Role of Particle Size in Nanocrystalline TiO₂-Based Photocatalysts

TLDR

The study systematically investigates how particle size influences the performance of pure and doped nanocrystalline TiO₂ photocatalysts, using a wet‑chemical synthesis that yields near‑agglomeration‑free particles with precisely controlled sizes and dopant distributions. TiO₂ particles of 6 nm and 11 nm were doped with Fe³⁺ to suppress surface recombination, while 21 nm particles received Nb⁵⁺ dopants and a minor Pt surface dispersion to promote electron–hole separation, all produced via the versatile wet‑chemical route. Results show that particle size critically affects electron–hole recombination, with the optimal Fe³⁺ concentration decreasing as size increases, and that the engineered nanocrystalline TiO₂ catalysts outperform Degussa P25 in chloroform photodecomposition.

Abstract

This paper presents a systematic study on the role of particle size in pure and doped nanocrystalline TiO2 photocatalysts, which was made possible by a versatile wet-chemical process capable of generating near-agglomeration-free TiO2 with well-controlled particle sizes and dopant dispersion. It is shown that particle size is a crucial factor in the dynamics of the electron/hole recombination process. For TiO2 particles with 6 or 11 nm diameter, Fe3+ dopants were added to inhibit the charge carrier surface recombination. The optimal Fe3+ dopant concentration for different particle sizes was identified, and this concentration was found to decrease with increasing particle size. To assist electron and hole separation in TiO2 with 21 nm diameter, Nb5+ dopants were introduced in combination with minor surface Pt dispersion. These carefully engineered nanocrystalline TiO2 catalysts showed higher reactivities than Degussa P25 TiO2 material in photocatalytic decomposition of chloroform.