Bismuth oxyiodide as a highly efficient room temperature NOx gas sensor: Role of surface orientations on sensing performance

Abstract

In the pursuit of developing fast and reliable gas sensors, a new ternary oxide semiconductor, a bismuth oxyiodide (BiOI)-based sensing material, has been reported with desirable adsorption energy, short recovery time, and high sensitivity and selectivity for detecting nitrogen oxide mixtures (NO_x, typically NO and NO₂). The structural, electronic, and transport properties of both (001) and (012) planes of BiOI surfaces upon the adsorption of six environmentally relevant gases (NO, NO₂, SO₂, SO₃, O₂, and H₂O) are systematically explored using a combination of density functional theory (DFT) and non-equilibrium Green's function (NEGF) methods. The results indicate that BiOI (001) exhibits weak interaction with these gases, with the highest adsorption energy observed for NO. In contrast, the BiOI (012) surface shows enhanced adsorption stability for these gases, particularly acceptable strong adsorption to NO₂, indicating its promising capability for detecting these gases with high specificity. Moreover, it demonstrates the most intense chemisorption for SO₃, suggesting it to be a reliable SO₃ adsorbent/cleaner. The obtained transport characteristics, including current-voltage (I-V) and resistance-voltage (R-V) curves, further highlight the higher selectivity of the BiOI (001) device towards NO and the BiOI (012) device towards NO₂ against the other gases. Furthermore, the transmission spectra analyses reveal that the BiOI-based sensor can electrically discriminate the target gas molecules from other considered gas molecules. Besides, the practical application possibilities of both orientations are explored by estimating their recovery time, and the results show that the BiOI sensor has excellent recovery times at room temperature (NO/BiOI (001) = 0.158 ns, and NO₂/BiOI (012) = 3.89 s), highlighting its potential as an ideal reversible gas-sensing material for detecting NO_x gases.