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Wang G, Guan Y, Wang Y, Ding Y, Yang L. Direct Laser Irradiation and Modification of 2D Te for Development of Volatile Memristor. MATERIALS (BASEL, SWITZERLAND) 2023; 16:738. [PMID: 36676475 PMCID: PMC9862747 DOI: 10.3390/ma16020738] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/22/2022] [Revised: 01/03/2023] [Accepted: 01/09/2023] [Indexed: 06/17/2023]
Abstract
Laser irradiation, as a kind of post-fabrication method for two-dimensional (2D) materials, is a promising way to tune the properties of materials and the performance of corresponding nano-devices. As the memristor has been regarded as an excellent candidate for in-memory devices in next-generation computing system, the application of laser irradiation in developing excellent memristor based on 2D materials should be explored deeply. Here, tellurene (Te) flakes are exposed to a 532 nm laser in the air atmosphere to investigate the evolutions of the surface morphology and atom structures under different irradiation parameters. Laser is capable of thinning the flakes, inducing amorphous structures, oxides and defects, and forming nanostructures by controlling the irradiation power and time. Furthermore, the laser-induced oxides and defects promote the migration of metal ions in Te, resulting in the formation of the conductive filaments, which provides the switching behavers of volatile memristor, opening a route to the development of next-generation nano-devices.
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Affiliation(s)
- Genwang Wang
- Key Laboratory of Microsystems and Microstructures Manufacturing, Ministry of Education, Harbin Institute of Technology, Harbin 150001, China
- School of Mechatronics Engineering, Harbin Institute of Technology, Harbin 150001, China
| | - Yanchao Guan
- Key Laboratory of Microsystems and Microstructures Manufacturing, Ministry of Education, Harbin Institute of Technology, Harbin 150001, China
- School of Mechatronics Engineering, Harbin Institute of Technology, Harbin 150001, China
| | - Yang Wang
- Key Laboratory of Microsystems and Microstructures Manufacturing, Ministry of Education, Harbin Institute of Technology, Harbin 150001, China
- School of Mechatronics Engineering, Harbin Institute of Technology, Harbin 150001, China
| | - Ye Ding
- Key Laboratory of Microsystems and Microstructures Manufacturing, Ministry of Education, Harbin Institute of Technology, Harbin 150001, China
- School of Mechatronics Engineering, Harbin Institute of Technology, Harbin 150001, China
| | - Lijun Yang
- Key Laboratory of Microsystems and Microstructures Manufacturing, Ministry of Education, Harbin Institute of Technology, Harbin 150001, China
- School of Mechatronics Engineering, Harbin Institute of Technology, Harbin 150001, China
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2
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Ma J, Oh K, Tagliabue G. Understanding Wavelength-Dependent Synergies between Morphology and Photonic Design in TiO 2-Based Solar Powered Redox Cells. THE JOURNAL OF PHYSICAL CHEMISTRY. C, NANOMATERIALS AND INTERFACES 2023; 127:11-21. [PMID: 36660095 PMCID: PMC9841569 DOI: 10.1021/acs.jpcc.2c05893] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/17/2022] [Revised: 11/21/2022] [Indexed: 06/17/2023]
Abstract
Solar powered redox cells (SPRCs) are promising for large-scale and long-term storage of solar-energy, particularly when coupled with redox flow batteries (RFBs). While efforts have primarily focused on heterostructure engineering, the potential of synergistic morphology and photonic design has not been carefully studied. Here, we investigate the wavelength-dependent effects of light-absorption and charge transfer characteristics on the performance of gold decorated TiO2-based SPRC photoanodes operating with RFB-compatible redox couples. Through an in-depth optical and photoelectrochemical characterization of three complementary TiO2 microstructures, namely nanotubes, honeycombs, and nanoparticles, we elucidate the combined effects of nanometer-scale semiconductor morphology and plasmonic design across the visible spectrum. In particular, thin-walled TiO2 nanotubes exhibit a ∼ 50% increase in solar-to-chemical efficiency (STC) compared to thick-walled TiO2 honeycombs thanks to improved charge transfer. Au nanoparticles both increase generation and interfacial charge transfer (above bandgap) and promote hot carrier injection (below bandgap) leading to a further 25% increase in STC. Overall, Au/TiO2 nanotubes achieve a high photocurrent at 0.098 mA/cm2 and an excellent STC of 0.06%, among the highest with respect to the theoretical limit. The incident photon to current efficiency and internal quantum efficiency are also superior to those of bare TiO2 showing maximum values of 54.7% and 67%, respectively. Overall, nanophotonic engineering that synergistically combines morphology optimization and plasmonic sensitization schemes offer new avenues for improving rechargeable solar-energy technologies such as solar redox flow batteries.
