The Dependence and Evolution Mechanism of Surface Structure of Electrodeposited Ni Films on Wettability

Porous metal films directly electrodeposited by using hydrogen bubbles as template have attracted widely attentions. However, the formation and evolution mechanism of pores are unclear. Lots of hydrogen bubbles are produced during electrodeposition, which will affect the surface structure of porous metal films. Wettability is an intrinsic property to adjust bubble separation and expected to change surface structure of electrodeposited metal film. In the paper, electrodeposited Ni was used as a model, and the effects of wettability on bubble characteristics and surface structure of Ni films were studied. The formation mechanism of pores was analyzed based on COMSOL simulation. The results indicated that the break-off diameter of bubbles decreased with the addition of sodium dodecyl sulfate (SDS) due to the decrease of contact angle and surface tension. Therefore, the pore size can be reduced. On superhydrophilic copper foil, rough Ni films without uniform pores were electrodeposited. On compact copper foil with the contact angel of 76o, honeycomb Ni films were obtained. On superhydrophobic copper foil, irregular Ni films with weak adhesion were electrodeposited and surface peeling happened easily. It was confirmed that pore formation was related to the protrusion growth of electrodeposited Ni.