Utilizing modeling, experiments, and statistics for the analysis of water-splitting photoelectrodes

Gaudy, Yannick Kenneth; Haussener, Sophia

doi:10.1039/c5ta07328f

Cited by 54 publications

(57 citation statements)

References 42 publications

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“…This indicates that the transfer of photogenerated holes from the electrode to water is not as efficient as the hole transfer from the electrode to H 2 O 2 .C omparing the charge-injection efficiency shown in Figure 6e,t he relativelyh igher efficiency for the PH 3 -treateds amples clearly suggests diminished surface state and suppressed recombination of photogenerated electrons with accumulated holes. [48] In addition, the effect of the overlayer becomes clearer and can be explained by the exhib- ited behaviors as both water oxidation co-catalyst and surfacestate passivation layer.T his dual effect leads to the cathodic shift of the photocurrent onset potential and improved photocurrent of the PH 3 -treateds amples.…”

Section: Resultsmentioning

confidence: 99%

Fe₂PO₅‐Encapsulated Reverse Energetic ZnO/Fe₂O₃ Heterojunction Nanowire for Enhanced Photoelectrochemical Oxidation of Water

Qin

et al. 2017

ChemSusChem

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Zinc oxide is regarded as a promising candidate for application in photoelectrochemical water oxidation due to its higher electron mobility. However, its instability under alkaline conditions limits its application in a practical setting. Herein, we demonstrate an easily achieved wet-chemical route to chemically stabilize ZnO nanowires (NWs) by protecting them with a thin layer Fe O shell. This shell, in which the thickness can be tuned by varying reaction times, forms an intact interface with ZnO NWs, thus protecting ZnO from corrosion in a basic solution. The reverse energetic heterojunction nanowires are subsequently activated by introducing an amorphous iron phosphate, which substantially suppressed surface recombination as a passivation layer and improved photoelectrochemical performance as a potential catalyst. Compared with pure ZnO NWs (0.4 mA cm ), a maximal photocurrent of 1.0 mA cm is achieved with ZnO/Fe O core-shell NWs and 2.3 mA cm was achieved for the PH -treated NWs at 1.23 V versus RHE. The PH low-temperature treatment creates a dual function, passivation and catalyst layer (Fe PO ), examined by X-ray photoelectron spectroscopy, TEM, photoelectrochemical characterization, and impedance measurements. Such a nano-composition design offers great promise to improve the overall performance of the photoanode material.

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Section: Resultsmentioning

confidence: 99%

Fe₂PO₅‐Encapsulated Reverse Energetic ZnO/Fe₂O₃ Heterojunction Nanowire for Enhanced Photoelectrochemical Oxidation of Water

Qin

et al. 2017

ChemSusChem

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“…63 Both the charge carrier concentration (here donor type) as well as charge carrier recombination have big influence on the photo-current onset potential as well as the photo-current density in general. 64 Assuming that the Fermi energy is not "pinned" to the surface, a high charge carrier density increases the band bending at the semiconductor-electrolyte interface and thus also the driving force for holes to oxidize the electrolyte.…”

Section: Resultsmentioning

confidence: 99%

ZnO Nanorod-Arrays as Photo-(Electro)Chemical Materials: Strategies Designed to Overcome the Material's Natural Limitations

Kegel

Povey

Pemble

2017

J. Electrochem. Soc.

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The urgent need for clean and storable energy drives many currently topical areas of materials research. Among the many materials under investigation zinc oxide is one of the most studied in relation to its use in photo-(electro)chemical applications. This study aims to give an overview of some of the main challenges associated with the use of zinc oxide for these applications: the high density of intrinsic defects which can lead to fast recombination, low visible light absorption and the occurrence of photo-corrosion. Employing simple low-temperature solution based methods; it is shown how defect-engineering can be used to increase the photoelectrochemical performance and how doping can strongly increase the visible light absorption of zinc oxide nanorod-arrays. Furthermore the deposition of ultra-thin titanium dioxide layers using atomic layer deposition is investigated as possible route for the protection of zinc oxide against photo-corrosion. As one of the most studied metal-oxides Zinc Oxide (ZnO) has already found its way into many industrial applications. Nevertheless enormous research interest is still focused on this earth-abundant, environmentally-friendly material as it offers interesting material properties such as a high exciton binding energy, a direct bandgap and comparably high charge carrier mobility.1 Furthermore the ability to grow ZnO nanostructures using a wide range of deposition techniques offers new perspectives for the material to be used in opto-electronics. Low-temperature solution based methods are of particular interest as possible routes to the low-cost growth of high surface-area nanostructures for the integration of ZnO into novel energy production and storage devices. The steadily growing research areas of solar water splitting and photo-catalysis are prominent examples of areas where interest in ZnO-based materials and devices may be found. [4][5][6][7][8][9][10][11] For these applications the nature of the semiconductor/electrolyte interface plays a crucial role. It is of the highest importance to carefully engineer the materials properties in order ensure effective charge carrier transport across the interface. In turn it must be the goal of materials research to tailor the ZnO toward these target applications, where possible addressing the key issues of:Low visible-light absorption.-Since ZnO exhibits a large bandgap (ca. 3.3 eV) only a small fraction of sunlight is absorbed thus dramatically hindering the use of ZnO for photo-(electro)chemical applications. A common strategy to change the electronic structure of a semiconductor is the introduction of dopants into the host material. In the case of ZnO the material has been doped with various elements whereby many studies focus on doping with transition metals (TMs) such as nickel, magnesium, iron or cobalt.7,12-17 Historically, research focused on transition metal doping has been fueled by the possible creation of ferromagnetism in these materials -especially in the case of cobalt doping. 12,15,[18][19][20][21] On the other h...

