Edge-enriched WS 2 nanosheets on carbon nanofibers boosts NO 2 detection at room temperature.

Two-dimensional (2D) transition metal dichalcogenides (TMDs) hold great promise for room temperature (RT) NO ₂ sensors. However, the exposure of the edges of TMDs with high adsorption capability and electronic activity remains a great obstacle to achieve high sensor sensitivity. Herein, we demonstrate a high-performance RT NO ₂ gas sensor based on WS ₂ nanosheets/carbon nanofibers (CNFs) composite with abundant intentionally exposed WS ₂ edges. Few-layer WS ₂ nanosheets are anchored on CNFs through a hydrothermal process. The approach permits to achieve a coating presenting an optimized active surface area and accessibility of the sensing layers. The exposure of WS ₂ edges remarkably improves the sensing properties. Consequently, the WS ₂ @CNFs composite exhibits excellent selectivity to NO ₂ at RT with improved response and much lower detection limit in comparison to the WS ₂ and CNFs counterparts. Density functional theory (DFT) calculations verify a surprisingly strong NO ₂ adsorption on WS ₂ edge sites (adsorption energy 3.40 eV) with a partial charge transfer of 0.394e, while a week adsorption on the basal surface of WS ₂ (adsorption energy 0.25 eV) with a partial charge transfer of 0.171e. The strategy proposed herein will be instructive to the design of efficient material structures for low-power NO ₂ sensors with optimized performances.
(Copyright © 2021. Published by Elsevier B.V.)