Enhancing NO2 gas sensing with ZnO/W18O49 heterostructures: Experimental insights and DFT analysis

Abstract

A highly advanced nitrogen dioxide (NO2) gas sensor, operational at both room temperature (RT) and elevated temperatures, has been engineered using a ZnO/WxOy heterostructure. Comprehensive experimental and theoretical analyses have meticulously evaluated the ZnO/WxOy heterostructure's unparalleled sensing performance. The samples were meticulously synthesized on Si/SiO2 substrates via a simple thermal evaporation method by a tube furnace. The morphology of pure ZnO was microdisks, while, after deposition of WxOy on these microdisks, an array nanorods grew on the ZnO disks. X-ray diffraction (XRD) pattern and X-ray photoelectron spectroscopy (XPS) results indicated, the WxOy nanorods have W18O49 phase. The heterostructured sensor exhibited an impressive sensitivity of approximately 44 and a remarkable selectivity of 54% towards 100 ppm NO2 at 150°C. The integration of W18O49 with ZnO significantly enhanced the sensor's response and recovery times. Notably, the ZnO/W18O49 sensor demonstrated extraordinary capability by detecting NO2 at concentrations as low as 2 ppb at 25°C (RT), a feat unattainable by pure ZnO. Cutting-edge density functional theory (DFT) calculations revealed substantial negative adsorption energies for both ZnO and ZnO/W18O49, unequivocally confirming their superior efficacy in NO2 detection.