Copper Foam Structures with Highly Porous Nanostructured Walls

A variety of copper foams with highly open porous walls have been successfully sculptured using the gas evolved in an electrochemical deposition process. The pore sizes and wall structures of the foams are tunable by adjusting the deposition conditions. In particular, the reduction in pore size is a result of lowering hydrophobic force of the generated hydrogen gas by adding bubble stabilizer (e.g., acetic acid) that suppresses the coalescence of bubbles, while the decrease in branch size in the foam wall is a consequence of the catalytic effect of chloride ions (added to the deposition bath) on the copper deposition reaction. For example, the size of the surface pore of a 100-μm-thick foam was reduced from 50 to about 25 μm by adding 0.1 M acetic acid to the deposition bath. With the addition of 1−50 mM HCl, the size of the copper branches was dramatically reduced; in particular, the average size of the elementary branches in the foam wall was reduced from 300 to 50 nm, forming nanostructured porous electrodes ideally suited for electrochemical and catalytic applications.