In this regard, Banerjee and co-workers synthesized the AFe2O4 (A=Cu, Ni, Co) spinels using the glycine-nitrate gel combustion method . Among these, CuFe2O4 was found to be a better catalyst, achieving 78% conversion at 1073 K. This high activity of CuFe2O4 is due to the high electronegativity of the Cu 2+ ion relative to Fe 2+ and Ni 2+ , which weakens the S-O bond in mixed metal oxides. As a result, CuFe2O4 has a low possibility of sulfation than other metal oxides. The estimated activation energies for CoFe2O4, CuFe2O4, and NiFe2O4 were 168.23, 116.91, and 229.16 kJ/mol, respectively. The same research group also explored chromium-based metal oxide ( Fe !(#$%) Cr !% O ' ) and found that maximum SO2 yield was achieved at 1073 K, with no indication of deactivation . In the SO3 decomposition step, SO3 interacts at the anchor site available on these metal surfaces and forms metal sulfates. These metal sulfates subsequently decompose into SO2 and oxygen through the dissociation of S-O bonds, making the thermal stability of metal sulfates crucial . The less thermally stable a sulfate is, the more susceptible it becomes to the dissociation of S-O bonds. The thermal stability of the S-O bond in the M-O-S linkage of the metal sulfate depends on the electronegativity of metal M and, as a result, on the polarization of the S-O bond. High electronegativity of metal M leads to weaker S-O bond strength and vice-versa. The electronegativity of ferrospinels follows the order of Fe 3+ >> Cu 2+ > Ni 2+ > Co 2+ . Therefore, the activity and activation energy of the three ferrospinels AFe2O4 (A=Cu, Ni, Co) are found to be in the order of CuFe2O4 > NiFe2O4 > CoFe2O4 . However, Co 3+ has a higher electronegativity than Fe 3+ and Cu 2+ 43 , and hence Co2FeO4 ferrospinels can be potential active catalysts in the thermochemical oxygen evolving high-temperature sulfuric acid decomposition reaction.