Mesocrystalline Zn-Doped Fe₃O₄ Hollow Submicrospheres: Formation Mechanism and Enhanced Photo-Fenton Catalytic Performance

Abstract

Uniform and magnetic recyclable mesocrystalline Zn-doped FeO hollow submicrospheres (HSMSs) were successfully synthesized via a simple one-pot solvothermal route and were used for efficient heterogeneous photo-Fenton catalyst. XRD, XPS, Raman spectroscopy, Mössbauer spectroscopy, SEM, HRTEM, and EDX analyses revealed that the shell of HSMSs is highly porous and assembled by oriented attachment of magnetite nanocrystal building blocks with Zn-rich surfaces. Furthermore, a possible formation mechanism of mesocrystalline hollow materials was proposed. First, FeO mesocrystals were assembled by oriented nanocrystals, and a Zn-rich amorphous shell grew on the surfaces. Then, Zn gradually diffused into FeO crystals to form Zn-doped FeO due to the Kirkendall effect with increasing the reaction time. Meanwhile, the inner nanocrystals would be dissolved, and outer particles would grow larger owing to the Ostwald ripening process, leading to the formation of a hollow structure with porous shell. The Zn-doped FeO HSMSs exhibited high and stable photo-Fenton activity for degradation of rhodamine B (RhB) and cephalexin under visible-light irradiation in the presence of HO, which results from their hollow mesocrystal structure and Zn doping. It could be easily separated and reused by an external magnetic field. The results suggested that the as-obtained magnetite hollow mesocrystals could be a promising catalyst in the photo-Fenton process.

Mesocrystals for photocatalysis: a comprehensive review on synthesis engineering and functional modifications

“…The Zn-doped hollow Fe 3 O 4 mesocrystals possessed high and stable photo-Fenton activity for the degradation of rhodamine B and cephalexin under visible-light irradiation in the presence of H 2 O 2 (Fig. 23c), 141 and it could be easily separated and reused by an external magnetic eld. In brief, metal ions were extensively employed as dopants for mesocrystal photocatalysts.…”

Nanosized Zincated Hydroxyapatite as a Promising Heterogeneous Photo-Fenton-Like Catalyst for Methylene Blue Degradation

“…en, photogenerated electrons could be trapped by H 2 O 2 , leading to the formation of • OH (equation (3)) [31]. At the same time, Zn 2+ ions after occupying electrons (equations (4)) were transformed into Zn which reacted with H 2 O 2 to form ZnO, a strong photocatalyst (equation 5) [32].…”

The Role of Metal-Doped into Magnetite Catalysts for the Photo-Fenton Degradation of Organic Pollutants

“…The H 2 O 2 decomposition in participate of doped metal is take place by two possible reaction pathways [41]: 1) the surface oxygen vacancies (Va surf ) mechanism and 2) the radicalar mechanism. In the first route, a H 2 O 2 molecule will be actived by oxygen vacancy on the oxide surface participates to form O 2 (Equations (19) and (20) …”