Designing highly efficient 3D porous Ni-Fe sulfide nanosheets based catalyst for the overall water splitting through component regulation.

Constructing efficient and stable bifunctional catalysts is essential to improve the conversion efficiency of overall water splitting (OWS). In this work, 3D porous Ni-Fe sulfide nanosheets supported on nickel foam (Ni-Fe-S/NF) were synthesized by a facile hydrothermal method. The optimized NiS-FeS/NF-2 electrode realized ultra-high efficiency for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). Benefiting from the unique 3D porous nanosheets structure and the strong electronic interactions between NiS and FeS through component regulation, low overpotentials of 253 and 262 mV are required to drive a current density of 100 mA cm for OER and HER, respectively. Importantly, NiS-FeS/NF-2 bifunctional catalyst only needs 1.55 and 1.75 V at 10 and 100 mA cm respectively and works continuously for at least 100 h. The work thus provides an extraordinary promising catalyst for OWS and can be envisioned of potential for large-scale applications.