Theoretical understanding of the effect of specifically adsorbed halide anions on Cu-catalyzed CO2 electroreduction activity and product selectivity

Lihui Ou; Wanli You; Junling Jin; Yuandao Chen

doi:10.1039/d3cp01900d

Theoretical understanding of the effect of specifically adsorbed halide anions on Cu-catalyzed CO₂ electroreduction activity and product selectivity

Phys Chem Chem Phys. 2023 Sep 13;25(35):23977-23987. doi: 10.1039/d3cp01900d.

Authors

Lihui Ou¹, Wanli You¹, Junling Jin¹, Yuandao Chen¹

Affiliation

¹ Hunan Provincial Key Laboratory of Water Treatment Functional Materials, Hunan Province Engineering Research Center of Electroplating Wastewater Reuse Technology, College of Chemistry and Materials Engineering, Hunan University of Arts and Science, Changde, 415000, China. lihuiou@huas.edu.cn.

PMID: 37644839
DOI: 10.1039/d3cp01900d

Abstract

Initial CO₂ electroreduction into CO and its subsequent electroreduction pathways were selected to study the effect of specifically adsorbed halide anions X^- (X = F, Cl, Br, I) on CO₂ electroreduction activity and product selectivity at Cu(111)/H₂O interfaces via DFT calculations. The calculated results show that the presence of halide anions can exert a notable effect on the CO₂ adsorption characteristics and that chemically adsorbed CO₂ molecules can be formed. Furthermore, the halide-anion-modified Cu(111)/H₂O interfaces could significantly enhance the initial CO₂ electroreduction into CO activity, which is regarded as the rate-determining step during CO₂ electroreduction at clean Cu(111)/H₂O interfaces. Analysis of the initial CO₂ electroreduction and Volmer reaction pathways showed that the halide-anion-modified Cu(111)/H₂O interfaces could suppress the HER and thus improve the CO₂ electroreduction activity and product selectivity. It is speculated that the enhanced initial CO₂ electroreduction activity at the F^--, Cl^--, Br^--, and I^--modified Cu(111)/H₂O interfaces may originate from the decreased work functions and anion radical ^·CO₂^- formations. Simultaneously, we concluded that dimer OCCO formations in the presence of halide anions were more favorable than CHO during CO electroreduction according to the order of I^- > Br^- > Cl^- > F^- and could result in the production of C₂ product, suggesting an improved CO₂ electroreduction product selectivity. The present analyses of electronic structure may explain the more favorable OCCO formations in the order of I^- > Br^- > Cl^- > F^-. The present understanding of this effect will provide an improved scientific guideline for the control of CO₂ electroreduction pathways and design of more efficient electrocatalysts.