Theoretical investigation of 2D FePc and CrPc monolayers as a promising gas sensor for detecting hazardous gases

In recent years, the worsening air pollution caused by industrialization and urbanization has a huge negative impact on human health and quality of life, making it urgent to explore stable, selective, and sensitive sensing materials for monitoring toxic gases in the air. In this study, the structure and electronic properties of two-dimensional Fe/Cr doped phthalocyanine (FePc/CrPc) monolayer were investigated using density functional theory, with a focus on their potential applications in gas sensing. The adsorption energies of FePc and CrPc for 11 kinds of gases were calculated, and their charge transfer, band structure, charge density difference, and density of states were analyzed to elucidate the mechanism underlying the detection of various hazardous gases by FePc and CrPc materials. The results indicate that NH3, NO2, SO2, CO, and NO gases all chemically adsorb on FePc and CrPc monolayers, primarily due to the strong hybridization between Fe/Cr-d orbitals and p orbitals of gases. Meanwhile, their adsorption strengths are much higher than those of common gases, indicating that FePc and CrPc have high capture ability for these toxic gases and are not affected by air humidity. Furthermore, the adsorption of NH3, NO2, SO2, CO, and NO gases causes significant changes in the conductivity, magnetic moment or work function of FePc and CrPc, demonstrating their strong sensitivity to these toxic gases. Therefore, the FePc and CrPc monolayers can be potential hazardous gas sensing materials, providing new insights for the design and production of high-performance gas sensing devices.