Controlled Synthesis of Hierarchical Nanostructured Metal Ferrite Microspheres for Enhanced Electrocatalytic Oxygen Evolution Reaction

Ferrite MFe2O4 (M = Ni, Co, etc.) metal oxides have been the focus of intense research, studied as promising electrocatalysts due to their good catalytic activity and stability for oxygen evolution reaction (OER). Structure engineering is a significant solution to achieve a high catalytic performance; further, optimizing the structure and specific surface area (SSA) of metal ferrite (CoFe2O4 and NiFe2O4) is regarded as a good choice. Herein, we designed hierarchical porous nanostructured CoFe2O4 and NiFe2O4 microspheres with the assistance of sodium dodecyl sulfonate by solvothermal and annealing methods. We found that three-dimensional microspheres assembled by nanoparticles and porous nanosheets exhibit higher SSAs for NiFe2O4 (158.47 m2 g–1) and CoFe2O4 (144.52 m2 g–1). Their higher SSA is much higher than those of other CoFe2O4-based and NiFe2O4-based materials. The as-prepared metal ferrite microspheres exhibit excellent OER electrocatalytic activity with lower Tafel slopes (55.2 and 58.2 mV dec–1) and lower overpotentials (235 and 280 mV) at a constant current density of 10 mA cm–2 and long-term stability, which is better than that of NiFe2O4 and CoFe2O4 bulks. This method for preparing a large SSA is expected to be applied in other spinel metal oxides.