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3
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Wang X, Wu J, Zhang Y, Sun Y, Ma K, Xie Y, Zheng W, Tian Z, Kang Z, Zhang Y. Vacancy Defects in 2D Transition Metal Dichalcogenide Electrocatalysts: From Aggregated to Atomic Configuration. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2022:e2206576. [PMID: 36189862 DOI: 10.1002/adma.202206576] [Citation(s) in RCA: 20] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/19/2022] [Revised: 09/15/2022] [Indexed: 06/16/2023]
Abstract
Vacancy defect engineering has been well leveraged to flexibly shape comprehensive physicochemical properties of diverse catalysts. In particular, growing research effort has been devoted to engineering chalcogen anionic vacancies (S/Se/Te) of 2D transition metal dichalcogenides (2D TMDs) toward the ultimate performance limit of electrocatalytic hydrogen evolution reaction (HER). In spite of remarkable progress achieved in the past decade, systematic and in-depth insights into the state-of-the-art vacancy engineering for 2D-TMDs-based electrocatalysis are still lacking. Herein, this review delivers a full picture of vacancy engineering evolving from aggregated to atomic configurations covering their development background, controllable manufacturing, thorough characterization, and representative HER application. Of particular interest, the deep-seated correlations between specific vacancy regulation routes and resulting catalytic performance improvement are logically clarified in terms of atomic rearrangement, charge redistribution, energy band variation, intermediate adsorption-desorption optimization, and charge/mass transfer facilitation. Beyond that, a broader vision is cast into the cutting-edge research fields of vacancy-engineering-based single-atom catalysis and dynamic structure-performance correlations across catalyst service lifetime. Together with critical discussion on residual challenges and future prospects, this review sheds new light on the rational design of advanced defect catalysts and navigates their broader application in high-efficiency energy conversion and storage fields.
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Affiliation(s)
- Xin Wang
- Academy for Advanced Interdisciplinary Science and Technology, Beijing Advanced Innovation Center for Materials Genome Engineering, Beijing Key Laboratory for Advanced Energy Materials and Technologies, University of Science and Technology Beijing, Beijing, 100083, P. R. China
- State Key Laboratory for Advanced Metals and Materials, School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing, 100083, P. R. China
| | - Jing Wu
- Academy for Advanced Interdisciplinary Science and Technology, Beijing Advanced Innovation Center for Materials Genome Engineering, Beijing Key Laboratory for Advanced Energy Materials and Technologies, University of Science and Technology Beijing, Beijing, 100083, P. R. China
- State Key Laboratory for Advanced Metals and Materials, School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing, 100083, P. R. China
| | - Yuwei Zhang
- Academy for Advanced Interdisciplinary Science and Technology, Beijing Advanced Innovation Center for Materials Genome Engineering, Beijing Key Laboratory for Advanced Energy Materials and Technologies, University of Science and Technology Beijing, Beijing, 100083, P. R. China
- State Key Laboratory for Advanced Metals and Materials, School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing, 100083, P. R. China
| | - Yu Sun
- Academy for Advanced Interdisciplinary Science and Technology, Beijing Advanced Innovation Center for Materials Genome Engineering, Beijing Key Laboratory for Advanced Energy Materials and Technologies, University of Science and Technology Beijing, Beijing, 100083, P. R. China
- State Key Laboratory for Advanced Metals and Materials, School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing, 100083, P. R. China
| | - Kaikai Ma
- Academy for Advanced Interdisciplinary Science and Technology, Beijing Advanced Innovation Center for Materials Genome Engineering, Beijing Key Laboratory for Advanced Energy Materials and Technologies, University of Science and Technology Beijing, Beijing, 100083, P. R. China
- State Key Laboratory for Advanced Metals and Materials, School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing, 100083, P. R. China
| | - Yong Xie
- Academy for Advanced Interdisciplinary Science and Technology, Beijing Advanced Innovation Center for Materials Genome Engineering, Beijing Key Laboratory for Advanced Energy Materials and Technologies, University of Science and Technology Beijing, Beijing, 100083, P. R. China
- State Key Laboratory for Advanced Metals and Materials, School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing, 100083, P. R. China
| | - Wenhao Zheng
- Academy for Advanced Interdisciplinary Science and Technology, Beijing Advanced Innovation Center for Materials Genome Engineering, Beijing Key Laboratory for Advanced Energy Materials and Technologies, University of Science and Technology Beijing, Beijing, 100083, P. R. China
