In situ synthesis of polyoxometalate-derived MoS2/phosphomolybdic acid composites for highly sensitive NO2 detection

MoS 2 is a promising gas sensing material due to its low resistance and low operating temperature. But the sensitivity of MoS 2 is limited by fast electron-hole complexation. In this work, phosphomolybdic acid (PMo 12 ) was used as precursor. After sulfurizing by one-step hydrothermal method , the generated MoS 2 and unspent PMo 12 can in-situ form MoS 2 /PMo 12 composite nanospheres . The gas sensing performances of the composite were comprehensively investigated. By adjusting hydrothermal reaction temperature, optimized sensitivity (MoS 2 /PMo 12 -240) to NO 2 gas can be gained. At a low operating temperature of 80 °C, the optimized response value to 100 ppm NO 2 gas is 2.466, which is higher than most reported MoS 2 -based NO 2 sensors. Moreover, MoS 2 /PMo 12 -240 composite also exhibits good selectivity, repeatability, long-term stability and humidity resistance. The mechanism of sensing performance enhancement was also analyzed and discussed. As a semiconductor-like material, PMo 12 can form heterojunction together with MoS 2 . The valence band of PMo 12 can capture the holes in MoS 2 and effectively suppresses electron-hole complexation. Thus the sensing performance can be improved. This work provides a new strategy for designing and constructing high performance sulfide composite gas sensors by introducing POMs .