Development of 3D open-cell structured Co-Ni catalysts by pulsed electrodeposition for hydrolysis of sodium borohydride

Structured cobalt–nickel catalysts were synthesized by roughening the nickel-foam surface and electrodepositing cobalt onto it for application to sodium-borohydride hydrolysis. The catalysts were prepared by incorporating aluminum onto the nickel-foam surface, increasing the nickel-foam surface area by subsequently leaching the aluminum, and electrodepositing cobalt. The cobalt was chronoamperometrically electrodeposited under the optimal condition (−2.0 V_Ag/AgCl) to prevent local cobalt deposition on the substrate edge. Additionally, the cobalt was uniformly deposited onto the porous nickel foam by pulsed chronoamperometric electrodeposition wherein voltages were alternated from −2.0 to −0.3 V_Ag/AgCl, to electroplate and dissolve the cobalt, respectively. Although the resulting structured cobalt–nickel catalysts exhibited 1.5 times higher catalytic activity than the porous nickel foam, the cobalt content was only 0.57 wt% of the whole sample. In addition, the structured cobalt–nickel catalyst showed higher stability than the porous nickel foam even after ultrasonication as an accelerated durability test. Therefore, pulsed electroplating is an effective method of increasing both catalyst activity and durability.