- State Key Laboratory for Advanced Metals and Materials, School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing, 100083, P. R. China
| | - Zhen Tian
- Academy for Advanced Interdisciplinary Science and Technology, Beijing Advanced Innovation Center for Materials Genome Engineering, Beijing Key Laboratory for Advanced Energy Materials and Technologies, University of Science and Technology Beijing, Beijing, 100083, P. R. China
- State Key Laboratory for Advanced Metals and Materials, School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing, 100083, P. R. China
| | - Zhuo Kang
- Academy for Advanced Interdisciplinary Science and Technology, Beijing Advanced Innovation Center for Materials Genome Engineering, Beijing Key Laboratory for Advanced Energy Materials and Technologies, University of Science and Technology Beijing, Beijing, 100083, P. R. China
- State Key Laboratory for Advanced Metals and Materials, School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing, 100083, P. R. China
| | - Yue Zhang
- Academy for Advanced Interdisciplinary Science and Technology, Beijing Advanced Innovation Center for Materials Genome Engineering, Beijing Key Laboratory for Advanced Energy Materials and Technologies, University of Science and Technology Beijing, Beijing, 100083, P. R. China
- State Key Laboratory for Advanced Metals and Materials, School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing, 100083, P. R. China
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Wells RA, Zhang M, Chen TH, Boureau V, Caretti M, Liu Y, Yum JH, Johnson H, Kinge S, Radenovic A, Sivula K. High Performance Semiconducting Nanosheets via a Scalable Powder-Based Electrochemical Exfoliation Technique. ACS NANO 2022; 16:5719-5730. [PMID: 35290010 DOI: 10.1021/acsnano.1c10739] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
The liquid-phase exfoliation of semiconducting transition metal dichalcogenide (TMD) powders into 2D nanosheets represents a promising route toward the scalable production of ultrathin high-performance optoelectronic devices. However, the harsh conditions required negatively affect the semiconducting properties, leading to poor device performance. Herein we demonstrate a gentle exfoliation method employing standard bulk MoS2 powder (pressed into pellets) together with the electrochemical intercalation of a quaternary alkyl ammonium. The resulting nanosheets are produced in high yield (32%) and consist primarily of mono-, bi-, triatomic layers with large lateral dimensions (>1 μm), while retaining the semiconducting polymorph. Exceptional optoelectronic performance of nanosheet thin-films is observed, such as enhanced photoluminescence, charge carrier mobility (up to 0.2 cm2 V-1 s-1 in a multisheet device), and photon-to-current efficiency while maintaining high transparency (>80%). Specifically, as a photoanode for iodide oxidation, an internal quantum efficiency up to 90% (at +0.3 V vs Pt) is achieved (compared to only 12% for MoS2 nanosheets produced via ultrasonication). Further using a combination of fluorescence microscopy and high-resolution scanning transmission electron microscopy (STEM), we show that our gently exfoliated nanosheets possess a defect density (2.33 × 1013 cm-2) comparable to monolayer MoS2 prepared by vacuum-based techniques and at least three times less than ultrasonicated MoS2 nanoflakes. Finally, we expand this method toward other TMDs (WS2, WSe2) to demonstrate its versatility toward high-performance and fully scalable van der Waals heterojunction devices.
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Affiliation(s)
- Rebekah A Wells
- Laboratory for Molecular Engineering of Optoelectronic Nanomaterials (LIMNO), Institute of Chemical Sciences and Engineering, École Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland
| | - Miao Zhang
- Laboratory of Nanoscale Biology (LBEN), Institute of Bioengineering, École Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland
| | - Tzu-Heng Chen
- Laboratory of Nanoscale Biology (LBEN), Institute of Bioengineering, École Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland
| | - Victor Boureau
- Interdisciplinary Center for Electron Microscopy (CIME), École Polytechnique Fédérale de Lausanne (EPFL), Lausanne 1015, Switzerland
| | - Marina Caretti
- Laboratory for Molecular Engineering of Optoelectronic Nanomaterials (LIMNO), Institute of Chemical Sciences and Engineering, École Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland
| | - Yongpeng Liu
- Laboratory for Molecular Engineering of Optoelectronic Nanomaterials (LIMNO), Institute of Chemical Sciences and Engineering, École Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland
| | - Jun-Ho Yum
- Laboratory for Molecular Engineering of Optoelectronic Nanomaterials (LIMNO), Institute of Chemical Sciences and Engineering, École Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland
| | - Hannah Johnson
- Laboratory for Molecular Engineering of Optoelectronic Nanomaterials (LIMNO), Institute of Chemical Sciences and Engineering, École Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland
