Enhanced photocatalytic activity of magnetically recyclable spherical Fe₃O₄/Cu₂O S-scheme heterojunction

In this study, magnetically recyclable spherical Fe₃O₄/Cu₂O particles comprising S-scheme heterojunctions were prepared by a simple hydrothermal approach using n-type semiconductor Fe₃O₄ as precursor and p-type semiconductor Cu₂O. A Fenton-like system was thus constructed via the addition to Fe₃O₄/Cu₂O of hydrogen peroxide. A rhodamine B (RhB) solution was used to simulate polluted wastewater, and photocatalytic RhB removal experiments were conducted under visible light irradiation. Powder X-ray diffractometry, vibrating-sample magnetometry, nitrogen adsorption-desorption, transmission electron microscopy, and X-ray photoelectron spectroscopy experiments were conducted to characterise Fe₃O₄ and Fe₃O₄/Cu₂O composite. The band gap of Fe₃O₄/Cu₂O was 1.76 eV, narrower than that of Fe₃O₄ (2.14 eV). The effects of the pH, sample dosage, hydrogen peroxide concentration, and RhB initial concentration on RhB removal were investigated. According to evidence, under the optimum reaction conditions, the RhB removal rate was 99.4%. The Fe₃O₄/Cu₂O composite exhibited good photocatalytic efficacy even after four cycles of testing. Based on the results of free radical capture experiments, hydroxyl radicals and holes cooperated as main reactive species in the photocatalytic system. The Fe₃O₄/Cu₂O photocatalyst can be easily removed based on magnetism, and it has been proven to be very effective for the degradation of RhB under both UV and visible light irradiation.