The Impact of the Crystalline Carbide Phase on the Sulfurization of Ultrathin Tungsten Carbide Nanoplates

Recent efforts have been made to integrate layered (MXenes) or non-layered (ultrathin) transition metal carbides (TMCs) with layered transition metal dichalcogenides (TMDs) forming vertical or in-plane heterostructures [1, 2]. Pioneering work by Rothschild et al. implemented a hydrogen sulfide (H₂S) heat treatment process to synthesize core-shell non-layered tungsten monocarbide (WC), layered tungsten disulfide (WS₂) nanoparticles [3]. In this work, we will present a combined experimental-computational approach that highlights the synthesis and structural characteristics of crystalline, non-layered tungsten carbide [4, 5] and layered WS₂ heterostructures synthesized via a two-step high temperature sulfurization in H₂S. We have synthesized highly crystalline tungsten mono- and semi-carbide (WC, W₂C) nanoplates via a bottom-up liquid metal chemical vapor deposition (LMCVD) process. We found that a high temperature heat treatment in H₂S partially converted the tungsten carbide nanoplates into crystalline, multilayer WS₂. Through scanning/transmission electron microscopy (S/TEM) we surveyed the structural relationship between tungsten carbide and the converted WS₂ and identified two conversion modes corresponding to WS₂ on the edge and basal surfaces of tungsten carbide. On the basal surface, distinct moiré patterns were observed corresponding to epitaxial and twisted WS₂ layers. This combined experimental-computational demonstrates that the crystalline phase (WC or W₂C) of the non-layered ultrathin tungsten carbide is critical for converting to layered TMDs and forming novel TMC/TMD heterostructures.<br/><br/>1. C. Chen, et al., Angewandte Chemie International Edition 57, 1864 (2018) <br/>2. A.J. Sredenschek, et al., Nature Materials 23, 460 (2024) <br/>3. A. Rothschild, et al., Chemical Communications 4, 363 (1999)<br/>4. M. Zeng, et al., Nano Energy 33, 356 (2017)<br/>5. C. Wang, et al., Advanced Electronic Materials 5, 1800839 (2019)