Humidity-Tolerant ppb-level NOx Sensors Based on Ag2Te/CeO2 Nanocomposites for Smart Greenhouse Farming

Monitoring trace levels of nitrogen oxides (NOx) in high-humidity agricultural greenhouse environments is essential for both crop growth and workers’ health. However, achieving reliable NOx detection under extreme humidity remains challenging. Herein, this work presents an ultralow-detection-limit and highly humidity-tolerant NOx 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 NOx sensors and offers a core device for smart agriculture.