Comparative DFT dual gas adsorption model of ZnO and Ag/ZnO with experimental applications as gas detection at ppb level.

By experimental and density functional theory (DFT) calculations, the toxic gases (O3 and NO2) sensing capability and mechanism of ZnO NRs and Ag/ZnO NRs have been comparatively studied in this work. The arrays of Ag NPs were employed as a templet for the growth of ZnO NRs. The experimental results show the response and adsorption rate towards the gases obviously change after adding Ag NPs in ZnO. From the TDOS plot, it has been observed that the HOMO-LUMO gap changes after interaction with different oxidizing gases similarly the peak intensity also decreases which confirms the electron has been transferred from ZnO to NO2 and O3. The response towards the gases decreases and the adsorption reaction rate has been calculated by the Eyring-Polanyi equation and found to be increased after adding Ag in the ZnO NRs which is very similar to our experimental data. We also find that the absorption coefficient is different for O3 and NO2. The mechanism of the gas sensor was explored. Finally, the findings of the response experiment and theoretical calculation were compared and found to be in good agreement.