Volume 63, Issue 24 e202403980
Research Article

The Tandem Nitrate and CO2 Reduction for Urea Electrosynthesis: Role of Surface N-Intermediates in CO2 Capture and Activation

Xingmiao Huang

Xingmiao Huang

Key Laboratory of Photochemistry, Institute of Chemistry Chinese Academy of Sciences, Beijing National Laboratory for Molecular Sciences, 100190 Beijing, P. R. China

University of Chinese Academy of Sciences, 100049 Beijing, P. R. China

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Yangfan Li

Yangfan Li

Key Laboratory of Photochemistry, Institute of Chemistry Chinese Academy of Sciences, Beijing National Laboratory for Molecular Sciences, 100190 Beijing, P. R. China

University of Chinese Academy of Sciences, 100049 Beijing, P. R. China

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Dr. Shijie Xie

Corresponding Author

Dr. Shijie Xie

State Key Laboratory of Fine Chemical, Frontiers Science Center for Smart Materials Oriented Chemical Engineering, School of Chemical Engineering, Dalian University of Technology, 116024 Dalian, P. R. China

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Qi Zhao

Qi Zhao

Key Laboratory of Photochemistry, Institute of Chemistry Chinese Academy of Sciences, Beijing National Laboratory for Molecular Sciences, 100190 Beijing, P. R. China

University of Chinese Academy of Sciences, 100049 Beijing, P. R. China

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Boyang Zhang

Boyang Zhang

Key Laboratory of Photochemistry, Institute of Chemistry Chinese Academy of Sciences, Beijing National Laboratory for Molecular Sciences, 100190 Beijing, P. R. China

University of Chinese Academy of Sciences, 100049 Beijing, P. R. China

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Zhiyong Zhang

Zhiyong Zhang

Key Laboratory of Photochemistry, Institute of Chemistry Chinese Academy of Sciences, Beijing National Laboratory for Molecular Sciences, 100190 Beijing, P. R. China

University of Chinese Academy of Sciences, 100049 Beijing, P. R. China

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Prof. Hua Sheng

Corresponding Author

Prof. Hua Sheng

Key Laboratory of Photochemistry, Institute of Chemistry Chinese Academy of Sciences, Beijing National Laboratory for Molecular Sciences, 100190 Beijing, P. R. China

University of Chinese Academy of Sciences, 100049 Beijing, P. R. China

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Prof. Jincai Zhao

Prof. Jincai Zhao

Key Laboratory of Photochemistry, Institute of Chemistry Chinese Academy of Sciences, Beijing National Laboratory for Molecular Sciences, 100190 Beijing, P. R. China

University of Chinese Academy of Sciences, 100049 Beijing, P. R. China

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First published: 08 April 2024
Citations: 54

Graphical Abstract

The electrocatalytic coupling reaction of carbon dioxide and nitrate serves as a sustainable strategy for urea synthesis under ambient conditions. Herein we proposed a urea generation pathway via the tandem reduction of nitrate and CO2, in which the critical C−N coupling is achieved by the interaction between the nitrate reduction intermediate of *NH2 and free CO2.

Abstract

Electrochemical reduction of CO2 and nitrate offers a promising avenue to produce valuable chemicals through the using of greenhouse gas and nitrogen-containing wastewater. However, the generally proposed reaction pathway of concurrent CO2 and nitrate reduction for urea synthesis requires the catalysts to be both efficient in both CO2 and nitrate reduction, thus narrowing the selection range of suitable catalysts. Herein, we demonstrate a distinct mechanism in urea synthesis, a tandem NO3 and CO2 reduction, in which the surface amino species generated by nitrate reduction play the role to capture free CO2 and subsequent initiate its activation. When using the TiO2 electrocatalyst derived from MIL-125-NH2, it intrinsically exhibits low activity in aqueous CO2 reduction, however, in the presence of both nitrate and CO2, this catalyst achieves an excellent urea yield rate of 43.37 mmol ⋅ g−1 ⋅ h−1 and a Faradaic efficiency of 48.88 % at −0.9 V vs. RHE in a flow cell. Even at a low CO2 level of 15 %, the Faradaic efficiency of urea synthesis remains robust at 42.33 %. The tandem reduction procedure was further confirmed by in situ spectroscopies and theoretical calculations. This research provides new insights into the selection and design of electrocatalysts for urea synthesis.

Conflict of interests

The authors declare no conflict of interest.

Data Availability Statement

The data that support the findings of this study are available in the supplementary material of this article.

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