Synthesis and morphology-dependent CO2 gas sensing properties of Ca & Al codoped ZnO nanostructures

Monitoring CO₂ emissions is critical due to their impact on climate change, necessitating the development of efficient gas sensors with high sensitivity and selectivity at moderate operating temperatures. This study investigated the gas-sensing performance of ZnO nanomaterials, particularly undoped ZnO and Ca,Al codoped ZnO, for CO₂ detection. Gas sensing measurements were conducted in a chamber with a fixed total flow rate of 1000 sccm, adjusting the temperature and CO₂ gas concentration between 1000 and 5000 ppm. Three types of ZnO nanomaterials, including nanowires (NWs), nanorods, and nanoparticles, were synthesized via a sol–gel method and evaluated for their gas-sensing capabilities. Among these, the NWs exhibited the highest response to CO₂. The Ca,Al codoped ZnO NWs demonstrated superior gas sensitivity, particularly at high CO₂ concentrations and at lower levels. The limit of detection for CO₂ was 6.65 ppm. Furthermore, the codoped ZnO NWs exhibited significant responses to various gases, with the highest response recorded for CO₂ (9.56 at 5000 ppm). This performance highlights the strong potential of the Ca,Al codoped ZnO NWs as effective gas sensors for CO₂ detection at moderate temperatures.