Two-dimensional delafossite cobalt oxyhydroxide as a toxic gas sensor

To the chain of development of 2D materials, recently synthesized ultrathin cobalt oxy-hydroxide (CoOOH) nano sheets gain potential interest due to its structural, electronic and other properties. We have studied the interaction mechanism of two toxic gases hydrogen peroxide (H₂O₂) and ammonia (NH₃) adsorbed over 2D CoOOH to understand the role of 2D CoOOH as a toxic gas sensor. We employ first principles based dispersion corrected density functional calculations to study the sensing behavior of 2D CoOOH towards H₂O₂ and NH₃ by calculating adsorption energy, electronic band structure, density of states (DOS) and work function. The electronic band structure, DOS and work function of 2D CoOOH are modulated after adsorption of H₂O₂ and NH₃ molecules. Adsorption of gas molecules confirms the sensing behavior of 2D CoOOH towards these molecules and depicts its use in a sensing device. The full phonon dispersion curves and phonon density of states reveal the dynamical stability of 2D CoOOH. The calculated adsorption energy of H₂O₂ and NH₃ molecules is −0.532 and −0.460 eV respectively which indicates the strong physisorption of these gases over 2D CoOOH. The ultrafast recovery time of 1239 and 1203 ns respectively were found for H₂O₂ and NH₃ on 2D CoOOH. The work function which is 6.29 eV found for 2D CoOOH, decreases to 5.63 eV for H₂O₂ as it follows the reduction process on 2D CoOOH, and increases to 6.44 eV for NH₃ molecules as it acts as oxidation gas on CoOOH. Our study reveals that the 2D CoOOH can be a better sensor for the H₂O₂ and NH₃ gases than some traditional two-dimensional materials.