong Chen, Peng Wang, Guofu Zhou, and Richard Nötzel
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Industrial electrochemistry ,TP250-261 ,Chemistry ,QD1-999 - Abstract
We present a basic, comprehensive study of the electrocatalytic activity of epitaxial InN/InGaN quantum dots (QDs) by cyclic voltammetry, electrochemical impedance spectroscopy, linear sweep voltammetry and capacitance-voltage measurements, using the ferro/ferricyanide redox probe. Key is the direct proof of the dependence of the catalytic activity on the QD structural properties and of the existence and overall tunability of high positive surface charge on the QDs being in origin of the catalytic activity together with the zero-dimensional electronic properties. This fundamental assessment paves the way to fine-tuning the artificial QD structure as efficient catalyst to further boost the performance of biosensors and photoanodes for solar hydrogen generation. Keywords: Quantum dots, InN, InGaN, Catalysis
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- 2019
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5. Ruthenium-Alloyed Iron Phosphide Single Crystal with Increased Fermi Level for Efficient Hydrogen Evolution
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Yu Kang, Yujia Han, Hedong Chen, Horst Borrmann, Peter Adler, Darius Pohl, Martin Hantusch, Markus König, Yangkun He, Yufei Ma, Xiaodong Wang, and Claudia Felser
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General Materials Science - Abstract
Transition metal phosphide alloying is an effective approach for optimizing the electronic structure and improving the intrinsic performance of the hydrogen evolution reaction (HER). However, obtaining 3d transition metal phosphides alloyed with noble metals is still a challenge owing to their difference in electronegativity, and the influence of their electronic structure modulated by noble metals on the HER reaction also remains unclear. In this study, we successfully incorporated Ru into an Fe
- Published
- 2022
6. Robust Ultrafine-Graphite-Sheet/Si@Carbon Microsphere with Double Protective Layers as High-Performance Lithium-Ion Battery Anode
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Hedong Chen, Wenxia Hu, Min Dong, Dao Wang, Yecheng Qiu, Lin Liu, Haiqing Qin, Fuming Chen, and Hou Xianhua
- Published
- 2023
7. Vertical 2-dimensional heterostructure SnS-SnS2 with built-in electric field on rGO to accelerate charge transfer and improve the shuttle effect of polysulfides
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Kangshou Lin, Xiang Liu, Xiaofeng Huang, Xianhua Hou, Yu Zhao, Zhoulu Wang, Hedong Chen, and Jinzhu Zhao
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Materials science ,business.industry ,chemistry.chemical_element ,Heterojunction ,Electrochemistry ,Cathode ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,law.invention ,Biomaterials ,Metal ,Colloid and Surface Chemistry ,chemistry ,law ,Electric field ,visual_art ,Electrode ,visual_art.visual_art_medium ,Optoelectronics ,business ,Carbon ,Electrical conductor - Abstract
Traditional carbon materials as sulfur hosts of Li-sulfur(Li-S) cathodes have slightly physical constraint for polysulfides, due to their no-polar property. Therefore, it is necessary to further enhance the affinity between sulfur hosts and polysulfides, and relieve the shuttle effects in the Li- S batteries. Herein, we report a novel vertical 2-dimensional (2D) p-SnS/n-SnS2 heterostructure sheets which grown on the surface of rGO. The excellent electrochemical properties of SnS-SnS2@rGO as Li-S cathode are ascribed to the stronger absorption effect of metal sulphides for polysulfides and the smooth trapping-diffusion-conversion effect of p-SnS/n-SnS2 heterostructure for polysulfides. As a conductive carrier for the growth of vertical 2D p-SnS/n-SnS2 heterostructure nanosheets, rGO can protect the steadiness and enhance the cycle stability of electrode, compared with heterostructure without rGO. In addition, the built-in electric field in the 2D p-SnS/n-SnS2 heterostructure during the discharge/charge processes can effectively accelerate charge transfer, and the charge transfer mechanism in SnS-SnS2 heterostructure during cycling has been investigated. At a rate capability of 2C, the designed SnS-SnS2@rGO as Li-S cathode delivers high specific capacities of 907 mAh g−1 and 571 mAh g−1 after the first cycle and 500 cycles, respectively, which shown excellent cycling ability.
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- 2022
8. Enhanced Light Trapping and Charge Separation via Pyramidal Cu2O/NiCo-LDH Photocathode for Efficient Water Splitting
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Yingzhi Zhao, Weiming Song, Dao Wang, Hedong Chen, and Guofu Zhou
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Materials Chemistry ,Electrochemistry ,Energy Engineering and Power Technology ,Chemical Engineering (miscellaneous) ,Electrical and Electronic Engineering - Published