- Advanced Materials Research, Toyota Motor Europe, B-1930 Zaventem, Belgium
| | - Sachin Kinge
- Advanced Materials Research, Toyota Motor Europe, B-1930 Zaventem, Belgium
| | - Aleksandra Radenovic
- Laboratory of Nanoscale Biology (LBEN), Institute of Bioengineering, École Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland
| | - Kevin Sivula
- Laboratory for Molecular Engineering of Optoelectronic Nanomaterials (LIMNO), Institute of Chemical Sciences and Engineering, École Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland
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5
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Tóth PS, Szabó G, Janáky C. Structural Features Dictate the Photoelectrochemical Activities of Two-Dimensional MoSe 2 and WSe 2 Nanostructures. THE JOURNAL OF PHYSICAL CHEMISTRY. C, NANOMATERIALS AND INTERFACES 2021; 125:7701-7710. [PMID: 33889225 PMCID: PMC8054242 DOI: 10.1021/acs.jpcc.1c01265] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/10/2021] [Revised: 03/19/2021] [Indexed: 06/12/2023]
Abstract
The exfoliation of layered materials into two-dimensional (2D) semiconductors creates new structural domains, for example, basal planes, defect-rich in-planes, and edge sites. These surface species affect the photoelectrochemical (PEC) performance, which in turn determines their applicability in solar energy conversion technologies. In this study, a custom-designed microdroplet cell-based spatially resolved PEC approach was employed to identify the structural parts and to measure the PEC activity of the mechanically exfoliated MoSe2 and WSe2 nanosheets for bulk, few-layer, and monolayer specimens. The PEC performance decreased with the decreasing thickness of nanoflakes, and the relative PEC activity (photo/total current) reduced by introducing more defects to the 2D flakes: 1-3% loss was found for in-plane defects and 30-40% for edge defects. While edge sites act as charge carrier recombination centers, their electrocatalytic activity is higher than that of the basal planes. The comparison of PEC activity of micromechanically and liquid phase exfoliated bulk and few-layer MoSe2 and WSe2 flakes further confirmed that the PEC performance of 2D flakes decreases with an increasing number of edge sites.
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Affiliation(s)
- Péter S. Tóth
- MTA
Premium Post Doctorate Research Program, University of Szeged, Szeged 6720, Hungary
- Department
of Physical Chemistry and Materials Science, Interdisciplinary Excellence
Center, University of Szeged, Szeged 6720, Hungary
| | - Gábor Szabó
- Department
of Physical Chemistry and Materials Science, Interdisciplinary Excellence
Center, University of Szeged, Szeged 6720, Hungary
| | - Csaba Janáky
- Department
of Physical Chemistry and Materials Science, Interdisciplinary Excellence
Center, University of Szeged, Szeged 6720, Hungary
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6
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Hill JW, Hill CM. Directly visualizing carrier transport and recombination at individual defects within 2D semiconductors. Chem Sci 2021; 12:5102-5112. [PMID: 34163749 PMCID: PMC8179556 DOI: 10.1039/d0sc07033e] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/25/2020] [Accepted: 02/08/2021] [Indexed: 12/13/2022] Open
Abstract
Two-dimensional semiconductors (2DSCs) are promising materials for a wide range of optoelectronic applications. While the fabrication of 2DSCs with thicknesses down to the monolayer limit has been demonstrated through a variety of routes, a robust understanding of carrier transport within these materials is needed to guide the rational design of improved practical devices. In particular, the influence of different types of structural defects on transport is critical, but difficult to interrogate experimentally. Here, a new approach to visualizing carrier transport within 2DSCs, Carrier Generation-Tip Collection Scanning Electrochemical Cell Microscopy (CG-TC SECCM), is described which is capable of providing information at the single-defect level. In this approach, carriers are locally generated within a material using a focused light source and detected as they drive photoelectrochemical reactions at a spatially-offset electrolyte interface created through contact with a pipet-based probe, allowing carrier transport across well-defined, µm-scale paths within a material to be directly interrogated. The efficacy of this approach is demonstrated through studies of minority carrier transport within mechanically-exfoliated n-type WSe2 nanosheets. CG-TC SECCM imaging experiments carried out within pristine basal planes revealed highly anisotropic hole transport, with in-plane and out-of-plane hole diffusion lengths of 2.8 µm and 5.8 nm, respectively. Experiments were also carried out to probe recombination across individual step edge defects within n-WSe2 which suggest a significant surface charge (∼5 mC m-2) exists at these defects, significantly influencing carrier transport. Together, these studies demonstrate a powerful new approach to visualizing carrier transport and recombination within 2DSCs, down to the single-defect level.
