The Experts below are selected from a list of 10386 Experts worldwide ranked by ideXlab platform
Ivan Bazarov - One of the best experts on this subject based on the ideXlab platform.
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ultra low emittance electron beams from multi alkali antimonide Photocathode operated with infrared light
Applied Physics Letters, 2016Co-Authors: Luca Cultrera, Adam Bartnik, Colwyn Gulliford, Hyeri Lee, Ivan BazarovAbstract:The intrinsic emittance of electron beams generated from a multi-alkali Photocathode operated in a high voltage DC gun is reported. The Photocathode showed sensitivity extending to the infrared part of the spectrum up to 830 nm. The measured intrinsic emittances of electron beams generated with light having wavelength longer than 800 nm are approaching the limit imposed by the thermal energy of electrons at room temperature with quantum efficiencies comparable to metallic Photocathodes used in operation of modern photoinjectors.
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intrinsic emittance reduction in transmission mode Photocathodes
Applied Physics Letters, 2016Co-Authors: Luca Cultrera, Ivan BazarovAbstract:High quantum efficiency (QE) and low emittance electron beams provided by multi-alkali Photocathodes make them of great interest for next generation high brightness photoinjectors. Spicer's three-step model well describes the photoemission process; however, some Photocathode characteristics such as their thickness have not yet been completely exploited to further improve the brightness of the generated electron beams. In this work, we report on the emittance and QE of a multi-alkali Photocathode grown onto a glass substrate operated in transmission and reflection modes at different photon energies. We observed a 20% reduction in the intrinsic emittance from the reflection to the transmission mode operation. This observation can be explained by inelastic electron-phonon scattering during electrons' transit towards the cathode surface. Due to this effect, we predict that thicker Photocathode layers will further reduce the intrinsic emittance of electron beams generated by Photocathodes operated in transmiss...
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monte carlo charge transport and photoemission from negative electron affinity gaas Photocathodes
Journal of Applied Physics, 2013Co-Authors: Siddharth Karkare, Luca Cultrera, D A Dimitrov, W J Schaff, Adam Bartnik, Eric Sawyer, Teresa Esposito, Ivan BazarovAbstract:High quantum yield, low transverse energy spread, and prompt response time make GaAs activated to negative electron affinity an ideal candidate for a Photocathode in high brightness photoinjectors. Even after decades of investigation, the exact mechanism of electron emission from GaAs is not well understood. Here, photoemission from such Photocathodes is modeled using detailed Monte Carlo electron transport simulations. Simulations show a quantitative agreement with the experimental results for quantum efficiency, energy distributions of emitted electrons, and response time without the assumption of any ad hoc parameters. This agreement between simulation and experiment sheds light on the mechanism of electron emission and provides an opportunity to design novel semiconductor Photocathodes with optimized performance.
Kazunari Domen - One of the best experts on this subject based on the ideXlab platform.
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efficient hydrogen evolution on cuins2 x zns 1 x solid solution based Photocathodes under simulated sunlight
Chemical Communications, 2019Co-Authors: Jiao Zhao, Takashi Hisatomi, Mamiko Nakabayashi, Naoya Shibata, Tsutomu Minegishi, Taro Yamada, Masao Katayama, Hiroyuki Kaneko, Miao Zhong, Kazunari DomenAbstract:A thin film of (CuInS2)x(ZnS)1−x has been developed as a Photocathode for solar water splitting for the first time. A superior photoelectrochemical performance has been achieved, mainly attributed to the formation of a solid solution by CuInS2 and ZnS, which proved to be an effective strategy to improve the onset potential and efficiency of CuInS2 Photocathodes.
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photoelectrochemical hydrogen evolution from water on a surface modified cdte thin film electrode under simulated sunlight
Journal of Materials Chemistry, 2017Co-Authors: Masao Katayama, Tsutomu Minegishi, Kazunari DomenAbstract:Photoelectrochemical hydrogen evolution from water using CdTe Photocathodes prepared by close spaced sublimation was investigated. A CdTe thin film deposited on a fluorine-doped tin oxide-coated (FTO) glass plate acted as the Photocathode. Surface modification of this Photocathode with Pt resulted in an increase in the cathodic photocurrent from only 0.01 to 0.14 mA cm−2 at 0.1 VRHE. Further surface modification with an approximately 80 nm-thick CdS layer dramatically increased both the cathodic photocurrent and the onset potential, from 0.14 to 6.0 mA cm−2 at 0.1 VRHE and from 0.2 to 0.6 VRHE, respectively, under simulated sunlight. The CdTe Photocathode showed stoichiometric hydrogen evolution from water, with a half-cell solar to hydrogen conversion efficiency of 0.9% at approximately 0.2 VRHE.
