The electrooxidation of biomass-derived aldehydes offers an energy-efficient alternative to the oxygen evolution reaction for hydrogen production. This work investigates the geometric dependence of Cu-based spinel oxides (inverse CuFe2O4, normal CuCo2O4, and mixed CuAl2O4) for glucose (aldehyde) oxidation. CuFe2O4 (with octahedral Cu sites) exhibits superior activity, while tetrahedrally Cu shows minimal activity foroxidation despite a larger surface area. The performance arises from an “electrochemical-chemical” coupled cycle: octahedral Cu2+ is readily reduced and regenerated via spontaneous reaction with aldehyd. Additionally, the rigid Fe-Oin CuFe2O4 anchors active Cu sites, inhibiting excessive reduction and enhancing stability. This study elucidates a clear structure-activity relationship, guiding the design of efficient spinel catalysts for biomass-coupled hydrogen production.

Electrocatalytic carbon-nitrogen coupling offers a promising green pathway for urea synthesis. However, under electroreduction conditions, copper-based catalysts inevitably to form low-activity metallic copper. Therefore, preventing copper over-reduction is critical to maintaining high catalytic activity. Hence, we propose a strategy of introducing high-valence oxides onto the surface of copper particles. The strong interaction between ZrO2 and Cu forms a Zr-O-Cu interface, which stabilizes high-valence Cu species against reconstruction, enhancing catalyst stability. Moreover, the electron-deficient copper sites generated at this interface facilitate the adsorption of C-/N-containing species, leading to enhanced coupling activity. This work provides a new insight for the design of highly active and stable catalysts for C - N coupling.

Electrocatalytic urea synthesis from CO2 and NOx provides a sustainable route for simultaneous chemical production and pollutant utilization. Although grain-boundary engineering has emerged as a promising strategy for promoting sluggish C-N coupling, why a grain-boundary-rich defective microenvironment can regulate selective urea formation remains insufficiently understood. Here, we employed TiO2 as a model catalyst and constructed polycrystalline grain boundaries to improve both the activity and selectivity for urea synthesis. Trace Fe species served mainly as structural inducers for grain-boundary formation and promoted the generation of oxygen-vacancy-related defective regions. Operando electrochemical impedance spectroscopy revealed enhanced interfacial charge transfer and faster interfacial response, while operando infrared spectroscopy tracked the evolution of carbon- and nitrogen-containing surface species and supported the formation of the *OCNO intermediate during selective C-N coupling. The results show that the grain-boundary-rich defective microenvironment facilitates interfacial activation and selective C-N coupling during CO2 and NOx co-reduction. This work highlights the important role of grain-boundary-rich defective structures in understanding why grain boundaries can promote selective electrocatalytic urea synthesis.

ABSTRACT The electrocatalytic synthesis of urea from carbon dioxide and nitrate represents a sustainable route, with the C─N coupling between *CO and *NO intermediates being critical. However, achieving high efficiency remains challenging due to insufficient control over intermediate adsorption and reaction pathways. In this work, we reveal that the coordination number (CN) of Cu inversely regulates the adsorption strength of *CO and *NO, while C─N coupling activity follows a volcano‐type relationship with CN. Alloying Cu with intrinsically inert Ga atoms lowers the CN of Cu, upshifts d ‐band center, and finely tunes intermediate adsorption, thereby facilitating the formation of the key *ONCO. The optimized Cu 0.875 Ga 0.115 catalyst, with a moderate CN of 9.3 situated between its counterparts (6.0 and 12.0), balances adsorption and coupling activity, delivering a desirable urea yield rate of 575.6 mmol h −1 g −1 and a Faradaic efficiency of 30.4% at −1.4 V versus RHE. This work underscores coordination engineering as an effective strategy for guiding efficient C─N coupling toward urea synthesis.

Electrocatalytic C─N coupling via the co-reduction of CO2 and NO3 - represents a promising route for sustainable urea synthesis under ambient conditions, simultaneously addressing critical challenges in energy sustainability and environmental remediation. However, its practical implementation is hindered by sluggish C─N coupling kinetics and the competing hydrogen evolution reaction (HER), which severely restricts energy conversion efficiency. Herein, we propose a tip-induced local electric field strategy that generates a self-enhanced concentration gradient to promote electrocatalytic C─N coupling. By constructing densely aligned Co3O4 nanoneedles on carbon cloth, an outstanding electrocatalytic performance was achieved, requiring only an ultra-low potential of -0.60 V versus reversible hydrogen electrode (RHE) while delivering a high urea yield rate of 49.63 umol h-1 cm-2 and a Faradic efficiency of 21.37%. Finite element simulations reveal that the nanoscale high-curvature tip generates an intensified local electric field, enriching potassium ions (K+) at the electrode-electrolyte interface to stabilize key intermediates and direct the reaction pathway toward C─N coupling. Moreover, a series of operando spectroscopic characterizations provide direct evidence for enhanced C─N coupling process under an intensified local electric field. This work offers a generalizable strategy for energy-efficient C─N coupling, paving the way for sustainable utilization of nitrogen and carbon resources.

