研究目的
To introduce oxygen vacancies into hematite (α-Fe2O3) photoanodes along with Sn doping to improve electric conductivity and photoelectrochemical performance for solar water oxidation.
研究成果
The study successfully introduces oxygen vacancies into Sn-doped hematite using a simple graphite-based annealing method, leading to enhanced electric conductivity, reduced charge transfer resistance, and improved photoelectrochemical performance for solar water oxidation, with up to 70% increase in photocurrent density. Oxygen vacancies improve both charge transport and surface charge separation efficiencies. The strategy is effective and can be extended to other oxide photoanodes.
研究不足
The improvement in photocurrent density due to oxygen vacancies is less significant at higher Sn doping levels. The method may not be universally applicable to all photoanodes without optimization, and the conductivity of FTO substrate can degrade with increased annealing temperature or time.
1：Experimental Design and Method Selection:
The study uses a one-pot annealing method on graphite to create a local reducing atmosphere for introducing oxygen vacancies and Sn doping into hematite nanorod arrays. This is compared to annealing on SiO2 powders.
2：Sample Selection and Data Sources:
Hematite photoanodes are prepared on FTO substrates via hydrothermal synthesis and annealing. Materials include FTO glass, urea, ferric chloride hexahydrate, SiO2, and graphite.
3：List of Experimental Equipment and Materials:
Equipment includes muffle furnace, quartz tube furnace, CHI 660C electrochemical workstation, Xe arc lamp, SEM (FEI Sirion 200), HRTEM (FEI Tecnai G2 F30), XRD (PANalytical B.V. Empyrean), XPS (Thermo Fisher ESCALab250), Raman spectrometer (WITec Alpha300), and simultaneous thermal analyzer (NETZSCH STA449F3). Materials are specified in the paper.
4：3). Materials are specified in the paper. Experimental Procedures and Operational Workflow:
4. Experimental Procedures and Operational Workflow: FeOOH nanorods are hydrothermally grown on FTO, annealed to hematite, then further annealed on graphite or SiO2 at high temperatures (e.g., 770°C for 20 min). Photoelectrochemical measurements are conducted in a three-electrode setup with 1 M NaOH electrolyte.
5：Data Analysis Methods:
Data analysis includes linear sweep voltammetry, electrochemical impedance spectroscopy, Mott-Schottky plots, XPS, Raman spectroscopy, and UV-Vis absorbance to assess photocurrent, donor density, charge transfer resistance, and material properties.
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SEM
Sirion 200
FEI
Used for characterizing the morphology of hematite samples.
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HRTEM
Tecnai G2 F30
FEI
Used for high-resolution transmission electron microscopy to analyze microstructure.
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XRD
Empyrean
PANalytical B.V.
Used for X-ray diffraction to confirm crystal structure of samples.
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XPS
ESCALab250
Thermo Fisher
Used for X-ray photoelectron spectroscopy to analyze surface compositions.
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Raman spectrometer
Alpha300
WITec
Used for Raman spectroscopy to detect oxygen vacancies.
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FTO glass
14 Ω per square
Wuhan Geao Science and Education Instruments Co., Ltd.
Used as conductive substrates for hematite photoanodes.
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Simultaneous thermal analyzer
STA449F3
NETZSCH
Used for thermo-gravimetric analysis of graphite.
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Electrochemical workstation
CHI 660C
ChenHua
Used for photoelectrochemical and electrochemical measurements.
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Xe arc lamp
150 W
Used as a light source for simulated sunlight.
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Autoclave
Used for hydrothermal synthesis of FeOOH nanorods.
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Muffle furnace
Used for annealing FeOOH to hematite at 550°C for 2 h.
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Quartz tube furnace
Used for high-temperature annealing on graphite or SiO2.
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