In this scenario, transition metal oxides based on perovskites, pyrochlores, and spinels have been considered as promising candidates for the oxygen reduction/evolution activity, thanks to their structural robustness, cost, accessibility and stable performances in aqueous alkaline electrolytes. Among these different structures , spinel based oxides pose superior ORER performance, due to their mixed valence states and 2+ valence ion in 6 fold coordination4. Spinels (AB2O4) with earth abundant 3d transition metals (Fe, Co, Ni, Cu, and Mn) are considered to be alternative to the noble metals. By altering the B site ion or using different A and B combinations, surface redox sites and metal–oxygen bonds, subsequently leads to superior performance. Spinel catalyst performance greatly depends on composition, shape, size, and structure5. Ni and Fe based materials are attractive due to their abundance and performance 6.
In this work, we synthesized spinel NiFe2O4 through the modified co-precipitation method and the resulting samples were heat treated showing different particle sizes. The various sample phases and morphologies were characterized using XRD and TEM. Their structure to electrochemical performance relationship was studied in three electrode electrochemical setup. Their electrochemical ORR activities were characterized by linear sweep voltammetry by RDE in oxygen saturated 0.1 M KOH. Electrode activity was measured using the CV in the potential range of -0.9 to 0.7 V vs Hg/HgO and stable performances by chronoamperometry. Particle sizes to electrochemical activity of the catalysts were systematically investigated.
This work is funded by the Swedish Energy Agency.
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