Formation of Cu nanostructured electrode surfaces by an annealing–electroreduction procedure to achieve high-efficiency CO2 electroreduction

An effective fibrous Cu electrode surface, created using a procedure combining high-temperature annealing and electroreduction, is explored for CO2 reduction to produce useful fuels. The nanostructure of this Cu electrode surface contains a layer of nanofibers or nanofibers surrounded by kernels with 30–100 nm diameters. With a specific surface area as high as 458 cm2 per geometric electrode surface area, this nanostructured electrode is found to have a high activity toward CO2 reduction, indicated by its more positive reduction potentials and higher catalytic current density than a smooth Cu electrode. The Faradaic efficiency for HCOO− production is 43%, and the electrode surface remains stable during 19 h of electrolysis — better results than with smooth Cu under identical conditions.