Light-assisted room temperature gas sensing performance and mechanism of direct Z-scheme MoS/SnO crystal faceted heterojunctions.

Light assistance and construction of heterojunctions are both promising means to improve the room temperature gas sensing performance of MoS recently. However, enhancing the separation efficiency of photo-generated carriers at interface and adsorption ability of surface have become the bottleneck problem to further improve the room temperature gas sensing performance of MoS-based heterojunctions under light assistance. In the present study, a novel direct Z-scheme MoSSnO heterojunction was designed through crystal facets engineering and its room temperature gas sensing properties under light assistance was studied. It was found that the heterojunction showed outstanding room temperature NO sensing performance with a high response of 208.66 toward 10 ppm NO together with excellent recovery characteristics and selectivity. The gas sensing mechanism study suggested that high-energy {221} crystal facets of SnO and MoS directly formed Z-scheme heterojunction, which could greatly improve the separation efficiency of photo-generated carriers with high redox capacity. Moreover, {221} facets greatly enhanced adsorption ability towards NO. This work not only opens up the application of Z-scheme heterojunctions in gas sensing, which will greatly promotes the development of room temperature light-assisted gas sensors, but also provides a new idea for the construction of direct Z-scheme heterojunctions through crystal facets engineering.