Nano-MnO2 anchored on exfoliated MXene with exceptional and stable Fenton oxidation performance for organic micropollutants

Abstract

Peroxymonosulfate (PMS) Fenton-like systems have emerged as promising alternatives to hydrogen peroxide (H₂O₂). Fenton systems are currently used in the industry owing to their highly efficient utilization rate of oxidizing agents and wide operating pH ranges. Heterogeneous Fenton-like catalysts are promising candidates in this regard. However, self-aggregation and generation of ambiguous reactive oxygen species greatly restrict their broad application in practical settings. Herein, a redox reaction between exfoliated MXene and KMnO₄ facilitates the in-situ deposition of MnO₂ nanoparticles on the surface of Ti-deficient vacancies of MXene (MXene/MnO₂). Owing to the advantages of MXene with fast charge transfer and MnO₂ with strong PMS activation ability, the engineered MXene/MnO₂@PVDF catalytic membrane exhibited enhanced activity and excellent long-term stability for various refractory organic pollutants. Experimental observations, combined with density functional theory calculations, revealed that the exposed Mn sites effectively promoted the generation of ¹O₂. Interestingly, the widespread pathway for the direct generation of ¹O₂ via high-valent Mn-oxo phases has a high energy barrier (3.34 eV). In contrast, the pathway that uses the •OOH species as intermediates to produce ¹O₂ is energetically more viable (1.84 eV). This work offers insights into the in-situ engineering of transition metal-oxides on MXene-based membranes, facilitating their implementation in remediating micropollutant-contaminated environmental water.