Novel synthesis of magnetic, porous C/ZnFe₂O₄ photocatalyst with enhanced activity under visible light based on the Fenton-like reaction

Magnetic visible-light-driven photocatalyst, porous C/ZnFe₂O₄ (denoted as C/ZFO-CE) was fabricated via a CO₂-mediated ethanol route. CO₂-mediated ethanol route largely mitigated the solvent strength and facilitated the homogenous deposition of ZnFe₂O₄ (ZFO) through the coordination of metallic cation with CO₃^2- and HCO₃^- anions, which were hydrolyzed from CO₂ and H₂O, thereby avoiding additional precipitant. Moreover, the HCO₃^-, CO₃^2- and NO₃^- in the system acted as templates for the formation of porous C avoiding the additional organic mesoporous templates, thus reducing the synthesis cost. For the degradation of RhB and phenol, the C/ZFO-CE system in presence of minute H₂O₂ exhibited remarkably improved catalytic performance compared with the systems of H₂O₂, ZFO, C/ZFO-CE, C/ZFO-E (C/ZnFe₂O₄ synthesized in pure ethanol) and C/ZFO-E in the presence of minute H₂O₂. Furthermore, 2.0 mL of H₂O₂ (30%) combined with C/ZFO-CE obtained the maximum degradation efficiencies of 100% for RhB within 60 min and 91% for phenol within 120 min. The high efficiency for degradation of pollutants over C/ZFO-CE catalyst in the presence of minute H₂O₂ was possibly attributed to the strong harvest of visible light, the improved separation efficiency of the photoinduced charges and the overall OH production by the "photo-Fenton" process. The existence of OH during photodegradation process was evidenced via the PL-TA (photoluminescence-terephthalic acid) technique, ESR spectra and trapping experiments of active species using different scavengers. Furthermore, a possible reaction mechanism involving the Fenton-like reaction for the photodegradation of pollutants is proposed based on the experimental results.