Construction of functionally graded high-entropy alloy catalyst for peroxymonosulfate activation: Mechanism of...

A functionally graded high-entropy alloy catalyst FeCoNiCuRu_0.5@nitrogen-doped carbon (FeCoNiCuRu_0.5@NC) was designed to address catalytic function regulation and active-site stability challenges in peroxymonosulfate-based advanced oxidation processes. Featuring a spatially separated architecture with a RuC composite shell and a polymetallic alloy core, the catalyst suppresses transition metal dissolution, reducing ion leaching by 65.5 % versus conventional counterparts. The catalyst achieved complete carbamazepine (CBZ) removal within 30 min with a rate constant (k) of 0.460 min^-1 at pH 3, and singlet oxygen (¹O₂) and sulfate radicals (SO₄^•-) were identified as the dominant active species. At pH 7, this rate constant (0.158 min^-1) showed a twofold increase over that of FeCoNiCu@nitrogen-doped carbon (FeCoNiCu@NC) and a fivefold enhancement over that of Ru@ nitrogen-doped carbon (Ru@NC). The concentrations of SO₄^•-and ¹O₂ over FeCoNiCuRu_0.5@NC are 1.97 and 3.38-fold higher, respectively, than those over FeCoNiCu@NC. This enhancement correlates with the superior charge transfer capability of the Ru-modified catalyst system. Remarkably, the FeCoNiCuRu_0.5@NC demonstrates unprecedented pH tolerance (pH 3-11) and stability. Its dual-active-species configuration enables simultaneous degradation of electron-rich and electron-deficient pollutants, establishing a new paradigm for designing robust high-entropy alloy catalysts.