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Affiliation(s)
- Joshua W Hill
- Department of Chemistry, University of Wyoming, 1000 E University Ave Laramie WY 82071 USA
| | - Caleb M Hill
- Department of Chemistry, University of Wyoming, 1000 E University Ave Laramie WY 82071 USA
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7
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Kong H, Kwon J, Paeng D, Jung WJ, Ghimire S, Dho J, Yoo JH, Hong S, Jung J, Shin J, Grigoropoulos CP, Ko SH, Yeo J. Laser-Induced Crystalline-Phase Transformation for Hematite Nanorod Photoelectrochemical Cells. ACS APPLIED MATERIALS & INTERFACES 2020; 12:48917-48927. [PMID: 32989982 DOI: 10.1021/acsami.0c11999] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Generally, a high-temperature postannealing process is required to enhance the photoelectrochemical (PEC) performance of hematite nanorod (NR) photoanodes. However, the thermal annealing time is limited to a short duration as thermal annealing at high temperatures can result in some critical problems, such as conductivity degradation of the fluorine-doped tin oxide film and deformation of the glass substrate. In this study, selective laser processing is introduced for hematite-based PEC cells as an alternative annealing process. The developed laser-induced phase transformation (LIPT) process yields hematite NRs with enhanced optical, chemical, and electrical properties for application in hematite NR-based PEC cells. Owing to its improved properties, the LIPT-processed hematite NR PEC cell exhibits an enhanced water oxidation performance compared to that processed by the conventional annealing process. As the LIPT process is conducted under ambient conditions, it would be an excellent alternative annealing technique for heat-sensitive flexible substrates in the future.
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Affiliation(s)
- Heejung Kong
- Novel Applied Nano Optics Lab, Department of Physics, Kyungpook National University, 80 Daehak-ro, Bukgu, Daegu 41566, Korea
| | - Jinhyeong Kwon
- Intelligent Manufacturing System, Korea Institute of Industrial Technology, 89 Yangdaegiro-gil, Ipjang-myon, Seobuk-gu, Cheonan, Chungcheongnam-do 31056, Korea
| | - Dongwoo Paeng
- Laser Thermal Lab, Department of Mechanical Engineering, University of California, Berkeley, Berkeley, California 94720, United States
| | - Won Jun Jung
- Department of Physics, Kyungpook National University, 80 Daehak-ro, Bukgu, Daegu 41566, Korea
| | - Santosh Ghimire
- Department of Physics, Kyungpook National University, 80 Daehak-ro, Bukgu, Daegu 41566, Korea
| | - Joonghoe Dho
- Department of Physics, Kyungpook National University, 80 Daehak-ro, Bukgu, Daegu 41566, Korea
| | - Jae-Hyuck Yoo
- Physical and Life Sciences and NIF and Photon Sciences, Lawrence Livermore National Laboratory, Livermore, California 94550, United States
| | - Sukjoon Hong
- Department of Mechanical Engineering, Hanyang University, 55 Hanyangdaehak-ro, Sangnok-gu, Ansan, Gyeonggi-do 15588, Korea
| | - Jinwook Jung
- Applied Nano and Thermal Science Lab, Department of Mechanical Engineering, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul 151-742, Korea
| | - Jaeho Shin
- Applied Nano and Thermal Science Lab, Department of Mechanical Engineering, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul 151-742, Korea
| | - Costas P Grigoropoulos
- Laser Thermal Lab, Department of Mechanical Engineering, University of California, Berkeley, Berkeley, California 94720, United States
| | - Seung Hwan Ko
- Applied Nano and Thermal Science Lab, Department of Mechanical Engineering, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul 151-742, Korea
| | - Junyeob Yeo
- Novel Applied Nano Optics Lab, Department of Physics, Kyungpook National University, 80 Daehak-ro, Bukgu, Daegu 41566, Korea
- Department of Hydrogen and Renewable Energy, Kyungpook National University, 80 Daehak-ro, Bukgu, Daegu 41566, Korea
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8
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Zhang H, Dunklin JR, Reid OG, Yun SJ, Nanayakkara SU, Lee YH, Blackburn JL, Miller EM. Disentangling oxygen and water vapor effects on optoelectronic properties of monolayer tungsten disulfide. NANOSCALE 2020; 12:8344-8354. [PMID: 32236241 DOI: 10.1039/c9nr09326e] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
By understanding how the environmental composition impacts the optoelectronic properties of transition metal dichalcogenide monolayers, we demonstrate that simple photoluminescence (PL) measurements of tungsten disulfide (WS2) monolayers can differentiate relative humidity environments. In this paper, we examine the PL and photoconductivity of chemical vapor deposition grown WS2 monolayers under three carefully controlled environments: inert gas (N2), dry air (O2 in N2), and humid nitrogen (H2O vapor in N2). The WS2 PL is measured as a function of 532 nm laser power and exposure time and can be decomposed into the exciton, trion, and lower energy state(s) contributions. Under continuous illumination in either O2 or H2O vapor environment, we find dramatic (and reversible) increases in PL intensity relative to the PL in an inert environment. The PL bathochromically shifts in an O2 environment and is dominated by increased trion emission and diminished exciton emission. In contrast, the WS2 PL increase in a H2O environment results from an overall increase in emission from all spectral components where the exciton contribution dominates. The drastic increases in PL are anticorrelated with corresponding decreases in photoconductivity, as measured by time-resolved microwave conductivity. The results suggest that both O2 and H2O react photochemically with the WS2 monolayer surface, modifying the optoelectronic properties, but do so via distinct pathways. Thus, we use these optoelectronic differences to differentiate the amount of humidity in the air, which we show with 0%, 40%, and 80% relative humidity environments. This deeper understanding of how ambient conditions impact WS2 monolayers enables novel humidity sensors as well as a better understanding of the correlation between TMDC surface chemistry, light emission, and photoconductivity. Moreover, these WS2 measurements highlight the importance of considering the impact of the local environment on reported results.
