A Rapid ppb Level Room Temperature NO₂ Sensing by Using BiVO₄–CeO₂ Composites with DFT Interpretation

This study describes the successful synthesis of a series of bismuth vanadate and ceria nanocomposites (BiVO 4 –CeO 2 ). The surface morphology, chemical composition, and sensing properties of as-synthesized samples have been analyzed using X-ray diffraction analysis (XRD), transmission electron microscope (TEM), scanning electron microscope (SEM), X-ray photoelectron spectrometer (XPS), and ultraviolet–visible light (UV–vis) spectrometer. Moreover, during gas sensing measurements, the gas sensor based on BiVO 4 –CeO 2 (1:1) demonstrated the best gas-sensing properties for nitrogen dioxide (NO 2 ) at room temperature, including a high response value (17 toward 1 ppm), fast response time (37 s toward 1 ppm), rapid recovery time (31 s toward 1 ppm), and ultralow detection limit (0.05 ppm). This may be explained by its superior structural characteristics, increased absorption capacity, and the synergistic effect of heterojunction. In addition, calculations based on the density function theory (DFT) were performed to validate the experimentally observed results. The variation in the different energy levels of the BiVO 4 –CeO 2 nanocomposite validates the gas sensing mechanism and charge transfer during gas interactions.