Porous nanosheets-assembled NiMoO4–NiO microflowers for high-selectivity to NO2

This study synthesized a porous structure of NiMoO₄–NiO microflowers assembled with uniform nanosheets using a facile hydrothermal technique and calcination method. The unique porous microflower, consisting of the nanosheets assembled together, provides abundant space for gas diffusion and channels for electron transport. The gas sensor, fabricated using the NiMoO₄–NiO microflowers, exhibited outstanding sensing behaviors towards NO₂ gas. It showed a higher response value of 36.9 at 210 °C, with short response/recovery times of 30 s/16 s for 100 ppm NO₂ gas. The detection limit for NO₂ gas was 207 ppb. Additionally, it demonstrated high selectivity to NO₂ gas and excellent long-term stability. Furthermore, the sensor was tested under different relative humidity conditions. The superior NO₂ sensing properties are attributed to the abundant p-p heterojunctions, synergistic catalytic effect between the NiMoO₄ and the NiO, and the porous microflowers. The NiMoO₄–NiO microflowers sensor shows great promise for detecting NO₂ gas in practical applications.