Heightened photocatalytic performance of ZnMoO₄ by incorporation of cobalt heteroatom to enhance oxygen defects for boosted pharmaceutical degradation

Water pollution by pharmaceutical drugs has raised concerns as this negatively impacts human health and the entire ecological system. Herein, a highly efficient Zn_1-xCo_xMoO₄ photocatalyst with oxygen vacancy (ZCMx-O_V) and enhanced visible light absorption was designed and synthesized through heteroatom inclusion. The x-ray photoelectron spectroscopy and electron paramagnetic resonance confirmed the formation of oxygen vacancies, while ultraviolet-visible analysis indicated enhanced visible light absorption. The rate of tetracycline (TC) elimination by optimal ZCM2 was 6.88, 1.75, and 1.47 times higher than those of ZM, ZCM1, and ZCM3, respectively. Again, the rate of ZCM2 towards tetracycline degradation was 1.38, 1.32, and 1.26 folds in deionized water compared to diverse water matrices such as snow, tape, and lake water. Tetracycline was mainly removed by holes (h⁺) and superoxide (^•O₂⁻) as confirmed by trapping experiments and EPR analysis. The density functional theory (DFT) Fukui index predictions confirmed vulnerable bonds of TC attacked by oxygen radicals. This study provides a fresh perspective and valid reference for designing highly active and efficient photocatalytic material through heteroatom introduction for pharmaceutical degradation and can be extended to other pollutants of emerging concern.