Characterization of mesoporous Zn doped NiCo2O4 rods produced by hydrothermal method for NOx gas sensing application

We report the characterization and NO_x gas sensing properties of Zn doped NiCo₂O₄ mesoporous rods obtained through a simple hydrothermal approach. X-ray powder diffraction confirms the spinel structure with cell parameter (a) of 8.110 Å. X-ray photoelectron spectroscopy studies reveal the oxidation states of metal oxides. N₂-adsorption-desorption analysis and electron microscopic studies show the mesoporous nature of the sample. The specific surface area is found to be 76 m² g⁻¹ with an average pore diameter of 21 nm. The thick film of Zn doped NiCo₂O₄ mesoporous rods exhibit good gas sensing characteristics towards NO_x. Gas response of the sensor increases with concentration of NO_x from 2 ppm to 200 ppm. It has a response time of 28 s and recovery time of 30 s towards 10 ppm NO_x gas at 200 °C. The NO_x gas concentration dependent responses and cyclic tests of the sensor demonstrate better reliability and reproducibility with regards to NO_x gas sensing.