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Electrical and photocatalytic properties of boron-doped ZnO nanostructure grown on PET – ITO flexible substrates by hydrothermal method

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ABSTRACT

––––: Boron-doped zinc oxide sheet-spheres were synthesized on PETITO flexible substrates using a hydrothermal method at 90 °C for 5 h. The results of X-ray diffraction and X-ray photoelectron spectroscopy indicated that the B atoms were successfully doped into the ZnO lattice, the incorporation of B led to an increase in the lattice constant of ZnO and a change in its internal stress. The growth mechanism of pure ZnO nanorods and B-doped ZnO sheet-spheres was specifically investigated. The as-prepared BZO/PETITO heterojunction possessed obvious rectification properties and its positive turn-on voltage was 0.4 V. The carrier transport mechanisms involved three models such as hot carrier tunneling theory, tunneling recombination, and series-resistance effect were explored. The BZO/PETITO nanostructures were more effective than pure ZnO to degrade the RY 15, and the degradation rate reached 41.45%. The decomposition process with BZO nanostructure followed first-order reaction kinetics. The photocurrent and electrochemical impedance spectroscopy revealed that the B-doping could promote the separation of photo-generated electron-hole pairs, which was beneficial to enhance the photocatalytic activity. The photocurrent density of B-doped and pure ZnO/PETITO were 0.055 mA/cm2 and 0.016 mA/cm2, respectively. The photocatalytic mechanism of the sample was analyzed by the energy band theory.

No MeSH data available.


Energy band diagram of the BZO/PET–ITO heterojunction in a thermal equilibrium state.e−, electron; h+, hole; χ electron affinity; hv, photon energy; EC, conduction band; EV, valence band; EF, Fermi level; ·OH, hydroxyl radical; Eb, built-in electric field.
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f11: Energy band diagram of the BZO/PET–ITO heterojunction in a thermal equilibrium state.e−, electron; h+, hole; χ electron affinity; hv, photon energy; EC, conduction band; EV, valence band; EF, Fermi level; ·OH, hydroxyl radical; Eb, built-in electric field.

Mentions: The photocatalytic reaction principle of the sheet-sphere-shaped BZO grown on PET–ITO is analyzed by means of energy band theory without considering the interface state (Fig. 11). When the BZO/PET–ITO heterojunction is under UV luminescence with a wavelength of 365 nm (3.397 eV), electrons at the top of the valence band can absorb the photon energy to directly transit to the conduction band. The photo-induced carrier of holes (electrons) is created in the valence band (conduction band) of ZnO and PET–ITO. This principle is similar to the ref. 35 reported by Low et al., in which the TiO2-based p-n heterojunction photocatalyst be used to CO2 reduction. The built-in electric field (Eb) presented at the interface forces holes (electrons) to transfer from the valence band of n-type BZO (conduction band of PET–ITO) to the valence band of p-type PET–ITO (conduction band of BZO). The effective separation of the photo-production charge carriers increases, which greatly reduces the probability of electron-hole pair recombination and extends the lifetime of photo-generated carriers, result in the activity of ZnO/PET–ITO worked as the photocatalyst is accelerated. Moreover, the light-generated electrons can be captured by the oxidizing substances in the mixed solution to proceed the reduction reaction, so that the O2 dissolved in water is transformed into the superoxide anion free radical O2−, . The H2O and OH− adsorbed on the surface of the ZnO nanostructures can be oxidized to the hydroxyl radical ·OH by the photo-generated holes acting as a strong oxidizing agent.


Electrical and photocatalytic properties of boron-doped ZnO nanostructure grown on PET – ITO flexible substrates by hydrothermal method
Energy band diagram of the BZO/PET–ITO heterojunction in a thermal equilibrium state.e−, electron; h+, hole; χ electron affinity; hv, photon energy; EC, conduction band; EV, valence band; EF, Fermi level; ·OH, hydroxyl radical; Eb, built-in electric field.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5304159&req=5

f11: Energy band diagram of the BZO/PET–ITO heterojunction in a thermal equilibrium state.e−, electron; h+, hole; χ electron affinity; hv, photon energy; EC, conduction band; EV, valence band; EF, Fermi level; ·OH, hydroxyl radical; Eb, built-in electric field.
Mentions: The photocatalytic reaction principle of the sheet-sphere-shaped BZO grown on PET–ITO is analyzed by means of energy band theory without considering the interface state (Fig. 11). When the BZO/PET–ITO heterojunction is under UV luminescence with a wavelength of 365 nm (3.397 eV), electrons at the top of the valence band can absorb the photon energy to directly transit to the conduction band. The photo-induced carrier of holes (electrons) is created in the valence band (conduction band) of ZnO and PET–ITO. This principle is similar to the ref. 35 reported by Low et al., in which the TiO2-based p-n heterojunction photocatalyst be used to CO2 reduction. The built-in electric field (Eb) presented at the interface forces holes (electrons) to transfer from the valence band of n-type BZO (conduction band of PET–ITO) to the valence band of p-type PET–ITO (conduction band of BZO). The effective separation of the photo-production charge carriers increases, which greatly reduces the probability of electron-hole pair recombination and extends the lifetime of photo-generated carriers, result in the activity of ZnO/PET–ITO worked as the photocatalyst is accelerated. Moreover, the light-generated electrons can be captured by the oxidizing substances in the mixed solution to proceed the reduction reaction, so that the O2 dissolved in water is transformed into the superoxide anion free radical O2−, . The H2O and OH− adsorbed on the surface of the ZnO nanostructures can be oxidized to the hydroxyl radical ·OH by the photo-generated holes acting as a strong oxidizing agent.

View Article: PubMed Central - PubMed

ABSTRACT

––––: Boron-doped zinc oxide sheet-spheres were synthesized on PETITO flexible substrates using a hydrothermal method at 90 °C for 5 h. The results of X-ray diffraction and X-ray photoelectron spectroscopy indicated that the B atoms were successfully doped into the ZnO lattice, the incorporation of B led to an increase in the lattice constant of ZnO and a change in its internal stress. The growth mechanism of pure ZnO nanorods and B-doped ZnO sheet-spheres was specifically investigated. The as-prepared BZO/PETITO heterojunction possessed obvious rectification properties and its positive turn-on voltage was 0.4 V. The carrier transport mechanisms involved three models such as hot carrier tunneling theory, tunneling recombination, and series-resistance effect were explored. The BZO/PETITO nanostructures were more effective than pure ZnO to degrade the RY 15, and the degradation rate reached 41.45%. The decomposition process with BZO nanostructure followed first-order reaction kinetics. The photocurrent and electrochemical impedance spectroscopy revealed that the B-doping could promote the separation of photo-generated electron-hole pairs, which was beneficial to enhance the photocatalytic activity. The photocurrent density of B-doped and pure ZnO/PETITO were 0.055 mA/cm2 and 0.016 mA/cm2, respectively. The photocatalytic mechanism of the sample was analyzed by the energy band theory.

No MeSH data available.