Double-Layer Carbon Encapsulated Co Particles Combined with Ionic Liquid for Enhancing Electrochemical Detection of Oxygen

As one kind of potential electrolyte material, ionic liquids (ILs) have been widely applied in miscellaneous electrochemistry fields because of their good stability, wide electrochemical window, and nonevaporation at room temperature. Even so, limitations such as low conductivity and poor electrochemical performance still remain when they serve as electrolytes for sensors. Herein, the Co-N/C microcube electrochemical catalyst with N-doped carbon confined Co particles was fabricated via precipitation and carbonization methods. The Co-N/C microcube possesses a rich surface area, internal voids, and good electrochemical activity that are conducive to the catalytic performance of oxygen reduction in ionic liquid electrolytes. Co-N/C was mixed with the pure ionic liquid 1-butyl-1-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide ([C₄mpyrr][TFSI]) to form the composite electrolyte Co-N/C/[C₄mpyrr][TFSI], and the sensing performance of Co-N/C/[C₄mpyrr][TFSI] was visibly enhanced compared with [C₄mpyrr][TFSI]. Noticeably, the optimized composite electrolyte Co-N/C-700/[C₄mpyrr][TFSI] exhibited excellent oxygen concentration detecting abilities with a sensitivity of 0.1545 μA/[% O₂] and a linear correlation of 0.9991 between response current and O₂ concentration in cyclic voltammetry. Meanwhile, chronoamperometry ensured the responsiveness in a wide range of O₂ concentrations from 0 to 100%. This work paves a new way for promoting the oxygen sensing performance including sensitivity, responsibility, and stability of ionic liquid electrolytes by the addition of Co-N/C-700.