Converting harmful nitrate waste into value-added chemicals represents a promising alternative for achieving the electrocatalytic upgrading of NO3- and maintaining the global nitrogen balance. Nonetheless, improving the electrochemical performance and revealing reaction mechanisms still requires further investigation to meet the practical application requirements. Herein, we summarize the development of electrochemical NO3- reduction reaction (NO3RR) and C-N coupling reaction under pulsed-potential conditions. In the section on NO3RR, the electrocatalytic reaction systems for direct conversion of NO3- to NH3 are summarized. In the section on coupling, the C-N coupling reactions of NO3- with CO2 for urea synthesis, and with organic molecules for amino compounds synthesis are reviewed. The corresponding reaction mechanisms for different reaction systems are compared with the aid of theoretical calculations. Finally, the challenges and future perspectives are proposed. The pulsed-potential electrolysis for nitrate reduction not only increases the concentration of the local NO3-, key reactant, and intermediate species, but also restores the oxidation state of the active sites, providing guidance and reference for a nitrogen economy.

Electrocatalytic C-N coupling represents a green synthesis platform, yet the dynamic evolution of catalyst surfaces during the reaction remains poorly understood. Here, we report a nitrate-dominated, preferential facet evolution on Cu single crystals that directs less active (110) and (100) facets toward the highly active (111) configuration. The Cu(111) surface delivers a urea yield of 5.2 mg h-1 cm-2 from CO2 and NO3 -, outperforming (110) and (100) by about 4- and 26-fold, respectively, while maintaining excellent stability. Experimental and theoretical analyses reveal that this facet reconstruction is associated with spontaneous chemical interaction between nitrate and metallic copper, alongside the thermodynamic stability of the Cu(111) facet. Significantly, the pristine Cu(111) surface consistently outperforms Cu(110) and Cu(100), highlighting its intrinsic catalytic superiority. This work provides insights into nitrate-dominated C-N coupling, advancing the design of dynamically active electrocatalysts.

To ease the scarcity of lithium (Li) resource and cut down on environmental pollution, an efficient, selective, inexpensive and sustainable Li recycling process from waste batteries is needed, which is yet to be achieved. Here, we report a low-potential photoelectrochemical (PEC) system that selectively and efficiently extracts Li metals from multi-cation electrolytes under 1 sun illumination. Based on the difference of redox potential, we can get rid of the disturbance of other cations (i.e., Fe, Co and Ni ions) by a bias-free PEC device to realize the extraction of high-purity Li metals on a coplanar Si-based photocathode-TiO2 photoanode tandem device at 2 V of applied bias (far less than the redox potentials of Li+/Li). In such system, the extraction rate of Li metals (purity > 99.5

The electrocatalytic C─N coupling of carbon dioxide and nitrate presents a promising approach for environmentally friendly urea synthesis. In this work, we propose a strategy to boost efficient and durable urea synthesis by coupling the electrochemical and chemical steps. Utilizing fullerene (C 60 ) as a redox-active electron mediator during the electrochemical reduction process, we effectively inhibit the irreversible reduction deactivation of positively charged copper (Cu δ+ ) active sites. The electron-accepting fullerene form ions (C 60 n– ) that engage in a spontaneous chemical redox reaction with nitrate ions, producing nitrite ions and regenerating neutral C 60 (C 60 n– + NO 3 – → C 60  + NO 2 – ). This recycling mechanism closes the electron transfer loop while optimizing the overall reaction pathway. The urea yield rate is dramatically increased to 385.9 mmol h −1 g −1 , accompanied by long-term durability. Our findings provide a valuable framework for designing highly efficient electrocatalyst for coupling reactions, advancing the field of sustainable urea synthesis.

Oxygen release and electrolyte decomposition under high voltage endlessly exacerbate interfacial ramifications and structural degradation of high energy-density Li-rich layered oxide (LLO), leading to voltage and capacity fading. Herein, the dual-strategy of CrxB complex coating and local gradient doping is simultaneously achieved on LLO surface by a one-step wet chemical reaction at room temperature. Density functional theory (DFT) calculations prove that stable B-O and Cr-O bonds through the local gradient doping can significantly reduce the high-energy O 2p states of interfacial lattice O, which is also effective for the near-surface lattice O, thus greatly stabilizing the LLO surface. Besides, differential electrochemical mass spectrometry (DEMS) indicates that the CrxB complex coating can adequately inhibit oxygen release and prevents the migration or dissolution of transition metal ions, including allowing speedy Li+ migration. The voltage and capacity fading of the modified cathode (LLO-CrB) are adequately suppressed, which are benefited from the uniformly dense cathode electrolyte interface (CEI) composed of balanced organic/ inorganic composition. Therefore, the specific capacity of LLO-CrB after 200 cycles at 1C is 209.3 mA hg-1 (with a retention rate of 95.1%). This dual-strategy through a one-step wet chemical reaction is expected to be applied in the design and development of other anionic redox cathode materials. (c) 2024 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. and Science Press. All rights are reserved, including those for text and data mining, AI training, and similar technologies.

