Two-dimensional (2D) transition metal dichalcogenides MX2 (M = Mo; X = Te, Se) have three crystalline phases: the semiconducting 2H as well as the metallic 1T and 1T’. The 2H phase is usually more stable than both the 1T and 1T’ phases. Here, through comprehensive first-principles calculations, we found that the phase stability of MX2 can be tuned by appropriate selection of metal substrates. The 1T’ phase of MoTe2 has lower energy than the 2H phase when laid on Cu(111), Ni(111), and Ti(0001) surfaces, while a MoSe2 monolayer on Ti(0001) substrate also favors the 1T’ phase. Electronic accumulation on Mo atoms in these MX2 monolayers due to the metal substrates plays a key role in inducing the 2H-to-1T’ phase crossover. We further predict that 1T’-MoTe2/ Cu(111), 1T’-MoTe2/Ni(111), and 1T’-MoTe2/Ti(0001) show high catalytic activity for hydrogen evolution reaction when Te vacancies are introducted. These findings offer new insights into the phase stability and electrocatalytic applications of 2D MX2 of keen current interest.
