Adsorption mechanism of formaldehyde, ammonia and sulfur dioxide gases on inexpensive metal-doped ZnO surface: A DFT study

Here, the adsorption mechanisms and detection performance of three different hazardous gases, including formaldehyde (CH2O), ammonia (NH3), and sulfur dioxide (SO2), on undoped ZnO and inexpensive metal-doped ZnO surfaces were studied by density functional theory (DFT). CH2O and NH3 are physically adsorbed on the zinc top site (t-site) and six-membered ring pore site (p-site) on the undoped ZnO surface, and the adsorption energies are-0.56 eV and-0.32 eV. The difference is that SO2 is weakly chemisorbed on bridge site (b-site) of ZnO surface with an adsorption energy of 1.78 eV. The adsorption energy of Al-doped ZnO for CH2O, NH3, and SO2 is higher than that of undoped ZnO, reaching-1.64 eV,-1.69 eV, and-3.62 eV respectively. The adsorption properties of Cu-doped ZnO for CH2O and SO2 are not significantly improved with exception of NH3. Collectively, the adsorption mechanism of undoped and doped ZnO or hazardous gases is elucidated, which provides theoretical guidance for the further utilization of ZnO substrate materials in the field of gas sensitivity.

Automated summary

In this study, the adsorption mechanisms and detection performance of formaldehyde, ammonia, and sulfur dioxide on undoped and metal-doped ZnO surfaces were investigated using density functional theory. The results showed that formaldehyde and ammonia were physically adsorbed on the undoped ZnO surface, while sulfur dioxide was weakly chemisorbed. The adsorption energy was enhanced when ZnO was doped with metals. These findings provide theoretical guidance for the application of ZnO substrate materials in gas sensitivity research.