Electrochemically Activated Copper Electrodes

A polycrystalline copper electrode was activated by creating a nanostructured and highly electrocatalytic surface through an appropriate electrochemical treatment in NaOH. It was demonstrated that a thick layer of nanoneedles can be formed on copper substrate after (scan rate ) between and vs or by anodization for at . Energy dispersive X-ray analysis, X-ray diffraction, X-ray photoelectron spectroscopy, and in situ Raman spectroscopy analyses revealed that the conversion of orthorhombic to face-centered-cubic Cu is completed after between and at . However, copper obtained from the reduction of the thickest nanoneedle films formed by a repetitive fast cycling or by anodization at appeared as nanowires, whereas the electrode anodized at 0 or recovered a quasi-smooth original copper surface. The presence of high-energy sites on these Cu nanostructures was highlighted by cyclic voltammetry in the pseudo-capacitive potential region, where premonolayer oxidation was observed with an unusually high magnitude at unusually low potentials. As a result, a remarkable improvement of the electrocatalytic activity of the activated Cu electrodes for the nitrate electroreduction was observed.