Letsoalo, MRDima, Ratshilumela SMaluta, NEShingange, K2025-08-252025-08-252025-040925-83881873-4669https://doi.org/10.1016/j.jallcom.2025.179881http://hdl.handle.net/10204/14382This study investigates the gas detection of ethylene (C2H4) using cobalt oxide (Co3O4) structures synthesized via hydrothermal method for 6, 12, and 24 hrs. X-ray diffraction (XRD) confirmed the strong crystallinity. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) revealed a sheet-like morphology forming hierarchical structures, with the surface area obtained through the Brunauer-Emmett-Teller (BET) method decreasing as the reaction duration increased. Selectivity studies conducted at 100 ◦C using 100 ppm of several gases (CH4, CO, C3H6O, C2H5OH, and C6H6) revealed distinct responses among the different Co3O4-based sensors. The Co3O4_6hrs-based sensor exhibited high selectivity for C2H4, whereas the Co3O4_12hrs-based sensor showed a strong response to C2H5OH. Additionally, the Co3O4_24hrs sensor demonstrated a high response to C6H6. Notably, the Co3O4_6hrs sensor recorded the highest overall response of 49.6 and exhibited rapid response and recovery times of 27 seconds and 42 seconds, respectively. BET and Photoluminescence (PL) analyses indicated that the superior performance of the Co3O4_6 hrs sensor was due to its high surface area and defects. Density functional theory (DFT) calculations were used to provide insights into the gas-sensing mechanisms. The calculations were performed using the Perdew–Burke–Ernzerhof (PBE) exchange–correlation functional within the generalized gradient approximation (GGA) for optimization. DFT calculations showed that the gas performance of Co3O4 towards ethylene is influenced by the physisorption gas adsorption mechanism and electron transfer process. In the future, optimizing defect engineering could further enhance the sensor performance.AbstractenCo3O4Sheet-likeHierarchicalGas detectionEthylene DFTArticlen/a