Synthesis and characterization of sodium hafnium oxide (Na₂HfO₃) and its high-temperature CO₂ sorption properties

Abstract

The CO2 sorption properties of sodium hafnium oxide (Na2HfO3) were investigated in this study. Na2HfO3 was synthesized by solid-state synthesis using Na2CO3 and HfO2 as starting materials. The solid-state synthesized...

Deciphering the existence of hexagonal sodium zirconate CO2 sorbent

“…After reaching a consistently stable CO2 capture capacity (i.e. 20 cycles), the CO2 capture capacities of both NZO-M and NZO-H were comparable at 3.84 and 4.06 mmol g −1 (16.90 and 17.87 wt.%), respectively (note that small difference in the CO2 uptake was also related to synthesis batch variations, which was previously discussed18 ) These observations could be explained as follows: Directly after synthesis, different degree of the Na + and O 2− site occupancies were applicable to NZO-M and NZO-H, with NZO-H having a lower Na + and O 2− site occupancy than NZO-M. Consequently, NZO-M had more Na + and O 2− available to react with CO2 to form Na2CO3 than NZO-H, 2) after the first cycle, the Na + and O 2− site occupancies of https://doi.org/10.26434/chemrxiv-2023-4c69m ORCID: https://orcid.org/0000-0002-4072-4324 Content not peer-reviewed by ChemRxiv. License: CC BY-NC-ND 4.0…”

“…Previous studies have reported the presence of stacking faults in similar mixed-metal oxides, such as Na2HfO3 and Li2MnO3. [16][17][18]22 Indeed, the streaks seen in the 3D ED data of NZO-M and NZO-H (Figure 2d) points to a disorder with the stacking of the Na + + Zr 4+ layers.…”

“…; B 4+ = Mn 4+ , Ti 4+ , etc.). [16][17][18][19] In the Na + + Zr 4+ mixed-metal layers, the Na + and Zr 4+ cations form a hexagonal arrangement to minimise the Coulombic repulsion between the cations (Figure 3a and b). 20 This ordered arrangement gives rise to superstructure reflections in the 3D ED and PXRD patterns that cannot be indexed by the hexagonal R-3m space group symmetry.…”

Rethinking the existence of hexagonal sodium zirconate CO2 sorbent

“…Previous studies have reported the presence of stacking faults in similar mixedmetal oxides, such as Na 2 HfO 3 and Li 2 MnO 3 . [22][23][24]28 Indeed, the streaks seen in the 3D ED data of NZO-M and NZO-H (Fig. 2d) point to disorder in the stacking of the Na + + Zr 4+ layers.…”

“…; B 4+ = Mn 4+ , Ti 4+ , etc.). [22][23][24][25] In the Na + + Zr 4+ mixedmetal layers, the Na + and Zr 4+ cations form a hexagonal arrangement to minimize the coulombic repulsion between the cations (Fig. 3a and b).…”