Direct Synthesis of 1T’ WSe2 Nanosheets

The different polymorphic phases of transition metal dichalcogenides (TMDs) have attracted enormous interest in the last decade. Tailoring the lattice symmetry within individual TMD layers enables to achieve very different electronic properties ranging from semiconducting (2H phase) to metallic and semimetallic (1T/1T’ phases) with the same material composition.<br/>The metallic and semimetallic 1T’ phases are particularly appealing for electrocatalytic hydrogen production from acid water, they exhibit anisotropic electrical transport, and they can exhibit properties of large gap quantum spin Hall (QSH) insulators in monolayer form at room temperature (such as 1T’ WSe₂). The direct synthesis of the 1T/1T’ metastable phases of high purity and in measurable quantities remains challenging. Here, we present our work on the scalable bottom-up synthesis of the metastable 1T’ phase of WSe₂based on the reaction between molecular precursors in liquid phase [1]. We designed a kinetically-controlled bottom-up synthesis from molecular precursors to enable the formation of the metastable phase at 300 C. The 1T’ WSe₂ nanosheets exhibit a semimetallic nature evidenced by an enhanced electrocatalytic activity for hydrogen evolution reaction as compared to the 2H WSe₂. Further, we demonstrate how this synthesis approach can be applied to obtain the metastable phases of different materials, with emphasis on MoSe₂.<br/><br/>[1] M. S. Sokolikova, P. C. Sherrell, P. Palczynski, V. L. Bemmer and C. Mattevi, <i>Nat. Commun.</i>, 2019, <b>10</b>, 712.