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.