- 2022
9. Enhanced continuous desalination performance with iron-complexed malonate redox couples.
- Author
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Minxian Han, Lufan Tang, Yidong Xiao, Minzhang Li, Hedong Chen, Songsiriritthigul, Prayoon, Than Zaw Oo, Mono Zaw, Lwin, Nyein Wint, Aung, Su Htike, Karthick, R., and Fuming Chen
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- 2023
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10. One-Compartment InGaN Nanowire Fuel Cell in the Light and Dark Operating Modes
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Guofu Zhou, Yingzhi Zhao, Jiaxun Song, Hedong Chen, Yongjie Chen, Lujia Rao, and Richard Nötzel
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Materials science ,business.industry ,General Chemical Engineering ,Nanowire ,General Chemistry ,Glassy carbon ,Article ,Cathode ,Dielectric spectroscopy ,law.invention ,Catalysis ,Chemistry ,law ,Fuel cells ,Optoelectronics ,Cyclic voltammetry ,business ,QD1-999 - Abstract
A one-compartment H2O2 photofuel cell (PFC) with a photoanode based on InGaN nanowires (NWs) is introduced for the first time. The electrocatalytic and photoelectrocatalytic properties of the InGaN NWs are studied in detail by cyclic voltammetry, current versus time measurements, photovoltage measurements, and electrochemical impedance spectroscopy. In parallel, IrO x (OH) y as the co-catalyst on the InGaN NWs is evaluated to boost the catalytic activity in the dark and light. For the PFC, Ag is the best as the cathode among Ag, Pt, and glassy carbon. The PFC operates in the dark as a conventional fuel cell (FC) and under illumination with 25% increased electrical power generation at room temperature. Such dual operation is unique, combining FC and PFC technologies for the most flexible use.
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- 2021
11. Fluorine substitution and pre-sodiation strategies to boost energy density of V-based NASICON-structured SIBs: Combined theoretical and experimental study
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Kangshou Lin, Qiqi Liu, Yu Zhou, Hedong Chen, Jiefei Liu, Jin-Zhu Zhao, and Xianhua Hou
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General Chemical Engineering ,Environmental Chemistry ,General Chemistry ,Industrial and Manufacturing Engineering - Published
- 2023
12. Identification of Interface Structure for a Topological CoS
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Yu, Kang, Yangkun, He, Darius, Pohl, Bernd, Rellinghaus, Dong, Chen, Marcus, Schmidt, Vicky, Süß, Qingge, Mu, Fan, Li, Qun, Yang, Hedong, Chen, Yufei, Ma, Gudrun, Auffermann, Guowei, Li, and Claudia, Felser
- Abstract
Transition metal chalcogenides such as CoS
- Published
- 2022
13. Inter-facet composition modulation of III-nitride nanowires over pyramid textured Si substrates by stationary molecular beam epitaxy
- Author
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Xingyu Wang, Dan Wang, Peng Wang, Hongjie Yin, Guofu Zhou, Hedong Chen, Hao Wang, Lujia Rao, Changkun Song, and Richard Nötzel
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Materials science ,Photoluminescence ,business.industry ,Nanowire ,Cathodoluminescence ,02 engineering and technology ,Nitride ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Ridge (differential geometry) ,01 natural sciences ,Atomic and Molecular Physics, and Optics ,0104 chemical sciences ,Optoelectronics ,General Materials Science ,Electrical and Electronic Engineering ,Facet ,0210 nano-technology ,business ,Molecular beam epitaxy ,Pyramid (geometry) - Abstract
InGaN nanowires (NWs) are grown on pyramid textured Si substrates by stationary plasma-assisted molecular beam epitaxy (PA-MBE). The incidence angles of the highly directional source beams vary for different pyramid facets, inducing a distinct inter-facet modulation of the In content of the InGaN NWs, which is verified by spatial element distribution analysis. The resulting multi-wavelength emission is confirmed by photoluminescence (PL) and cathodoluminescence (CL). Pure GaN phase formation dominates on certain facets, which is attributed to extreme local growth conditions, such as low active N flux. On the same facets, InGaN NWs exhibit a morphology change close to the pyramid ridge, indicating inter-facet atom migration. This cross-talk effect due to inter-facet atom migration is verified by a decrease of the inter-facet In content modulation amplitude with shrinking pyramid size. A detailed analysis of the In content variation across individual pyramid facets and element distribution line profiles reveals that the cross-talk effect originates mainly from the inter-facet atom migration over the convex pyramid ridge facet boundaries rather than the concave base line facet boundaries. This is understood by first-principles calculations showing that the pyramid baseline facet boundary acts as an energy barrier for atom migration, which is much higher than that of the ridge facet boundary. The influence of the growth temperature on the inter-facet In content modulation is also presented. This work gives deep insight into the composition modulation for the realization of multi-color light-emitting devices based on the monolithic growth of InGaN NWs on pyramid textured Si substrates.
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- 2020
14. Scalable Synthesis of Si/C Microspheres with 3D Conducting Nanosized Porous Channels as High-Performance Anodes in LIBs
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Xianhua Hou, Hedong Chen, Shimin Huang, Shaofeng Wang, Haiqing Qin, Shenggong He, and Wei Shan
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Materials science ,Silicon ,General Chemical Engineering ,Composite number ,Energy Engineering and Power Technology ,chemistry.chemical_element ,Anode ,Microsphere ,Fuel Technology ,chemistry ,Chemical engineering ,Spray drying ,Lithium ,Porosity ,Carbon - Abstract
To relieve the volume expansion of silicon during lithium insertion/desertion process, we designed fluffy rice carbon/nano-Si@C (FRC/NP-Si@C) composite with stable structure via spray drying, a lar...
