Cactus-like NiCo2S4@NiFe LDH hollow spheres as an effective oxygen bifunctional electrocatalyst in alkaline solution.

• A novel cactus-like NiCo 2 S 4 @NiFe LDH hollow sphere has been developed. • The strong electronic interactions of heterointerface greatly enhance the electronic transfer. • The outer NiFe LDH is capable of protecting inner NiCo 2 S 4 to reduce its corrosion. • The NiCo 2 S 4 @NiFe LDH achieves a small potential gap of only 0.667 V in 0.1 M KOH. The high-performance non-precious electrocatalysts for both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are crucial to the practical application of fuel cells and metal-air batteries. Herein, a novel cactus-like NiCo 2 S 4 @NiFe LDH hollow sphere assembled by one-dimensional (1D) NiFe LDH nanowires and two-dimensional (2D) NiFe LDH nanosheets on the NiCo 2 S 4 hollow spheres is prepared by a facile hydrothermal method. The outer NiFe LDH nanowires and NiFe LDH nanosheets can effectively suppress the collapse and corrosion of inner NiCo 2 S 4 hollow structure during long-term stability tests. The integration of the effective OER electrocatalyst NiFe LDH into NiCo 2 S 4 to form heterostructures, as well as the strong electronic interaction between NiCo 2 S 4 and NiFe LDH, can greatly boost both ORR and OER activities. Due to the above merits, the NiCo 2 S 4 @NiFe LDH achieves remarkably a small potential gap (ΔE = Ej=10-E 1/2) of only 0.667 V. This work offers a facile strategy to design efficient catalysts with heterostructures. [ABSTRACT FROM AUTHOR]