High-valent metal-oxo species heterogeneous activation making use of MoS2 in a novel Electro-Fenton System: pH-independent catalytic environment and nonradical generation mechanism

Abstract

High-valent metal-oxo (HVMO) species emerge as promising reactive species for decontamination owing to its long and stable life expectancy. Nevertheless, it is challenging to generate HVMO using solid-phase catalysts, considering high orbital occupancy of transition metals disfavor electron migrations. Herein, we propose a universal MoS2 co-catalyst capable of inducing electronic delocalization in a layered double hydroxide composite of Co and Fe, in turn acting as a HVMO evolution booster. In this heterogeneous electro-Fenton system, the spontaneous generation of high-valent cobalt-oxo (CoIV = O) and high-valent iron-oxo (FeIV = O, FeV = O and FeVI = O) was facilitated by MoS2 configuration, accepting self-motivated electron transfer, pivotally shifting d-band centers and lowering the energy barrier by 2.81–11.62 eV. Noteworthy, HVMO production at pH 9 compensated for the sluggish Fenton’s reaction rate in alkaline, increasing over 20 % contaminant decay and shortening treatment time by ∼ 4 h even in practical aqueous matrices (tap and river water). Depending upon the pH, HVMO exhibits a distinct degradation pathway of norfloxacin (model organics), compared with other reactive oxygen species, yielding different intermediates of varying toxicity levels. This study comprehensively showcased the feasibility of activating HVMO generation by MoS2 in heterogeneous mediation, unveiled a pH-independent strategy to degrade pollutants, thereby expanding the applicability of Fenton’s technology.