High-sensitive electrochemical oxygen gas sensor with zero power consumption based on Pt/CMK-3-COOH modified ionic liquid as composite electrolyte

The modification of ionic liquid electrolytes is of particular importance for the development of high-performance electrochemical oxygen sensors with zero power consumption but still quite challenging. Herein, we designed and synthesized an electrochemical oxygen sensor based on the modified Pt/CMK-3-COOH-[EMIM][OAc] ionic liquid as composite electrolyte, where the -COOH functional group was introduced by acidifying CMK to provide hydrogen protons, and then Pt nanoparticles with different contents were loaded to improve the activity of the sensor towards O₂ gas as well as the conductivity of ionic liquid. Such composite ionic liquid sensor exhibits excellent O₂ detection ability with high sensitivity (0.58 μA/[%O₂]), high stability, wide detection range (0.4-10%), and zero-power consumption, along with the detection limit as low as 0.4%. Furthermore, it has humidity-independent gas-sensing characteristic. Moreover, density functional theory (DFT) calculations combined with experimental results were applied to deeply unveil the improved O₂ sensing mechanism. Compared with CMK, the introduction of Pt/CMK-3-COOH material increases the conductivity of the ionic liquid, decreases the adsorption energy of the sensor for O₂ and hydrogen protons, promotes the oxygen reduction reaction, and simulates the transfer of effective charge, thereby significantly improving O₂ sensing. This work provides a high-performance ionic liquid oxygen sensor, showing potential application in zero-power consumption and low concentration O₂ detection.