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	Exploration of a novel electrochemical C-N coupling process: Urea synthesis from direct air carbon capture with nitrate wastewater
	Chen, Ying1,2; Liu, Yuan1,3; Hu, Shujie1; Wu, Di1; Zhang, Mengyue1; Cheng, Zhiliang2
	2024-02-25
摘要	Direct air capture (DAC) can be used to decrease the CO2 concentration in the atmosphere, but this requires substantial energy consumption. If residual waste carbon (in the form of bicarbonate solution) from DAC can be directly reused, it might present a novel method for overcoming the aforementioned challenges. Electrochemical C-N coupling methods for synthesizing urea have garnered considerable attention for waste carbon utilization, but the carbon source is high-purity CO2. No research has been conducted regarding the application of bicarbonate solution as the carbon source. This study proposes a proof-of-concept electrochemical C-N coupling process for synthesizing urea using bicarbonate solution from DAC as the carbon source and nitrate from wastewater as the nitrogen source. These results confirmed the feasibility of synthesizing urea using a threeelectrode system employing TF and CuInS2/TF as the working electrodes via potentiostatic electrolysis. Under the optimal conditions (initial pH 5.0 and applied potential of -1.3 V vs. Ag/AgCl), the urea yield after 2 h of electrolysis reached 3017.2 mu g h-1 mgcat.-1 and an average Faradaic efficiency of 19.6 %. The in-situ attenuated total reflection surface-enhanced infrared absorption spectroscopy indicated a gradual increase in the intensity of the -CONH bond signal on the surface of the CuInS2/TF electrode as the reaction progressed. This implied that this bond may be a key chemical group in this process. The density functional theory calculations demonstrated that *CONH was a pivotal intermediate during C-N coupling, and a two-step C-N coupling reaction path was proposed. *NH + *CO primarily transformed into *CONH, followed by the conversion reaction of *CONH + *NO to *NOCONH2. This study offers a groundbreaking approach for waste carbon utilization from DAC and holds the potential to furnish technical underpinnings for advancing electrochemical C-N coupling methods.
关键词	C-N coupling Bicarbonate Waste carbon Urea synthesis Direct air capture Electrocatalytic
DOI	10.1016/j.scitotenv.2023.169722
发表期刊	SCIENCE OF THE TOTAL ENVIRONMENT
ISSN	0048-9697
卷号	913页码:11
通讯作者	Liu, Yuan(liuyuan@cigit.ac.cn) ; Cheng, Zhiliang(purper@cqut.edu.cn)
收录类别	SCI
WOS记录号	WOS:001154622900001
语种	en