A closer examination of the role and impact of carbon within TiO₂ nanotubes on H₂ evolution and photoelectrochemical performance was carried out. Carbon is inherently present in nanotubes as remnant organic electrolyte used in the anodization processes. This residue serves as a carbon source during annealing in air, and when exposed to UV light, the carbon undergoes modification, thus resulting in enhanced photocatalytic efficiency.

Abstract

Titanium dioxide (TiO₂) is the material of choice for photocatalytic and electrochemical applications owing to its outstanding physicochemical properties. However, its wide bandgap and relatively low conductivity limit its practical application. Modifying TiO₂ with carbon species is a promising route to overcome these intrinsic complexities. In this work, we propose a facile method to modify TiO₂ nanotubes (NTs) based on the remnant organic electrolyte retained inside the nanotubes after the anodization process, that is, without removing it by immersion in ethanol. Carbon-modified TiO₂ NTs (C-TiO₂ NTs) showed enhanced H₂ evolution in photocatalysis under UV illumination in aqueous solutions. When the C-TiO₂ NTs were subjected to UV light illumination, the carbon underwent modification, resulting in higher measured photocurrents in the tube layers. After UV illumination, the IPCE of the C-TiO₂ NTs was 4.4-fold higher than that of the carbon-free TiO₂ NTs.