Enhanced charge separation in TiO₂/nanocarbon hybrid photocatalysts through coupling with short carbon nanotubes

Abstract

The interfacial contact between TiO₂ and graphitic carbon in a hybrid composite plays a critical role in electron transfer behavior, and in turn, its photocatalytic efficiency. Herein, we report a new approach for improving the interfacial contact and delaying charge carrier recombination in the hybrid by wrapping short single-wall carbon nanotubes (SWCNTs) on TiO₂ particles (100 nm) <i>via</i> a hydration-condensation technique. Short SWCNTs with an average length of 125 ± 90 nm were obtained from an ultrasonication-assisted cutting process of pristine SWCNTs (1-3 μm in length). In comparison to conventional TiO₂-SWCNT composites synthesized from long SWCNTs (1.2 ± 0.7 μm), TiO₂ wrapped with short SWCNTs showed longer lifetimes of photogenerated electrons and holes, as well as a superior photocatalytic activity in the gas-phase degradation of acetaldehyde. In addition, upon comparison with a TiO₂-nanographene "quasi-core-shell" structure, TiO₂-short SWCNT structures offer better electron-capturing efficiency and slightly higher photocatalytic performance, revealing the impact of the dimensions of graphitic structures on the interfacial transfer of electrons and light penetration to TiO₂. The engineering of the TiO₂-SWCNT structure is expected to benefit photocatalytic degradation of other volatile organic compounds, and provide alternative pathways to further improve the efficiency of other carbon-based photocatalysts.