Air plasma treated TiO2/MWCNT composite for enhanced photocatalytic activity

TiO2-NGQD composite photocatalysts with switchable photocurrent response

A series of titanium dioxide-nitrogen doped graphene quantum dot (TiO₂-NGQD) composite photocatalysts were synthesized through a simple hydrothermal reaction with varied NGQD content. Through a proposed Z-Scheme heterojunction, the composites were able to achieve increased photocurrent generation and photocatalytic degradation of phenol under both full spectrum and visible only illumination. The prepared composites were able to switch from anodic to cathodic photocurrent by changing the light source from full spectrum to visible wavelengths. The photocatalytic capabilities of the composites were tested by degrading phenol and this was monitored via nuclear magnetic resonance. All composites outperformed the commercial standard P25 TiO₂ under both full spectrum and visible irradiation, with the 8 wt% NGQD composite showing a visible improvement of over 600% compared to P25. With the ability to manipulate the generation of majority charge carriers, TiO₂-NGQDs have significant potential not only in photocatalysis, but in far reaching applications such as energy harvesting and water splitting.

Single-Molecule Imaging of Reactive Oxygen Species on a Semiconductor Nano-Heterostructure for Understanding Photocatalytic Heterogeneity in Aqueous

We constructed a single-molecule fluorescence imaging technique to monitor the spatiotemporal distribution of the hydroxyl radical (•OH) on TiO₂-attached multiwalled carbon nanotubes (TiO₂-MWCNTs) in aqueous. We found the heterogeneous distribution of •OH is closely related to the composition and heterostructure of the catalysts. The dynamic •OH production rate was evaluated by counting the single-molecule fluorescent bursts. We further confirmed the production of •OH on TiO₂-MWCNTs mainly occurred via electron reduction during the aqueous photocatalytic process. Our study reveals the mechanism of reactive oxygen species involved photocatalytic reaction and guides the design of advanced semiconductor photocatalysts.