Structural and thermochemical chemisorption of CO ₂ on Li _4+x(Si _1-xAl _x)O ₄ and Li _4-x(Si _1-xV _x)O ₄ solid solutions

Different Li ₄SiO ₄ solid solutions containing aluminum (Li _4+x(Si _1-xAl _x)O ₄) or vanadium (Li _4-x(Si _1-xV _x)O ₄) were prepared by solid state reactions. Samples were characterized by X-ray diffraction and solid state nuclear magnetic resonance. Then, samples were tested as CO ₂ captors. Characterization results show that both, aluminum and vanadium ions, occupy silicon sites into the Li ₄SiO ₄ lattice. Thus, the dissolution of aluminum is compensated by Li ¹⁺ interstitials, while the dissolution of vanadium leads to lithium vacancies formation. Finally, the CO ₂ capture evaluation shows that the aluminum presence into the Li ₄SiO ₄ structure highly improves the CO ₂ chemisorption, and on the contrary, vanadium addition inhibits it. The differences observed between the CO ₂ chemisorption processes are mainly correlated to the different lithium secondary phases produced in each case and their corresponding diffusion properties.