ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Inhibition of photocatalytic phenol degradation by doped rutile TiO₂: toward more safe and stable UV filter formulations

Olga Hlushko, Georgii Sokolsky, Oleksandr Shtyka, Waldemar Maniukiewicz, and Tomasz Maniecki

Physical chemistry department, Igor Sikorsky Kyiv Polytechnic Institute, Kyiv, Ukraine

E-mail: georgii.sokolsky@gmail.com

Received: 10 November 2025  Accepted: 13 January 2026

Abstract:

Photocatalytic activity of rutile was intentionally reduced by band gap engineering with the aim of developing the safe and stable UV filter formulations. The samples of rutile were doped with 2.5 mol% of Ce³⁺, Mn²⁺, Al³⁺, and Mg²⁺ via chemical co-precipitation at pH = 10–11 with subsequent heat treatment at 350 °C. Photocatalytic degradation of phenol demonstrated pronounced inhibition: Mg²⁺ completely suppressed activity, Mn²⁺ reduced it fourfold, and Ce³⁺ and Al³⁺ caused moderate decreases. X-ray diffraction revealed dopant-induced changes in lattice parameters. Diffuse reflectance spectroscopy (Kubelka–Munk analysis) showed a band gap narrowing (0.05–0.10 eV) and a conduction band edge shift (+ 0.01–0.06 V(SHE)). Positive conduction band edge shift vs. О₂/О₂· process causes minimal ROS generation for Mn²⁺ and Mg²⁺-doped rutile samples. The screening surface states’ effect has the most distinct inhibition contribution for Mg(OH)₂-to-MgO transition at around 350 °C. This counter-intuitive inhibition, contrasting with most doping studies aiming at enhancement of activity, supports Mg- and Mn-modified rutile as promising candidates for physical UV filters.

Keywords: Rutile; Doping; Photocatalytic activity; Inhibition; UV-filters; Cosmetics

Full paper is available at www.springerlink.com.

DOI: 10.1007/s11696-026-04677-w

Chemical Papers 80 (4) 4139–4148 (2026)