O-vacancy Mediated Partially Inverted Ferrospinels for Enhanced Activity in the Sulfuric Acid Decomposition for Hydrogen Production

Understanding tailored CO3O4 spinel with Fe3+ doping is challenging due to the surface state characterization of bifunctional catalysts with higher cation diversity. Doping the secondary metal creates a double spinel structure (a hybrid of normal and inverted spinels), enhancing catalytic properties by generating more active oxygen vacancies. Cobalt-rich (FeCo2O4) hybrid spinel and iron-rich (CoFe2O4) inverted spinel are synthesized using a wet impregnation method, supported over oxidized SiC (pretreated SiC) for improved metal-support interaction. FeCo2O4 on pretreated SiC exhibits the highest catalytic activity (90% conversion at 1173 K) and stability (over 100 h) in the sulfuric acid decomposition of the iodine-sulfur (IS) process for hydrogen production. This improved performance is attributed to the high electronegativity of Co3+, oxygen vacancies, and strong metal-support interaction. The high electronegativity of Co3+ weakens the S-O bond in M-S-O, enhancing the catalytic activity of the spinels. These results are further corroborated by detailed characterization and density functional theory calculations.