Fast Response Room Temperature Amperometric Gas Sensors with Modified Fe–N–C Electrodes for ppb-Level H2S Detection

Monitoring halitosis indirectly by detecting H2S biomarkers with gas sensors is an emerging technique that holds great promise. However, developing H2S sensors with exceptional selectivity and sensitivity, as well as a detection limit in the ppb range, remains a significant technological challenge. To address these issues, we have fabricated amperometric H2S gas sensors utilizing modified Fe–N–C catalysts as electrodes. The modified Fe–N–C catalyst obtained by heat treatment of ammonium chloride salt exhibits a higher specific surface area, improved ORR catalytic performance, and excellent stability in acidic environments, which enhance the sensitivity and durability of amperometric H2S sensors. The amperometric sensors demonstrate a sensitivity of up to 502.0 nA ppm–1 for H2S and exhibit rapid response time with only 22.5 s for response and 9.0 s for recovery time toward 3 ppm of H2S. Moreover, they display good sensitivity (approximately 1506.0 nA at 3 ppm of H2S) and achieve a low limit of detection (LOD) of around 0.01 ppm. Additionally, the sensors exhibit excellent selectivity while being capable of detecting changes in trace amounts of H2S concentration within an exhaled breath environment. Our study presents experimental evidence demonstrating the successful detection of H2S in exhaled breath using amperometric sensors with modified Fe–N–C electrodes.