Quasi-Binary Transition Metal Dichalcogenide Alloys: Thermodynamic Stability Prediction, Scalable Synthesis and Application*

Quasibinary alloying in transition metal dichalcogenides (TMDCs) has been successfully used to improve applications including optoelectronics and catalysis. However, the vast compositional space of possible TMDC alloys remains largely unexplored. To guide the synthesis of such alloys, we present ab-initio calculations of equilibrium phase diagrams for 25 TMDC alloys: M_1-x M'_xX₂ and MX_2(1-x) X'_2x (M,M'= V, Nb, Ta, Mo, W; X,X'= S, Se). We verify the predictions made by these phase diagrams by synthesizing a subset of 12 alloys using scalable chemical vapor transport. We demonstrate the ability to exfoliate these alloys into few-layers. One of these alloys, Nb_1-xTa_xS₂, is shown to have outstanding thermal stability, exceptional CO₂ reduction activity with near zero overpotential, and excellent energy efficiency in a Li-air battery. Our work highlights the large number of TMDC alloys accessible to a scalable synthesis-process. By expanding beyond group VI TMDC alloys, this study lays the groundwork for studying how alloying in group V TMDCs affects novel properties such as superconductivity, magnetism, and topological properties.