Tailoring ZnO/CuO/CuAlO₂ PEO coatings on brass via heat treatment for enhanced visible-light photocatalysis

Plasma electrolytic oxidation (PEO) was employed to fabricate porous ceramic layers on a brass substrate in an aluminate-based electrolyte. The influence of subsequent heat treatment on structure-property relationships was investigated in relation to visible-light photodegradation of methylene blue (MB). Annealing at 425 degrees C balanced nanostructure formation and microcrack control, while reducing water contact angle to 11.6 degrees (from similar to 29 degrees), enhancing hydrophilicity. Grazing incidence X-ray diffraction (XRD) revealed ZnO, CuO, and CuAlO2 phases alongside substrate peaks; X-ray photoelectron spectroscopy (XPS) confirmed Cu2+ species and Al 2p signals consistent with CuAlO2. Optical measurements showed a direct band gap of similar to 2.86 eV, and Mott-Schottky analysis indicated predominantly n-type behavior with junction features consistent with embedded p-type CuO. The sample annealed at 425 degrees C for 2 h (holding time had no significant effect) was identified as optimal, achieving 54 % MB removal at 15 ppm under visible light-13 % higher than the as-prepared coating. Activation of peroxymonosulfate (PMS) produced a clear synergy (synergy factor approximate to 2.57), significantly boosting MB abatement. Matrix ion tests revealed nuanced effects: PO43- and Cl- enhanced removal (63 % and 57 %), while NO3- suppressed it (similar to 44 %). Reuse tests showed similar to 13 % drop after the second cycle, followed by stable performance over four cycles. Scavenger experiments identified the roles of reactive oxygen species and clarified the underlying photocatalytic mechanisms. Based on detected intermediates, a plausible degradation pathway for MB was proposed. Overall, heat treatment (425 degrees C/2 h) optimizes morphology, wettability, and junction-assisted charge separation in ZnO/CuO/CuAlO2 PEO coatings, enabling robust visible-light photocatalysis.

Dergi

CERAMICS INTERNATIONAL

Yıl

2026

Cilt

52

Sayı

4

Sayfa

5031-5049

ISSN

0272-8842

eISSN

1873-3956

DOI

10.1016/j.ceramint.2025.12.277

WoS UID

WOS:001677729100001