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

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Understanding the characterization of a tailored Co 3 O 4 spinel with Fe 3+ doping poses a challenge due to the surface state complexity in bifunctional catalysts with higher cation diversity. Doping with secondary metal results in a double spinel structure (a hybrid of normal and inverted spinels). This enhances the catalytic properties by generating more active oxygen vacancies. The cobalt-rich (FeCo 2 O 4 ) hybrid spinel and iron-rich (CoFe 2 O 4 ) inverted spinel are synthesized using a wet impregnation method, supported over oxidized SiC (SiC-Pretrt) for an improved metal–support interaction. FeCo 2 O 4 on pretreated SiC exhibits the highest catalytic activity (90% conversion at 1173 K) and stability (over 100 h) in sulfuric acid decomposition of the iodine–sulfur process for hydrogen production. This improved performance is attributed to the high electronegativity of Co 3+, oxygen vacancies, and strong metal–support interaction. The high electronegativity of Co 3+ 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.