Metal substrates-induced phase transformation of monolayer transition metal dichalcogenides for hydrogen evolution catalysis

Monolayer transition metal dichalcogenides can normally exist in several structural polymorphs with distinct electrical, optical, and catalytic properties. Effective control of the relative stability and transformation of different phases in these materials is thus of critical importance for applications. Using density functional theory calculations, we investigate the effects of low-work-function metal substrates including Ti, Zr, and Hf on the structural, electronic, and catalytic properties of monolayer MoS₂ and WS₂. The results indicate that such substrates not only convert the energetically stable structure from the 1H phase to the 1T'/1T phase, but also significantly reduce the kinetic barriers of the phase transformation. Furthermore, our calculations also indicate that the 1T' phase of MoS₂ with Zr or Hf substrate is a potential catalyst for the hydrogen evolution reaction.