Photoassisted self-Fenton-like activity of oxygen vacancy-rich iron oxychloride nanofibers

Abstract

This is the first report on the photoassisted catalytic degradation of organic pollutants, viz., methylene blue (MB), rhodamine B and malachite green, by iron oxychloride (FeOCl) sans any added oxidants. Under direct solar irradiation, 87% of MB degrades in 30 minutes, catalysed by FeOCl nanofibers showing photoassisted self-Fenton-like (PSFL) activity. PSFL activity is observed for FeOCl, without any second components such as carbon dots and without the external addition of Fe²⁺ ions. The reaction follows pseudo-second order kinetics with a rate constant of (10.9 ± 0.4) × 10⁻² min⁻¹. Detailed studies on the catalytic mechanism were carried out by employing radical scavengers. The ˙OH radicals are identified to be directly degrading the dye molecules. The valence and conduction band edges are estimated to be at +1.3 and −1.1 V vs. NHE, respectively, which are suitable to enable the in situ generation of H₂O₂via the oxygen reduction reaction. Detailed analysis of the catalyst after use provides insights into how the alteration of its structure affects its catalytic properties. The structure–property correlation and the crucial role of oxygen vacancies as adsorption sites for oxygen as well as active sites for the in situ generation of H₂O₂ are discussed in detail.