Constructing adsorption site‐enhanced ZnWO ₄ /Li ₆ W ₂ O ₉ heterojunction sensing electrode for efficient performance in impedancemetric NO ₂ sensor

Abstract The application of NO 2 sensor reduces the emission of NO 2 from the industry and automotive vehicles. However, insufficient electrocatalytic activity and adsorption to NO 2 of sensing electrode (SE) limit the sensitivity increment of NO 2 sensor. Thus, a novel ZnWO 4 /Li 6 W 2 O 9 heterojunction SE is constructed by molten salt method for the zirconia‐based impedancemetric NO 2 sensor. The influence of the ZnWO 4 /Li 6 W 2 O 9 ratio on the performance of the sensor is investigated. The results show that Li 6 W 2 O 9 in‐situ formation on the surface of the ZnWO 4 in LiNO 3 molten at a low temperature of 300 °C. The incorporation of Li 6 W 2 O 9 enhances both the adsorption property and electrocatalytic activity of the SE, simultaneously, resulting in a significant increase in the sensitivity of sensor. The sensitivity increases gradually with the increasing incorporation of Li 6 W 2 O 9 . The sensitivity of ZnWO 4 /37.5% Li 6 W 2 O 9 sensor is significantly increased by 124% compared to the pristine ZnWO 4 sensor and exhibits the largest sensitivity of 25.19 (°) decade −1 at 400 °C. Moreover, the ZnWO 4 /Li 6 W 2 O 9 sensor also displays excellent selectivity, long‐term stability, and repeatability. The introduction of in‐situ formation by molten salt method is an effective strategy to develop gas sensors with large sensitivity.