Facile Synthesis of Template-Free SnS₂ with Different Morphologies and Excellent Gas-Sensing Performance for NO₂ Gas-Sensor Applications

Herein, SnS₂ particles with two different morphologies are synthesized using a template-free one-step hydrothermal method. Flower- and plate-like SnS₂ are obtained using different solvents, ethyl alcohol, and deionized water, respectively, under the same synthesis conditions. The flower-like SnS₂ had a larger surface area and higher concentration of sulfur vacancies than plate-like SnS₂. The effects of the specific surface area and the number of sulfur vacancies in the gas-sensing materials are studied using the gas-sensing characteristics of SnS₂ in the two morphologies. The gas sensitivities at 25 °C under 1 ppm NO₂ are 73.5 and 129.5 for flower- and plate-like SnS₂, respectively. Both the flower- and plate-like SnS₂ gas sensors exhibited good gas selectivity for NO₂ against SO₂, CO, and NH₃ at 25 °C. The response and recovery times are 540 and 1407 s for the flower-like SnS₂ and 214 and 18 s for the plate-like SnS₂, respectively. It is confirmed that a large specific surface area and the number of sulfur vacancies adversely affected the response and recovery times. Therefore, the plate-like gas sensor is expected to be a good candidate for NO₂ gas-sensing applications at 27 °C.