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–V 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.