Synergistic coupling of carbon dioxide and nitrate for efficient electrosynthesis of urea using Cu-doped CeO₂ nanorods

Abstract

The electrocatalytic co-reduction of carbon dioxide (CO₂) and nitrate (NO₃^–) to urea represents a sustainable alternative to energy-intensive industrial synthesis processes. Herein, we report copper-doped cerium oxide nanorods (Cu-CeO₂) as an efficient catalyst for this reaction, achieving a urea yield of 358.5 mg∙h^–1∙g^–1 at –0.7 V vs. reversible hydrogen electrode with 21.1% Faradaic efficiency. In situ Fourier transform infrared spectroscopy analysis reveals that during electrocatalytic urea synthesis, CO₂ activation at the catalyst surface generates carbonyl-containing intermediates (*CO), which couple with nitrogenous species (NH_x) derived from NO₃^– reduction. The key coupling reaction intermediate *NHCO was detected, and the *NHCO intermediate played a crucial role in promoting C–N bond formation. The stability of this intermediate directly facilitated the successful formation of urea. These findings elucidate the reaction pathway mediated by the Cu-CeO₂ catalyst, establishing a theoretical foundation for subsequent catalyst design optimization.

Graphical abstract

Keywords

CeO₂ / Cu doping / C–N coupling / electrosynthesis / urea

References

[1] Lan R , Tao S W , Irvine J T . A direct urea fuel cell-power from fertiliser and waste. Energy & Environmental Science, 2010, 3(4): 438–441

[2] Wan Y C , Zheng M Y , Yan W , Zhang J J , Lv R T . Fundamentals and rational design of heterogeneous C–N coupling electrocatalysts for urea synthesis at ambient conditions. Advanced Energy Materials, 2024, 14(28): 2303588

[3] Pérez-Fortes M , Bocin-Dumitriu A , Tzimas E . CO₂ utilization pathways: techno-economic assessment and market opportunities. Energy Procedia, 2014, 63: 7968–7975

[4] Li J , Zhan G M , Yang J H , Quan F J , Mao C L , Liu Y , Wang B , Lei F C , Li L J , Chan A W . . Efficient ammonia electrosynthesis from nitrate on strained ruthenium nanoclusters. Journal of the American Chemical Society, 2020, 142(15): 7036–7046

[5] Xu M Q , Wu F F , Zhang Y , Yao Y H , Zhu G P , Li X Y , Chen L , Jia G , Wu X H , Huang Y J . . Kinetically matched C–N coupling toward efficient urea electrosynthesis enabled on copper single-atom alloy. Nature Communications, 2023, 14(1): 6994

[6] Lv C D , Zhong L X , Liu H J , Fang Z W , Yan C S , Chen M X , Kong Y , Lee C , Liu D B , Li S Z . . Selective electrocatalytic synthesis of urea with nitrate and carbon dioxide. Nature Sustainability, 2021, 4(10): 868–876

[7] Huang Z C , Yang B P , Zhou Y L , Luo W Q , Chen G , Liu M , Liu X H , Ma R Z , Zhang N . Tungsten nitride/tungsten oxide nanosheets for enhanced oxynitride intermediate adsorption and hydrogenation in nitrate electroreduction to ammonia. ACS Nano, 2023, 17(24): 25091–25100

[8] Yang C J , Li Z , Xu J P , Jiang Y J , Zhu W L . Electrocatalytic C–N coupling for urea synthesis: a critical review. Green Chemistry, 2024, 26(9): 4908–4933

[9] Ge R Y , Huo J J , Lu P , Dou Y H , Bai Z C , Li W X , Liu H K , Fei B , Dou S X . Multifunctional strategies of advanced electrocatalysts for efficient urea synthesis. Advanced Materials, 2024, 36(49): 2412031

[10] Chen C , Zhu X R , Wen X J , Zhou Y Y , Zhou L , Li H , Tao L , Li Q L , Du S Q , Liu T T . . Coupling N₂ and CO₂ in H₂O to synthesize urea under ambient conditions. Nature Chemistry, 2020, 12(8): 717–724

[11] Zhu X R , Zhou X C , Jing Y , Li Y F . Electrochemical synthesis of urea on MBenes. Nature Communications, 2021, 12(1): 4080

[12] Kyriakou V , Garagounis I , Vourros A , Vasileiou E , Stoukides M . An electrochemical haber-bosch process. Joule, 2020, 4(1): 142–158

[13] Geng J , Ji S H , Jin M , Zhang C , Xu M , Wang G Z , Liang C H , Zhang H M . Ambient electrosynthesis of urea with nitrate and carbon dioxide over iron-based dual-sites. Angewandte Chemie International Edition, 2023, 62(6): e202210958

[14] Wei X X , Wen X J , Liu Y Y , Chen C , Xie C , Wang D D , Qiu M Y , He N H , Zhou P , Chen W . . Oxygen vacancy-mediated selective C–N coupling toward electrocatalytic urea synthesis. Journal of the American Chemical Society, 2022, 144(26): 11530–11535

[15] Feng Y G , Yang H , Zhang Y , Huang X Q , Li L G , Cheng T , Shao Q . Te-doped Pd nanocrystal for electrochemical urea production by efficiently coupling carbon dioxide reduction with nitrite reduction. Nano Letters, 2020, 20(11): 8282–8289

