Synthesis, electrochemical impedance spectroscopy study and photoelectrochemical behaviour of as-deposited and annealed WO 3  films

Levinas, Ramūnas; Цынцару, Н.; Lelis, Martynas; Cesiulis, H.

doi:10.1016/j.electacta.2016.12.112

Cited by 19 publications

(8 citation statements)

References 30 publications

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“…If the relative permittivity ε r were to be known, the width of the depletion zone could be calculated. The ε r of WO 3 is known to vary based on electrodeposition conditions, but for illustration purposes a value of 33.3 (obtained for WO 3 films formed by anodization in 0.3 M oxalic acid (Levinas et al, 2017)) will be considered. Then the width and volume of the space charge layer is calculated, and the values of charge carrier density are presented as a function of applied potential in Figure 7C.…”

Section: Photo Electrochemical Impedance Studymentioning

confidence: 99%

Improved Photocatalytic Water Splitting Activity of Highly Porous WO3 Photoanodes by Electrochemical H+ Intercalation

Levinas¹,

Цынцару

Murauskas³

et al. 2021

Front. Chem. Eng.

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WO3 photoanodes are widely used in photoelectrochemical catalysis, but typically the as-synthesized material is annealed before application. It is therefore desirable to explore less energy-intensive treatments. In this study, WO3 films of up to 3.9 μm thickness were obtained by galvanostatic anodization of tungsten foil in a neutral-pH Na2SO4 and NaF electrolyte, also containing a NaH2PO2 additive (to suppress O2 accumulation on the pore walls). Additionally, the WO3 photoanodes were modified by applying a cathodic reduction (H+ intercalation) and anodic activation treatment in-situ. XPS spectra revealed that intercalation modifies WO3 films; the amount of W5+-O and O-vacancy bonds was increased. Furthermore, subsequent activation leads to a decrease of the W5+ signal, but the amount of O-vacancy bonds remains elevated. The as-prepared and reduced (intercalated & activated) films were tested as OER photoanodes in acidic 0.1 M Na2SO4 media, under illumination with a 365 nm wavelength LED. It was observed that thinner films generated larger photocurrents. The peculiarities detected by XPS for reduced films correlate well with their improved photocatalytic activity. Photo-electrochemical impedance and intensity modulated photocurrent spectroscopies were combined with steady-state measurements in order to elucidate the effects of H+ intercalation on photoelectrochemical performance. The reduction results in films with enhanced photoexcited charge carrier generation/separation, improved conductivity, and possibly even suppressed bulk recombination. Thus, the intercalation & activation adopted in this study can be reliably used to improve the overall activity of as-synthesized WO3 photoanodes, and particularly of those that are initially poorly photoactive.

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Section: Photo Electrochemical Impedance Studymentioning

confidence: 99%

Improved Photocatalytic Water Splitting Activity of Highly Porous WO3 Photoanodes by Electrochemical H+ Intercalation

Levinas¹,

Цынцару

Murauskas³

et al. 2021

Front. Chem. Eng.

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“…The circuit is composed of one resistance (Rs) and two R-CPE time constants. The R S is linked to the electrolyte resistance, the first time constant (R 1 -CPE 1 ) to the resistance to the recombination of the electron–hole pairs and the second (R 2 -CPE 2 ) to the resistance from WO 3 to the electrolyte [ 45 , 46 , 47 , 49 , 50 ]. In this circuit, constant phase elements (CPE) are implemented as substitutes for capacitors to simulate the non-ideality of electrochemical capacitances.…”

Section: Resultsmentioning

confidence: 99%

Degradation of Methylparaben Using Optimal WO3 Nanostructures: Influence of the Annealing Conditions and Complexing Agent

et al. 2022

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In this work, WO3 nanostructures were synthesized with different complexing agents (0.05 M H2O2 and 0.1 M citric acid) and annealing conditions (400 °C, 500 °C and 600 °C) to obtain optimal WO3 nanostructures to use them as a photoanode in the photoelectrochemical (PEC) degradation of an endocrine disruptor chemical. These nanostructures were studied morphologically by a field emission scanning electron microscope. X-ray photoelectron spectroscopy was performed to provide information of the electronic states of the nanostructures. The crystallinity of the samples was observed by a confocal Raman laser microscope and X-ray diffraction. Furthermore, photoelectrochemical measurements (photostability, photoelectrochemical impedance spectroscopy, Mott–Schottky and water-splitting test) were also performed using a solar simulator with AM 1.5 conditions at 100 mW·cm−2. Once the optimal nanostructure was obtained (citric acid 0.01 M at an annealing temperature of 600 °C), the PEC degradation of methylparaben (CO 10 ppm) was carried out. It was followed by ultra-high-performance liquid chromatography and mass spectrometry, which allowed to obtain the concentration of the contaminant during degradation and the identification of degradation intermediates. The optimized nanostructure was proved to be an efficient photocatalyst since the degradation of methylparaben was performed in less than 4 h and the kinetic coefficient of degradation was 0.02 min−1.

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“…The Nyquist profile was fitted with the equivalent circuit model (inset), where R1 is the resistance of the external circuit, R2 represents the charge transfer resistance, and R3 refers to the charge transfer resistance of the electrode/electrolyte interface. 32 The radius of CuWO 4 /WO 3 -1 photoanode is the smallest at both low-frequency and high-frequency regions, indicating that CuWO 4 /WO 3 heterojunction results in a muchaccelerated charge transfer with reduced resistance at the electrode/electrolyte interface (Table S6 †). Therefore, the CuWO 4 /WO 3 -1 heterojunction has the highest photogenerated carrier separation rate.…”

Section: Catalysis Science and Technology Papermentioning

confidence: 99%

Interfacial engineering of CuWO₄/WO₃ thin films precisely fabricated by ultrasonic spray pyrolysis for improved solar water splitting

Cao

Sun

Duan

et al. 2023

Catal. Sci. Technol.

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Synthesis, electrochemical impedance spectroscopy study and photoelectrochemical behaviour of as-deposited and annealed WO 3 films

Cited by 19 publications

References 30 publications

Improved Photocatalytic Water Splitting Activity of Highly Porous WO3 Photoanodes by Electrochemical H+ Intercalation

Improved Photocatalytic Water Splitting Activity of Highly Porous WO3 Photoanodes by Electrochemical H+ Intercalation

Degradation of Methylparaben Using Optimal WO3 Nanostructures: Influence of the Annealing Conditions and Complexing Agent

Interfacial engineering of CuWO₄/WO₃ thin films precisely fabricated by ultrasonic spray pyrolysis for improved solar water splitting

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Synthesis, electrochemical impedance spectroscopy study and photoelectrochemical behaviour of as-deposited and annealed WO 3 films

Cited by 19 publications

References 30 publications

Improved Photocatalytic Water Splitting Activity of Highly Porous WO3 Photoanodes by Electrochemical H+ Intercalation

Improved Photocatalytic Water Splitting Activity of Highly Porous WO3 Photoanodes by Electrochemical H+ Intercalation

Degradation of Methylparaben Using Optimal WO3 Nanostructures: Influence of the Annealing Conditions and Complexing Agent

Interfacial engineering of CuWO4/WO3 thin films precisely fabricated by ultrasonic spray pyrolysis for improved solar water splitting

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Interfacial engineering of CuWO₄/WO₃ thin films precisely fabricated by ultrasonic spray pyrolysis for improved solar water splitting