Gas Sensing Properties of Pd-Decorated GeSe Monolayer toward Formaldehyde and Benzene Molecules: A First-Principles Study

In this study, the gas sensing properties of formaldehyde (HCHO) and benzene (C6H6) adsorbed on two-dimensional (2D) pristine GeSe and Pd-decorated GeSe (Pd–GeSe) monolayers are studied by using first-principles calculations. The adsorption energies, electronic properties, optical properties, sensitivity, and recovery time of the gas adsorption systems have been thoroughly investigated. It is found that the adsorption of C6H6 on two substrate surfaces and the adsorption of HCHO on pristine GeSe are examples of physical adsorption. However, after HCHO adsorption on the Pd–GeSe monolayer, the adsorption system exhibits an increased adsorption energy of −1.21 eV, which is more favorable compared with the other adsorption systems studied. Moreover, the electron localization function and charge transfer from Pd–GeSe to HCHO are significantly enhanced, indicating distinct chemical adsorption behavior. Furthermore, it demonstrates a larger band gap change rate of 18.8% and a significant enhancement of optical absorption upon the adsorption of HCHO on the Pd–GeSe monolayer. Additionally, the appropriate sensitivity and moderate recovery time for the adsorption of HCHO on the Pd–GeSe surface indicate that the Pd–GeSe monolayer possesses an outstanding sensing capability for HCHO gas.