Enhancement of the CO2 Sensing/Capture through High Cationic Charge in M-ZrO2 (Li+, Mg2+, or Co3+): Experimental and Theoretical Studies
Academic Article in Scopus
The capture and storage of CO2 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 ZrO2, i.e., M-ZrO2 (M = Li+, Mg2+, or Co3+), 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 ZrO2 (whose crystalline phases: monoclinic and tetragonal are transformed into a single-phase such as tetragonal for LiZrO2 and cubic for MgZrO2 or CoZrO2) shows a complete disappearance of the XRD monoclinic signal, and it is consistent with HRTEM lattice fringes: 2.957 nm for ZrO2 (101, tetragonal/monoclinic), 3.018 nm for tetragonal LiZrO2, 2.940 nm for cubic MgZrO2, and 1.526 nm for cubic CoZrO2. The samples are thermally stable, resulting an average size of ~5.0-15 nm. The surface of LiZrO2 creates the oxygen deficiency, while for Mg2+ (0.089 nm), since the size of the atom is relatively greater than that of Zr4+ (0.084 nm), the replacement of Zr4+ by Mg2+ in sublattice is difficult; thus, a decrease of the lattice constant was noticed. Since the high band gap energy (¿E > 5.0 eV) is suitable for CO2 adsorption, the samples were employed for the selective detection/capture of CO2 by using electrochemical impedance spectroscopy (EIS) and direct current resistance (DCR), showing that CoZrO2 is capable of CO2 capture about 75%. If M+ ions are deposited within the ZrO2 matrix, then the charge imbalance allows CO2 to interact with the oxygen species to form CO32- which produces a high resistance (21.04 × 106 (¿, Ohm)). The adsorption of CO2 with the samples was also theoretically studied showing that the interaction of CO2 with MgZrO2 and CoZrO2 is more feasible than with LiZrO2, subscribing to the experimental data. The temperature effect (273 to 573 K) for the interaction of CO2 with CoZrO2 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, CO2 would preferably interact with ZrO2c (ERS = ¿19.29 kJ/mol) than for ZrO2m (22.4 J/mmol (ZrO2c = cubic; ZrO2m = monoclinic).
