Photochemical Charge Separation at Particle Interfaces: The n-BiVO<sub>4</sub>–p-Silicon System

Yang, Yuxin; Wang, Jiarui; Zhao, Jing; Nail, Benjamin A.; Yuan, Xing; Guo, Yihang; Osterloh, Frank E.

doi:10.1021/acsami.5b00257

Cited by 44 publications

(46 citation statements)

References 49 publications

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“…Spectra obtained in this way provide information about the carrier type, 32 mid gap states, 33,34 defects, 35 and electrochemical reactions at interfaces, 36 38 Previous studies indicate a dependence of the maximum photovoltage on the absorber film thickness. 32,39 In order to study this effect, the CuBi 2 O 4 film thickness on FTO was varied.…”

Section: Resultsmentioning

confidence: 99%

Electronic structure, photovoltage, and photocatalytic hydrogen evolution with p-CuBi₂O₄ nanocrystals

et al. 2016

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a As a visible light active p-type semiconductor, CuBi2O4 is of interest as a photocatalyst for the generation of hydrogen fuel from water. Here we present the first photovoltage and photocatalytic measurements on this material and DFT results on its band structure. Single crystalline CuBi2O4 nanoparticles (25.7 ± 4.7 nm) were synthesized from bismuth and cupric nitrate in water under hydrothermal conditions. Powder X-ray diffraction (XRD) confirms the CuBi2O4 structure type and UV-Vis spectroscopy observes a 1.75 eV optical band gap. Surface photovoltage (SPV) measurements on CuBi2O4 nanoparticle films on fluorine doped tin oxide yield 0.225 V positive photovoltage at >1.75 eV photon energy confirming holes as majority carriers. The photovoltage is reversible and limited by light absorption. When dispersed in 0.075 M aqueous potassium iodide solution, the CuBi2O4 particles support photochemical hydrogen evolution of up to 16 µmol h-1 under ultraviolet but not under visible light. Based on electrochemical scans, CuBi2O4 is unstable towards reduction at -0.2 V, but pH-dependent photocurrents of 6.45 A cm -2 with an onset potential of +0.75 V vs. NHE can be obtained with 0.01 M Na2S2O8 as a sacrificial electron acceptor. The photoelectrochemical properties of CuBi2O4 can be explained on the basis of the band structure of the material. DFT calculations show the valence and conduction band edges to arise primarily from the combination of O 2p and Cu 3d orbitals, respectively, with additional contributions from Cu 3d and Bi 6s orbitals just below the Fermi level. Trapping of photoelectrons in the Cu 3d band is the cause for reductive photocorrosion of the material, while the p-type conductivity arises from copper vacancy states near the VB edge. These findings provide an improved understanding of the photophysical properties of p-CuBi2O4 and its limitations as a proton reduction photocatalyst.A) The DFT+U electronic band structures of (left) pristine CuBi2O4 and (right) VCu -CuBi2O4. The Fermi level (EF) is set at 0 eV. The presence of VCu leads to partial occupation of the bands around the VB edge. This gives rise to p-type behavior in CuBi2O4. B) The DFT+U projected density of states of VCu -CuBi2O4.

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Section: Resultsmentioning

confidence: 99%

Electronic structure, photovoltage, and photocatalytic hydrogen evolution with p-CuBi₂O₄ nanocrystals

et al. 2016

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“…Measurements were conducted in vacuum after wetting the films with a drop of methanol. Methanol acts as a sacrificial electron donor and improves the photovoltage signal from BiVO 4 by reacting with the photoholes …”

Section: Resultsmentioning

confidence: 99%

Enhancing the Photoactivity of Faceted BiVO₄ via Annealing in Oxygen‐Deficient Condition

