Interface Engineering of Semiconductor Electrodes for Photoelectrochemical Water Splitting: Application of Surface Characterization with Photoelectron Spectroscopy

Jaegermann, Wolfram; Kaiser, Bernhard; Ziegler, Jürgen; Klett, Joachim

doi:10.1007/978-3-319-29641-8_5

Cited by 14 publications

(25 citation statements)

References 155 publications

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“…• C for 10 min, rinsed, and then subjected to a final 6 min oxide removal step in NH 4 F. 18 Subsequently, the sample was thoroughly rinsed, dried under N 2 , mounted on a sample holder and introduced into ultra high vacuum (UHV) at the Darmstadt Integrated System for Fundamental research (DAISY Fun) 19 within 5 minutes of the last preparation step.…”

Section: Methodsmentioning

confidence: 99%

The Impact of Different Si Surface Terminations in the (001) n-Si/NiOx Heterojunction on the Oxygen Evolution Reaction (OER) by XPS and Electrochemical Methods

Tengeler

Fingerle

Calvet

et al. 2018

J. Electrochem. Soc.

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The interaction between (001) n-Si and NiO x was investigated with regard to the oxygen evolution reaction (OER), applicable either for water splitting or CO 2 reduction. Thin layers of nickel oxide were deposited step by step by reactive sputter deposition and analyzed in-situ after each step using X-ray photoelectron spectroscopy (XPS). This was performed for silicon with different surface preparations: H-termination, thermally grown oxide (2 Å) and a monolayer of native oxide (4 Å). Upon contact formation the initial flatband like situation in the Si substrates changed to a 0.35 to 0.4 eV upward band bending for all three heterojunctions, with an alignment of the valence bands favorable to hole extraction. With near identical heterojunction performance and identical NiO x catalyst layers (η(10 mA/cm 2 ) = 0.44 ± 0.01 V vs. RHE on Ni) an equally identical performance for the OER would be expected. While the native oxide covered sample shows the expected performance in cyclic voltammetry measurements the others fall short of expectations. Using chopped light measurements, this under-performance could be attributed to a higher density of defect states at the silicon surface. Apparently a 4Å SiO 2 layer is sufficient protection to prevent the formation of defect states during NiO x deposition, thinner protective layers or none at all result in increased defect states, while thicker layers perform poorly due to their high resistance. Direct photoelectrochemical devices are an exciting approach to the storage of renewable energies. Depending on the preferred energy cycle they can be used either for water splitting or CO 2 reduction, in the end it is only a question of the employed catalysts and necessary overpotentials. A direct photoelectrochemical device has two main functional parts, which do not necessarily have to be physically separate. First, there is the photoabsorber, basically a solar cell, who has to supply the necessary photovolage U ph and photocurrent J ph to power the desired redox reaction. Second, the catalytic surface, which is in direct contact with the electrolyte and should be catalytically active, thus allowing high current densities at low overpotentials η. In an ideal case the total device performance should be a result of those two contributions only.Initial research on water splitting was focused on a single semiconducting material performing well in both functions. This was first demonstrated on a TiO 2 electrode by Fujishima and Honda in 1972. 1 In such a device the photoabsorber functionality is defined by the interface junction between semiconductor and electrolyte. Investigated materials were mostly wide bandgap materials, as they could, in theory, provide the necessary U ph .However, the double function of the semiconductor electrolyte interface makes an evaluation of such devices difficult, as it is hard to determine whether a lack of performance is a result from poor current voltage (IE) behavior of the junction or the poor catalytic performance of the material. Furthermore, t...

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Section: Methodsmentioning

confidence: 99%

The Impact of Different Si Surface Terminations in the (001) n-Si/NiOx Heterojunction on the Oxygen Evolution Reaction (OER) by XPS and Electrochemical Methods

Tengeler

Fingerle

Calvet

et al. 2018

J. Electrochem. Soc.

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“…oxide removal step in NH 4 F. 18 Chemicals used (all VLSI standards) were 96% H 2 SO 4 , 31% H 2 O 2 , 5% HF, and 40% NH 4 F. The sample was then thoroughly rinsed and dried under nitrogen flow, before being introduced into the ultra-high vacuum (UHV) deposition and analysis system Darmstadt Integrated System for Fundamental Research (DAISY-Fun) 19 within 5 min. Following the growth of an 8 Å thermal oxide layer, NiO x was deposited on the sample via reactive magnetron sputtering.…”

Section: Methodsmentioning

confidence: 99%

Water Interaction with Sputter-Deposited Nickel Oxide on n-Si Photoanode: Cryo Photoelectron Spectroscopy on Adsorbed Water in the Frozen Electrolyte Approach

