NiWO4 Microflowers on Multi-Walled Carbon Nanotubes for High-Performance NH3 Detection

NiWO 4 microflowers with a large surface area up to 79.77 m 2 ·g –1 are synthesized in situ via a facile coprecipitation method. The NiWO 4 microflowers are further decorated with multi-walled carbon nanotubes (MWCNTs) and assembled to form composites for NH 3 detection. The as-fabricated composite exhibits an excellent NH 3 sensing response/recovery time (53 s/177 s) at a temperature of 460 °C, which is a 10-fold enhancement compared to that of pristine NiWO 4 . It also demonstrates a low detection limit of 50 ppm; the improved sensing performance is attributed to the porous structure of the material, the large specific surface area, and the p–n heterojunction formed between the MWNTs and NiWO 4 . The gas sensitivity of the sensor based on daisy-like NiWO 4 /MWCNTs shows that the sensor based on 10 mol % (MWN10) has the best gas sensitivity, with a sensitivity of 13.07 to 50 ppm NH 3 at room temperature and a detection lower limit of 20 ppm. NH 3, CO 2, NO 2, SO 2, CO, and CH 4 are used as typical target gases to construct the NiWO 4 /MWCNTs gas-sensitive material and study the research method combining density functional theory calculations and experiments. By calculating the morphology and structure of the gas-sensitive material NiWO 4 (110), the MWCNT load samples, the vacancy defects, and the influence law and internal mechanism of gas sensitivity were described.