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simultaneous enhancement of photovoltage and charge transfer in cu2o based Photocathode using buffer and protective layers
Applied Physics Letters, 2016Co-Authors: Takashi Hisatomi, Osamu Watanabe, Mamiko Nakabayashi, Naoya Shibata, Kazunari Domen, Jeanjacques DelaunayAbstract:Coating n-type buffer and protective layers on Cu2O may be an effective means to improve the photoelectrochemical (PEC) water-splitting performance of Cu2O-based Photocathodes. In this letter, the functions of the buffer layer and protective layer on Cu2O are examined. It is found that a Ga2O3 buffer layer can form a buried junction with Cu2O, which inhibits Cu2O self-reduction as well as increases the photovoltage through a small conduction band offset between the two semiconductors. The introduction of a TiO2 thin protective layer not only improves the stability of the Photocathode but also enhances the electron transfer from the Photocathode surface into the electrolyte, thus resulting in an increase in photocurrent at positive potentials. These results show that the selection of overlayers with appropriate conduction band positions provides an effective strategy for obtaining a high photovoltage and high photocurrent in PEC systems.
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efficient solar hydrogen production from neutral electrolytes using surface modified cu in ga se2 Photocathodes
Journal of Materials Chemistry, 2015Co-Authors: Hiromu Kumagai, Tsutomu Minegishi, Naotoshi Sato, Taro Yamada, Jun Kubota, Kazunari DomenAbstract:The effects of a phosphate buffer electrolyte and surface modification with thin conductor layers on the photoelectrochemical properties of CdS and Pt-modified polycrystalline Cu(In,Ga)Se2 (CIGS) Photocathodes were investigated. The photocurrent obtained from Pt/CdS/CIGS electrodes, in which the CIGS layer was fabricated by co-evaporation using a three stage method, clearly increased in a phosphate buffer electrolyte solution as a result of promotion of the hydrogen evolution reaction. The half-cell solar-to-hydrogen efficiency (HC-STH) of this device reached a maximum of 5.4% at 0.30 VRHE even under neutral conditions. Furthermore, significant enhancement of the hydrogen evolution reaction on a CIGS Photocathode by surface modification with thin conductor layers was observed. The enhancement was due to the promoted charge transfer between the underlying Photocathode and water through the Pt catalyst. The HC-STH of a CIGS Photocathode modified with a conductive Mo/Ti layer (Pt/Mo/Ti/CdS/CIGS) was as high as 8.5% at 0.38 VRHE, a value that exceeds those previously reported for Photocathodes based on polycrystalline thin films.
Saeid Masudypanah - One of the best experts on this subject based on the ideXlab platform.
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nanoengineered advanced materials for enabling hydrogen economy functionalized graphene incorporated cupric oxide catalyst for efficient solar hydrogen production
Global challenges (Hoboken NJ), 2020Co-Authors: G K Dalapati, Saeid Masudypanah, Roozbeh Siavash Moakhar, Sabyasachi Chakrabortty, Siddhartha Ghosh, Ajay Kushwaha, Reza Katal, Chin Sheng Chua, Gong XiaoAbstract:: Cupric oxide (CuO) is a promising candidate as a Photocathode for visible-light-driven photo-electrochemical (PEC) water splitting. However, the stability of the CuO Photocathode against photo-corrosion is crucial for developing CuO-based PEC cells. This study demonstrates a stable and efficient Photocathode through the introduction of graphene into CuO film (CuO:G). The CuO:G composite electrodes are prepared using graphene-incorporated CuO sol-gel solution via spin-coating techniques. The graphene is modified with two different types of functional groups, such as amine (-NH2) and carboxylic acid (-COOH). The -COOH-functionalized graphene incorporation into CuO Photocathode exhibits better stability and also improves the photocurrent generation compare to control CuO electrode. In addition, -COOH-functionalized graphene reduces the conversion of CuO phase into cuprous oxide (Cu2O) during photo-electrochemical reaction due to effective charge transfer and leads to a more stable Photocathode. The reduction of CuO to Cu2O phase is significantly lesser in CuO:G-COOH as compared to CuO and CuO:G-NH2 Photocathodes. The photocatalytic degradation of methylene blue (MB) by CuO, CuO:G-NH2 and CuO:G-COOH is also investigated. By integrating CuO:G-COOH Photocathode with a sol-gel-deposited TiO2 protecting layer and Au-Pd nanostructure, stable and efficient Photocathode are developed for solar hydrogen generation.