[16] Zhang X R , Zhu X R , Bo S W , Chen C , Qiu M Y , Wei X X , He N H , Xie C , Chen W , Zheng J Y . . Identifying and tailoring C-N coupling site for efficient urea synthesis over diatomic Fe-Ni catalyst. Nature Communications, 2022, 13(1): 5337

[17] Chen C , Li S , Zhu X R , Bo S W , Cheng K , He N H , Qiu M Y , Xie C , Song D , Z Liu Y Z . . Balancing sub-reaction activity to boost electrocatalytic urea synthesis using a metal-free electrocatalyst. Carbon Energy, 2023, 5(10): e345

[18] Wang F , He S , Chen H , Wang B , Zheng L R , Wei M , Evans D G , Duan X . Active site dependent reaction mechanism over Ru/CeO₂ catalyst toward CO₂ methanation. Journal of the American Chemical Society, 2016, 138(19): 6298–6305

[19] VanHandel G , Blumenthal R . The temperature and oxygen pressure dependence of the ionic transference number of nonstoichiometric CeO_2−x. Journal of the Electrochemical Society, 1974, 121(9): 1198

[20] Xu X L , Liu L Y , Tong Y Y , Fang X Z , Xu J W , Jiang D-E , Wang X . Facile Cr³⁺-doping strategy dramatically promoting Ru/CeO₂ for low-temperature CO₂ methanation: unraveling the roles of surface oxygen vacancies and hydroxyl groups. ACS Catalysis, 2021, 11(9): 5762–5775

[21] Ding Y , Huang L S , Zhang J B , Guan A X , Wang Q H , Qian L P , Zhang L J , Zheng G F . Ru-doped, oxygen-vacancy-containing CeO₂ nanorods toward N₂ electroreduction. Journal of Materials Chemistry A, 2020, 8(15): 7229–7234

[22] López-Rodríguez S , Davó-Quiñonero A , Bailón-García E , Lozano-Castelló D , Bueno-López A . Effect of Ru loading on Ru/CeO₂ catalysts for CO₂ methanation. Molecular Catalysis, 2021, 515: 111911

[23] Wang Z Q , Liu H H , Wu X P , Hu P , Gong X Q . Hydride generation on the Cu-doped CeO₂ (111) surface and its role in CO₂ hydrogenation reactions. Catalysts, 2022, 12(9): 963

[24] Yan Y , Wong R J , Ma Z R , Donat F L , Xi S B , Saqline S , Fan Q W H , Du Y H , Borgna A , He Q . . CO₂ hydrogenation to methanol on tungsten-doped Cu/CeO₂ catalysts. Applied Catalysis B: Environmental, 2022, 306: 121098

[25] Guo C , Wei S X , Zhou S N , Zhang T , Wang Z J , Ng S P , Lu X Q , Wu C M L , Guo W Y . Initial reduction of CO₂ on Pd-, Ru-, and Cu-doped CeO₂ (111) surfaces: effects of surface modification on catalytic activity and selectivity. ACS Applied Materials & Interfaces, 2017, 9(31): 26107–26117

[26] Wang Z H , Li Y C , Zhao X , Chen S Q , Nian Q S , Luo X , Fan J J , Ruan D G , Xiong B Q , Ren X D . Localized alkaline environment via in situ electrostatic confinement for enhanced CO₂-to-ethylene conversion in neutral medium. Journal of the American Chemical Society, 2023, 145(11): 6339–6348

[27] Zhan P , Liu X S , Zhang S D , Zhu Q , Zhao H Q , Ren C , Zhang J W , Lu L , Cai D , Qin P Y . Electroenzymatic reduction of furfural to furfuryl alcohol by an electron mediator and enzyme orderly assembled biocathode. ACS Applied Materials & Interfaces, 2023, 15(10): 12855–12863

[28] Keuleers R , Desseyn H , Rousseau B , Van Alsenoy C . Vibrational analysis of urea. The Journal of Physical Chemistry A, 1999, 103(24): 4621–4630

[29] Bossa J B , Theulé P , Duvernay F , Borget F , Chiavassa T . Carbamic acid and carbamate formation in NH: CO ices-UV irradiation versus thermal processes. Astronomy & Astrophysics, 2008, 492(3): 719–724

[30] Zhang S B , Geng J , Zhao Z , Jin M , Li W Y , Ye Y X , Li K , Wang G Z , Zhang Y X , Yin H J . . High-efficiency electrosynthesis of urea over bacterial cellulose regulated Pd-Cu bimetallic catalyst. Energy & Environmental Science: Catalysis, 2023, 1(1): 45–53

[31] Manivannan M , Rajendran S . Investigation of inhibitive action of urea-Zn²⁺ system in the corrosion control of carbon steel in sea water. International Journal of Engineering Science and Technology, 2011, 3(11): 8048–8060

[32] Chitsiga T , Daramola M O , Wagner N , Ngoy J . Effect of the presence of water-soluble amines on the carbon dioxide (CO₂) adsorption capacity of amine-grafted poly-succinimide (PSI) adsorbent during CO₂ capture. Energy Procedia, 2016, 86: 90–105

[33] Yao Y , Zhu S Q , Wang H J , Li H , Shao M H . A spectroscopic study on the nitrogen electrochemical reduction reaction on gold and platinum surfaces. Journal of the American Chemical Society, 2018, 140(4): 1496–1501

RIGHTS & PERMISSIONS

Higher Education Press