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“…12 Berger et al 13 presented a basic 1-dimensional model for light absorbers and electrolysis with applicability to both wired and wireless PEC systems. Gaudy et al 14 extended the 1D model by adding detailed wave propagation modeling and an advanced semiconductor-electrolyte interface model accounting for pinning and unpinning of interface states. Haussener et al 3,15 developed a 2-dimensional PEC model focusing on the charge transport in the electrolyte and reaction kinetics incorporating the idealized Shockley-Queisser limit for the photoabsorber approximation.…”

mentioning

confidence: 99%

Integrated Photo-Electrochemical Solar Fuel Generators under Concentrated Irradiation

Tembhurne

Haussener

2016

J. Electrochem. Soc.

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We investigate the direct conversion of solar energy and water into a storable fuel via integrated photo-electrochemical (IPEC) devices. Here we focus particularly on a device design which uses concentrated solar irradiation to reduce the use of rare and expensive components, such as light absorbers and catalysts. We present a 2-dimensional coupled multi-physics model using finite element and finite volume methods to predict the performance of the IPEC device. Our model accounts for charge generation and transport in the photoabsorber, charge transport in the membrane-separated catalysts, electrochemical reaction at the catalytic sites, fluid flow and species transport in the porous charge collectors and channels, and radiation absorption and heat transfer for all components. We then develop performance optimization strategies utilizing device design, component and material choice, and adaptation of operational conditions. Our model predicts that operation under high irradiation is possible and that dedicated thermal management can ensure high performant operation. The model shows to be a valuable tool for the design of IPEC devices under concentrated irradiation at elevated temperatures. To our knowledge, it is the most detailed yet computationally low-cost model of an IPEC device reported. The solar energy received on earth's surface can meet mankind's current and future energy demand.1,2 Direct conversion of solar energy and water into chemical energy via photo-electrochemical (PEC) processes is one viable route for renewable fuel processing and energy storage. Integrated photo-electrochemical (IPEC) devices, i.e. composed of an integrated buried photovoltaic (PV) component and an integrated electrochemical component (consisting of membraneseparated catalysts and porous charge collectors), allow circumvention of some of the challenges imposed by solid-liquid interfaces in traditional PEC devices, while also exhibiting potential to operate at higher efficiencies and lower cost than externally wired (non-integrated) PV plus electrolyzer (EC) devices. [3][4][5] We refer to the design as "integrated" to signify that the PV and electrolyzer components are area-matched and in direct contact, allowing heat transfer from one component to the other and for thermal management strategies to be applied. In order to increase the economic competitiveness of IPEC devices compared to conventional hydrogen generation pathways, we consider concentration of irradiation. [6][7][8] This leads to large driving current densities (approximately proportional to the concentration factor), and thus introduces larger overpotentials and potential mass transport limitations.9 Concentration also decreases the performance of the photoactive components due to increased temperature. On the other hand, the kinetics are enhanced with increased temperature. Ionic transport in the solid electrolyte is also enhanced with increased temperature, but this increase stops abruptly and sharply drops at temperatures above 120• C due to membrane dry out. ...

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Utilizing modeling, experiments, and statistics for the analysis of water-splitting photoelectrodes

Abstract: A multi-physics model of a planar water-splitting photoelectrode was developed, validated, and used to identify and quantify the most significant materials-related bottlenecks in photoelectrochemical device performance.

Cited by 54 publications

References 42 publications

Fe₂PO₅‐Encapsulated Reverse Energetic ZnO/Fe₂O₃ Heterojunction Nanowire for Enhanced Photoelectrochemical Oxidation of Water

Fe₂PO₅‐Encapsulated Reverse Energetic ZnO/Fe₂O₃ Heterojunction Nanowire for Enhanced Photoelectrochemical Oxidation of Water

ZnO Nanorod-Arrays as Photo-(Electro)Chemical Materials: Strategies Designed to Overcome the Material's Natural Limitations

Integrated Photo-Electrochemical Solar Fuel Generators under Concentrated Irradiation

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Utilizing modeling, experiments, and statistics for the analysis of water-splitting photoelectrodes

Abstract: A multi-physics model of a planar water-splitting photoelectrode was developed, validated, and used to identify and quantify the most significant materials-related bottlenecks in photoelectrochemical device performance.

Cited by 54 publications

References 42 publications

Fe2PO5‐Encapsulated Reverse Energetic ZnO/Fe2O3 Heterojunction Nanowire for Enhanced Photoelectrochemical Oxidation of Water

Fe2PO5‐Encapsulated Reverse Energetic ZnO/Fe2O3 Heterojunction Nanowire for Enhanced Photoelectrochemical Oxidation of Water

ZnO Nanorod-Arrays as Photo-(Electro)Chemical Materials: Strategies Designed to Overcome the Material's Natural Limitations

Integrated Photo-Electrochemical Solar Fuel Generators under Concentrated Irradiation

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Fe₂PO₅‐Encapsulated Reverse Energetic ZnO/Fe₂O₃ Heterojunction Nanowire for Enhanced Photoelectrochemical Oxidation of Water

Fe₂PO₅‐Encapsulated Reverse Energetic ZnO/Fe₂O₃ Heterojunction Nanowire for Enhanced Photoelectrochemical Oxidation of Water