Potential Detection of CO ₂ Gas by Wood-Ash-Substituted Clay Composites for Cleanroom Facilities

The present study introduces an ultrasensitive CO2 gas sensor developed from waste wood ash, which is utilized as a substitute in clay to form wood ash/clay composites aimed at cleanroom air quality regulation. Optimized compositions {(wood ash; x = 0, 5, 10, 15 wt %) and clay (100-x wt %)} were synthesized via a bottom-up solid-state reaction method, sintered at 1050 °C for 3 h, and labeled CWA0, CWA5, CWA10, and CWA15, respectively. SEM analysis revealed that CWA15 exhibited the highest porosity, while HRTEM confirmed interplanar spacing corresponding to SiO2 (quartz, hexagonal), CaAl2Si2O8 (anorthite, triclinic), and AlKSi2O6 (leucite, tetragonal), aligning well with XRD results. EDAX verified elemental presence including C, O, Na, Mg, Al, Si, Zr, K, Ca, and Fe. UV–vis analysis showed that CWA15 had the lowest band gap (∼3.36 eV). XPS identified surface-active sites associated with Oads deficiencies, while BET confirmed meso-porosity (pore diameter ∼ 3.802 nm) in CWA15, contributing to rapid CO2 adsorption. The thin-film CWA15 sensor demonstrated exceptional CO2 sensing performance, achieving the highest S.R. of ∼ 3.58 and a detection limit (LOD) of ∼81 ppm, with fast response and recovery times (TRes/TRec = 10.17 s/11.5 s). These significant features make it highly effective for real-time monitoring in cleanrooms. This work highlights the development of a sensitive CO2 gas sensor that offers sustainable potential for air quality control.