January 6, 2026 Dataset Open Access

Data publication: Catalytic Activity of Cobalt Ferrites in Water Oxidation Reactions and Its Defect Dependency

Rabe, Anna; Elsherif, Ahmed Gamal Attallah; Eggert, Benedikt; Hirschmann, Eric; Salamon, Soma; Landers, Joachim; Kämmerer, Lea; Cosanne, Nicolas; Koul, Adarsh; Budiyanto, Eko; Schuhmann, Wolfgang; Behrens, Malte; Wende, Heiko

CoFe2O4 (CFO) nanoparticles were synthesized via controlled co-precipitation with subsequent calcination at 400 °C, 500 °C, and 600 °C to systematically investigate the influence of thermal treatment on mesostructure, catalytic performance, and especially defect landscape. Structural characterization revealed enhanced crystallinity, sintering, and reduced defect concentration with increasing calcination temperature. Mössbauer spectroscopy and magnetometry indicated increased inversion parameters, improved magnetic alignment, and reduced spin canting, which is consistent with enhanced atomic diffusion during calcination and structural ordering. Positron annihilation lifetime spectroscopy confirmed a calcination-dependent decrease in vacancy-type defects. Catalytic testing showed diverging trends: chemical water oxidation (CAN test) activity increased with calcination temperature, but electrochemical oxygen evolution (OER) activity decreased. The opposing behavior is attributed to distinct differences in mechanism: CAN test reactivity is dominated by surface site availability, whereas OER benefits from defect mediated conductivity and charge-transfer. These results underline the pivotal role of defect engineering while tailing spinel catalysts and highlight that optimal mesostructures depend strongly on the target reaction