Nanoporous Nickel by Electrochemical Dealloying

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We report on the synthesis of nanoporous Ni (NP Ni) materials, discuss their morphology, and investigate their electrocatalytic properties in alkaline electrolytes. NP Ni was obtained by the electrochemical dealloying of co-sputtered, X-ray amorphous Ni-Al alloy films in diluted KOH. The solution pH and applied potential were chosen so that Al would selectively dissolve while Ni would remain immune and would not form a passive layer. Upon dealloying, NP Ni develops a nanofibrous morphology, different from the 3-D network of interconnected ligaments observed for nanoporous Au. This is likely due to the inhomogeneity of the Ni-Al precursor, which may tend to form Al-enriched grain boundaries. Relative to smooth Ni, NP Ni showed little or no catalytic enhancement towards the hydrogen evolution and oxygen evolution reactions. We attribute this effect to either i) the pore occlusion caused by nascent gas, and/or ii) the presence of oxides on the surface which may passivate potential active sites.
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