- Published
- 2020
15. Construct pseudo-capacitance of a flexible 3D-entangled carbon nanofiber film as freestanding anode for dual-ion full batteries
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Xianhua Hou, Kaixiang Shen, Haiqing Qin, and Hedong Chen
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010302 applied physics ,Battery (electricity) ,Materials science ,business.industry ,Carbon nanofiber ,Electrolyte ,Condensed Matter Physics ,01 natural sciences ,Capacitance ,Atomic and Molecular Physics, and Optics ,Electronic, Optical and Magnetic Materials ,Anode ,Specific surface area ,Nanofiber ,0103 physical sciences ,Optoelectronics ,Electrical and Electronic Engineering ,business ,Voltage - Abstract
We construct a remarkable freestanding and porous carbon nanofibers (FPCNFs) as anode materials in the dual-ion full battery. The dual-ion battery (DIB) based on electrolyte including the Li+ and PF6− has a high operating voltage from 3.0 to 5.0 V. The entangled and crossed carbon nanofiber film creates plenty of porous with a high specific surface area (200 m2g−1) to contribute to the pseudo-capacitance effect. The dual-ion full batteries exhibit a stable long-life property up to 500 cycles, an approximately above 4.0V high operating average discharge voltage and an energy density delivering almost 185 W h kg−1 at 0.1 A g−1. The FPCNFs can be a potential alternative toward a cost-efficient high energy density battery anode.
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- 2020
16. A new dual-ion hybrid energy storage system with energy density comparable to that of ternary lithium ion batteries
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Xianhua Hou, Shaofeng Wang, Zongping Shao, Hedong Chen, and Shenggong He
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Supercapacitor ,Materials science ,Renewable Energy, Sustainability and the Environment ,Double-layer capacitance ,02 engineering and technology ,General Chemistry ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Electrochemistry ,01 natural sciences ,Capacitance ,Cathode ,Energy storage ,0104 chemical sciences ,Anode ,law.invention ,Capacitor ,Chemical engineering ,law ,General Materials Science ,0210 nano-technology - Abstract
Supercapacitors that store energy through dual electrochemical layer capacitance or surface faradaic redox reactions are characterized by their fast charging/discharging capability, high power densities, and long cycling lifetime. However, the low energy density of supercapacitors seriously inhibits their practical applications. Herein, a dual-ion hybrid energy storage system using expanded graphite (EG) as the anion-intercalation supercapacitor-type cathode and graphite@nano-silicon@carbon (Si/C) as the cation intercalation battery-type anode is designed for efficient energy storage. The Si/C anode, synthesized by interfacial adhesion between nanosilicon and graphite with the help of pitch, demonstrates high specific capacity, remarkable cycling stability, and enhanced rate capability. Meanwhile, the EG cathode, which stores energy based on electrochemical double layer capacitance through its unique faradaic pseudocapacitive negative anion intercalation behaviour, demonstrates high energy densities of 462.9–356.5 W h kg−1 at power densities of 403–7130 W kg−1. The resulting Si/C//EG hybrid system delivered highly attractive energy densities of 252–222.6 W h kg−1 at power densities of 215–5420 W kg−1, which are superior to those of conventional electrochemical double layer capacitors and lithium-ion capacitors, making the dual-ion hybrid system a new type of energy storage device capable of achieving fast and efficient energy storage.
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- 2020
17. Spatial Surface Charge Engineering for Electrochemical Electrodes
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Yinping Qian, Richard Nötzel, Hongjie Yin, Guofu Zhou, Lujia Rao, Hedong Chen, Xingyu Wang, Peng Wang, and Lingyun Xie
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Materials science ,lcsh:Medicine ,02 engineering and technology ,010402 general chemistry ,Epitaxy ,Electrochemistry ,01 natural sciences ,Reference electrode ,Article ,Nanoscience and technology ,Surface charge ,lcsh:Science ,Kelvin probe force microscope ,Multidisciplinary ,business.industry ,lcsh:R ,021001 nanoscience & nanotechnology ,0104 chemical sciences ,Electrochemical gas sensor ,Quantum dot ,Electrode ,Optoelectronics ,lcsh:Q ,0210 nano-technology ,business - Abstract
We introduce a novel concept for the design of functional surfaces of materials: Spatial surface charge engineering. We exploit the concept for an all-solid-state, epitaxial InN/InGaN-on-Si reference electrode to replace the inconvenient liquid-filled reference electrodes, such as Ag/AgCl. Reference electrodes are universal components of electrochemical sensors, ubiquitous in electrochemistry to set a constant potential. For subtle interrelation of structure design, surface morphology and the unique surface charge properties of InGaN, the reference electrode has less than 10 mV/decade sensitivity over a wide concentration range, evaluated for KCl aqueous solutions and less than 2 mV/hour long-time drift over 12 hours. Key is a nanoscale charge balanced surface for the right InGaN composition, InN amount and InGaN surface morphology, depending on growth conditions and layer thickness, which is underpinned by the surface potential measured by Kelvin probe force microscopy. When paired with the InN/InGaN quantum dot sensing electrode with super-Nernstian sensitivity, where only structure design and surface morphology are changed, this completes an all-InGaN-based electrochemical sensor with unprecedented performance.
