Interfacial engineering of Fe–O–Zn bonds in heterojunction photocatalysts: synergistic visible light PMS activation and electron transfer efficiency enhancement

Abstract

Traditional Fenton-like catalysts suffer from low efficiency and poor catalytic activity. In this study, Zn-modified α-Fe₂O₃ (FZ13) catalysts were prepared using a hydrothermal method, and their catalytic performance was evaluated for activating peroxymonosulfate (PMS) to degrade tetracycline (TC) under visible light. The results showed that the degradation efficiency of TC in the FZ13 + PMS + light system reached 84% (FZ13: 0.3 g L⁻¹, PMS: 3 mM, TC concentration: 40 mg L⁻¹, temperature: 25 °C, pH: 5.5), with a rate constant (k) of 0.0642 min⁻¹, which is 1.6 times higher than that of the unmodified α-Fe₂O₃ + PMS + light system. The heterojunction structure of FZ13 forms Fe–O–Zn bonds, enhancing electron transport efficiency, approximately 2.17 times that of the unmodified α-Fe₂O₃, and improving the separation of photogenerated electron–hole pairs. Additionally, FZ13 exhibits a high redox capacity, promoting electron transport and charge transfer. DFT calculations confirm that the adsorption energy of FZ13 (−5.826 eV) is higher than that of α-Fe₂O₃ (−4.6 eV), with FZ13 exhibiting metallic characteristics and a more stable hybrid peak further from the Fermi level. In the FZ13 + PMS + light system, the complex FZ13/PMS* is formed, which facilitates electron transfer and promotes the degradation of TC. SO₄˙⁻, ˙OH, O₂˙⁻, h⁺, e⁻ and ¹O₂ also co-participate in the TC degradation process. This study offers a feasible strategy for photo-assisted activation of PMS using Fenton-like catalysts.