Humidity-Tolerant ppb-level NO<i>_x</i> Sensors Based on Ag₂Te/CeO₂ Nanocomposites for Smart Greenhouse Farming

Monitoring trace levels of nitrogen oxides (NO<i>_x</i>) in high-humidity agricultural greenhouse environments is essential for both crop growth and workers' health. However, achieving reliable NO<i>_x</i> detection under extreme humidity remains challenging. Herein, this work presents an ultralow-detection-limit and highly humidity-tolerant NO<i>_x</i> sensor based on Ag₂Te/CeO₂ nanocomposites. To the best of our knowledge, this is the first demonstration of Ag₂Te/CeO₂ heterostructures for gas sensing. Among the as-prepared samples, the optimal Ag₂Te/CeO₂ sample, with a molar ratio of 1:2, exhibited superior response and an ultralow detection limit of 5 ppb NO₂ at 65 °C. The sensor response retained over 92% of its regular response even at 99% relative humidity. Density functional theory (DFT) calculations suggest that minimal H₂O adsorption on Ag₂Te and strong NO₂ adsorption on CeO₂, along with the formation of an n-n heterojunction, synergistically enhanced performance. Moreover, the sensor was further integrated into an Internet of Plants (IoP) environmental monitoring system. This work provides a new strategy for designing humidity-tolerant NO<i>_x</i> sensors and offers a core device for smart agriculture.