Surface Modification of a NiS2 Nanoarray with Ni(OH)2 toward Superior Water Reduction Electrocatalysis in Alkaline Media

Interface engineering has been demonstrated to be effective in promoting hydrogen evolution reaction (HER) in an alkaline solution. Herein, we report that the HER activity of a NiS2 nanoarray on a titanium mesh (NiS2/TM) in alkaline media is greatly boosted by the electrodeposition of Ni(OH)2 onto NiS2 [Ni(OH)2-NiS2/TM]. Ni(OH)2-NiS2/TM only needs an overpotential of 90 mV to deliver 10 mA cm-2 in 1.0 M KOH. Density functional theory calculations confirm that Ni(OH)2-NiS2 has a lower water dissociation free energy and a more optimal hydrogen adsorption free energy than NiS2.