Use of pyrophosphate and boric acid additives in the copper-zinc alloy electrodeposition and chemical dealloying

Abstract

Over the last decade, nanoporous metals have attracted a growing attention due to the combination of structural and functional properties, such as their very high surface to volume ratio and mechanical rigidity. A recent and versatile process producing nanoporous metals is the dealloying of an initial alloy, i.e. the selective dissolution of the more reactive element of the alloy. In this work, we report on a method of CuZn alloy formation, without the use of furnaces or expensive techniques, and its subsequent chemical dealloying leading to nanoporous copper. Co-electrodeposition of CuZn alloys on a copper substrate is performed using pyrophosphate as a complexing agent in presence of boric acid, copper sulfate and zinc sulfate. The electrochemical behavior of this system is characterized by cyclic voltammetry, showing that a copper-zinc alloy is formed at -1.5 V vs. SCE. Cauliflower-like Zn-rich gamma-brass and epsilon-brass coatings are obtained by co-electrodeposition. The thickness, the structure and the composition of the electrodeposited alloy can be tuned by varying the electrodeposition conditions. Thicker and rougher coatings with a higher zinc content are formed at more cathodic conditions. The electrodeposited CuZn coatings were chemically dealloyed, and a two-step dealloying protocol leads to open framework nanoporous copper templates, which are a material of interest for energy storage, biosensors, and catalysis applications. (C) 2019 Published by Elsevier B.V.