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- 2019
18. Vertical 2-dimensional heterostructure SnS-SnS
- Author
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Xiaofeng, Huang, Yu, Zhao, Kangshou, Lin, Xiang, Liu, Jinzhu, Zhao, Hedong, Chen, Zhoulu, Wang, and Xianhua, Hou
- Abstract
Traditional carbon materials as sulfur hosts of Li-sulfur(Li-S) cathodes have slightly physical constraint for polysulfides, due to their no-polar property. Therefore, it is necessary to further enhance the affinity between sulfur hosts and polysulfides, and relieve the shuttle effects in the Li- S batteries. Herein, we report a novel vertical 2-dimensional (2D) p-SnS/n-SnS
- Published
- 2021
19. Prepare and optimize NASICON-type Na4MnAl(PO4)3 as low cost cathode for sodium ion batteries
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Yiran Zheng, Jiefei Liu, Dan Huang, Hedong Chen, and Xianhua Hou
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General Physics and Astronomy ,Surfaces and Interfaces ,General Chemistry ,Condensed Matter Physics ,Surfaces, Coatings and Films - Published
- 2022
20. Si-based anode with hierarchical protective function and hollow ring-like carbon matrix for high performance lithium ion batteries
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Hedong Chen, Xianhua Hou, Lijun Fu, Guangzu Zhang, Kaixiang Shen, Yingchun Xia, Fuming Chen, Guofu Zhou, Shaofeng Wang, and Haiqing Qin
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Materials science ,Scanning electron microscope ,Graphene ,Composite number ,General Physics and Astronomy ,chemistry.chemical_element ,02 engineering and technology ,Surfaces and Interfaces ,General Chemistry ,Carbon nanotube ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,0104 chemical sciences ,Surfaces, Coatings and Films ,law.invention ,Anode ,chemistry ,Chemical engineering ,law ,Transmission electron microscopy ,Lithium ,0210 nano-technology ,Carbon - Abstract
Si-based anode with hierarchical protective function and hollow ring-like carbon matrix has been successfully designed and prepared by a simple one-step spray drying method. Nano-Si particles are coated by carbon layer and then encapsulated in a strong carbon matrix with hollow ring-like structure composed of carbon nanotubes and wrinkled graphene sheets. The Si-based anode, nano-Si@carbon/carbon nanotubes@graphene sheets, exhibits excellent electrochemical performance including high initial coloumbic efficiency, favorable cyclic stability and outstanding rate capability. The composite delivers an initial discharge/charge capacity of 2891.7/2533.3 mAh g−1 with a high initial coloumbic efficiency of 87.6%, high capacity of 1524.3 mAh g−1 after 130 cycles with high capacity retention of 92.4% (vs. 1618.4 mAh g−1 for the 100 cycles), and high capacity maintaining at 1073.2/1016.2 mAh g−1 at a large current density of 1.6 A g−1. Furthermore, the scanning electron microscopy and transmission electron microscopy images of the composite electrode after several operating cycles also indicate that composite electrode exhibits structural stability and nano-Si particles are still wrapped by the carbon matrix material. Therefore, the composite is very promising anode for lithium ion batteries.
- Published
- 2019
21. Anisotropic Piezoelectric Response from InGaN Nanowires with Spatially Modulated Composition and Topography over a Textured Si(100) Substrate
- Author
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Yinping Qian, Changkun Song, Hedong Chen, Lujia Rao, Guofu Zhou, Xingfu Wang, Peng Wang, and Richard Nötzel
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Materials science ,business.industry ,Schottky barrier ,Nanogenerator ,Nanowire ,02 engineering and technology ,Substrate (electronics) ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Piezoelectricity ,Electrical contacts ,0104 chemical sciences ,Condensed Matter::Materials Science ,Optoelectronics ,General Materials Science ,0210 nano-technology ,business ,Anisotropy ,Molecular beam epitaxy - Abstract
An anisotropic piezoelectric response is demonstrated from InGaN nanowires (NWs) over a pyramid-textured Si(100) substrate with an interfacet composition and topography modulation induced by stationary molecular beam epitaxy growth conditions, taking advantage of the unidirectional source beam flux. The variations of InGaN NWs between the pyramid facets are verified in terms of morphology, element distribution, and crystalline properties. The piezoelectric response is investigated by electrical atomic force microscopy (AFM) with a statistic analyzing method. Representative pyramids from the ensemble, on top of which InGaN NWs grown with a substrate held at an oblique angle, were characterized for understanding and confirming the degree of anisotropy. The positive deviated oscillation of the peak force error is identified as a measure of the effective AFM tip/NW interaction with respect to the electrical contact and mechanical deformation. The Schottky contact between the metal-coated AFM tip and the NWs on the different facets reveals distinctions consistent with the interfacet composition variation. The interfacet variation of the piezoelectric response of the InGaN NWs is first evaluated by electrical AFM under zero bias. The average current monotonically depends on the scan frequency, which determines the average peak force error, that is, mechanical deformation, with a facet characteristic slope. A piezoelectric nanogenerator device is fabricated out of a sample with an ensemble of pyramids, which exhibits anisotropic output under periodic directional pressing. This work provides a universal strategy for the synthesis of composite semiconductor materials with an anisotropic piezoelectric response.
