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Rough gold films as broadband absorbers for plasmonic enhancement of TiO 2 photocurrent over 400 – 800   nm

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ABSTRACT

Recent years have witnessed an increasing interest in highly-efficient absorbers of visible light for the conversion of solar energy into electrochemical energy. This study presents a TiO2-Au bilayer that consists of a rough Au film under a TiO2 film, which aims to enhance the photocurrent of TiO2 over the whole visible region and may be the first attempt to use rough Au films to sensitize TiO2. Experiments show that the bilayer structure gives the optimal optical and photoelectrochemical performance when the TiO2 layer is 30 nm thick and the Au film is 100 nm, measuring the absorption 80–90% over 400–800 nm and the photocurrent intensity of 15 μA·cm−2, much better than those of the TiO2-AuNP hybrid (i.e., Au nanoparticle covered by the TiO2 film) and the bare TiO2 film. The superior properties of the TiO2-Au bilayer can be attributed to the rough Au film as the plasmonic visible-light sensitizer and the photoactive TiO2 film as the electron accepter. As the Au film is fully covered by the TiO2 film, the TiO2-Au bilayer avoids the photocorrosion and leakage of Au materials and is expected to be stable for long-term operation, making it an excellent photoelectrode for the conversion of solar energy into electrochemical energy in the applications of water splitting, photocatalysis and photosynthesis.

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Scanning electron micrographs of the surface morphologies of different layers of the samples.(a) FTO glass; (b) Au NPs on FTO glass, deposited by the sputtering process; (c) rough Au film on FTO glass; (d) ALD-deposited TiO2 film on the rough Au film. The inset in (b) is the histogram of the size of Au NPs.
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f2: Scanning electron micrographs of the surface morphologies of different layers of the samples.(a) FTO glass; (b) Au NPs on FTO glass, deposited by the sputtering process; (c) rough Au film on FTO glass; (d) ALD-deposited TiO2 film on the rough Au film. The inset in (b) is the histogram of the size of Au NPs.

Mentions: Figure 2 displays the surface morphologies of the respective layers of the three types of TiO2-based samples. The surface of FTO glass itself is already very rough as shown in Fig. 2a. For the Au NPs on the FTO glass, the deposited thin Au film with a thickness around 8 nm is transformed to discontinuous Au NPs after the annealing as shown in Fig. 2b 2021. When viewed from the top, the Au NPs exhibit nearly round shape and similar particle size. The histogram of the particle size distribution is obtained with the free software ImageJ as shown in the inset of Fig. 2b. The Au NPs have an average size of 35 nm with a standard deviation of approximately 11 nm. When the thickness of the deposited Au film is increased to 100 nm, the surface of Au film becomes rough and thus a pattern of densely packed metallic cluster grows up, which seems like a collection of many Au nanostructures with large variations of shape and size, as shown in Fig. 2c. The TiO2 film deposited by the atomic layer deposition (ALD) process on the rough Au film has quite uniform grain size of TiO2 nanoparticles as shown in Fig. 2d. These structural layers in a larger area are shown in Fig. S1.


Rough gold films as broadband absorbers for plasmonic enhancement of TiO 2 photocurrent over 400 – 800   nm
Scanning electron micrographs of the surface morphologies of different layers of the samples.(a) FTO glass; (b) Au NPs on FTO glass, deposited by the sputtering process; (c) rough Au film on FTO glass; (d) ALD-deposited TiO2 film on the rough Au film. The inset in (b) is the histogram of the size of Au NPs.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5016800&req=5

f2: Scanning electron micrographs of the surface morphologies of different layers of the samples.(a) FTO glass; (b) Au NPs on FTO glass, deposited by the sputtering process; (c) rough Au film on FTO glass; (d) ALD-deposited TiO2 film on the rough Au film. The inset in (b) is the histogram of the size of Au NPs.
Mentions: Figure 2 displays the surface morphologies of the respective layers of the three types of TiO2-based samples. The surface of FTO glass itself is already very rough as shown in Fig. 2a. For the Au NPs on the FTO glass, the deposited thin Au film with a thickness around 8 nm is transformed to discontinuous Au NPs after the annealing as shown in Fig. 2b 2021. When viewed from the top, the Au NPs exhibit nearly round shape and similar particle size. The histogram of the particle size distribution is obtained with the free software ImageJ as shown in the inset of Fig. 2b. The Au NPs have an average size of 35 nm with a standard deviation of approximately 11 nm. When the thickness of the deposited Au film is increased to 100 nm, the surface of Au film becomes rough and thus a pattern of densely packed metallic cluster grows up, which seems like a collection of many Au nanostructures with large variations of shape and size, as shown in Fig. 2c. The TiO2 film deposited by the atomic layer deposition (ALD) process on the rough Au film has quite uniform grain size of TiO2 nanoparticles as shown in Fig. 2d. These structural layers in a larger area are shown in Fig. S1.

View Article: PubMed Central - PubMed

ABSTRACT

Recent years have witnessed an increasing interest in highly-efficient absorbers of visible light for the conversion of solar energy into electrochemical energy. This study presents a TiO2-Au bilayer that consists of a rough Au film under a TiO2 film, which aims to enhance the photocurrent of TiO2 over the whole visible region and may be the first attempt to use rough Au films to sensitize TiO2. Experiments show that the bilayer structure gives the optimal optical and photoelectrochemical performance when the TiO2 layer is 30 nm thick and the Au film is 100 nm, measuring the absorption 80–90% over 400–800 nm and the photocurrent intensity of 15 μA·cm−2, much better than those of the TiO2-AuNP hybrid (i.e., Au nanoparticle covered by the TiO2 film) and the bare TiO2 film. The superior properties of the TiO2-Au bilayer can be attributed to the rough Au film as the plasmonic visible-light sensitizer and the photoactive TiO2 film as the electron accepter. As the Au film is fully covered by the TiO2 film, the TiO2-Au bilayer avoids the photocorrosion and leakage of Au materials and is expected to be stable for long-term operation, making it an excellent photoelectrode for the conversion of solar energy into electrochemical energy in the applications of water splitting, photocatalysis and photosynthesis.

No MeSH data available.


Related in: MedlinePlus