Theoretical Study On The Mechanism Of Catalytic Hydrogen Evolution In Two-dimensional MoX₂?X=S,Se? Materials

Electrochemical hydrogen evolution reaction?HER?,one of the most promising technologies for the new energy development,has attracted worldwide attentions of the researchers in recent years.The large-scale production of the hydrogen is further limited by the traditional catalysts of noble metal Pt,owning to their rarity and high cost.To replace the noble metal Pt,seeking novel catalyst with more catalytic efficiency and low cost is hence becoming a significant topic for the current research.A large number of latest experiments show that the two-dimensional transition-metal dichalcogenides?TMDCs?are expected to replace Pt and become an ideal catalyst for the HER due to their unique layered structures and excellent physical and chemical properties.Based on the first-principles calculation of density function theory?DFT?,we studied the correlation between HER performances and atomic structures of different catalytic sites in 2H phase MoX₂?X=S,Se?and reveled the influences of the thermal stability in high temperature,the composition of Se:S and external strain on the HER performance of these materials.The detailed contents are summarized as follows:Firstly,the Gibbs free energies??G?of hydrogen adsorption on different lattice sites of single-layer 2H-phase MoX₂?X=S,Se?with different adsorption rates were systematically calculated and two ideal lattice sites as well as the adsorption rates were obtained with their corresponding?G closest to thermoneutral??G?0?.Based on the charge density differences?CDDs?and the electronegativity theory,the charge transfers and the bonding details of the hydrogen adsorption sites were analyzed,which can help us to explain the energies variations occurred.In addition,based on the molecular dynamics?MD?simulation of DFT,the influence of the thermal motion on the atomic stability of hydrogen adsorption at the higher temperatures was investigated with the atomistic dynamics of the hydrogen desorption as well as its critical temperature?⁸00 K?established.Secondly,based on the Mo edge site of MoS₂,the substitution effects of Se for S with different substitution ratios?Se:S=1:31–1:3?on the structure stabilities of[Mo(S_1-xSe_x)₂]as well as the HER performances were investigated.By comparing their HER performances on different selected sites,the best Se:S ratios?1:3?and the most stable Se:S ratios?1:31?were determined,respectively.Finally,the influences of uniaxial compression and tensile strains?-13–13%?on three selected structures of MoS₂,MoSe₂ and MoSe₁S₃,as well as their HER performances,were also studied.The effects of tensile and compressive strains on HER performances on different materials was obtained.Hydrogen catalysis mechanisms of single-layer?2H?MoS₂ and related materials can be easy to comprehend and provide theorey guidance for designing cheaper but efficient electro-catalysts by controlling the factors of structure,composition and stress.