NO₂ gas sensor with high selectivity and fast response based on Pt-loaded nanoporous GaN

In this work, we realized a room-temperature nitrogen dioxide (NO₂) gas sensor based on a platinum (Pt)-loaded nanoporous gallium nitride (NP-GaN) sensing material using the thermal reduction method and coreduction with the catalysis of polyols. The gas sensor gained excellent sensitivity to NO₂ at a concentration range of 200 ppm to 100 ppb, benefiting from the loading of Pt nanoparticles, and exhibited a short response time (22 s) and recovery time (170 s) to 100 ppm of NO₂ at room temperature with excellent selectivity to NO₂ compared with other gases. This phenomenon was attributed to the spillover effect and the synergic electronic interaction with semiconductor materials of Pt, which not only provided more electrons for the adsorption of NO₂ molecules but also occupied effective sites, causing poor sites for other gases. The low detection limit of Pt/NP-GaN was 100 ppb, and the gas sensor still had a fast response 70 d after fabrication. Besides, the gas-sensing mechanism of the gas sensor was further elaborated to determine the reason leading to its improved properties. The significant spillover impact and oxygen dissociation of Pt provided advantages to its synergic electronic interaction with semiconductor materials, leading to the improvement of the gas properties of gas sensors.