Experimental and Density Functional Theory Simulation Research on PdO-SnO₂ Nanosheet Ethanol Gas Sensors

Pure SnO₂ and 1 at.% PdO-SnO₂ materials were prepared using a simple hydrothermal method. The micromorphology and element valence state of the material were characterized using XRD, SEM, TEM, and XPS methods. The SEM results showed that the prepared material had a two-dimensional nanosheet morphology, and the formation of PdO and SnO₂ heterostructures was validated through TEM. Due to the influence of the heterojunction, in the XPS test, the energy spectrum peaks of Sn and O in PdO-SnO₂ were shifted by 0.2 eV compared with SnO₂. The PdO-SnO₂ sensor showed improved ethanol sensing performance compared to the pure SnO₂ sensor, since it benefited from the large specific surface area of the nanosheet structure, the modulation effect of the PdO-SnO₂ heterojunction on resistance, and the catalyst effect of PdO on the adsorption of oxygen. A DFT calculation study of the ethanol adsorption characteristics of the PdO-SnO₂ surface was conducted to provide a detailed explanation of the gas-sensing mechanism. PdO was found to improve the reducibility of ethanol, enhance the adsorption of ethanol's methyl group, and increase the number of adsorption sites. A synergistic effect based on the continuous adsorption sites was also deduced.