DFT calculation of hydrothermal mechanism on preparation of MoS₂

Basing on the simplest hydrothermal system containing deionized water, hexa-ammonium molybdate, and thiourea, hydrothermal mechanism on preparation of MoS₂ was studied by DFT calculation. Hydrothermal process was divided into four steps which covered ionization equilibrium, the hydrolysis of CS(NH₂)₂, the formation of intermediates, and the formation of MoS₂. Ionization equilibrium occurs at normal condition and determines the existence of Mo in the form of molybdic acid. Thiourea hydrolysis is rate-determining step in the process of hydrothermal which contains 10 elementary reactions. The formation of intermediates includes hydrogen transfer, dehydration, and vulcanization three steps which contain 18 elementary reactions, and the energy barrier of vulcanization is the highest. The formation of MoS₂ is divided into two steps, the first step is that MoO(OH)(SH)₃.H₂O reacts with MoO (SH)₄.H₂O to form layer MoS₂, and the second step is a very fast process that can affect the morphology of the products.