Synthesis and characterization of Ca-based layered double hydroxides as solid sorbents for carbon capture

The development of new sorbents for carbon capture that are (i) widely available, (ii) low cost, and (iii) require less energy for rejuvenation compared with current sorbent technologies is an area of significant interest to industries with point-source CO₂ emissions and those pursuing direct air capture (DAC). Here, we synthesized high purity Ca-based layered double hydroxides (LDHs) and performed a preliminary evaluation of their low-temperature carbon capture potential at high relative humidity (85 %). In particular, CaFe- and CaAl-LDHs with chloride as the interlayer anion were obtained through addition of a trivalent cation (Fe³⁺ or Al³⁺) to a Ca(OH)2 suspension in an inert environment. Characterization of the reaction products was carried out using scanning electron microscopy (SEM), powder X-ray diffraction (XRD) and attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy, where preliminary results showed successful synthesis of high-purity Ca-based LDHs. The synthesized samples were carbonated at 30 °C for 1 hr in a controlled environment with 85 % RH and 1 % CO₂. The carbonated samples were characterized using XRD and ATR-FTIR analysis, and subsequently subjected to thermal decomposition via TGA where the evolved gases were studied concurrently using FTIR analysis. Our results show that the chemical tailoring of Ca(OH)₂ may not only reduce its regeneration energy but also lead to an improved adsorption capacity.