Abstract
A plasmonic Ag/TiO2 photocatalytic composite was designed by selecting Ag quantum dots (Ag QDs) to act as a surface plasmon resonance (SPR) photosensitizer for driving the visible-light driven photoelectrocatalytic hydrogen evolution. Vertically oriented hierarchical TiO2 nanotube arrays (H-TiO2-NTAs) with macroporous structure were prepared through a two-step method based on electrochemical anodization. Subsequently, Ag QDs, with tunable size (1.3-21.0 nm), could be uniformly deposited on the H-TiO2 NTAs by current pulsing approach. The unique structure of the as-obtained photoelectrodes greatly improved the photoelectric conversion efficiency. The as-obtained Ag/H-TiO2-NTAs exhibited strong visible-light absorption capability, high photocurrent density, and enhanced photoelectrocatalytic (PEC) activity toward photoelectrocatalytic hydrogen evolution under visible-light irradiation (λ > 420 nm). The enhancement in the photoelectric conversion efficiency and activity was ascribed to the synergistic effects of silver and the unique hierarchical structures of TiO2 nanotube arrays, strong SPR effect, and anti-shielding effect of ultrafine Ag QDs.
Highlights
A photonic crystal layer with larger pore size has been proved an effective way to enhance the light adsorption capability[13]
The results indicated that loading Ag nanocrystals could greatly enhance the visible-light driven performance in photoelectrocatalytic hydrogen evolution owing to the strong SPR effect of Ag and free light-shielding
The X-ray diffraction (XRD) results indicated that the Ag/TiO2 composite electrodes prepared by the pulse electro-deposition method were composed of Ag nanocrystals and crystalline TiO2 anatase
Summary
A photonic crystal layer with larger pore size has been proved an effective way to enhance the light adsorption capability[13]. Coupling TiO2-NTAs with noble metal always suffers from the light shielding effect resulting from the larger nanocrystals size of metal[21]. The as-formed ultrafine Ag QDs enhanced hierarchical TiO2-NTAs film was utilized as a working electrode for the photoelectrocatalytic hydrogen evolution under visible-light irradiation, with the aid of a small bias voltage of 0.7 V vs a saturated calomel electrode (SCE). The results indicated that loading Ag nanocrystals could greatly enhance the visible-light driven performance in photoelectrocatalytic hydrogen evolution owing to the strong SPR effect of Ag and free light-shielding. The optimal size of Ag coupled with TiO2 TNAs was about 2.5 nm, delivering for the highest photoelectrocatalytic H2 evolution rate of about 124.4 μ mol*cm−2*h−1 Such Ag nanocrystals enhanced hierarchical TiO2-NTAs (Ag/H-TiO2-NTAs) electrode exhibited excellent photoelectrocatalytic activity toward hydrogen evolution under visible-light irradiation (λ > 420 nm)
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