Heterogeneous S-NiFe2O4@NiSe2 nanospheres for the oxygen evolution reaction with long-term stability†

Electrochemical water-splitting is a potential “green” approach to produce a large amount of hydrogen. However, its half reaction, the oxygen evolution reaction (OER), suffers sluggish dynamics and huge overpotential. This encumbers the energy conversion efficiency from electric energy to hydrogen energy, resulting in cost increases. Besides, rare metal catalysts such as RuO₂ and IrO₂ have high OER catalytic activity but they are low in reserve and expensive. Hence, exploration of highly efficient, stable and cheap transition metal-based electrocatalysts to speed up the OER rate is a rational approach. Herein, S-doped NiFe₂O₄@NiSe₂ nanospheres supported on nickel foam were synthesized through a simple one-pot hydrothermal method. Thanks to the unique structure, large surface area, numerous active sites, incorporation of S-anion atoms and synergistic effect between different components, S-doped NiFe₂O₄@NiSe₂ nanospheres showed extraordinarily efficient electrocatalytic activity towards the OER in alkaline medium. When the current density was 10 mA cm⁻², the OER overpotential was 190 mV. Meanwhile, it exhibited excellent long-term stability and was maintained at 10 mA cm⁻² for ≥94 h in a chronopotentiometry test.