Effects of MnII and EuIII Cation Exchange in Sepiolite‐Titanium Dioxide Nanocomposites in the Photocatalytic Degradation of Orange G

• Published in: ChemistrySelect (Weinheim) 2021-06, Vol.6 (21), p.5180-5190
• Main Authors: Cymes, Brittany A., Kugler, Alex J., Almquist, Catherine B., Edelmann, Richard E., Krekeler, Mark P. S.
• Format: Article
• Language: English
• Subjects: Cation exchange; Microporous materials; Photocatalysis; Sepiolite; Titanium dioxide
• ISSN: 2365-6549; 2365-6549
• DOI: 10.1002/slct.202100303

Two primary mechanisms of titanium dioxide (TiO2) efficiency inhibition in ultraviolet (UV)‐driven photocatalytic reactions are the high recombination rate and sintering. To address these challenges, TiO2 nanocrystals were grown in‐situ onto sepiolite modified with MnII and EuIII ions. The resulting nanocomposites were characterized and evaluated for photocatalytic activity for Orange G (OG) degradation under UV irradiation. Resultant reduction in activity over Mn‐sepiolite‐TiO2 is attributed to charge‐carrier scavenging by unstable Mn and adsorption‐mediated chromophore protection by Mn‐oxyhydroxide. Dye removal over Eu‐sepiolite‐TiO2 was only slightly more efficient than over the control despite relevant Eu concentrations; potentially related to inhibited TiO2‐Eu interfacial synergy and superoxide radical scavenging. The results of this investigation corroborate prior observations that substrate cation‐exchange results in unpredictable behavior of the cations introduced during subsequent fabrication steps which may be of benefit or detriment to the final material. Nanocomposite photocatalysts consisting of titanium dioxide nanoparticles grown in‐situ on MnII‐ or EuIII‐exchanged sepiolite fibers were fabricated and tested in ultraviolet‐assisted degradation of Orange G. We have confirmed this two‐step fabrication process results in unpredictable dopant migration and results in suboptimal hole (h+) and superoxide (.O2−) production and transport.