A highly sensitive ppb-level H₂S gas sensor based on fluorophenoxy-substituted phthalocyanine cobalt/rGO hybrids at room temperature

Abstract

The peripheral and non-peripheral substitution of 4-trifluoromethylphenoxy groups in the design of gas sensing phthalocyanine cobalt/reduced graphene oxide (rGO) hybrids with two different positions of the substituents was realized. Tetra-α(β)-(4-trifluoromethylphenoxy)phthalocyanine cobalt/reduced graphene oxide (3(4)-cF₃poPcCo/rGO) hybrids were prepared through noncovalent interaction, and were analyzed by FT-IR, UV-vis, TGA and SEM. The gas sensing performance of the cF₃poPcCo/rGO hybrid gas sensors towards ppb hydrogen sulfide (H₂S) was measured at room temperature. The results show that the 4-cF₃poPcCo/rGO sensor has better sensitivity, selectivity and reproducibility than the 3-cF₃poPcCo/rGO sensor, as well as a perfect linear response to the concentration of H₂S. For the 4-cF₃poPcCo/rGO sensor, the response sensitivity to 1 ppm H₂S is as high as 46.58, the response and recovery times are 600 s and 50 s for 1 ppm H₂S, and the detection limit is as low as 11.6 ppb. This is mainly due to the loose and porous structure of the cF₃poPcCo/rGO hybrids, the fact that graphene is an excellent conductive agent, and the fact that the electron-withdrawing capability of the trifluoromethyl group can increase the holes of rGO and PcCo. In addition, through electrochemical impedance spectroscopy (EIS) and <i>I</i>-<i>V</i> curves, and density functional theory, the influence of different positions of the substituents of cF₃poPcCo/rGO on the sensing performance and the sensing mechanism for improving sensitivity were discussed and confirmed in detail.