Abstract
The effectiveness of photocatalytic processes is dictated largely by plasmonic materials with the capability to enhance light absorption as well as the energy conversion efficiency. Herein, we demonstrate how to improve the plasmonic photocatalytic properties of TiO2/Al nano-void arrays by overlapping the localized surface plasmon resonance (LSPR) modes with the TiO2 band gap. The plasmonic TiO2/Al arrays exhibit superior photocatalytic activity boasting an enhancement of 7.2 folds. The underlying mechanisms concerning the radiative energy transfer and interface energy transfer processes are discussed. Both processes occur at the TiO2/Al interface and their contributions to photocatalysis are evaluated. The results are important to the optimization of aluminum plasmonic materials in photocatalytic applications.
Highlights
The scanning electron microscopy (SEM) images acquired from the evolving nano-void structure on the aluminum foil are depicted in Fig. 1(a) at different voltages of 40 V, 60 V, 80 V, and 100 V
It is reasonable to expect that Al nanoparticles support long-lived localized surface plasmon resonance (LSPR) modes with high optical cross-sections and that are tunable over a wide energy range, deep into the UV5
Our results show that photocurrent still exist without external voltage, meaning that the native Al2O3 oxide layer cannot totally hamper the spontaneous charge transfer process at the TiO2/Al interface and this process may promote the photocatalysis degradation
Summary
A series of aluminum nano-void arrays with different diameters is prepared using the porous anodic alumina template to identify the scale suitable for plasmonic photocatalysis. (b) Corresponding photocatalytic rate versus the TiO2/Al film fabrication voltage/nano-void diameter scale This is because the hole-scale d of the “higher voltage” film is enlarged so that the coupling efficiency between the plasmonic spectrum and TiO2 bandgap is improved (see Fig. 1c). Our results show that photocurrent still exist without external voltage, meaning that the native Al2O3 oxide layer cannot totally hamper the spontaneous charge transfer process at the TiO2/Al interface and this process may promote the photocatalysis degradation. LSPR improves photocatalysis efficiency via radiative energy transfer, especially when the aluminum plasmonic band is coupled with the TiO2 absorption band. The interfacial charge transfer process contributes to photocatalysis at the TiO2/Al interface irrespective of the native Al2O3 layer on the surfaces These results provide insights into aluminum plasmonic photocatalysis to improve photocatalysis efficiency
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