Fabrication of a room-temperature NO₂ gas sensor with high performance at the ppb level using an rGO/BiOCl heterostructure

In recent years, the continuous and accurate detection of human hazardous gases, such as NO₂, using a low-cost gas sensing device is quite important. For a new generation of gas sensors, rGO or 2-D materials have gained considerable attention. This work presents a low-temperature rGO/BiOCl heterojunction fabricated NO₂ gas sensor that exhibits an excellent response (R_g/R_a = 3.78) for NO₂ at 100 ppb compared to pristine BiOCl. The selected synthesis pathway results in the generation of a perforated floral morphology. Moreover, the sensor showed outperforming selectivity with a quick response/recovery of ∼9 s/21 s at ambient temperature (25 °C). Additionally, it has an ultralow LOD (∼0.06 ppb). Besides, the mechanism of gas sensing was initially elucidated through finite-difference time-domain (FDTD) simulation. This analysis confirms that rGO in BiOCl serves as a bridge, enhancing the transfer of electrons from BiOCl to NO₂ and resulting in a substantial increase in the depletion region and a heightened sensor response. Our fabricated NO₂ gas sensor offers a low gas detection limit with high accuracy and fast response at even lower temperatures.