A Flexible Indium Oxide Sensor With Anti-Humidity Property for Room Temperature Detection of Hydrogen Sulfide

In this work, flexible hydrogen sulfide (H ₂ S) sensors were prepared from nanocomposite mixtures of indium oxide (In ₂ O ₃ ), graphite flakes (Gt) and polystyrene (PS). Where In ₂ O ₃ was chosen as the sensing material. Gt flakes were added to adjust the sensor resistance in the range of 300-400 k Ω. Also, PS were added as a modifier to maintain the sensors integrity, adhesiveness and flexibility properties. A nanocomposite mixture of In ₂ O ₃ :10%Gt:17%PS emerged as a promising nanocomposite candidate to develop high performance sensors to detect H ₂ S gas. The flexible sensors were fabricated on top of flexible carbon electrodes that were screen-printed on polyethylene terephthalate (PET) substrate. Herein, we propose a sensitive H ₂ gas sensor to detect 100 ppb at room temperature while being resistant to humidity changes. These improvements have been attributed to additional benefits for the Gt flakes and the PS modifier. Both additives contributed to enhance the surface-to-volume ratio for the sensing thin film leading to a superior sensing performance for the In ₂ O ₃ based sensor. Furthermore, they improved the hydrophobic property for the sensors to develop their resistance to humidity changes. The sensing mechanism for sensors depends mainly on the sulfuration and/or partial sulfuration of In ₂ O ₃ by H ₂ S gas to form In ₂ S ₃ , which is conductive and responsible to decrease the sensor resistance.