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stable and efficient cuo based Photocathode through oxygen rich composition and au pd nanostructure incorporation for solar hydrogen production
ACS Applied Materials & Interfaces, 2017Co-Authors: Roozbeh Siavash Moakhar, Saeid Masudypanah, Ajay Kushwaha, Chin Sheng Chua, G K DalapatiAbstract:Enhancing stability against photocorrosion and improving photocurrent response are the main challenges toward the development of cupric oxide (CuO) based Photocathodes for solar-driven hydrogen production. In this paper, stable and efficient CuO-Photocathodes have been developed using in situ materials engineering and through gold-palladium (Au-Pd) nanoparticles deposition on the CuO surface. The CuO Photocathode exhibits a photocurrent generation of ∼3 mA/cm2 at 0 V v/s RHE. Time-of-flight secondary ion mass spectrometry (TOF-SIMS) analysis and X-ray spectroscopy (XPS) confirm the formation of oxygen-rich (O-rich) CuO film which demonstrates a highly stable Photocathode with retained photocurrent of ∼90% for 20 min. The influence of chemical composition on the Photocathode performance and stability has been discussed in detail. In addition, O-rich CuO Photocathodes deposited with Au-Pd nanostructures have shown enhanced photoelectrochemical performance. Linear scan voltammetry characteristic shows ∼25% enhancement in photocurrent after Au-Pd deposition and reaches ∼4 mA/cm2 at "0" V v/s RHE. Hydrogen evolution rate significantly depends on the elemental composition of CuO and metal nanostructure. The present work has demonstrated a stable Photocathode with high photocurrent for visible-light-driven water splitting and hydrogen production.
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rapid thermal annealing assisted stability and efficiency enhancement in a sputter deposited cuo Photocathode
RSC Advances, 2016Co-Authors: Saeid Masudypanah, Roozbeh Siavash Moakhar, Ajay Kushwaha, Chin Sheng Chua, Ten It Wong, G K DalapatiAbstract:We designed a stable and efficient CuO based Photocathode by tuning the crystallinity and surface morphology of films by rapid thermal treatment. The role of the annealing temperature on film crystallinity, optical absorption and grain size is studied. The impact of these parameters upon the photocatalytic water splitting performance of CuO films is investigated. We observed that a higher annealing temperature improves the film crystallinity and increases the grain size of CuO film, which significantly enhance the photocurrent generation capability. Rapid thermal annealing at 550 °C is found the best temperature to achieve the highest PEC performance. The thickness of the CuO Photocathodes is also optimized and we observed that 550 nm thick films results in the highest photocurrent of 1.68 mA cm−2. Our optimized CuO Photocathode has shown better stability against photo-corrosion and a 30% decrease in the initial value of photocurrent is measured after 15 min, while a 60% decrease in the photocurrent is noticed in case of the as-deposited film.
Thomas F. Jaramillo - One of the best experts on this subject based on the ideXlab platform.
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Highly Stable Molybdenum Disulfide Protected Silicon Photocathodes for Photoelectrochemical Water Splitting
ACS Applied Materials and Interfaces, 2017Co-Authors: Laurie A King, Thomas R. Hellstern, Joonsuk Park, Robert Sinclair, Thomas F. JaramilloAbstract:Developing materials, interfaces, and devices with improved stability remains one of the key challenges in the field of photoelectrochemical water splitting. As a barrier to corrosion, molybdenum disulfide is a particularly attractive protection layer for Photocathodes due to its inherent stability in acid, the low permeability of its basal planes, and the excellent hydrogen evolution reaction (HER) activity the MoS2 edge. Here, we demonstrate a stable silicon Photocathode containing a protecting layer consisting of molybdenum disulfide, molybdenum silicide, and silicon oxide which operates continuously for two months. We make comparisons between this system and another molybdenum sulfide–silicon Photocathode embodiment, taking both systems to catastrophic failure during photoelectrochemical stability measurements and exploring mechanisms of degradation. X-ray photoelectron spectroscopy and transmission electron microscopy provide key insights into the origins of stability.
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Designing active and stable silicon Photocathodes for solar hydrogen production using molybdenum sulfide nanomaterials
Advanced Energy Materials, 2014Co-Authors: Jesse D Benck, Kara D. Fong, Jakob Kibsgaard, Sang Chul Lee, Robert Sinclair, Thomas F. JaramilloAbstract:Silicon is a promising Photocathode for tandem photoelectrochemical water splitting devices, but efficient catalysis and long term stability remain key challenges. Here, it is demonstrated that with appropriately engineered interfaces, molybdenum sulfide nanomaterials can provide both corrosion protection and catalytic activity in silicon Photocathodes. Using a thin MoS2 surface protecting layer, MoS2-n+p Si electrodes that show no loss in performance after 100 h of operation are created. Transmission electron microscopy measurements show the atomic structure of the device surface and reveal the characteristics of the MoS2 layer that provide both catalytic activity and excellent stability. In spite of a low concentration of exposed catalytically active sites, these electrodes possess the best performance of any precious metal-free silicon Photocathodes with demonstrated long term stability to date. To further improve efficiency, a second molybdenum sulfide nanomaterial, highly catalytically active [Mo3S13]2− clusters, is incorporated. These Photocathodes offer a promising pathway towards sustainable hydrogen production.
