Highly Selective and Reversible Detection of Simulated Breath Hydrogen Sulfide Using Fe‐Doped CuO Hollow Spheres: Enhanced Surface Redox Reaction by Multi‐Valent Catalysts
Ki Beom Kim, Myung Sung Sohn, Sunhong Min, Ji‐Wook Yoon, Jin‐Sung Park, Ju Li, Young Kook Moon, Yun Chan Kang
Abstract
Abstract The precise and reversible detection of hydrogen sulfide (H 2 S) at high humidity condition, a malodorous and harmful volatile sulfur compound, is essential for the self‐assessment of oral diseases, halitosis, and asthma. However, the selective and reversible detection of trace concentrations of H 2 S (≈0.1 ppm) in high humidity conditions (exhaled breath) is challenging because of irreversible H 2 S adsorption/desorption at the surface of chemiresistors. The study reports the synthesis of Fe‐doped CuO hollow spheres as H 2 S gas‐sensing materials via spray pyrolysis. 4 at.% of Fe‐doped CuO hollow spheres exhibit high selectivity (response ratio ≥ 34.4) over interference gas (ethanol, 1 ppm) and reversible sensing characteristics (100% recovery) to 0.1 ppm of H 2 S under high humidity (relative humidity 80%) at 175 °C. The effect of multi‐valent transition metal ion doping into CuO on sensor reversibility is confirmed through the enhancement of recovery kinetics by doping 4 at.% of Ti‐ or Nb ions into CuO sensors. Mechanistic details of these excellent H 2 S sensing characteristics are also investigated by analyzing the redox reactions and the catalytic activity change of the Fe‐doped CuO sensing materials. The selective and reversible detection of H 2 S using the Fe‐doped CuO sensor suggested in this work opens a new possibility for halitosis self‐monitoring.