Phase-engineered transition-metal dichalcogenides for energy and electronics

Two-dimensional (2D) transition-metal dichalcogenides (TMDs) consist of over 40 compounds. Complex metal TMDs assume the 1T phase where the transition-metal atom coordination is octahedral. The 2H phase is stable in semiconducting TMDs where the coordination of metal atoms is trigonal prismatic. Stability issues have hampered the study of interesting phenomena in two-dimensional 1T phase TMDs. Phase conversion in TMDs involves transformation by chemistry at room temperature and pressure. It is possible to convert 2H phase 2D TMDs to the 1T phase or locally pattern the 1T phase on the 2H phase. The chemically converted 1T phase 2D TMDs exhibit interesting properties that are being exploited for catalysis, source and drain electrodes in field-effect transistors, and energy storage. We summarize the key properties of 2D 1T phase TMDs and their applications as electrodes for energy and electronics.