Toxic Gas Response for Nanostructured Cobalt Oxide Thin Films

Abstract

 The gas sensing properties of undoped Co₃O₄ and doped with Y₂O₃ nanostructures were investigated. The films were synthesized using the hydrothermal method on a seeded layer. The XRD, SEM analysis and gas sensing properties were investigated for the prepared thin films. XRD analysis showed that all films were polycrystalline, of a cubic structure with crystallite size of (12.6) nm for cobalt oxide and (12.3) nm for the Co₃O₄:6% Y₂O₃. The SEM analysis of thin films indicated that all films undoped Co₃O₄ and doped possessed a nanosphere-like structure.

The sensitivity, response time and recovery time to H₂S reducing and NO₂ oxidizing gases were tested at different operating temperatures. The resistance changed with exposure to the test gas. The results revealed that the Co₃O₄:6%Y₂O₃ possessed the highest sensitivity around 90% (at room temperature) and 62.5% (at 150 ^oC) when exposed to the reducing gas H₂S and oxidizing gas NO₂, respectively with 0.8sec for both recovery and response times.