- Published
- 2021
22. Selective Hydrogenation of Naphthalene to Decalin Over Surface‐Engineered α‐MoC Based on Synergy between Pd Doping and Mo Vacancy Generation
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Yufei Ma, Jianbin Liu, Meng Chen, Qun Yang, Hedong Chen, Guoqing Guan, Yanlin Qin, and Tiejun Wang
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Biomaterials ,Electrochemistry ,Condensed Matter Physics ,Electronic, Optical and Magnetic Materials - Published
- 2022
23. An InGaN/SiN x /Si Uniband Diode Photodetector
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Jiaxun Song, Xingyu Wang, Jinyou Xu, Yongjie Chen, Hedong Chen, Yingzhi Zhao, Guofu Zhou, and Richard Nötzel
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General Medicine - Published
- 2022
24. Multi-wavelength light emission from InGaN nanowires on pyramid-textured Si(100) substrate grown by stationary plasma-assisted molecular beam epitaxy
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Xingyu Wang, Lujia Rao, Guofu Zhou, Hongjie Yin, Peng Wang, Hedong Chen, Richard Nötzel, and Hao Wang
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010302 applied physics ,Fabrication ,Photoluminescence ,Materials science ,business.industry ,Scanning electron microscope ,Nanowire ,Cathodoluminescence ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,Wavelength ,0103 physical sciences ,Optoelectronics ,General Materials Science ,Light emission ,0210 nano-technology ,business ,Molecular beam epitaxy - Abstract
We demonstrate multi-wavelength light emission from InGaN nanowires (NWs) monolithically grown on pyramid-textured Si(100) substrates by plasma-assisted molecular beam epitaxy (MBE) under stationary conditions. Taking advantage of the highly unidirectional source material beam fluxes, the In content of the NWs is tuned on the different pyramid facets due to varied incidence angle. This is confirmed by distinct NW morphologies observed by scanning electron microscopy (SEM) and by energy-dispersive X-ray (EDX) element mapping. Photoluminescence and cathodoluminescence (CL) reveal multiple lines originating from InGaN NWs on the different pyramid facets. The anomalous temperature dependence of the emission wavelength results from carrier redistribution between localized or confined states, spontaneously formed within the NWs due to composition fluctuations, verified by high-resolution EDX elemental analysis. First-principles calculations show that the pyramid facet edges act as a barrier for atom migration and enhance atom incorporation. This leads to uniform composition within the facets for not too high a growth temperature, consistent with the SEM, EDX and CL results. At elevated temperature, InGaN decomposition and In desorption are enhanced on facets with low growth rate, accompanied by Ga inter-facet migration, leading to non-uniform composition over the Ga migration length which is deduced to be around 580 nm. Our study presents a method for the fabrication of multi-wavelength light sources by highly unidirectional MBE on textured Si substrates towards color temperature-tunable solid-state lighting and RGB light-emitting diode displays.
- Published
- 2020
25. Li1.1Na0.1Mn0.534Ni0.133Co0.133O2 as cathode with ameliorated electrochemical performance based on dual Li+/Na+ electrolyte
- Author
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Yajie Li, Kaixiang Shen, Shaofeng Wang, Bei Wang, Fuming Chen, Hedong Chen, Yu Zhou, and Xianhua Hou
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Materials science ,Scanning electron microscope ,General Chemical Engineering ,General Engineering ,Analytical chemistry ,General Physics and Astronomy ,02 engineering and technology ,Electrolyte ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Electrochemistry ,01 natural sciences ,Cathode ,0104 chemical sciences ,law.invention ,Dielectric spectroscopy ,law ,General Materials Science ,Calcination ,Cyclic voltammetry ,0210 nano-technology ,Faraday efficiency - Abstract
Layered Li-rich cathode materials Li1.2Mn0.534Ni0.133Co0.133O2 (LNCMN-0) and Na doping Li1.1Na0.1Mn0.534Ni0.133Co0.133O2 (LNCMN-0.1) are prepared successfully by a co-precipitation method and several consecutive calcination treatments. Besides, the phase structure, morphology, and electrochemical properties of the four samples are studied in detail using X-ray diffraction (XRD), scanning electron microscope (SEM), galvanostatic charge-discharge test, cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). Although the discharge capacity of spherical LNCMN-0.1 decreases slightly at 0.1 C (1 C = 250 mA g−1), compared to the pristine LNCMN-0, it is noteworthy that the LNCMN-0.1 matched with dual Li+/Na+ electrolyte exhibit superior stability performance at 1 C, as well as enhanced rate capability. The LNCMN-0.1 (Li+/Na+) delivers an initial discharge specific capacity of 267.61 mAh g−1 at 0.1 C between 2.0 and 4.8 V at room temperature and initial coulombic efficiency of 83.51%, which is higher than the LNCMN-0 samples (76.42 and 81.54%). The experimental results verify that Na doping combined with dual Li+/Na+ electrolyte can generate a synergistic effect, which is a promising idea to ameliorate the electrochemical performance for this material.
