S-Vacancies and Ag Nanoparticles in SnS2 Nanoflakes for Ethanol Sensing: A Combined Experimental and Theoretical Investigation

In recent years, the potential of two-dimensional layered metal dichalcogenides for gas-sensing applications has been explored. Both defect engineering and noble metal modification are powerful strategies to achieve higher gas sensitivity. In this paper, a combined experimental and theoretical study on a SnS2-based sensor is performed to demonstrate the effect of individual or cooperative modulation of S-vacancy (Vs) defect and Ag nanoparticles (nano-Ag) on its gas-sensing performance. Gas-sensing measurements indicate that Ag/Vs-SnS2 shows the strongest response upon exposure to ethanol and a response as high as 94.7% when the ethanol concentration was 15 ppm. Especially, the limit of detection value of Ag/Vs-SnS2 calculated based on the low concentration response data is 2.12 ppb, implying its ultra-sensitive characteristic to ethanol vapor. Meanwhile, the response time and recovery time to 5 ppm ethanol are 7 and 45 s, respectively, and the response error is about 1.8%. It is clarified theoretically that both Vs modulation and Ag modification could enhance the adsorption strength of ethanol molecules on the SnS2 surface, and the SnS2 with co-modification of Vs and nano-Ag (Ag/Vs-SnS2) exhibits the strongest adsorption for the ethanol molecule. The potential mechanism for the enhanced response of nano-Ag/Vs-SnS2 was also further analyzed and demonstrated. This work provides an efficient strategy for developing high-quality gas sensors capable of sensitively detecting ethanol at room temperature.