Degradation of molybdenum disulfide through cascade reactions with hydrogen peroxide in aqueous system

Transformation is a crucial process determining the lifespan and risk of MoS₂ nanomaterial during usage and after disposal. This study revealed the degradation of MoS₂ in the presence of H₂O₂ using experimental and computational methods. Experimental results showed that MoS₂ nanosheets were degraded by 45.1 % after 72-h incubation with H₂O₂. MoS₂ decomposed H₂O₂ into various reactive oxygen species, among which ·O₂^- played a dominant role breaking MoS₂ into fragments with defects and holes. Mo (IV) in MoS₂ catalyzed ·O₂^- formation through electron transfer towards H₂O₂. Additionally, electrons generated from cleavage of O-O in H₂O₂ initiated the O₂ reduction to generate ·O₂^-. The interaction of MoS₂ with ·O₂^- yielded soluble MoO₄^2- and SO₄^2-, and 22.4 % of Mo on residual MoS₂ was in the form of Mo (VI) after 72-h incubation. Density function theory calculations elucidated that·O₂^- is more potent than ·OH in adsorbing on MoS₂ ( -2.25 eV vs. -0.14 eV) to initiate reaction. The reaction occurred preferentially from Mo and adjacent S atoms, which transferred 1.07 electrons toward ·O₂^- to induce O-O cleavage and formation of O-M and O-S bonds. The obtained finding on MoS₂ degradation is fundamental for promoting sustainable applications and risk assessment of MoS₂-based nanomaterials.