Recent progress on NiFe2O4 spinels as electrocatalysts for the oxygen evolution reaction

As the main energy supply of human social activities, fossil fuels have caused serious pollution to the global environment, so it is extremely urgent to find new green renewable energy. Hydrogen has entered people's field of vision because of its high energy density, no carbon emission, easy storage, transportation, etc. However, the current industrial hydrogen production can still be realized by using fossil fuels, which cannot effectively solve the global pollution problem. Hydrogen production by electrocatalytic water splitting is green and has no byproducts, but its development is inhibited by thermodynamic and kinetic obstacles. Therefore, developing a reasonable electrocatalyst to reduce the reaction energy barrier is a difficult problem that must be overcome. Noble metals Ir, Ru, and their oxides have good performance when used as electrocatalysts, but they cannot be used on a large scale due to the cost and content of materials. Transition metals and their oxides, especially spinel materials, also have good performance as electrocatalysts. As a typical inverse spinel, NiFe2O4 is considered a promising OER electrocatalyst because of its high storage, low price, high stability, corrosion resistance, and environmental friendliness. In this paper, the achievements of NiFe2O4 used as electrocatalysts in recent years are reviewed. The evaluation parameters and reaction mechanism of OER were introduced firstly, then the physical and chemical properties, electronic structure, and synthesis methods of NiFe2O4 were introduced, and various modification strategies for improving the OER efficiency of NiFe2O4 in recent years were classified and analyzed emphatically, and the most effective strategies for modifying NiFe2O4 were found out. Then the development prospect of NiFe2O4 electrocatalyst has prospected.