Enhanced activity of Mg-Fe-O ferrites for two-step thermochemical CO2 splitting

• Published in: Journal of CO2 utilization 2018-07, Vol.26, p.544-551
• Main Authors: Huang, Jincheng, Fu, Yu, Li, Shenggang, Kong, Wenbo, Zhang, Jun, Sun, Yuhan
• Format: Article
• Language: English
• Subjects: CO production; CO2 splitting; Internal reaction; Mg-Fe-O ferrites; Self-regeneration
• ISSN: 2212-9820; 2212-9839
• DOI: 10.1016/j.jcou.2018.06.014

•Mg-Fe-O ferrites with different mole fraction were used for two-step thermochemical CO2 splitting.•The self-regenerative property associated with sintering-resistance was conformed for the Mg-Fe-O ferrites.•The bulk redox species were involved into the redox reaction driven by the internal reaction.•The self-regenerative FM-0.2 with internal reaction yields 2.2 times more CO than FM-0.5.•A kinetic analysis corresponding to the bulk cation diffusion was established. Fe-based ferrites have been investigated as the most promising and active redox materials for two-step thermochemical CO2 splitting. Reactions are conducted in a two-step cycle, in which the ferrites are generally reduced at 1400 °C in an inert atmosphere, then the reduced ferrites are re-oxidized by reacting with CO2 at 1000 °C to produce CO. In this work, Mg-Fe-O ferrites (designated as FM-x, x denotes as the mole fraction of Fe2O3 to MgO + Fe2O3) were screened for activity in two-step thermochemical CO2 splitting. Ferrites were characterized by differential scanning calorimetry (DSC), X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman and Mössbauer spectroscopies. The self-regenerative function and internal reaction, which are responsible for the initial higher CO production rate and a greater utilization of the bulk ferrites, respectively, were confirmed for Mg-Fe-O ferrites. Consequently, the self-regenerative FM-0.2 with internal reaction possesses a 2.2 times higher CO yield as compared with that of FM-0.5. Kinetic analysis was conducted in consideration of various solid state reaction models, and bulk diffusion, which is an indication of internal reaction, was found to be the crucial factor for the accessibility of the bulk redox species.