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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.
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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positive onset potential and stability of cu2o based Photocathodes in water splitting by atomic layer deposition of a ga2o3 buffer layer
Energy and Environmental Science, 2015Co-Authors: Takashi Hisatomi, Osamu Watanabe, Mamiko Nakabayashi, Naoya Shibata, Kazunari Domen, Jeanjacques DelaunayAbstract:The Cu2O-based photocathode is considered as one of the most promising Photocathodes for high performance water splitting under sunlight. However, the relatively negative onset potential for H2 production of these Photocathodes impedes further optimization of the solar-to-fuel conversion efficiency. Here, a thin Ga2O3 buffer layer is introduced between the Cu2O absorber layer and the TiO2 protective layer by atomic layer deposition to increase the photovoltage. For the optimized TiO2 deposition temperature, the Pt/TiO2/Ga2O3/Cu2O electrode achieves a high cathodic photocurrent of −2.95 mA cm−2 at 0 V vs. RHE and an extremely positive onset potential of 1.02 V vs. RHE (defined as the potential where photocathodic current reaches 20 μA cm−2 under air-mass 1.5 global illumination), benefiting from a buried p–n junction and a favorable band alignment. The Pt/TiO2/Ga2O3/Cu2O electrodes exhibit a stable cathodic current for 2 h under continuous illumination of a 500 W Xe lamp for the TiO2 deposition temperatures below 180 °C.
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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.
Daniel F Sievenpiper - One of the best experts on this subject based on the ideXlab platform.
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electron emission by long and short wavelength lasers essentials for the design of plasmonic Photocathodes
Journal of Applied Physics, 2018Co-Authors: Ebrahim Forati, Daniel F SievenpiperAbstract:The theory of electron emission by metallic Photocathodes under the exposure of long wavelength lasers will be studied. Photon energy in long wavelength lasers is less than the work function of the photocathode's material and can only emit electrons via tunneling through the potential barrier. The optical resonance effects (e.g., plasmonic resonances) will be studied as an improvement to the performance of Photocathodes. This paper is intended to provide self-sufficient materials to design optical resonant surfaces (e.g., metasurfaces) for electron emission applications.The theory of electron emission by metallic Photocathodes under the exposure of long wavelength lasers will be studied. Photon energy in long wavelength lasers is less than the work function of the photocathode's material and can only emit electrons via tunneling through the potential barrier. The optical resonance effects (e.g., plasmonic resonances) will be studied as an improvement to the performance of Photocathodes. This paper is intended to provide self-sufficient materials to design optical resonant surfaces (e.g., metasurfaces) for electron emission applications.
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electron emission by long and short wavelength lasers essentials for the design of plasmonic Photocathodes
Journal of Applied Physics, 2018Co-Authors: Ebrahim Forati, Daniel F SievenpiperAbstract:The theory of electron emission by metallic Photocathodes under the exposure of long wavelength lasers will be studied. Photon energy in long wavelength lasers is less than the work function of the photocathode's material and can only emit electrons via tunneling through the potential barrier. The optical resonance effects (e.g., plasmonic resonances) will be studied as an improvement to the performance of Photocathodes. This paper is intended to provide self-sufficient materials to design optical resonant surfaces (e.g., metasurfaces) for electron emission applications.
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electron emission by long and short wavelength lasers essentials for the design of plasmonic Photocathodes
arXiv: Applied Physics, 2018Co-Authors: Ebrahim Forati, Daniel F SievenpiperAbstract:Theory of electron emission by metallic Photocathodes under the exposure of long wavelength lasers will be studied. Energy of photons in long wavelength lasers is less than the work function of the photocathode material, and can only emit electrons via tunneling through the potential barrier. The optical resonance effect (e.g. plasmonic resonances) will be studied as an improvement to the performance of Photocathodes. This paper is intended to provide self-sufficient materials to design optical resonant surfaces (e.g. metasurfaces) for electron emission applications.
I Benzvi - One of the best experts on this subject based on the ideXlab platform.
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long lifetime of bialkali Photocathodes operating in high gradient superconducting radio frequency gun
Scientific Reports, 2021Co-Authors: Erdong Wang, S Belomestnykh, V N Litvinenko, Igor Pinayev, Mengjia Gaowei, J Skaritka, I BenzviAbstract:High brightness, high charge electron beams are critical for a number of advanced accelerator applications. The initial emittance of the electron beam, which is determined by the mean transverse energy (MTE) and laser spot size, is one of the most important parameters determining the beam quality. The bialkali Photocathodes illuminated by a visible laser have the advantages of high quantum efficiency (QE) and low MTE. Furthermore, Superconducting Radio Frequency (SRF) guns can operate in the continuous wave (CW) mode at high accelerating gradients, e.g. with significant reduction of the laser spot size at the photocathode. Combining the bialkali photocathode with the SRF gun enables generation of high charge, high brightness, and possibly high average current electron beams. However, integrating the high QE semiconductor photocathode into the SRF guns has been challenging. In this article, we report on the development of bialkali Photocathodes for successful operation in the SRF gun with months-long lifetime while delivering CW beams with nano-coulomb charge per bunch. This achievement opens a new era for high charge, high brightness CW electron beams.
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bi alkali antimonide Photocathodes for high brightness accelerators
APL Materials, 2013Co-Authors: S. Schubert, X. Liang, T. Rao, I Benzvi, H A Padmore, M Ruizoses, T Kamps, Erik Muller, Kathrin Muller, X TongAbstract:Alkali-antimonide Photocathodes were grown on Si(100) and studied by means of XPS and UHV-AFM to validate the growth procedure and morphology of this material. The elements were evaporated sequentially at elevated substrate temperatures (first Sb, second K, third Cs). The generated intermediate K-Sb compound itself is a photocathode and the composition of K2.4Sb is close to the favored K3Sb stoichiometry. After cesium deposition, the surface layer is cesium enriched. The determined rms roughness of 25 nm results in a roughness domination of the emittance in the photoinjector already above 3 MV/m.
Takashi Hisatomi - 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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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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positive onset potential and stability of cu2o based Photocathodes in water splitting by atomic layer deposition of a ga2o3 buffer layer
Energy and Environmental Science, 2015Co-Authors: Takashi Hisatomi, Osamu Watanabe, Mamiko Nakabayashi, Naoya Shibata, Kazunari Domen, Jeanjacques DelaunayAbstract:The Cu2O-based photocathode is considered as one of the most promising Photocathodes for high performance water splitting under sunlight. However, the relatively negative onset potential for H2 production of these Photocathodes impedes further optimization of the solar-to-fuel conversion efficiency. Here, a thin Ga2O3 buffer layer is introduced between the Cu2O absorber layer and the TiO2 protective layer by atomic layer deposition to increase the photovoltage. For the optimized TiO2 deposition temperature, the Pt/TiO2/Ga2O3/Cu2O electrode achieves a high cathodic photocurrent of −2.95 mA cm−2 at 0 V vs. RHE and an extremely positive onset potential of 1.02 V vs. RHE (defined as the potential where photocathodic current reaches 20 μA cm−2 under air-mass 1.5 global illumination), benefiting from a buried p–n junction and a favorable band alignment. The Pt/TiO2/Ga2O3/Cu2O electrodes exhibit a stable cathodic current for 2 h under continuous illumination of a 500 W Xe lamp for the TiO2 deposition temperatures below 180 °C.