Enhanced sensing performance of the amperometric gas sensor by laser-patterning of the polymer membrane electrode

Ultraviolet laser patterning has been employed for enhancing the sensing performance of the electrochemical gas sensors. Two kinds of catalyst layers (platinum for CO and gold for SO2) coated on the polytetrafluoloethylene film have been selectively removed by KrF laser irradiation. The laser fluence, repetition rate and number of shots were carefully controlled to avoid the damage of the membrane substrate. The threshold fluences for complete removal of gold film and PTFE-bonded platinum layer are about 60 and 500 mJ/cm2, respectively. The sensors (especially the SO2 sensors) with patterned catalyst electrodes exhibit excellent sensing capabilities in sensitivity as well as the response and recovery times. The sensitivity of the SO2 sensor with patterned sensing electrode is about 0.63 μA/ppm, 14 times improved as compared with the unpatterned sensor. The response and recovery times are shortened from 11 and 17 s to 6 and 9 s, respectively. The signal-to-noise ratio is improved by two times. Due to the original good porous microstructure of the PTFE-bonded platinum layer, the improvement of the patterned CO sensor is not as much as that of the patterned SO2 sensor. However, the sensitivity is doubled. The great enhancement in the sensing performance is attributed to the increase of the electrochemically active surface area and the higher diffusion efficiency.