Figure 1: Preparation and characterization for 3D Cu foil.

(a) Schematic presentation of the procedures to prepare a 3D porous Cu foil from a planar Cu foil. (b) X-ray diffraction profiles of Cu(OH)2 on the Cu foil and the final 3D Cu foil. The insets show digital images of the corresponding samples. (c) SEM images of the porous Cu (scale bar, 50 μm). The inset shows the high-magnification image (scale bar, 2 μm).