Enhancement of H2S sensing performance of rGO decorated CuO thin films: Experimental and DFT Studies.

We demonstrate a highly selective and sensitive CuO thin film-based low concentration H2S sensor. The sensitivity was improved around three times by decorating with reduced graphene oxide (rGO) nanosheets. CuO thin films were deposited by Chemical Vapor Deposition followed by inter-digital electrodes fabrication by thermal evaporations system. Crystal structure of CuO was confirmed by X-ray diffraction. The sensing response of pristine CuO was found around 54% at 100 °C and 100 ppm of H2S. In contrast, the sensing response was enhanced to 167% by decorating with rGO of 1.5 mg/ml concentration solution. The sensing was improved due to the formation of heterojunctions between the rGO and CuO. The developed sensor was examined under various gas environments and found to be highly selective towards H2S gas. The improvement in sensing response have been attributed to increased hole concentration in CuO in the presence of rGO due to the Fermi level alignment and an increase absorption of H2S molecules at the rGO/CuO heterojunction. Further, electronic structure calculations show the physisorption behavior of H2S molecule on the different adsorption sites. The detailed insight of gas sensing mechanism is discussed based on experimental results and electronic structure calculations.