Cu₂S Nanorods Decorated with NiFe-Layered Double Hydroxide Nanosheets as Bifunctional Electrocatalysts for Hydrogen Evolution in Alkaline Saline Water/Seawater

The progress of highly efficient and stable nonprecious metallic-based electrocatalysts for the hydrogen evolution reaction (HER) in saline water/seawater is of great importance for the mass-scale production of hydrogen energy. Herein, a nanostructured NiFe-LDH/Cu 2 S heterostructure is constructed by growing NiFe-LDH nanosheets onto Cu 2 S nanorods. This heterostructure possesses exceptional HER performances with η 10 = 36 mV (η 10 indicates the overpotential at a current density of 10 mA cm 2 ) and worked stably over 100 h in alkaline saline water. Moreover, the heterojunction catalyst acts as a bifunctional electrocatalyst for the anode and cathode, achieving a cell voltage of η 10 = 1.463 V, which is superior to many reported electrocatalysts. The improvement of catalytic performance of NiFe-LDH/Cu 2 S can be ascribed to the charge redistribution on the heterointerface that accelerates the dissociation process caused by the formation of Ni with low electron cloud density. Moreover, the obtained covalent S–O bonds are beneficial to the adsorption of H*. In addition, NiFe-LDH/Cu 2 S also exhibits considerable catalytic performances in seawater electrolytes, delivering a cell voltage of η 10 = 1.483 V with a stability of 27 h. We present a promising bifunctional electrocatalyst for water electrolysis in alkaline saline water/seawater which may find wide applications in the area of hydrogen energy.