Synergy of Active Sites and Charge Transfer in Branched WO 3 /W 18 O 49 Heterostructures for Enhanced NO 2 Sensing.

Achieving reliable detection of trace levels of NO ₂ gas is essential for environmental monitoring and protection of human health protection. Herein, a thin-film gas sensor based on branched WO ₃ /W ₁₈ O ₄₉ heterostructures was fabricated. The optimized WO ₃ /W ₁₈ O ₄₉ sensor exhibited outstanding NO ₂ 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 NO ₂ under different air quality conditions. This work provides an effective strategy for constructing WO ₃ /W ₁₈ O ₄₉ heterostructures for developing NO ₂ gas sensors with an excellent sensing performance.