Synergy of Active Sites and Charge Transfer in Branched WO₃/W₁₈O₄₉ Heterostructures for Enhanced NO₂ Sensing

Achieving reliable detection of trace levels of NO₂ gas is essential for environmental monitoring and protection of human health protection. Herein, a thin-film gas sensor based on branched WO₃/W₁₈O₄₉ heterostructures was fabricated. The optimized WO₃/W₁₈O₄₉ sensor exhibited outstanding NO₂ sensing properties with an ultrahigh response value (1038) and low detection limit (10 ppb) at 50 °C. Such excellent sensing performance could be ascribed to the synergistic effect of accelerated charge transfer and increased active sites, which is confirmed by electrochemical impedance spectroscopy and temperature-programmed desorption characterization. The sensor exhibited an excellent detection ability to NO₂ under different air quality conditions. This work provides an effective strategy for constructing WO₃/W₁₈O₄₉ heterostructures for developing NO₂ gas sensors with an excellent sensing performance.