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

Abstract 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 NiCo2S4@NiFe LDH hollow sphere assembled by one-dimensional (1D) NiFe LDH nanowires and two-dimensional (2D) NiFe LDH nanosheets on the NiCo2S4 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 NiCo2S4 hollow structure during long-term stability tests. The integration of the effective OER electrocatalyst NiFe LDH into NiCo2S4 to form heterostructures, as well as the strong electronic interaction between NiCo2S4 and NiFe LDH, can greatly boost both ORR and OER activities. Due to the above merits, the NiCo2S4@NiFe LDH achieves remarkably a small potential gap (ΔE = Ej=10-E1/2) of only 0.667 V. This work offers a facile strategy to design efficient catalysts with heterostructures.