Highly sensitive and selective sensing-performance of 2D Co-decorated phthalocyanine toward NH3, SO2, H2S and CO molecules

Developing excellent sensing-materials for detecting and monitoring toxic gases in the air is significant for environmental monitoring and industrial emission evaluation. Herein, the first-principles calculations were employed to systematically investigate the adsorption characteristics of twelve different gas molecules (NH3, NO, NO2, SO2, H2S, CO, CO2, CH4, H2O, H2, O2, N2) on the two-dimensional phthalocyanine (Pc) and Co decorated phthalocyanine (CoPc), the electronic properties of various adsorption systems and their sensing-mechanism were also elucidated. The results show that the toxic NH3, NO, NO2, SO2, H2S are chemically adsorbed on the pristine Pc surface, whereas the poor sensitivity of Pc monolayer makes it not suitable to be a sensing-material. By contrast, the CoPc monolayer exhibits the appropriate adsorption strength toward the six poisonous gases (NH3, NO, NO2, SO2, H2S, CO), which is detailedly explained by the analysis of charge transfer, charge density difference and density of states. Moreover, the CoPc monolayer possesses high selectivity to those six gases even if it is in a humid environment. The CoPc monolayer also has excellent sensitivity for those toxic gases due to the obvious variations of bandgap, magnetic moment or work function. Additionally, the recovery time of NH3, SO2, H2S and CO is estimated to be about 3.91 min, 0.02 s, 24.19 ns and 226.38 ns at room temperature, respectively. Consequently, the CoPc monolayer based gas sensor has a great potential application for the NH3, SO2, H2S and CO detection.