CO2 Sorption-Desorption and Physical Properties of BaCO3/CuO Composites

Abstract

A simple wet chemical route for the synthesis of barium carbonate (BaCO3) has been followed by the use of atmospheric carbon dioxide (CO2) as a carbon source while copper oxide (CuO) has been synthesized via precipitation method. Phase analysis, purity and crystallite size have been confirmed by X-ray powder diffraction (XRPD) which indicated that all the samples are in single phase with crystallite size; BaCO3 = 52.4, CuO = 86.5 nm. Field emission scanning electron microscopy (FESEM) helped in determining morphology of samples, both BaCO3 and CuO showed spherical geometry with average particle size; BaCO3 = 200, CuO = 150 nm. Energy dispersive X-ray spectroscopy (EDX) confirmed the presence of required elements in the samples. Fourier transform infrared (FTIR) confirmed the bonding between CO2 and barium sample by appearance of a vibration band near 1410 cm-1 which is due to the reaction with the surface oxygen atoms while thermogravimetric analysis (TGA) was verified the absorption of CO2 along with the degradation temperature of BaCO3 (~1400 °C). TGA results proved that sample can successfully absorb CO2 till 1100 °C and absorbance reduces at high temperatures. BaCO3 was further allowed to undergo cyclic heat treatment which showed that after 3 cycles the sample withholds CO2 due to formation of BaO-liquid-BaCO3 equilibria that arrests the further loss of CO2. The effect of CuO on the carbonation and decarbonation of BaCO3 was also studied and it was found that CuO reacts with BaO forming BaCuO2 that does not allow the complete re-absorbance of CO2. The content of CuO controls optical and dielectric properties in BaCO3/CuO composites. The band gap decreases systematically from 3.09 eV to 1.52 eV due to increased CuO contents in the composites, whereas, dielectric behavior of the composites does not show a systematic trend due to inhomogeneities (porosity, grains, defects) in the structures which are more pronounced at high frequencies. High dielectric values (104 to 105) of the composites at low frequency (100 Hz) have been observed with low value of tangent loss. AC conductivity showed unique variation with frequency which has been explained by translational reorientational hopping.