English
Although understanding the competitive adsorption behavior of gas sensors is important, it still needs to be clarified. Especially the influence of water molecules on the adsorption of gases by two-dimensional materials. This study used non-destructive measurement and second harmonic generation (SHG) technology to explore the potential of layered two-dimensional materials as candidate materials for gas sensing. The focus of this study is to analyze the adsorption of oxygen, ammonia, and water vapor on the surface of WS2 by studying the evolution of electric dipoles and electric fields. The use of a simplified key hyperpolarization model (SBHM) has laid the foundation for gas sensors utilizing high-quality two-dimensional materials. This method helps detect changes in materials due to environmental influences, including inevitable water molecules. The hyperpolarization obtained by SBHM shows significant consistency with the Langmuir adsorption model, confirming the physical adsorption in the system. In addition, the competitive effects between gases were explored by comparing the experimental results with theoretical predictions based on Boltzmann distribution and density functional theory (DFT) calculations. This highlights the effectiveness of SHG and SBHM in studying gas adsorption on layered van der Waals materials.