- Published
- 2018
26. Milled flake graphite/plasma nano-silicon@carbon composite with void sandwich structure for high performance as lithium ion battery anode at high temperature
- Author
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Shaofeng Wang, Xianhua Hou, Bo Wu, Haiqing Qin, Qiang Ru, Yingchun Xia, Hedong Chen, and Fuming Chen
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Void (astronomy) ,Materials science ,Silicon ,Composite number ,chemistry.chemical_element ,02 engineering and technology ,General Chemistry ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Electrochemistry ,01 natural sciences ,0104 chemical sciences ,Ion ,chemistry ,Electrode ,General Materials Science ,Composite material ,0210 nano-technology ,Current density ,Faraday efficiency - Abstract
To reduce the influence from volume expansion of silicon during lithium lithiation/delithiation, milled flake graphite/plasma nano-silicon@carbon (MFG/PNSi@C) composite with void sandwich structure is synthesized by assembling thin MFG (thickness of 150 nm) sheets loading with carbon-coated PNSi (plasma nano-silicon) via a facile spray drying method. The MFG/PNSi@C composite, as lithium ion battery anode, exhibits excellent electrochemical performance at room temperature and displays an outstanding cyclic property even at high temperature. The MFG/PNSi@C electrode delivers reversible capacity of 1141 mAh g−1, and high initial Coulombic efficiency of 84.4%, and capacity retention of 84.1% after 200 cycles at a current density of 0.1 A g−1. Even at the current density of 0.2 and 0.4 A g−1, the reversible capacities of 1168 and 1102 mAh g−1 can be achieved respectively, with the capacity retention of 68.9% and 63.9% after 200 cycles. Even the work temperature goes up 60 °C, the discharge/charge capacities of 832/808 mAh g−1 can be obtained at a current density of 0.1 A g−1. The stable cyclic performance is mainly due to the void sandwich structure of the MFG/PNSi@C composite, which dramatically shortens lithium ion diffusion path and pitch carbon shell can buffer huge volume expansion.
- Published
- 2018
27. Graphene-decorated sphere Li2S composite prepared by spray drying method as cathode for lithium-sulfur full cell
- Author
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Xianhua Hou, Junjun Wu, Shejun Hu, Zeming Zhong, Hedong Chen, and Shaofeng Wang
- Subjects
Battery (electricity) ,Materials science ,Scanning electron microscope ,Graphene ,General Chemical Engineering ,Composite number ,General Engineering ,Oxide ,General Physics and Astronomy ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Cathode ,0104 chemical sciences ,law.invention ,Anode ,chemistry.chemical_compound ,Chemical engineering ,chemistry ,law ,Spray drying ,General Materials Science ,0210 nano-technology - Abstract
In this work, a graphene-decorated Li2S cathode has been prepared via spray drying method using Li2SO4, graphene oxide and sucrose as raw materials. During spray drying, sucrose melts and embeds Li2SO4 when Li2SO4 were sprayed out with graphene oxide and sucrose, and becomes sphere particles. The as-prepared Li2S composite was received after a heat treatment under nitrogen atmosphere. X-ray diffraction patterns confirm the cubic structure of Li2S and scanning electron microscope images reveal that Li2S and carbon components stay in sphere structure with diameter around 20 μm. The sphere Li2S composite shows enhanced performance when acts as cathode. Under current density of 100 mA g−1, a specific discharge capacity of 778 mAh g−1 has been achieved and the battery cycled over 60 rounds. Furtherly, the sphere composite was coupled with silicon/graphite anode to construct full cell system, suggesting large possibility to work with the current lithium-ion battery anodes.
- Published
- 2018
28. A Double Core-shell Structure Silicon Carbon Composite Anode Material for a Lithium Ion Battery
- Author
-
Hedong Chen, Xiaoqiao Hu, Haiqing Qin, Benli Chu, Xianhua Hou, Qiang Ru, and Shimin Huang
- Subjects
Materials science ,Lithium vanadium phosphate battery ,Silicon ,Composite number ,chemistry.chemical_element ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Nanowire battery ,Lithium-ion battery ,0104 chemical sciences ,Electronic, Optical and Magnetic Materials ,Anode ,law.invention ,chemistry ,Chemical engineering ,law ,Graphite ,0210 nano-technology ,Carbon - Abstract
Silicon with high theoretical specific capacity is a promising anode material, but the poor electronic conductivity and excessive volume expansion hinder its practical application. In order to solve this problem, a novel double core-shell structure composite Si/G/C-CVD coated by pitch pyrolysis and CVD (Chemical Vapor Deposition) carbon has been prepared. In the Si/G/C-CVD composite, nano-silicon particles and pitch particles are embedded on the surface of graphite particles, then the second carbon layer via CVD is added. The double carbon layer can protect nano-silicon particles from direct exposure to the electrolyte and enhance the electrochemistry performance during the lithium intercalation/extraction process. The as-prepared Si/G/C-CVD composite demonstrates superior electrochemical performance, with enhanced specific reversible capacity (688.44 mAh g−1 at 100 mA g− 1), excellent rate performance (261.66 mAh g−1 even at the specific current of 1.6A g− 1) and good cycle performance with little fading (91% after 155 cycles).
