Edge-enriched WS₂ nanosheets on carbon nanofibers boosts NO₂ detection at room temperature

Two-dimensional (2D) transition metal dichalcogenides (TMDs) hold great promise for room temperature (RT) NO₂ 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 NO₂ gas sensor based on WS₂ nanosheets/carbon nanofibers (CNFs) composite with abundant intentionally exposed WS₂ edges. Few-layer WS₂ 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 WS₂ edges remarkably improves the sensing properties. Consequently, the WS₂@CNFs composite exhibits excellent selectivity to NO₂ at RT with improved response and much lower detection limit in comparison to the WS₂ and CNFs counterparts. Density functional theory (DFT) calculations verify a surprisingly strong NO₂ adsorption on WS₂ edge sites (adsorption energy 3.40 eV) with a partial charge transfer of 0.394e, while a week adsorption on the basal surface of WS₂ (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 NO₂ sensors with optimized performances.