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Affiliation(s)
- Hanyu Zhang
- Materials and Chemical Science and Technology Directorate, National Renewable Energy Laboratory, 15013 Denver West Parkway, Golden, Colorado 80401, USA.
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9
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Wang L, Nilsson ZN, Tahir M, Chen H, Sambur JB. Influence of the Substrate on the Optical and Photo-electrochemical Properties of Monolayer MoS 2. ACS APPLIED MATERIALS & INTERFACES 2020; 12:15034-15042. [PMID: 32141285 DOI: 10.1021/acsami.9b21230] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Substrates influence the electrical and optical properties of monolayer (ML) MoS2 in field-effect transistors and photodetectors. Photoluminescence (PL) and Raman spectroscopy measurements have shown that conducting substrates can vary the doping concentration and influence exciton decay channels in ML-MoS2. Doping and exciton decay dynamics are expected to play a major role in the efficiency of light-driven chemical reactions, but it is unclear to what extent these factors contribute to the photo(electro)catalytic properties of ML-MoS2. Here, we report spatially resolved PL, Raman, and photo-electrochemical current measurements of 5-10 μm-wide ML-MoS2 triangles deposited on pairs of indium-doped tin oxide (ITO) electrodes that are separated by a narrow insulating quartz channel [i.e., an ITO interdigitated array (IDA) electrode]. Optical microscopy images and atomic force microscopy measurements revealed that the ML-MoS2 triangles lie conformally on the quartz and ITO substrates. The PL spectrum of MoS2 shifts and decreases in intensity in the ITO region, which can be attributed to differences in nonradiative and radiative exciton decay channels. Raman spectra showed no significant peak shifts on the two substrates that would have indicated a substrate-induced doping effect. We spatially resolved the photo-electrochemical current because of hole-induced iodide oxidation and observed that ML-MoS2 produces lower photocurrents in the quartz region than in the ITO region. The correlated PL, Raman, and photocurrent mapping data show that the MoS2/quartz interface diminishes fast nonradiative exciton decay pathways but the photocurrent response in the quartz region is likely limited by inefficient in-plane carrier transport to the ITO electrode because of carrier recombination with S vacancies in MoS2 or charged impurities in the quartz substrate. Nonetheless, the experimental methodology presented herein provides a framework to evaluate substrate engineering strategies to tune the (photo)electrocatalytic properties of two-dimensional materials.
