Enhancement of the CO Sensing/Capture through High Cationic Charge in M-ZrO (Li, Mg, or Co): Experimental and Theoretical Studies.

The capture and storage of CO are of growing interest in atmospheric science since greenhouse gas emission has to be reduced considerably in the near future. The present paper deals with the doping of cations on ZrO, i.e., M-ZrO (M = Li, Mg, or Co), defecting the crystalline planes for the adsorption of carbon dioxide. The samples were prepared by the sol-gel method and characterized completely by different analytical methods. The deposition of metal ions on ZrO (whose crystalline phases: monoclinic and tetragonal are transformed into a single-phase such as tetragonal for LiZrO and cubic for MgZrO or CoZrO) shows a complete disappearance of the XRD monoclinic signal, and it is consistent with HRTEM lattice fringes: 2.957 nm for ZrO (101, tetragonal/monoclinic), 3.018 nm for tetragonal LiZrO, 2.940 nm for cubic MgZrO, and 1.526 nm for cubic CoZrO. The samples are thermally stable, resulting an average size of ∼5.0-15 nm. The surface of LiZrO creates the oxygen deficiency, while for Mg (0.089 nm), since the size of the atom is relatively greater than that of Zr (0.084 nm), the replacement of Zr by Mg in sublattice is difficult; thus, a decrease of the lattice constant was noticed. Since the high band gap energy (Δ > 5.0 eV) is suitable for CO adsorption, the samples were employed for the selective detection/capture of CO by using electrochemical impedance spectroscopy (EIS) and direct current resistance (DCR), showing that CoZrO is capable of CO capture about 75%. If M ions are deposited within the ZrO matrix, then the charge imbalance allows CO to interact with the oxygen species to form CO which produces a high resistance (21.04 × 10 (Ω, Ohm)). The adsorption of CO with the samples was also theoretically studied showing that the interaction of CO with MgZrO and CoZrO is more feasible than with LiZrO, subscribing to the experimental data. The temperature effect (273 to 573 K) for the interaction of CO with CoZrO was also studied by the docking method and observed the cubic structure is more stable at high temperatures as compared to the monoclinic geometry. Thus, CO would preferably interact with ZrO ( = -19.29 kJ/mol) than for ZrO (22.4 J/mmol (ZrO = cubic; ZrO = monoclinic).