CO₂ Capture by Nickel Hydroxide Interstratified in the Nanolayered Space of a Synthetic Clay Mineral

Abstract

Clay minerals can adsorb large amounts of CO2 and are present in anthropogenic storage sites for CO2. Nanoscale functionalization of smectite clay minerals is essential for developing technologies for carbon sequestration based on these materials and for safe-guarding relevant long-term carbon storage sites. We investigate the adsorption mechanisms of CO2 in dried and hydrated synthetic Ni-exchanged fluorohectorite clayusing a combination of powder X-ray diffraction, Raman spectroscopy, and inelastic neutron scattering. Both dried and hydrated Ni-exchanged fluorohectorite show crystalline swelling and spectroscopic changes in response to CO2 exposure. These changes can be attributed to interactions with [Ni­(OH)0.83(H2O)1.17]0.37 1.17+-interlayer species, and swelling occurs solely in the interlayers where this condensed species is present. The experimental conclusions are supported by density functional theory simulations. This work demonstrates a hitherto overlooked important mechanism, where a hydrogenous species present in the nanospace of a clay mineral creates sorption sites for CO2.

CO2 Adsorption Enhanced by Tuning the Layer Charge in a Clay Mineral

“…As no ordered superstructure is observed for Ni-Hec 0.3 after C16 exchange, these results represent the (001) Bragg reflection of a random interstratification ( Figure 1 ), while for Ni-Hec 0.5 and Ni-Hec 0.7 , it corresponds to the (002) reflection of an ordered interstratification ( Figures 2 and 3 ). Similar to what was observed for Ni-Hec 0.5 by Hunvik et al, 14 with an increasing pressure of CO 2 the Bragg reflection moves to lower q values as a result of the swelling process. Swelling is an inherent one-dimensional process, in which the Bragg reflections gradually move as the number of swollen interlayers increases and thus the relative contribution of the interstratified stacks becomes larger.…”

“…Compared to the capacity of amine-modified montmorillonite (2.4 mmol/g), 45 our reported capacity is a little lower. However, because both our current and previous 14 investigations indicate that only half of the interlayers are active in the adsorption process, there is a potential to double the capacity if [Ni(OH) 2– x (H 2 O) x ] y x + islands can be condensed in all interlayers.…”

“…The corrected generalized gradient approximation developed by Berland and Hyldgaard 38 was employed to account for the van der Waals interactions. On the basis of the crystallographic structure of our previous work, 14 the layer charges were modified by substituting Mg with Li atoms in the supercell (multiple unit cells). We systematically explored four layer charges (0.25, 0.5, 0.75, and 1.0 pfu), which were chosen to resemble the experimental stoichiometry.…”

“… 14 The CO 2 could be grafted as a bicarbonate to the condensed nickel hydroxide species. 14 To investigate the layer charge dependency in a systematic manner, we have conducted X-ray and neutron diffraction and gravimetric adsorption measurements on dry Ni-Hec prepared with three different layer charges, 0.3, 0.5, and 0.7 pfu. The samples were dried to at least 120 °C to ensure the removal of interlayer water and water coordinated to uncondensed interlayer cations, while preserving the clay layers and the nickel hydroxide in the chlorite-like layers.…”

Controlled sample environment for studying solid–gas interactions by in situ powder X-ray diffraction

“…5(a)] under vacuum and then maintaining the sample at 50 C during the pressure cycle. The details and interpretation of the experimental data are part of a separate study (Hunvik et al, 2020).…”