Fingerle

Tengeler

Calvet

et al. 2018

J. Electrochem. Soc.

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The interaction of water with a magnetron-sputtered nickel oxide thin film on an n-type silicon photoanode is investigated in perspective to oxygen evolution. The substrate was exposed in-situ stepwise to gas phase water up to 10 L at liquid N 2 temperature and analyzed via X-ray and UV photoelectron spectroscopy in the so called frozen electrolyte approach. Photoemission of the pristine NiO x layer shows the presence of stoichiometric NiO and Ni 2 O 3 as well as of non-stoichiometric phases. In the monolayer range, molecular and dissociative adsorption is detected assigned to the NiO respective Ni 2 O 3 phase. Initially, the emission of the molecular adsorbed water species interacting with NiO is found at 0.8 eV lower binding energies as compared to water related emission for higher coverages with binding energies commonly assigned to H 2 O-H 2 O interaction. In addition to the chemical analysis, the electronic structure of the n-Si/SiO Most semiconducting materials, especially silicon, are unstable and degrade or passivate rapidly under photoanodic conditions in aqueous electrolytes.1 Nickel oxide thin films are promising catalysts for the hydrogen and the oxygen evolution reaction (OER) 2 and provide chemically stable coatings for silicon, while being transparent, antireflective and electronically conductive in addition.3-5 Elementary charge transfer processes located at a solid/liquid interface, are still scarcely approached by scientific studies on an atomistic scale.6 Especially the energetics of the photocatalytic dissociation of water on semiconducting materials is still unclear. In general, the determination of the chemical and electronic interaction at the interface between metal oxides and liquid electrolytes on an atomistic scale via surface science methods suffers from the so-called pressure gap. 7,8 One way to bridge the gap, model experiments at low temperatures can be utilized to monitor the surface chemistry by means of photoelectron spectroscopy under ultra-high vacuum. Regarding double layer formation, the frozen-electrolyte approach has already shown its potential in the past. 9 The principle mechanism of the oxygen evolution (OER) at nickel hydroxide based electrodes was investigated early on a more chemical basis 10 with various phase transitions involved. 11 It has been found that Ni(OH) 2 and NiOOH species at the surface are a prerequisite for any photocatalytic activity. However, the exact mechanism is still under debate 12 with the role of nickel oxide only little discussed. A first step for a better understanding is to study the reactivity of a pristine nickel oxide surface upon water adsorption. For NiO(100) it has been demonstrated that a perfect surface exhibits no reactive interaction with H 2 O unless oxygen vacancies induce the dissociation of water 13 or adsorbed O 2− ions at defect sites on a pre-oxidized surface enhance the reactivity. In contrast to NiO(100), theoretical studies predict dissociative water adsorption for NiO(111).14 Further to oxygen vacancies sub-coordinated ...

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“…ZnWO 4 thin films were deposited using the dual magnetron sputtering setup at the DArmstadt Integrated SYstem for FUNdamental research (DAISY-FUN), described in greater detail elsewhere [19]. The ZnO target (2.0" diameter, 99.99% purity, Mateck, Jülich, Germany) that operated with an RF signal at 13.56 MHz and the W target (2.0" diameter, 99.95% purity, Lesker, Jefferson Hills, PA, USA) that operated with a DC signal were mounted onto 2.0" MEIVAC MAK sputter deposition sources.…”

Section: Methodsmentioning

confidence: 99%

Reactive Dual Magnetron Sputtering: A Fast Method for Preparing Stoichiometric Microcrystalline ZnWO4 Thin Films

et al. 2021

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Thin films of ZnWO4, a promising photocatalytic and scintillator material, were deposited for the first time using a reactive dual magnetron sputtering procedure. A ZnO target was operated using an RF signal, and a W target was operated using a DC signal. The power on the ZnO target was changed so that it would match the sputtering rate of the W target operated at 25 W. The effects of the process parameters were characterized using optical spectroscopy, X-ray diffraction, and scanning electron microscopy, including energy dispersive X-ray spectroscopy as well as X-ray photoelectron spectroscopy. It was found that stoichiometric microcrystalline ZnWO4 thin films could be obtained, by operating the ZnO target during the sputtering procedure at a power of 55 W and by post-annealing the resulting thin films for at least 10 h at 600 °C. As FTO coated glass substrates were used, annealing led as well to the incorporation of Na, resulting in n+ doped ZnWO4 thin films.

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Interface Engineering of Semiconductor Electrodes for Photoelectrochemical Water Splitting: Application of Surface Characterization with Photoelectron Spectroscopy

Cited by 14 publications

References 155 publications

The Impact of Different Si Surface Terminations in the (001) n-Si/NiOx Heterojunction on the Oxygen Evolution Reaction (OER) by XPS and Electrochemical Methods

The Impact of Different Si Surface Terminations in the (001) n-Si/NiOx Heterojunction on the Oxygen Evolution Reaction (OER) by XPS and Electrochemical Methods

Water Interaction with Sputter-Deposited Nickel Oxide on n-Si Photoanode: Cryo Photoelectron Spectroscopy on Adsorbed Water in the Frozen Electrolyte Approach

Reactive Dual Magnetron Sputtering: A Fast Method for Preparing Stoichiometric Microcrystalline ZnWO4 Thin Films

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