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Affiliation(s)
- Li Wang
- Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523, United States
| | - Zach N Nilsson
- Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523, United States
| | - Muhammad Tahir
- Department of Physics, Colorado State University, Fort Collins, Colorado 80523, United States
| | - Hua Chen
- Department of Physics, Colorado State University, Fort Collins, Colorado 80523, United States
- School of Advanced Materials Discovery (SAMD), Colorado State University, Fort Collins, Colorado 80523, United States
| | - Justin B Sambur
- Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523, United States
- School of Advanced Materials Discovery (SAMD), Colorado State University, Fort Collins, Colorado 80523, United States
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10
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Goggin DM, Zhang H, Miller EM, Samaniuk JR. Interference Provides Clarity: Direct Observation of 2D Materials at Fluid-Fluid Interfaces. ACS NANO 2020; 14:777-790. [PMID: 31820924 DOI: 10.1021/acsnano.9b07776] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Monolayer particles of two-dimensional (2D) materials represent a scientifically and technologically interesting class of anisotropic particles with colloidal-scale lateral sizes but sub-nanometer thicknesses. This atomic-scale thickness leads to interesting phenomena that can be exploited in next-generation thin-film technologies, and fluid-fluid interfaces provide a potentially scalable platform to confine, assemble, and deposit functional thin films of 2D materials. However, directly observing how these materials interact and assemble into a given film morphology is experimentally challenging because of their sub-nanometer thicknesses. Here, we demonstrate the ability to directly observe graphene, molybdenum disulfide (MoS2), and hexagonal boron nitride (h-BN) particles at fluid-fluid interfaces using interference reflection microscopy (IRM). Monolayer MoS2 and graphene particles demonstrated >10% optical contrast at an air-water interface, which allowed us to quantitatively analyze in situ images of self-assembled MoS2 particles and to map trajectories of interacting graphene particles. Additionally, the Brownian motion of a graphene particle was tracked and analyzed in the context of passive microrheology theory for 2D particle probes. Our results demonstrate how IRM can be used to obtain quantitative spatiotemporal information regarding the self-assembly and dynamics of 2D materials at fluid-fluid interfaces. It will have a significant impact on our ability to investigate systems of atomically thin particles at fluid-fluid interfaces, an area that has fundamental scientific importance and materials science applications but has suffered from a lack of direct, in situ observation techniques.
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Affiliation(s)
- David M Goggin
- Department of Chemical and Biological Engineering , Colorado School of Mines , Golden , Colorado 80401 , United States
| | - Hanyu Zhang
- Chemistry and Nanoscience Center , National Renewable Energy Laboratory , Golden , Colorado 80401 , United States
| | - Elisa M Miller
- Chemistry and Nanoscience Center , National Renewable Energy Laboratory , Golden , Colorado 80401 , United States
| | - Joseph R Samaniuk
- Department of Chemical and Biological Engineering , Colorado School of Mines , Golden , Colorado 80401 , United States
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Wang L, Tahir M, Chen H, Sambur JB. Probing Charge Carrier Transport and Recombination Pathways in Monolayer MoS 2/WS 2 Heterojunction Photoelectrodes. NANO LETTERS 2019; 19:9084-9094. [PMID: 31738855 DOI: 10.1021/acs.nanolett.9b04209] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Monolayer heterojunctions such as MoS2/WS2 are attractive for solar energy conversion applications because the interfacial electric field spatially separates charge carriers in less than 100 fs. Photoelectrochemical cells represent an intriguing platform to collect the spatially separated carriers. However, the recombination, transport, and interfacial charge transfer processes that take place following the ultrafast charge separation step have not been investigated. Here we demonstrate novel charge recombination and transport pathways in monolayer MoS2/WS2 photoelectrochemical cells by spatially resolving the net collection of carriers (i.e., the photocurrent) at the single nanosheet level. We discovered an excitation-wavelength-dependent recombination pathway that depends on the heterojunction stacking configuration and the carrier generation profile in the heterostructure. Photocurrent mapping measurements revealed that charge transport occurs parallel to the layers over micrometer-scale distances even though the indium tin oxide electrode and liquid electrolyte provide efficient charge extraction pathways via intimate electron- and hole-selective contacts. Our results reveal how composition heterogeneity influences the performance of bulk heterojunction electrodes made from randomly oriented nanosheets and provide critical insight into the design of efficient heterojunction photoelectrodes for solar energy conversion applications.
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Wang L, Schmid M, Sambur JB. Single nanoparticle photoelectrochemistry: What is next? J Chem Phys 2019; 151:180901. [PMID: 31731844 DOI: 10.1063/1.5124710] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Semiconductor photoelectrochemistry is a fascinating field that deals with the chemistry and physics of photodriven reactions at solid/liquid interfaces. The interdisciplinary field attracts (electro)chemists, materials scientists, spectroscopists, and theorists to study fundamental and applied problems such as carrier dynamics at illuminated electrode/electrolyte interfaces and solar energy conversion to electricity or chemical fuels. In the pursuit of practical photoelectrochemical energy conversion systems, researchers are exploring inexpensive, solution-processed semiconductor nanomaterials as light absorbers. Harnessing the enormous potential of nanomaterials for energy conversion applications requires a fundamental understanding of charge carrier generation, separation, transport, and interfacial charge transfer at heterogeneous nanoscale interfaces. Our current understanding of these processes is derived mainly from ensemble-average measurements of nanoparticle electrodes that report on the average behavior of trillions of nanoparticles. Ensemble-average measurements conceal how nanoparticle heterogeneity (e.g., differences in particle size, shape, and surface structure) contributes to the overall photoelectrochemical response. This perspective article focuses on the emerging area of single particle photoelectrochemistry, which has opened up an exciting new frontier: direct investigations of photodriven reactions on individual nanomaterials, with the ability to elucidate the role of particle-dependent properties on the photoelectrochemical behavior. Here, we (1) review the basic principles of photoelectrochemical cells, (2) point out the potential advantages and differences between bulk and nanoelectrodes, (3) introduce approaches to single nanoparticle photoelectrochemistry and highlight key findings, and (4) provide our perspective on future research directions.