Tan

Suyanto

Denko

et al. 2016

Part & Part Syst Charact

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Thermal annealing of metal oxides in oxygen‐deficient atmosphere, particularly reducing hydrogen gas, has been demonstrated to induce oxygen vacancy formation for enhanced photoactivity of the materials. Here, it is demonstrated that argon annealing (another prevalently used oxygen‐deficient gas) in the temperature range of 300–700 °C greatly affects the activity of dual‐faceted BiVO4 microcrystals for photocatalytic O2 generation and photocurrent generation. While treatment at 300 °C has little to no effect, higher temperatures of 500 and 700 °C significantly improve the crystallinity, alter the local structure distortion, and reduce the bandgap energy of the treated BiVO4. The higher temperature treatment also favors formation of new subgap states attributed to oxygen vacancies, as supported by surface photovoltage and electron paramagnetic resonance spectroscopies. Despite the most profound improvements in structural, optical, and electronic properties displayed by the 700 °C‐treated BiVO4, the sample annealed at 500 °C exhibits the highest photoactivity. The lower activity of the 700 °C‐treated BiVO4 is ascribed to the creation of bismuth vacancies and the loss of well‐defined crystal facets, contributing to impeded electron transport and poor charge separation.

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“…Yang et al have been successfully prepared α-Fe 2 O 3 /GO composites by a hydrothermal method and researched its electrochemical performance. [52] α-Fe 2 O 3 /GO composite as electrode materials can be applied to the pseudocapacitance on account of the oxidation and reduction reaction between Fe 3+ and Fe 2+ . The α-Fe 2 O 3 mesocrystals can enlarge specific surface area (ca.…”

Section: α-Fe 2 O 3 /Go Compositesmentioning

confidence: 99%

α‐Fe₂O₃ Based Carbon Composite as Pure Negative Electrode for Application as Supercapacitor

Chen

2019

Eur J Inorg Chem

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Supercapacitors have drawn the great attention of researchers as green energy storage devices. Until now, serious positive electrodes for asymmetric cells have been developed noticeably. Nevertheless, negative electrode materials have been less explored, especially pseudocapacitive materials. In this review, the impact of the morphology and composition of hematite (α‐Fe2O3) based carbon composite as pure negative electrode are discussed. Besides, the specific capacitance, electrochemical stability, power density, and energy density of those materials are covered. The asymmetric supercapacitor using α‐Fe2O3 based carbon composite electrode shows high energy density, which can compete with batteries.

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Photochemical Charge Separation at Particle Interfaces: The n-BiVO₄–p-Silicon System

Cited by 44 publications

References 49 publications

Electronic structure, photovoltage, and photocatalytic hydrogen evolution with p-CuBi₂O₄ nanocrystals

Electronic structure, photovoltage, and photocatalytic hydrogen evolution with p-CuBi₂O₄ nanocrystals

Enhancing the Photoactivity of Faceted BiVO₄ via Annealing in Oxygen‐Deficient Condition

α‐Fe₂O₃ Based Carbon Composite as Pure Negative Electrode for Application as Supercapacitor

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Photochemical Charge Separation at Particle Interfaces: The n-BiVO4–p-Silicon System

Cited by 44 publications

References 49 publications

Electronic structure, photovoltage, and photocatalytic hydrogen evolution with p-CuBi2O4 nanocrystals

Electronic structure, photovoltage, and photocatalytic hydrogen evolution with p-CuBi2O4 nanocrystals

Enhancing the Photoactivity of Faceted BiVO4 via Annealing in Oxygen‐Deficient Condition

α‐Fe2O3 Based Carbon Composite as Pure Negative Electrode for Application as Supercapacitor

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Product

Resources

About

Photochemical Charge Separation at Particle Interfaces: The n-BiVO₄–p-Silicon System

Electronic structure, photovoltage, and photocatalytic hydrogen evolution with p-CuBi₂O₄ nanocrystals

Electronic structure, photovoltage, and photocatalytic hydrogen evolution with p-CuBi₂O₄ nanocrystals

Enhancing the Photoactivity of Faceted BiVO₄ via Annealing in Oxygen‐Deficient Condition

α‐Fe₂O₃ Based Carbon Composite as Pure Negative Electrode for Application as Supercapacitor