Room-Temperature NH3 Sensor Capable of Fast Response and Humidity Resistance Based on In Situ Polymerized PANI/WO3

Polyaniline (PANI) is regarded as a prospective sensing material for room-temperature NH 3 detection owing to its high sensitivity and selectivity. In this study, WO 3 nanoflowers were prepared via a simple chemical bath deposition method, and PANI/WO 3 heterojunctions were subsequently fabricated through an in situ polymerization process. To evaluate the contribution of the heterojunction to gas-sensing performance, four sensors with different composite ratios were constructed. Among them, the optimized PW1-2 sensor exhibits a response of 3.8–100 ppm NH 3 at room temperature, which is 1.6 times higher than that of pure PANI. Notably, it achieves an ultrafast response time of only 26 s, representing an 8.8-fold improvement over pure PANI (230 s), along with near-complete desorption capability. Furthermore, PW1-2 demonstrates excellent humidity resistance, with stable responses ranging from 3.7 to 3.97 under 40–80% relative humidity. Comprehensive characterization by x-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy TEM, x-ray photoelectron spectroscopy (XPS), Raman spectroscopy, thermogravimetric analysis (TGA), and Brunauer–Emmett–Teller (BET) analysis reveals that PANI nanofibers uniformly wrap around WO 3 nanoflowers, forming p–n heterojunctions at the interface. XPS analysis shows that PW1-2 possesses the highest protonation degree (51.88%), which correlates with its superior sensing performance. Unlike conventional PANI/WO 3 composites, the enhanced performance is not primarily attributed to specific surface area or porosity but rather to the synergistic effect of morphological characteristics and heterojunction formation. Compared with previously reported PANI/WO 3 sensors, our PW1-2 sensor offers significantly faster response, better humidity tolerance, and complete desorption. This work provides a promising strategy for designing high-performance, humidity-resistant room-temperature NH 3 sensors. Graphical