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

Abstract

Novel, hierarchical, flower-like Ag/Cu₂O and Au/Cu₂O nanostructures were successfully fabricated and applied as efficient electrocatalysts for the electrochemical reduction of CO₂. Cu₂O nanospheres with a uniform size of ~180 nm were initially synthesized. Thereafter, Cu₂O 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/Cu₂O, having a hierarchical, flower-like nanostructure with intersecting Ag nanoflakes encompassing an inner Cu₂O sphere, was prepared. The as-prepared Ag_x/Cu₂O samples presented higher Faradaic efficiencies (FE) for CO and relatively suppressed H₂ evolution than the parent Cu₂O nanospheres due to the combination of Ag with Cu₂O in the former. Notably, the highest CO evolution rate was achieved with Ag_0.125/Cu₂O 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/Cu₂O composite, where the FE_CO (10%) was even higher than that of Ag_0.125/Cu₂O. Importantly, the results reveal that Ag_0.125/Cu₂O and Au_0.6/Cu₂O both exhibit remarkably improved stability relative to Cu₂O. This study presents a facile method of developing hierarchical metal-oxide composites as efficient and stable electrocatalysts for the electrochemical reduction of CO₂.

Key words： bimetallic nanostructure; hierarchical metal/oxide nanomaterial; galvanic replacement; electrochemical reduction of CO₂

Acknowledgements

We are grateful to the Analysis and Test Center of Tianjin University for providing XRD, SEM, and TEM characterization. We also acknowledge the National Natural Science Foundation of China (Grant Nos. 21576204 and 21206117) for financial support.

Electronic Supplementary Material

Supplementary material is available in the online version of this article at https://doi.org/10.1007/s11705-019-1854-8 and is accessible for authorized users.

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