Edge-enriched SnS2 nanosheets on graphene for chemiresistive room temperature NH3 sensors

Transition metal dichalcogenides (TMDs) with a larger surface area, abundant surface defect, and controlled electrical performance are promising in field of gas sensor. While, their drawbacks are low sensitivity, sluggish recovery kinetics, and poor selectivity. Herein, graphene is functionalized with SnS2 nanosheets by a hydrothermal process. Compared to pure SnS2 and graphene, the room-temperature response to 500 ppm NH3 is about 91.32 %, which is increased by 1700 % and 63.63 %, respectively. With increase of temperature and humidity, the baseline resistance and NH3-sensing response decreases strongly. The effect of temperature and humidity on resistance change of composites is high and the desired NH3-sensing response of composites may not yet be reached due to its high sensitivity towards humidity and temperature fluctuations. Additionally, the roomtemperature response to 100 ppm NO2 is only about 17.83 %, which is much smaller than that of NH3 (62.36 %) and the resistance couldn't recovery to initial value, behaving the poor recovery performance for NO2. The Density-functional theory calculations reveal that the stronger NH3 adsorption ability of SnS2, higher carrier mobility of graphene, and more effective charge transfer at p-n heterointerface contribute to the enhancement.