Surface oxidation and electron transfer of MoS₂ during friction

The oxidation and electron transfer on the surface of MoS₂ during friction are studied by means of electron spin resonance (ESR) and X - ray photoelectron spectroscopy (XPS). As the results, it is inferred that Mo⁴⁺ changed to Mo⁶⁺ ions in the friction failure process of MoS₂ via Mo⁵⁺ ion intermediate. The complexity of the oxidation process on the surface of MoS₂ during friction has also been noticed. Moreover, there exist a variety of chemical states of Mo during the oxidation process, and the oxidation of Mo is characteristic of single electron transfer in the Mo4d orbit.