Enhancing TiO2 Photocatalytic Activity

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Photocatalysts absorb light to generate electron-hole pairs and facilitate reduction-oxidation reactions, all without altering the catalyst material. In the presence of ambient water and oxygen, photocatalysts can assist with water splitting reactions for hydrogen generation as well as produce reactive oxygen species (ROS), namely hydroxyl and oxygen radicals, which may be used for various cleaning applications [1].

TiO₂, a semiconducting metal oxide, has been heavily considered for its photocatalytic capabilities because of its chemical inertness, long-term stability under various conditions, low cost, and availability for commercial use. Oftentimes, TiO₂ must be fabricated into nanostructures with high surface area to provide an abundance of active sites for maximal photocatalytic performance [1].

With relatively low applied powers, our plasma cleaners are well-suited for treating such nanostructures and limiting surface modification to the nanoscale level without affecting the crystal structure or structural integrity. Here, we explore an application that utilizes plasma treatment on TiO₂ nanostructures.

MODIFY TiO₂ NANOSHEETS TO ENHANCE HYDROGEN GENERATION

Kong et al. demonstrated the use of plasma treatment on TiO₂ (B) nanosheets to introduce surface defects, thereby enhancing the photocatalytic activity. Argon plasma etched organic contamination and created a porous structure with higher surface area, thereby exposing more active sites without altering the TiO₂ crystal structure.

Plasma also induced the formation of oxygen vacancies and Ti³⁺ defects on the surface. The O vacancies facilitated the adsorption of the reactant molecules to increased reaction efficiency. In addition, this defect generation effectively narrowed the energy band gap of TiO₂ from >3 eV (UV range) to within the energy range of visible light, extending light absorption into the visible spectrum.

From performing hydrogen generation and photochemical measurements, the authors found that the photoresponse current density from plasma-treated TiO₂ was 4 times that of pristine (untreated) TiO₂ under full spectrum illumination. This improved photocatalytic performance may ultimately enhance the efficiency of water splitting reactions for hydrogen generation. 

Supplemental References (Do not report using Harrick Plasma instruments)

[1] Hashimoto K, Irie H and Fujishima A. “TiO₂ photocatalysis: a historical overview and future prospects”. J. J. Appl. Phys. (2005) 44: 8269-8295.