An official website of the United States government
Electrochemical C–N coupling via the coreduction of CO2and nitrogenous species (N2/NOx) presents a sustainable route to synthesize value‐added C–N compounds under mild conditions. However, competing pathways and mismatched intermediate kinetics hinder the selective formation of products like urea, amines, and amides. Recent advances reveal that rational modulation of the electrochemical microenvironment can effectively steer reaction pathways and stabilize coupling‐relevant intermediates. This review systematically summarizes how microenvironment engineering, originally developed for CO2and NOxreduction reactions, can be leveraged to enhance C–N coupling efficiency and selectivity. The key strategies are categorized into 1) catalyst‐centered design (e.g., ligand coordination, defect engineering, and morphology control), 2) ionic and electrolyte modifications (e.g., cation/pH effects), and 3) dynamic approaches such as pulsed electrolysis. These methods shape local fields, surface coverage, and mass transport properties, ultimately directing reactants toward cross‐coupling over competing routes. By drawing parallels with well‐established CO2RR/NOxRR systems and showcasing emerging examples in C–N coupling, the central role of microenvironment control is highlighted. Finally, a perspectives on strategies to further improve activity, selectivity, and atom economy in future C–N coupling systems are offered.
more »
« less
Electrocatalytic C-N Coupling: Advances in Urea Synthesis and Opportunities for Alternative Products
Urea is an essential fertilizer produced through the industrial synthesis of ammonia (NH3) via the Haber–Bosch process, which contributes ≈1.2% of global annual CO2emissions. Electrocatalytic urea synthesis under ambient conditions via CN coupling from CO2and nitrogen species such as nitrate (NO3−), nitrite (NO2−), nitric oxide (NO), and nitrogen gas (N2) has gained interest as a more sustainable route. However, challenges remain due to the unclear reaction pathways for urea formation, competing reactions, and the complexity of the resulting product matrix. This review highlights recent advances in catalyst design, urea quantification, and intermediate identification in the CN coupling reaction for electrocatalytic urea synthesis. Furthermore, this review explores future prospects for industrial CN coupling, considering potential nitrogen and carbon sources and examining alternative CN coupling products, such as amides and amines.
more »
« less
- PAR ID:
- 10586690
- Publisher / Repository:
- Wiley-VCH
- Date Published:
- Journal Name:
- ChemSusChem
- ISSN:
- 1864-5631
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Urea synthesis through the simultaneous electrocatalytic reduction of N2and CO2molecules under ambient conditions holds great promises as a sustainable alternative to its industrial production, in which the development of stable, highly efficient, and highly selective catalysts to boost the chemisorption, activation, and coupling of inert N2and CO2molecules remains rather challenging. Herein, by means of density functional theory computations, we proposed a new class of two‐dimensional nanomaterials, namely, transition‐metal phosphide monolayers (TM2P, TM = Ti, Fe, Zr, Mo, and W), as the potential electrocatalysts for urea production. Our results showed that these TM2P materials exhibit outstanding stability and excellent metallic properties. Interestingly, the Mo2P monolayer was screened out as the best catalyst for urea synthesis due to its small kinetic energy barrier (0.35 eV) for C–N coupling, low limiting potential (−0.39 V), and significant suppressing effects on the competing side reactions. The outstanding catalytic activity of the Mo2P monolayer can be ascribed to its optimal adsorption strength with the key *NCON species due to its moderate positive charges on the Mo active sites. Our findings not only propose a novel catalyst with high‐efficiency and high‐selectivity for urea production but also further widen the potential applications of metal phosphides in electrocatalysis.more » « less
-
Electroreduction of carbon dioxide (CO2) or carbon monoxide (CO) toward C2+hydrocarbons such as ethylene, ethanol, acetate and propanol represents a promising approach toward carbon-negative electrosynthesis of chemicals. Fundamental understanding of the carbon─carbon (C-C) coupling mechanisms in these electrocatalytic processes is the key to the design and development of electrochemical systems at high energy and carbon conversion efficiencies. Here, we report the investigation of CO electreduction on single-atom copper (Cu) electrocatalysts. Atomically dispersed Cu is coordinated on a carbon nitride substrate to form high-density copper─nitrogen moieties. Chemisorption, electrocatalytic, and computational studies are combined to probe the catalytic mechanisms. Unlike the Langmuir-Hinshelwood mechanism known for copper metal surfaces, the confinement of CO adsorption on the single-copper-atom sites enables an Eley-Rideal type of C-C coupling between adsorbed (*CO) and gaseous [CO(g)] carbon moxide molecules. The isolated Cu sites also selectively stabilize the key reaction intermediates determining the bifurcation of reaction pathways toward different C2+products.more » « less
-
Abstract The electrochemical reduction of nitrates (NO3−) enables a pathway for the carbon neutral synthesis of ammonia (NH3), via the nitrate reduction reaction (NO3RR), which has been demonstrated at high selectivity. However, to make NH3synthesis cost‐competitive with current technologies, high NH3partial current densities (jNH3) must be achieved to reduce the levelized cost of NH3. Here, the high NO3RR activity of Fe‐based materials is leveraged to synthesize a novel active particle‐active support system with Fe2O3nanoparticles supported on atomically dispersed Fe–N–C. The optimized 3×Fe2O3/Fe–N–C catalyst demonstrates an ultrahigh NO3RR activity, reaching a maximum jNH3of 1.95 A cm−2at a Faradaic efficiency (FE) for NH3of 100% and an NH3yield rate over 9 mmol hr−1cm−2. Operando XANES and post‐mortem XPS reveal the importance of a pre‐reduction activation step, reducing the surface Fe2O3(Fe3+) to highly active Fe0sites, which are maintained during electrolysis. Durability studies demonstrate the robustness of both the Fe2O3particles and Fe–Nxsites at highly cathodic potentials, maintaining a current of −1.3 A cm−2over 24 hours. This work exhibits an effective and durable active particle‐active support system enhancing the performance of the NO3RR, enabling industrially relevant current densities and near 100% selectivity.more » « less
-
Electrocatalytic coreduction of carbon dioxide (CO2) and nitrate (NO3–) offers a sustainable route to the synthesis of urea. A major challenge for this reaction is enhancing C–N coupling, which is strongly influenced by catalyst composition and surface morphology. Here, we use grand-canonical density functional theory (GC-DFT) to model how the exposed facet of Ag and Cu electrodes affects the intrinsic kinetics of C–N coupling, comparing stepped (211) and terrace (100, 111) surfaces under applied electrochemical potentials in acidic media. We predict that low-coordination stepped surfaces (211) exhibit superior C–N coupling activity compared to terraces. Linear scaling relations link reaction energies and activation barriers with coadsorption energies for key C–N coupling steps with the coadsorption energies of C- and N-species, providing a thermodynamic descriptor for intermediate coupling. The potential-dependence origins of representative C–N coupling reactions are dominated by capacitive and dipole-field effects, which are larger for CO2 coupling than for CO coupling. These insights reveal why stepped sites are more active for the first C–N coupling step and may guide nanostructuring strategies to design electrocatalysts for CO2–NO3– coreduction.more » « less
- Free Publicly Accessible Full Text
-
Accepted Manuscript
- Journal Article:
- https://doi.org/10.1002/cssc.202402566
