Preparation of C/Ho co-doped TiO2 for enhancing the photocatalytic degradation efficiency of tetracycline hydrochloride

Abstract

A C/Ho co-doped TiO₂ catalyst was prepared by the precipitation–calcination method using Ti₃C₂T_x as the precursor and carbon source. X-ray diffractometry, transmission electron microscopy, X-ray photoelectron spectroscopy, N₂ adsorption–desorption isotherms, UV-Vis diffuse reflectance spectroscopy, photoluminescence spectroscopy, and photoelectrochemical measurements were used for characterization. The C doped anatase TiO₂ prepared by calcining Ti₃C₂T_x maintained the two-dimensional lamellar structure of the Ti₃C₂T_x precursor, and the carbon dopant was present on the surface of TiO₂ in the form of C–O and CO, whereas Ho³⁺ was mainly doped into the lattice of TiO₂, forming Ho–O bonds with oxygen instead of Ti⁴⁺. The band gap of the C/Ho co-doped TiO₂ photocatalyst was reduced as compared to that of pristine TiO₂, which can improve the utilization efficiency of visible light. When the doping ratio of Ho was 5% (CHT-0.05), the photocatalyst had the highest photocurrent and degradation efficiency of tetracycline hydrochloride (86.4%). The reaction mechanism for the photocatalytic degradation of TCH by the C/Ho co-doped TiO₂ photocatalyst was investigated and showed that superoxide radicals (˙O₂⁻) and holes (h⁺) were the main species that influenced the results. The prepared photocatalyst had good catalytic performance over four cycles, and it was stable and suitable for wastewater treatment.