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Affiliation(s)
- Li Wang
- Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523, USA
| | - Merranda Schmid
- Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523, USA
| | - Justin B Sambur
- Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523, USA
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Lu X, Liu R, Wang Q, Xu C. In Situ Integration of ReS 2/Ni 3S 2 p-n Heterostructure for Enhanced Photoelectrocatalytic Performance. ACS APPLIED MATERIALS & INTERFACES 2019; 11:40014-40021. [PMID: 31603643 DOI: 10.1021/acsami.9b13891] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
The excellent light absorption, low electron-hole recombination rate, and fast reaction kinetics of photogenerated charges are urgently needed for photoelectrochemical (PEC) water splitting. Herein, a novel p-n heterostructure photoelectrode (ReS2/Ni3S2) is constructed via a one-step hydrothermal method, which shows remarkable HER activity under illumination such as a low overpotential (η10) of 106 mV, high IPCE of 10-15%, and good stability. High-resolution transmission electron microscopy (HRTEM) and X-ray photoelectron spectroscopy (XPS) reveal that the intimate interface and strong electron interaction between ReS2 and Ni3S2 can enhance the light adsorption and provide abundant active sites. The transient absorption (TA) spectroscopy and impedance spectroscopy analyses (EIS) demonstrate the prolonged carrier lifetime and fast charge transfer. All of these are responsible for the improvement of reaction kinetics. This work provides a brand new avenue to explore efficient photoelectrocatalysts for water splitting.
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Affiliation(s)
- Xiaoying Lu
- State Key Laboratory of Applied Organic Chemistry, Laboratory of Special Function Materials and Structure Design of the Ministry of Education, College of Chemistry and Chemical Engineering , Lanzhou University , Lanzhou 730000 , China
| | - Ruitong Liu
- State Key Laboratory of Applied Organic Chemistry, Laboratory of Special Function Materials and Structure Design of the Ministry of Education, College of Chemistry and Chemical Engineering , Lanzhou University , Lanzhou 730000 , China
| | - Qiang Wang
- State Key Laboratory of Applied Organic Chemistry, Laboratory of Special Function Materials and Structure Design of the Ministry of Education, College of Chemistry and Chemical Engineering , Lanzhou University , Lanzhou 730000 , China
| | - Cailing Xu
- State Key Laboratory of Applied Organic Chemistry, Laboratory of Special Function Materials and Structure Design of the Ministry of Education, College of Chemistry and Chemical Engineering , Lanzhou University , Lanzhou 730000 , China
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Hill JW, Hill CM. Directly Mapping Photoelectrochemical Behavior within Individual Transition Metal Dichalcogenide Nanosheets. NANO LETTERS 2019; 19:5710-5716. [PMID: 31287956 DOI: 10.1021/acs.nanolett.9b02336] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
Spatial variations in photoelectrochemical reaction rates within individual p-type WSe2 nanosheets were mapped through the application of scanning electrochemical cell microscopy (SECCM). The simultaneous topographical and electrochemical information provided via SECCM directly revealed how both sheet thickness and the presence of defect structures affect the local rate of photoelectrochemical reactions for both outer sphere and inner sphere redox couples. Sheet thickness was found to play a dramatic role in reaction rates, with onset potentials shifting by as much as 0.5 V over thicknesses of 20-120 nm, attributable to the inability of thin sheets to support independent space charge layers. Step/edge features were found to play a detrimental role for the outer sphere redox couple investigated (Ru(NH3)63+ reduction), with taller steps having larger effects on performance. Shorter step features were found to be beneficial for hydrogen evolution, showing a controlled density of defect features is desirable for inner sphere processes. The studies presented here not only provide valuable, quantitative insights into the behavior of transitional metal dichalcogenide materials but also demonstrate the power of applying SECCM to the study of photoelectrochemical systems, particularly those involving two-dimensional (2D) materials.
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Affiliation(s)
- Joshua W Hill
- Department of Chemistry , University of Wyoming , 1000 E. University Ave , Laramie , Wyoming 82071 , United States
| | - Caleb M Hill
- Department of Chemistry , University of Wyoming , 1000 E. University Ave , Laramie , Wyoming 82071 , United States
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