Combined effects of sea urchin-like structure and mixed Cu⁺/Cu⁰ states on promoting C₂ formation in electrocatalytic CO₂ reduction

Abstract

Surface engineering and Cu valence regulation are essential factors in improving the C₂ selectivity during the electrochemical reduction of CO₂. Herein, we present a sea urchin-like CuO/Cu₂O catalyst derived from rhombic dodecahedra Cu₂O through one-step oxidation/etching method where the mixed Cu⁺/Cu⁰ states are formed via in situ reduction during electrocatalysis. The combined effects of the morphology and the mixed Cu⁺/Cu⁰ states on C–C coupling are evaluated by the Faradaic efficiency of C₂ and the C₂/C₁ ratio obtained in an H-cell. R-CuO/Cu₂O exhibited 49.5% Faradaic efficiency of C₂ with a C₂/C₁ ratio of 3.1 at −1.4 V vs. reversible hydrogen electrode, which are 1.5 and 3.2 times higher than those of R-Cu₂O, respectively. Using a flow-cell, 68.0% Faradaic efficiency of C₂ is achieved at a current density of 500 mA·cm⁻². The formation of the mixed Cu⁺/Cu⁰ states was confirmed by in situ Raman spectra. Additionally, the sea urchin-like structure provides more active sites and enables faster electron transfer. As a result, the excellent C₂ production on R-CuO/Cu₂O is primarily attributed to the synergistic effects of the sea urchin-like structure and the stable mixed Cu⁺/Cu⁰ states. Therefore, this work presents an integrated strategy for developing Cu-based electrocatalysts for C₂ production through electrochemical CO₂ reduction.

Key words： CO₂ electrolysis; sea urchin-like structure; Cu⁺/Cu⁰; C₂ products

Competing interests

The authors declare that they have no competing interests.

Acknowledgements

This work was supported by the National Natural Science Foundation of China (Grant No. 22178266). We are grateful to Donghai Mei group of Tiangong University for providing in situ Raman spectroscopy tests. We thank Prof. Xiaolei Wang and Dr. Mahrima Majid of University of Alberta for polishing English language of the full text.

Electronic Supplementary Material

Supplementary material is available in the online version of this article at https://doi.org/10.1007/s11705-024-2393-5 and is accessible for authorized users.

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