H2S Sensing Properties of Macroporous In2O3-Based Sensors

Improvement of H2S sensing properties of In2O3-based sensors has been attempted by optimizing their microstructure and compositions. Macroporous (mp-) In2O3 films with well-developed spherical macropores were fabricated by a modified sol-gel technique employing polymethylmethacrylate (PMMA) microspheres with a diameter of 400 nm or 800 nm as a template, and one of three kinds of oxides (cobalt, nickel and iron oxides) was mixed with In2O3 frameworks of the mp-films. The introduction of macropores to the In2O3 films was effective in improving the response to H2S only at 200 degrees C. The addition of cobalt oxide to mp-In2O3 improved the sensor response to H2S drastically, while it resulted in terribly slow response and recovery speeds. On the other hand, the addition of iron or nickel oxide achieved a fast response speed with a relatively large response to H2S. As a result of optimization of the additive amount of iron oxide to In2O3, mp-In2O3 mixed with 6 mol% FeO1.5 (3 mol% as Fe2O3) was the most promising sensor material to detect H2S in air.