Facile electrochemical preparation of three-dimensional porous Cu films by potential perturbation

A 3-dimentional (3D) micro-nano hierarchical porous Cu film was fabricated by surface rebuilding of smooth Cu substrates in a blank solution of 1 M NaOH with square wave potential perturbation. The potential step from 0.4 to −2.5 V (vs. SCE) and a frequency of 50 Hz were chosen for the fabrication. The pore formation and Cu nanostructure evolution were characterized by scanning electron microscopy. The fabrication process involved fast Cu electrochemical oxidation–reduction and suitable rate of H2 releasing. During the repeated Cu oxidation–reduction, the Cu atoms were removable, forming dendrite-like structures. At the same time, the formed H2 bubbles acted as a dynamic template to shape the formation of micropores. The effect of H2 bubble as a template on the size of the formed micropores was demonstrated by adding a small amount of surfactant (cetyltrimethylammonium bromide, CTAB) into the basic solution to adjust the size of the bubbles. The as-prepared 3D porous Cu showed high electrocatalytic activity toward the reduction of NO3− and H2O2. The present in situ preparation method was green, convenient and required neither Cu(II) species and additives in solution nor post-treatment for template removal.