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.
Highlights
Neighboring nanostructures, and enables the broadband absorption in the visible wavelength range from 400 to 800 nm, acting effectively as a broadband visible-light absorber. This kind of visible-light absorbers have already been used in photothermal systems that rely on the heat[10,14], but their great potential for the photocurrent generation has been merely overlooked
We further examine the influence of the thickness of TiO2 film on the properties of the TiO2-Au bilayer, and find that the optimal thickness is 30 nm
The characteristic color of Au NPs is pinkish, which turns into jade color after the coverage of the 30-nm-thick TiO2 film to form the TiO2-AuNP hybrid
Summary
Neighboring nanostructures, and enables the broadband absorption in the visible wavelength range from 400 to 800 nm, acting effectively as a broadband visible-light absorber. It is seen that the TiO2-Au bilayer has the highest response under every monochromatic light illumination, showing significant enhancement by a factor of about 2 as compared to the TiO2-AuNP hybrid and the bare TiO2 film.
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