Effect of Ce_0.9Gd_0.1O_1.95 as a promoter upon the oxygen transfer properties of MgMnO_3-δ-Ce_0.9Gd_0.1O_1.95 composite oxygen carrier materials for chemical looping combustion

Chemical looping combustion (CLC) is a promising carbon capture and storage (CCS) technology whose efficiency and cost primarily relies on the oxygen carrier materials used. In this paper, gadolinium-doped ceria (GDC, Ce_0.9Gd_0.1O_1.95) was added as a promoter to improve the oxygen transfer rate of MgMnO_3-δoxygen carrier materials. Increasing GDC content significantly increased the oxygen transfer rate of MgMnO_3-δ-GDC composites for the reduction reaction due to an increase in the surface adsorption of CH₄via oxygen vacancies formed on the surface of the GDC. On the other hand, the oxygen transfer rate for the oxidation reaction decreased linearly with increasing GDC content due to the oxygen storage ability of GDC. Adsorbed oxygen molecules preferentially insert themselves into oxygen vacancies of the GDC lattice rather than reacting with (Mg,Mn)O to form MgMnO= during the oxidation reaction.