- Published
- 2017
29. Nanogenerator with direction sensitive piezoelectric response based on InGaN nanowires over ridge textured Si (1 1 0) substrate with inter-facet topography modulation
- Author
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Lujia Rao, Peng Wang, Changkun Song, Hedong Chen, Richard Nötzel, Dao Wang, and Guofu Zhou
- Subjects
Materials science ,business.industry ,Nanogenerator ,Nanowire ,General Physics and Astronomy ,02 engineering and technology ,Surfaces and Interfaces ,General Chemistry ,Substrate (electronics) ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Ridge (differential geometry) ,01 natural sciences ,Piezoelectricity ,Signal ,0104 chemical sciences ,Surfaces, Coatings and Films ,Optoelectronics ,0210 nano-technology ,business ,Beam (structure) ,Molecular beam epitaxy - Abstract
Direction sensitive piezoelectric response is demonstrated from a nanogenerator based on an InGaN nanowires array on a ridge textured Si (1 1 0) substrate with inter-facet topography modulation. Under stationary molecular beam epitaxy, distinct variations of the inclination orientation of the InGaN nanowires are created due to the different beam flux incidence angle between the facets, which act as the primary factor for the asymmetric piezoelectric output. The piezoelectric properties were first studied using an electrical atomic force microscope (AFM) in contact scan mode at zero bias. The InGaN NWs on opposite ridge facets show different piezoelectric output distribution under the same scanning geometry. The difference of the tangential force component due to the varied NWs tilting angle, applied on the NWs by the AFM probe tip, explains the non-uniform piezoelectric signal distribution. A capacitor type piezoelectric nanogenerator (PNG) device was fabricated, which exhibits pronounced direction sensitive piezoelectric response under rotated external pressure. This work gives a universal strategy on synthesis of composite semiconductor materials with anisotropic piezoelectric response in terms of a self-powered force direction sensitive angle sensor piezoelectric nanogenerator device.
- Published
- 2021
30. 3D InGaN nanowire arrays on oblique pyramid-textured Si (311) for light trapping and solar water splitting enhancement
- Author
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Hedong Chen, Xianhua Hou, Lujia Rao, Hongjie Yin, Xingyu Wang, Richard Nötzel, Guofu Zhou, Yinping Qian, Huapeng Ye, Xingfu Wang, and Peng Wang
- Subjects
Photocurrent ,Fabrication ,Materials science ,Renewable Energy, Sustainability and the Environment ,business.industry ,Nanowire ,Finite-difference time-domain method ,02 engineering and technology ,Trapping ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Planar ,Optoelectronics ,General Materials Science ,Electrical and Electronic Engineering ,0210 nano-technology ,business ,Pyramid (geometry) ,Molecular beam epitaxy - Abstract
We study Ⅲ-nitride nanowire (NW) anti-reflection structures employed as photoelectrocatalyst for solar water splitting. We found that 1D vertical InGaN NW arrays tilted by 73° exhibit maximized photocurrent. Therefore, we grow 3D InGaN NW arrays on the facets of oblique pyramid-textured Si (311) (OPSi/InGaN) by plasma-assisted molecular beam epitaxy, exhibiting facets tilted by 73°. In addition, using finite difference time domain simulations we find the crucial impact of the asymmetry of the oblique pyramid InGaN NW arrays on the light trapping. Compared with InGaN NWs grown on a planar Si substrate (Si/InGaN), the OPSi/InGaN photoanode exhibits ~500% enhancement of the photocurrent due to various light trapping effects attributed to: 1D vertical NW arrays, their tilt, 3D arrangement and asymmetry. Decorated with NiOOH co-catalyst, the OPSi/InGaN photoanode exhibits photocurrent densities in the mA cm−2 range. The present research provides a rational design for the fabrication of nanostructured photoelectrocatalyst with enhanced light absorption.
