Synergistic interactions of Cu and N on surface altered amorphous TiO2 nanoparticles for enhanced photocatalytic oxidative desulfurization of dibenzothiophene

Abstract

Amorphous TiO₂ (AT) nanoparticles were prepared by a simple sol–gel method and subsequent incorporation with copper (5–20 wt%) via an electrochemical method in the presence of a supporting electrolyte, tetraethylammonium perchlorate (TEAP), was used to synthesize CuO/TiO₂ (CAT) catalysts. The physicochemical properties of the catalysts were studied by XRD, N₂ adsorption–desorption, TEM, FTIR, XPS, ESR and UV-Vis DRS. Photocatalytic testing on the oxidative desulfurization of dibenzothiophene (DBT) under UV and visible light irradiation demonstrated that the CAT catalysts were active under both conditions. It was found that Ti³⁺ surface defects (TSD), oxygen vacancies (V_o), CuO, Ti–O–N/O–Ti–N and Ti–O–Cu bonds played an important role in photooxidation. The TSD, V_o, CuO, N 1s and Cu 2p states in the CAT catalysts acted as electron trappers to hinder electron–hole recombination. In addition, these TSD, V_o, N 1s and Cu 2p species also contributed to the lowering of the CAT band gap, which enabled photooxidation to be carried out in the visible light region. The photooxidation followed a pseudo-first order Langmuir–Hinshelwood model with adsorption being the controlling step.