Ultrathin CuFe-based high entropy oxide nano-micro-sheets for visible-light-driven tetracycline degradation

Tetracycline (TC) is a kind of widely used antibiotic and its improper discharge to the environment brings serious threats to ecosystems and human health. The photocatalytic degradation of these organic pollutants with CuFe oxide attracts many attentions. High-entropy oxide (HEO) emerges as a promising material recently due to its excellent activity and stability in various fields. In this study, CuFe-based HEO with ultrathin nano-micro-sheet (Cu y Fe z Ce 4 Al 0.5 Zr 0.5 O x , thickness ∼5.63 nm) was successfully fabricated and utilized as an efficient photocatalyst for TC removal under visible-light irradiation. By controlling experiments and adjusting the Cu/Fe atomic ratios, we found that CuFeO x with the same structure as CuFe-based HEO cannot be obtained without adding other elements and specific Cu/Fe ratio is required for the HEO formation. The optimized Cu 2 Fe 2 Ce 4 Al 0.5 Zr 0.5 O x HEO (Cu 2 Fe 2 ) could achieve 73.1 % degradation efficiency of TC with 53.1 % of total organic carbon (TOC) removal, much higher than CuO and Fe 2 O 3 mono-counterparts. Mechanism investigation showed that the CuFe-based HEO works with O₂·⁻, h⁺ and e⁻ as main active species, probably in a different reaction path from Fe 2 O 3 or CuFeO x system due to the high entropy effect. This study provides an experimental basis for HEO materials design and gives insights on the photocatalytic organic pollutants’ degradation with CuFe-based HEO.