Enhancing SO<sub>2</sub> Sensing Performance of a\nFuel Cell-Type Sensor with N‑Doped Cu/CNT Aerogel Electrode\nand COF/Nafion Electrolyte

Sulfur dioxide (SO<sub>2</sub>) is\na common environmental pollutant\nwith significant hazards. However, sensors for SO<sub>2</sub> real-time\nmonitoring at room temperature often face problems such as a poor\nresponse and sluggish recovery. In this work, a fuel cell-type gas\nsensor based on nitrogen-doped carbon nanotube (CNT) aerogels loaded\nwith Cu particle electrode material and COF/Nafion composite electrolyte\nwas developed, which exhibited excellent SO<sub>2</sub> sensitivity\nand fast response/recovery. The aerogel scaffold provided a high specific\nsurface area and high electrical conductivity, and Cu particles provided\ngood catalytic activity to SO<sub>2</sub>. In addition, N doping further\nenhanced the SO<sub>2</sub> capture capability and conductivity of\nthe electrode material. For electrolyte construction, covalent organic\nframework (COF) nanosheets were synthesized by a bottom-up approach\nand blended with Nafion to prepare the COF/Nafion membrane; the composite\nmembrane showed higher proton conductivity. Owing to these advantages,\nthe fuel cell-type sensor exhibited an outstanding response of −3008.5\nnA to 50 ppm of SO<sub>2</sub> with a rapid response time (35 s) and\nrecovery time (77 s). Moreover, the rigid nanochannels of COF nanosheets\nimproved the water retention properties of the electrolyte; this will\nhelp to simplify the structure of fuel cell-type sensors and provide\na significant stimulus for their miniaturization. Based on the great\nsensing performance, a fuel cell-type SO<sub>2</sub> sensor is integrated\ninto a portable detector and evaluated in the context of dynamic environmental\nmonitoring. The results show that the fuel cell-type sensor with the\ncarefully designed electrode and electrolyte will have great potential\nin environmental monitoring and safety assurance.