Mechanism of WS 2 Nanotube Formation Revealed by in Situ / ex Situ Imaging

作者：Vojtěch Kundrát, Libor Novák, Kristýna Bukvišová, Jakub Zálešák, Eva Kolíbalová, Rita Rosentsveig, M. B. Sreedhara, Hila Shalom, Lena Yadgarov, Alla Zak, Miroslav Kolı́bal, Reshef Tenne · 发表于：ACS Nano · 年份：2024 · DOI：10.1021/acsnano.4c01150 · 被引用次数：14 · 研究领域：Nanowire Synthesis and Applications、2D Materials and Applications、MXene and MAX Phase Materials

High Resolution Image Download MS PowerPoint Slide Multiwall WS 2 nanotubes have been synthesized from W 18 O 49 nanowhiskers in substantial amounts for more than a decade. The established growth model is based on the “surface-inward” mechanism, whereby the high-temperature reaction with H 2 S starts on the nanowhisker surface, and the oxide-to-sulfide conversion progresses inward until hollow-core multiwall WS 2 nanotubes are obtained. In the present work, an upgraded in situ SEM μReactor with H 2 and H 2 S sources has been conceived to study the growth mechanism in detail. A hitherto undescribed growth mechanism, named “receding oxide core”, which complements the “surface-inward” model, is observed and kinetically evaluated. Initially, the nanowhisker is passivated by several WS 2 layers via the surface-inward reaction. At this point, the diffusion of H 2 S through the already existing outer layers becomes exceedingly sluggish, and the surface-inward reaction is slowed down appreciably. Subsequently, the tungsten suboxide core is anisotropically volatilized within the core close to its tips. The oxide vapors within the core lead to its partial out-diffusion, partially forming a cavity that expands with reaction time. Additionally, the oxide vapors react with the internalized H 2 S gas, forming fresh WS 2 layers in the cavity of the nascent nanotube. The rate of the receding oxide core mode increases with temperatures above 900 °C. The growth of nanotubes in the atmospheric ...