Electrodeposition of graded Ni-S film for hydrogen evolution reaction

Electrodeposited Ni-S films provide excellent catalytic properties for hydrogen evolution. In contradiction to this, the wider application is still blocked by their weak mechanical and electrochemical stability. The present work aims to study the formation of electrodeposited Ni-S graded film with varying sulfur content of the individual layers. The possibility of preparing Ni-S graded film by sequential changing the deposition current density is discussed. The prepared graded film consists of three layers: S-low layer, S-medium layer and S-high layer. The graded film is uniform and the compatibility between the three layers is good. The electrochemical analysis shows that the Ni-S graded film generates a higher catalytic activity for the hydrogen evolution reaction in comparison with non-graded Ni-S films. And the graded film shows a higher electrochemical stability without appearing any cracks during a long-term electrolysis test. (C) 2017 Elsevier B.V. All rights reserved.