Enhancing SO₂ Sensing Performance of a Fuel Cell-Type Sensor with N-Doped Cu/CNT Aerogel Electrode and COF/Nafion Electrolyte

Sulfur dioxide (SO₂) is a common environmental pollutant with significant hazards. However, sensors for SO₂ real-time monitoring at room temperature often face problems such as a poor response and sluggish recovery. In this work, a fuel cell-type gas sensor based on nitrogen-doped carbon nanotube (CNT) aerogels loaded with Cu particle electrode material and COF/Nafion composite electrolyte was developed, which exhibited excellent SO₂ sensitivity and fast response/recovery. The aerogel scaffold provided a high specific surface area and high electrical conductivity, and Cu particles provided good catalytic activity to SO₂. In addition, N doping further enhanced the SO₂ capture capability and conductivity of the electrode material. For electrolyte construction, covalent organic framework (COF) nanosheets were synthesized by a bottom-up approach and blended with Nafion to prepare the COF/Nafion membrane; the composite membrane showed higher proton conductivity. Owing to these advantages, the fuel cell-type sensor exhibited an outstanding response of -3008.5 nA to 50 ppm of SO₂ with a rapid response time (35 s) and recovery time (77 s). Moreover, the rigid nanochannels of COF nanosheets improved the water retention properties of the electrolyte; this will help to simplify the structure of fuel cell-type sensors and provide a significant stimulus for their miniaturization. Based on the great sensing performance, a fuel cell-type SO₂ sensor is integrated into a portable detector and evaluated in the context of dynamic environmental monitoring. The results show that the fuel cell-type sensor with the carefully designed electrode and electrolyte will have great potential in environmental monitoring and safety assurance.