Interfaces modulation strategy to synthesize bifunctional electrocatalyst for highly efficient overall water splitting

The synthesis of high efficient bifunctional non-noble metal electrocatalysts for overall water splitting is crucial for sustainable energy conversion. Here, a free-standing and heterointerfaces-rich fluffy rectangular spongy-like core-shell NiS/CoS/CC-3 bifunctional electrocatalyst for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is designed and synthesized by optimizing the thickness of the NiS shell. The electrochemical performance of the NiS/CoS/CC-3 electrocatalyst is investigated in alkaline solutions. Benefiting from the unique rectangular spongy-like structural features, the abundant heterointerfaces between NiS and CoS, as well as the good synergy between its each component, the obtained NiS/CoS/CC-3 catalyst shows outstanding electrocatalytic activities and stability for both HER and OER. The overpotential is 102 mV for HER and 290 mV for OER at 10 mA cm(-2), respectively. Moreover, the two-NiS/CoS/CC-3 as both the cathode and anode catalyst in alkaline solution achieves a current density of 10 mA cm(-2) at a potential of 1.57 V. Meanwhile, the electrolyzer shows outstanding electrochemistry durability with an unchanged current density for 72 h. The results illustrate that the as-prepared heterointerfaces-rich NiS/CoS/CC-3 electrocatalyst can be used as a high-efficiency catalyst for overall water splitting (OWS). This synthetic strategy is also important for other composite materials in a variety of energy-related application fields.