Tuning the photocatalytic activity of Ti-based LDHs using divalent cations for enhanced tetracycline hydrochloride degradation

Abstract

Ti-based layered double hydroxides (LDHs) have attracted extensive attention due to their excellent photocatalytic performance. In this paper, Ti-based LDHs with different divalent metal ions (M²⁺) and molar ratios were synthesized by regulating the type of M²⁺ in Ti-based LDHs (MTi–LDHs). The results show that the prepared MTi–LDHs all have a layered structure, and the main factors affecting the photocatalytic performance are the electron transfer resistance, transient photocurrent density and bandgap width. All four MTi–LDHs exhibit the capacity to photodegrade tetracycline hydrochloride (TCH). Among them, ZnTi–LDH and NiTi–LDH demonstrate lower charge transfer resistance and suitable bandgaps, achieving TCH removal rates of 86.0% and 95.1% in static tests, respectively, and 46.7% and 40.4% in dynamic tests. Radical quenching experiments indicate that the primary species are ˙O₂⁻ and ¹O₂. Liquid chromatography–mass spectrometry (LC–MS) revealed three possible TCH degradation pathways. This study investigates the structural design of MTi–LDHs and their effects on photocatalytic performance, providing a reference for their application in photocatalytic TCH degradation.