Highly selective ppb-level H2S sensor based on the walnut-like Bi2MoO6 at low temperature

The walnut-like Bi2MoO6 (BMO) hollow microspheres, assembled by nanosheets, were synthesized by a facile solvothermal method based on MoO3 hollow spheres. The Bi2MoO6 compound was calcined at the temperature of 200 °C, 400 °C and 450 °C (denoted as BMO-200, BMO-400 and BMO-450) to measure the gas-sensing properties. The sensor based on BMO-400 exhibits a significant selectivity, a high stability and response, a good repeatability and humidity-resistivity and a better linear relationship to H2S gas at the concentration range of 1–100 ppm level and 0.1–100 ppb level at a low operating temperature of 133 °C. In addition, the detection limit of the sensor towards H2S gas is as low as 0.1 ppb (S = 1.98). According to the sensing mechanism discussed based on X-ray photoelectron spectroscopy (XPS) and gas chromatography-mass spectrometry (GC–MS) analyses, the improvement of response may be attributed to the high oxygen content adsorbed on the surface of the Bi2MoO6 material and the unique hollow structure.