Strongly Enhancing Photocatalytic Activity of TiO2 Thin Films by Multi-Heterojunction Technique

Abstract

The photocatalysts of immobilized TiO2 film suffer from high carrier recombination loss when compared to its powder form. Although the TiO2 with rutile-anatase mixed phases has higher carrier separation efficiency than those with pure anatase or rutile phase, the single junction of anatase/rutile cannot avoid the recombination of separated carriers at the interface. In this study, we propose a TiO2/SnO2/Ni multi-heterojunction structure which incorporates both Schottky contact and staggered band alignment to reduce the carrier recombination loss. The low carrier recombination rate of TiO2 film in TiO2/SnO2/Ni multi-heterojunction structure was verified by its low photoluminescence intensity. The faster degradation of methylene blue for TiO2/SnO2/Ni multi-junctions than for the other fabricated structures, which means that the TiO2 films grown on the SnO2/Ni/Ti coated glass have a much higher photocatalytic activity than those grown on the blank glass, SnO2-coated and Ni/Ti-coated glasses, demonstrated its higher performance of photogenerated carrier separation.

Photocatalytic Degradation of Acid Orange 7 by NiO-TiO2/TiO2 Bilayer Film Photo-Chargeable Catalysts

“…A rougher surface results in better adsorption, as there is a larger surface area. In addition, a rougher surface could enhance photocatalytic activity by increasing light absorptivity because of more contact points with incident light [25,26]. Another reason is that TiO 2 is an n-type semiconductor that has photocatalytic activity but is limited by electron-hole recombination, while NiO, a p-type semiconductor, is coupled with TiO 2 creating a type-II p-n heterojunction [27] in the BLF catalyst.…”

Enhancement of photocatalytic activity by femtosecond-laser induced periodic surface structures of Si

“…Thereby our method can open a possibility of enhancement of photocatalytic activity by exploiting multiple mechanisms. Lastly it has to be noted that recently some pre-material growth-step on substrate like in situ polymerization [32] , plasma surface modification [33] , multi-heterojunction [34] have been demonstrated to enhance the photocatalytic activity of TiO 2 thin film. In terms of simplicity, reproducibility and controllability our method can be much better than the in situ polymerization and plasma surface modification whereas multi-heterojunction can be used in conjunction with our method thereby increasing the photocatalytic activity drastically.…”

Combined Structural and Plasmonic Enhancement of Nanometer-Thin Film Photocatalysis for Solar-Driven Wastewater Treatment

“…Nevertheless, thin film photocatalysts lack in efficiency compared to nanoparticles due to their lower surface area and fewer reactive sites. Hence, different strategies have been employed to improve their performance, such as thermally induced nanocrack networks in sputtered TiO 2 films to enhance the surface area, or semiconductor heterojunctions to enhance photocatalytic activity under UV , and extend the absorption to the visible range . Utilizing plasmonic nanostructures to enhance photocatalysis is another promising route toward the commercialization of solar-driven photocatalysis. , It is based on the collective oscillations of electrons in the metal under illumination (plasmons), which generate intense and strongly localized electric fields in the vicinity of the metallic nanostructures.…”