Three-dimensional highly interconnected copper nanowire networks (see. Fig. 1) are designed and fabricated by electrodeposition in etched ion-track polymer templates with interconnected nanochannels. The templates are synthesized by sequential swift heavy ion irradiation of polymer foils under various angles, followed by a selective etching procedure that transforms the generated ion tracks into nanochannels. Copper is then potentiostatically electrodeposited into the nanochannels using a Cu₂SO₄-based electrolyte at 60 °C. Subsequent dissolution of the polymer leads to free-standing nanowire networks with electrochemically active surface areas of up to 500 cm² on a 1.8 cm² planar sample area. The electrochemically active surface area of each sample is determined by measurements of the double-layer capacitance as a function of length, diameter, and number density of the nanowires.

The Cu nanowire networks are applied as catalysts for electrochemical CO₂ reduction. The conversion efficiency and selectivity towards liquid and gas phase products is studied as a function of applied potential. Morphology and crystalline structure of the nanowire networks are investigated before and after CO₂ reduction by scanning electron microscopy, X-ray diffraction and transmission electron microscopy, evidencing that the structure of the network remains stable for CO₂ reduction reactions in a potential region between -0.5 V and ‑0.93 V vs. RHE.