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 CoFe(2)O4 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 m(2) g(-1)) and CoFe2O4 (144.52 m(2) 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 CoFe(2)O(4 )bulks. This method for preparing a large SSA is expected to be applied in other spinel metal oxides.