Visible Light-Driven High-Entropy Narrow Band Gap (YLaTbDyHo)MnO Photocatalyst: Structural Characterization, Selective Removal, DFT Calculation, and Photocatalytic Mechanism.

A (YLaTbDyHo)MnO (AMnO) high-entropy oxide was prepared by a simple polyacrylamide gel method and the addition of Y, La, Tb, Dy, and Ho elements in an equal molar ratio to the position of the Y element of YMnO. The high-entropy AMnO catalyst exhibits a high selectivity for degrading -C═O, -NH, and -OH bonds, as demonstrated by the results. When the catalyst content and initial contaminant concentration were 1 g/L and 50 mg/L, respectively, the degradation percentages of tetracycline hydrochloride (TC) at pH 6.4 and doxycycline hydrochloride (DOX) at pH 3.8 by the AMnO catalyst reached 77.33% and 90.86%, respectively. Using TC as a representative, the degradation pathway of TC degraded by an AMnO catalyst and the toxicity of the intermediate were studied by using LC-MS and toxicity assessment software. First-principles calculation determined that the AMnO catalyst is a narrow band gap semiconductor. The results confirmed that hole, hydroxyl, and superoxide radicals are the main active species of the AMnO catalysts for the degradation of pollutants. A novel strategy and technical guidance are presented in this study to synthesize novel narrow band gap high-entropy oxides that can degrade pollutants in wastewater.