G K Dalapati - One of the best experts on this subject based on the ideXlab platform.
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nanoengineered advanced materials for enabling hydrogen economy functionalized graphene incorporated cupric oxide catalyst for efficient solar hydrogen production
Global challenges (Hoboken NJ), 2020Co-Authors: G K Dalapati, Saeid Masudypanah, Roozbeh Siavash Moakhar, Sabyasachi Chakrabortty, Siddhartha Ghosh, Ajay Kushwaha, Reza Katal, Chin Sheng Chua, Gong XiaoAbstract:: Cupric oxide (CuO) is a promising candidate as a Photocathode for visible-light-driven photo-electrochemical (PEC) water splitting. However, the stability of the CuO Photocathode against photo-corrosion is crucial for developing CuO-based PEC cells. This study demonstrates a stable and efficient Photocathode through the introduction of graphene into CuO film (CuO:G). The CuO:G composite electrodes are prepared using graphene-incorporated CuO sol-gel solution via spin-coating techniques. The graphene is modified with two different types of functional groups, such as amine (-NH2) and carboxylic acid (-COOH). The -COOH-functionalized graphene incorporation into CuO Photocathode exhibits better stability and also improves the photocurrent generation compare to control CuO electrode. In addition, -COOH-functionalized graphene reduces the conversion of CuO phase into cuprous oxide (Cu2O) during photo-electrochemical reaction due to effective charge transfer and leads to a more stable Photocathode. The reduction of CuO to Cu2O phase is significantly lesser in CuO:G-COOH as compared to CuO and CuO:G-NH2 Photocathodes. The photocatalytic degradation of methylene blue (MB) by CuO, CuO:G-NH2 and CuO:G-COOH is also investigated. By integrating CuO:G-COOH Photocathode with a sol-gel-deposited TiO2 protecting layer and Au-Pd nanostructure, stable and efficient Photocathode are developed for solar hydrogen generation.
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stable and efficient cuo based Photocathode through oxygen rich composition and au pd nanostructure incorporation for solar hydrogen production
ACS Applied Materials & Interfaces, 2017Co-Authors: Roozbeh Siavash Moakhar, Saeid Masudypanah, Ajay Kushwaha, Chin Sheng Chua, G K DalapatiAbstract:Enhancing stability against photocorrosion and improving photocurrent response are the main challenges toward the development of cupric oxide (CuO) based Photocathodes for solar-driven hydrogen production. In this paper, stable and efficient CuO-Photocathodes have been developed using in situ materials engineering and through gold-palladium (Au-Pd) nanoparticles deposition on the CuO surface. The CuO Photocathode exhibits a photocurrent generation of ∼3 mA/cm2 at 0 V v/s RHE. Time-of-flight secondary ion mass spectrometry (TOF-SIMS) analysis and X-ray spectroscopy (XPS) confirm the formation of oxygen-rich (O-rich) CuO film which demonstrates a highly stable Photocathode with retained photocurrent of ∼90% for 20 min. The influence of chemical composition on the Photocathode performance and stability has been discussed in detail. In addition, O-rich CuO Photocathodes deposited with Au-Pd nanostructures have shown enhanced photoelectrochemical performance. Linear scan voltammetry characteristic shows ∼25% enhancement in photocurrent after Au-Pd deposition and reaches ∼4 mA/cm2 at "0" V v/s RHE. Hydrogen evolution rate significantly depends on the elemental composition of CuO and metal nanostructure. The present work has demonstrated a stable Photocathode with high photocurrent for visible-light-driven water splitting and hydrogen production.
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rapid thermal annealing assisted stability and efficiency enhancement in a sputter deposited cuo Photocathode
RSC Advances, 2016Co-Authors: Saeid Masudypanah, Roozbeh Siavash Moakhar, Ajay Kushwaha, Chin Sheng Chua, Ten It Wong, G K DalapatiAbstract:We designed a stable and efficient CuO based Photocathode by tuning the crystallinity and surface morphology of films by rapid thermal treatment. The role of the annealing temperature on film crystallinity, optical absorption and grain size is studied. The impact of these parameters upon the photocatalytic water splitting performance of CuO films is investigated. We observed that a higher annealing temperature improves the film crystallinity and increases the grain size of CuO film, which significantly enhance the photocurrent generation capability. Rapid thermal annealing at 550 °C is found the best temperature to achieve the highest PEC performance. The thickness of the CuO Photocathodes is also optimized and we observed that 550 nm thick films results in the highest photocurrent of 1.68 mA cm−2. Our optimized CuO Photocathode has shown better stability against photo-corrosion and a 30% decrease in the initial value of photocurrent is measured after 15 min, while a 60% decrease in the photocurrent is noticed in case of the as-deposited film.
