Influence of Inorganic Anions on the Chemical Stability of Molybdenum Disulfide Nanosheets in the Aqueous Environment

Abstract

Chemical stability is closely associated with the transformations and bioavailabilities of engineered nanomaterials and is a key factor that governs broader and long-term application. With the growing utilization of molybdenum disulfide (MoS 2 ) nanosheets in water treatment and purification processes, it is crucial to evaluate the stability of MoS 2 nanosheets in aquatic environments. Nonetheless, the effects of anionic species on MoS 2 remain largely unexplored. Herein, the stability of chemically exfoliated MoS 2 nanosheets (ceMoS 2 ) was assessed in the presence of inorganic anions. The results showed that the chemical stability of ceMoS 2 was regulated by the nucleophilicities and the resultant charging effects of the anions in aquatic systems. The anions promote the dissolution of ceMoS 2 by triggering a shift in the chemical potential of the ceMoS 2 surface as a function of the anion nucleophilicity (i.e., charging effect). Fast charging with HCO 3 − and HPO 4 2− /H 2 PO 4 − was validated by a phase transition from 1T to 2H and the emergence of Mo V , and it promoted oxidative dissolution of the ceMoS 2 . Additionally, under sunlight, ceMoS 2 dissolution was accelerated by NO 3 − . These findings provide insight into the ion-induced fate of ceMoS 2 and the durability and risks of MoS 2 nanosheets in environmental applications.