Ultrafast Growth of a Cu(OH)₂-CuO Nanoneedle Array on Cu Foil for Methanol Oxidation Electrocatalysis

A swift potentiostatic anodization method for growing a 5-7 μm tall nanoneedle array of Cu(OH)₂-CuO on Cu foil within 100 s has been developed. This catalytic electrode when screened for methanol oxidation electrocatalysis in 1 M KOH with 0.5 M methanol, delivered a current density as high as 70 ± 10 mA cm^-2 at 0.65 V versus Hg/HgO which is superior to the performance of many related catalysts reported earlier. The observed activity enhancement is attributed to the formation of both Cu(OH)₂-CuO nanoneedle arrays of high active surface area over the metallic Cu foil. In addition, the Cu(OH)₂-CuO/Cu electrode had also exhibited excellent stability upon prolonged potentiostatic electrocatalytic oxidation of methanol while retaining the charge-transfer characteristics. Growth of such highly ordered assembly of Cu(OH)₂-CuO nanoneedles within a minute has never been achieved before. When compared to its oxygen evolution reaction activity, the addition of 0.5 M methanol has lowered the overpotential at 10 mA cm^-2 by 334 mV, which is significant. This encourages the use of methanol as a sacrificial anolyte for energy-saving production of H₂ from water electrolysis.