Hydrogen production from dry reforming of methane, using CO₂ previously chemisorbed in the Li₆Zn_1-xNi_xO₄ solid...

Li₆ZnO₄ was chemically modified by nickel addition, in order to develop different compositions of the solid solution Li₆Zn_1-xNi_xO₄. These materials were evaluated bifunctionally; analyzing their CO₂ capture performances, as well as on their catalytic properties for H₂ production via dry reforming of methane (DRM). The crystal structures of Li₆Zn_1-xNi_xO₄ solid solution samples were determined through X-ray diffraction, which confirmed the integration of nickel ions up to a concentration around 20 mol%, meanwhile beyond this value, a secondary phase was detected. These results were supported by XPS and TEM analyses. Then, dynamic and isothermal thermogravimetric analyses of CO₂ capture revealed that Li₆Zn_1-xNi_xO₄ solid solution samples exhibited good CO₂ chemisorption efficiencies, similarly to the pristine Li₆ZnO₄ chemisorption trends observed. Moreover, a kinetic analysis of CO₂ isothermal chemisorptions, using the Avrami-Erofeev model, evidenced an increment of the constant rates as a function of the Ni content. Since Ni²⁺ ions incorporation did not reduce the CO₂ capture efficiency and kinetics, the catalytic properties of these materials were evaluated in the DRM process. Results demonstrated that nickel ions favored hydrogen (H₂) production over the pristine Li₆ZnO₄ phase, despite a second H₂ production reaction was determined, methane decomposition. Thereby, Li₆Zn_1-xNi_xO₄ ceramics can be employed as bifunctional materials.