Magnetically separable Z-scheme ZnFe2O4/MoS2 photocatalyst for boosting photo-Fenton degradation activity by a hole-mediated mechanism

The development of high-efficiency and robust photocatalysts is imperative and challenging in advanced oxidation processes (AOPs). Herein, magnetically separable ZnFe2O4/MoS2 photocatalyst was prepared by a simple hydrothermal method. The degradation characteristics of several organic pollutants (rhodamine B (RhB), methyl orange, methylene blue, and antibiotic tetracycline) were investigated with/without the addition of H2O2 under visible light irradiation. It is found that the synergistic effect of Z-scheme ZnFe2O4/MoS2 photocatalyst and photo-fenton-like reaction promotes the decomposition of H2O2, accelerates the separation efficiency of photogenerated electrons and holes, and thus improves the photocatalytic activity. The RhB photo-degradation of the constructed Z-scheme ZnFe2O4/MoS2 (96.3%) photocatalyst in the absence of H2O2 for 100min is better than that of MoS2 (74.8%) and ZnFe2O4 (6.2%), with a rate constant of 0.0332min-1. The slight amount of H2O2 boosts the photocatalytic performance significantly. Its degradation rate is 98.6% within 8min with the rate constant of 0.396min-1, 12 times higher than that of ZnFe2O4/MoS2 photocatalyst without H2O2. The magnetic separation, recycling stability and neutral solution process are also confirmed in ZnFe2O4/MoS2 system, indicating the enormous potential of this photocatalyst in environmental remediation and waste water treatment. The hole-mediated oxidation mechanism has been proposed instead of conventional active radicals of •OH based on the free radicals capture and electron spin resonance experiments. MoS2 plays a crucial role in facilitating the H2O2 decomposition and realizing the conversion circulation from Fe3+ to Fe2+ by the redox cycling as a co-catalyst. This study provides insights into the photocatalytic mechanism of Z-scheme photo-Fenton heterojunction photocatalysts, conducive to the development of high-efficient and stable photocatalysts in AOPs.