- Published
- 2021
31. Mass-producible method for preparation of a carbon-coated graphite@plasma nano-silicon@carbon composite with enhanced performance as lithium ion battery anode
- Author
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Qiang Ru, Hedong Chen, Zhoulu Wang, Shaofeng Wang, Xianhua Hou, Xiaoqiao Hu, Haiqing Qin, Xiang Liu, Lijun Fu, Yuping Wu, and Shejun Hu
- Subjects
Materials science ,General Chemical Engineering ,Composite number ,chemistry.chemical_element ,02 engineering and technology ,Plasma ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Lithium-ion battery ,0104 chemical sciences ,Anode ,Lithium ion battery anode ,chemistry ,Chemical engineering ,Spray drying ,Electrochemistry ,Graphite ,0210 nano-technology ,Carbon - Abstract
Carbon-coated core-shell structure artificial graphite@plasma nano-silicon@carbon (AG@PNSi@C) composite, applying as lithium ion battery anode material, has been prepared via spray drying method. The plasma nano-silicon (
- Published
- 2017
32. Facile spray drying synthesis of porous structured ZnFe2O4 as high-performance anode material for lithium-ion batteries
- Author
-
Hedong Chen, Qiang Ru, Shejun Hu, Kwok Ho Lam, Xianhua Hou, and Junwei Mao
- Subjects
Materials science ,chemistry.chemical_element ,Sintering ,Nanotechnology ,02 engineering and technology ,Electrolyte ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,Atomic and Molecular Physics, and Optics ,0104 chemical sciences ,Electronic, Optical and Magnetic Materials ,Anode ,chemistry ,Chemical engineering ,Transmission electron microscopy ,Lithium ,Electrical and Electronic Engineering ,0210 nano-technology ,Porosity ,Current density ,Faraday efficiency - Abstract
Porous ZnFe2O4 nanorods have been successfully prepared by a simple spray-drying process followed by sintering. The structure and morphology of the samples were characterized by X-ray diffraction, field emission scanning electron microscopy and transmission electron microscopy. The porous structured ZnFe2O4 materials are successfully used as potential anode material for lithium-ion batteries. Electrochemical results show that the anodes exhibit good cycling performance and rate capability. The anode exhibits initial discharge capacity of approximately 1459 mAh g−1 with an initial coulombic efficiency of 77.8% at a constant density of 100 mA g−1. The discharge capacity of the ZnFe2O4 retained 1458 mA h g−1 after 120 cycles at the current rate of 100 mA g−1 and 456 mA h g−1 could be obtained at the current density of 5000 mA g−1 after 200 cycles. The discharge capacities can still be as high as 778 mAh g−1 at a high rate of 3000 mA g−1. Such remarkable electrochemical properties could be ascribed to the unique porous morphology with large surface area and porosity that were beneficial to facilitate the diffusion of Li ions and electrolyte into the electrodes, meanwhile prevent volume expansion/contraction during lithiation/dislithiation processes.
- Published
- 2016
33. Electrochemical properties of core–shell nano-Si@carbon composites as superior anode materials for high-performance Li-ion batteries
- Author
-
Qiang Ru, Lina Qu, Shejun Hu, Xianhua Hou, Hedong Chen, Haiqing Qin, Yuan Huang, and Kwok Ho Lam
- Subjects
Materials science ,chemistry.chemical_element ,Nanotechnology ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,Atomic and Molecular Physics, and Optics ,0104 chemical sciences ,Electronic, Optical and Magnetic Materials ,law.invention ,Anode ,Chemical engineering ,chemistry ,law ,Spray drying ,Electrode ,Calcination ,Particle size ,Electrical and Electronic Engineering ,0210 nano-technology ,Current density ,Carbon ,Faraday efficiency - Abstract
Si@carbon composites have been successfully prepared via spray drying and subsequent calcination using PSA microspheres, nano-silicon and natural graphite as raw materials. Nano-silicon with a 20–100 nm particle size is prepared by radio-frequency electromagnetic induction. Such small nano-silicon particles can effectively accommodate the volume expansion of the Si@carbon anode. Additionally, the unique core–shell structure of Si@carbon composites can effectively alleviate the agglomeration of nano-silicon particles. Electrochemical tests show that the Si/carbon electrode delivers a high initial discharge capacity of approximately 1404.27 mAh g−1 with an initial coulombic efficiency of 82.4 %. The discharge specific capacity remains as high as 73.6 % after 100 charging-discharging cycles, demonstrating the electrode material’s good cycle stability. In addition, the corresponding specific capacity of the Si@carbon composites electrode remains at around 1150 mAh g−1 at a current density of 1 A g−1. And when the current density is 0.1 A g−1, its specific capacity can still remain at around 920 mAh g−1, indicating excellent capacity reversibility. Therefore, Si@carbon composites are superior anode materials for high-performance Li-ion batteries.
- Published
- 2016
34. Identification of Interface Structure for a Topological CoS 2 Single Crystal in Oxygen Evolution Reaction with High Intrinsic Reactivity
- Author
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Yu Kang, Yangkun He, Darius Pohl, Bernd Rellinghaus, Dong Chen, Marcus Schmidt, Vicky Süß, Qingge Mu, Fan Li, Qun Yang, Hedong Chen, Yufei Ma, Gudrun Auffermann, Guowei Li, and Claudia Felser
- Subjects
General Materials Science - Abstract
Transition metal chalcogenides such as CoS2 have been reported as competitive catalysts for oxygen evolution reaction. It has been well confirmed that surface modification is inevitable in such a process, with the formation of different re-constructed oxide layers. However, which oxide species should be responsible for the optimized catalytic efficiencies and the detailed interface structure between the modified layer and precatalyst remain controversial. Here, a topological CoS2 single crystal with a well-defined exposed surface is used as a model catalyst, which makes the direct investigation of the interface structure possible. Cross-sectional transmission electron microscopy of the sample reveals the formation of a 2 nm thickness Co3O4 layer that grows epitaxially on the CoS2 surface. Thick CoO pieces are also observed and are loosely attached to the bulk crystal. The compact Co3O4 interface structure can result in the fast electron transfer from adsorbed O species to the bulk crystal compared with CoO pieces as evidenced by the electrochemical impedance measurements. This leads to the competitive apparent and intrinsic reactivity of the crystal despite the low surface geometric area. These findings are helpful for the understanding of catalytic origins of transition metal chalcogenides and the designing of high-performance catalysts with interface-phase engineering.
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