Time-Dependent Surface Structure Evolution of NiMo Films Electrodeposited Under Super Gravity Field as Electrocatalyst for Hydrogen Evolution Reaction

Abstract

The surface structures of the electrodeposited NiMo films from compact to porous structure are adjusted by the combination of gravity acceleration and electrodeposition time. The evolution mechanism of surface structure is discussed based on the protrusion growth theory. The dependence of catalytic activity of the NiMo films for hydrogen evolution reaction (HER) on surface structure evolution is studied. The results indicate that compact NiMo layer is first electrodeposited, and then protrusions are formed. Finally, the protrusions rapidly grow and form a porous structure. It is found that only the compact NiMo films are electrodeposited under normal gravity condition due to a long induced time for the protrusions formation. Under super gravity field, the induced time for the protrusions formation is only less than 5 min owing to the enhanced mass transfer by the gravity-induced convection and hydrogen bubble agitation convection. So, a porous structure is easily formed under high gravity acceleration and...