α−Fe₂O₃/rGO cooperated with tri-alkyl-substituted-imidazolium ionic liquids for enhancing oxygen sensing

Ionic liquids are widely employed as electrolytes for electrochemical oxygen sensing due to their excellent physical and chemical properties. Recently, combining inorganic electrochemically active materials with ionic liquids are becomes intensively interesting to improve oxygen sensor performance. In this paper, two imidazolyl-based ionic liquids 1-ethyl-2,3-dimethylimidazole bis((trifluoromethyl)sulfonyl)imide [Emmim][TFSI] and 1-butyl-2,3-dimethylimidazole bis((trifluoromethyl)sulfonyl)imide [Bmmim][TFSI] with three saturated alkyl substituents on the aromatic ring were prepared by a traditional two-step method. Under the electrochemical test, both ionic liquids exhibit a certain responsibility to different concentrations of oxygen. Subsequently, α-Fe₂O₃/rGO was prepared by hydrothermal method and then mixed with the ionic liquids to prepare a composite ionic liquid electrolyte for detecting a wide range of oxygen concentrations. The response performance of prepared composite electrolyte toward the oxygen is improved, which exhibits a sensitivity of 0.1041 μA/[%O₂] to gradually changed oxygen concentration and a linear correlation (R²) of 0.9997 between oxygen reduction peak currents. Hence, the results show that the pure ionic liquid has a certain ability to detect oxygen, while adding α-Fe₂O₃/rGO compounds further improve responsibility, stability and sensitivity of composite electrolyte to oxygen.