Tuning valence-variable single atomic metal for efficient antibiotic degradation and in situ chlorinated byproduct elimination under current pulsation

Abstract

Electrocatalytic oxidation is a promising technique for antibiotic-contaminated wastewater treatment; however, the concomitant production of toxic chlorinated byproducts remains an obstacle. Herein, a dual-functional single-atom heterojunction, Rh/Mn-SAH, was tailored to create an alternating oxidation–reduction environment within an identical electrode for current pulsation. Importantly, an interlayered Rhⁿ⁺–O–Mnⁿ⁺ pseudocapacitive electronic bridge was constructed, which reversibly electro-triggered the formation of metastable high-valent and low-valent metal species during anodic and cathodic cycles, respectively, with an increase in their steady-state concentration by over 2–3 orders of magnitude, thereby inducing alternate antibiotic degradation and byproduct elimination. Consequently, in anodic cycles, a normalized tetracycline degradation kinetic constant of 8.1 × 10⁻⁷ m s⁻¹ was achieved, superior to those of the reported state-of-the-art electrodes, and tetracycline degradation shifted from the reactive chlorine species (RCS)-dominated pathway toward the RCS-free pathway along with alleviated byproduct generation, while in cathodic cycles, byproducts could be in situ eliminated by up to 40 times.