Facile synthesis of hierarchical flower-like Ag/Cu2O and Au/Cu2O nanostructures and enhanced catalytic performance in electrochemical reduction of CO2

Novel, hierarchical, flower-like Ag/Cu 2 O and Au/Cu 2 O nanostructures were successfully fabricated and applied as efficient electrocatalysts for the electrochemical reduction of CO 2 . Cu 2 O nanospheres with a uniform size of ∼180 nm were initially synthesized. Thereafter, Cu 2 O was used as a sacrificial template to prepare a series of Ag/Cu2O composites through galvanic replacement. By varying the Ag/Cu atomic ratio, Ag 0.125 /Cu 2 O, having a hierarchical, flower-like nanostructure with intersecting Ag nanoflakes encompassing an inner Cu 2 O sphere, was prepared. The as-prepared Ag x /Cu 2 O samples presented higher Faradaic efficiencies (FE) for CO and relatively suppressed H 2 evolution than the parent Cu 2 O nanospheres due to the combination of Ag with Cu 2 O in the former. Notably, the highest CO evolution rate was achieved with Ag 0.125 /Cu 2 O due to the larger electroactive surface area furnished by the hierarchical structure. The same hierarchical flower-like structure was also obtained for the Au 0.6 /Cu 2 O composite, where the FE CO (10%) was even higher than that of Ag 0.125 /Cu 2 O. Importantly, the results reveal that Ag 0.125 /Cu 2 O and Au 0.6 /Cu 2 O both exhibit remarkably improved stability relative to Cu 2 O. This study presents a facile method of developing hierarchical metal-oxide composites as efficient and stable electrocatalysts for the electrochemical reduction of CO 2 .