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.