Bimetallic Multi-Level Layered Co-NiOOH/Ni₃ S₂ @NF Nanosheet for Hydrogen Evolution Reaction in Alkaline Medium

Development of efficient non-noble metal catalysts for water splitting is of great significance but challenging due to the sluggish kinetics of the hydrogen evolution reaction (HER) in alkaline medium. Herein, a bimetallic multi-level layered catalytic electrode composed of Ni₃ S₂ nanosheets with secondary Co-NiOOH layer of 3D porous and free-standing cathode in alkaline medium is reported. This integrated synergistic catalytic electrode exhibits excellent HER electrocatalytic performance. The resultant Ni_0.67 Co_0.33 /Ni₃ S₂ @NF electrode displays the highest HER activity with only overpotentials of 87 and 203 mV to afford current densities of 10 and 100 mA·cm^-2 , respectively, and its Tafel slope is 80 mV·dec^-1 . The chronopotentiometry operated at high current density of 50 mA·cm^-2 shows negligible deterioration, indicating better stability of Ni_0.67 Co_0.33 /Ni₃ S₂ @NF electrode than Pt/C (20 wt.%). Such a desirable catalytic performance is attributed to the modification of physical and electronic structure that exposes abundant active sites and improves the intrinsic catalytic activity toward HER, which is also confirmed by electrochemically active surface area and X-ray photoelectron spectroscopy analysis. This work provides a strong support for the rational design of high-performance bimetallic electrodes for industrial water splitting.