The effective recycling of metals, reduction of environmental pollution, and promotion of resource sustainability have emerged as critical research priorities. Photoelectrochemical (PEC) technology has demonstrated distinct advantages over conventional methods in both metal pollution remediation and resource recovery, yet substantial challenges remain for its practical implementation. This review systematically examines recent advancements in PEC metal ions (Li+, Cu2+, Ni2+, Ag+, et al.) recovery technology form lithium battery, seawater, and metallic wastewater. The integrated strategy of photoelectrode design, ion selective membrane optimization, and microbial synergy was systematically explored for the first time, and an interdisciplinary path from laboratory to industrial implementation of PEC technology was proposed. It is structured into three comprehensive sections. Initially, the fundamental working mechanisms and key influencing factors of PEC metal recovery was elucidated. Subsequently, a detailed analysis of PEC system design strategies is summarized, including photoelectrode architecture, electrolytic cell optimization, and ion-permeable membrane engineering, while identifying technical barriers in current PEC metal ions recovery processes. Conclusively, a forward-looking perspective on the future development of PEC technology was provided. The ongoing research and practical applications of this technology in metal ion recovery for resource recycling are expected to create new opportunities.

Electrocatalytic C─N coupling offers a sustainable alternative to energy‐intensive industrial processes for urea synthesis. Herein, we design conjugated polymer‐based molecular reactors featuring interlayer diatomic Cu–N 4 sites and precisely tunable spacings (4.0, 4.6, and 5.7 Å) to optimize CO 2 and nitrate coupling. The 4.0 Å‐spaced copper polyphthalocyanine (CuPPc‐4.0) delivers a remarkable urea yield rate of 460.0 mmol h −1 g −1 with 26.1% Faradaic efficiency at −1.3 V (versus RHE), outperforming wider‐spaced analogs. The optimal 4.0 Å cavity spatially confines reactants and intermediates, matching urea's molecular dimensions (3.5 Å), thereby enhancing C–N coupling and urea synthesis activity, while the layered AA stacking structure stabilizes unbonded diatomic Cu configurations, preventing aggregation and ensuring durability. Mechanistic studies reveal that while ball‐milling treatment increases single‐atom exposure, it disrupts the layered architecture and eliminates interlayer diatomic sites, reducing activity by about 50%. This work demonstrates a multidimensional catalyst design integrating atomic precision and molecular confinement for sustainable electrosynthesis.

The electrocatalytic C-N coupling of CO2 with NOx for green synthesis of urea has emerged as a prominent research, with the design of highly efficient electrocatalyst being a critical challenge. Here, we investigated the C-N coupling activity of CO2 with nitrite by modulating different crystal facets of TiO2. It was shown that the TiO2 (100) single-crystal facet is capable of optimizing the adsorption and desorption of reactive intermediates and the introduction of CO2 facilitates the C-N coupling process. Compared to other facets, the TiO2 (100) achieved higher urea yield (212.2 mmol h-1 g-1) and Faradaic efficiency, showing commendable structural and performance stability. This study presents the potential for the application of single-facet electrocatalysts in the area of electrocatalytic C-N coupling.

Electrocatalytic co-reduction of nitrate (NO3 -) and carbon dioxide (CO2) for urea synthesis offers an eco-friendly solution to mitigate nitrate contamination and reduce the energy demands. The investigation of the catalyst geometric and electronic structures is critical to elucidating the reaction mechanisms for the design of high-performance catalysts. Herein, this work systematically studied the cobalt (Co) atom geometric configurations in Co-based spinel oxides for C-N coupling reaction. It demonstrated that C-N coupling is more likely to take place at octahedral Co (CoOh) sites instead of tetrahedral Co (CoTd) sites and the CoOh sites in spinel structures facilitating both electron and ion transport. Leveraging the synergistic effect between CoOh and CoTd sites, Co3O4 achieved the highest Faradaic efficiency and urea yield. Meanwhile, isotope labeling experiment confirmed the urea formation through the C-N coupling of CO2 and NO3 -. By replacing inactive tetrahedral cobalt atoms with copper atoms, the catalytic performance was further enhanced. This study provides key design principles for high-performance metal oxide catalysts for C-N coupling reactions.

The electrocatalytic C−N coupling of the greenhouse gas carbon dioxide and N2/nitrate presents a promising approach to the conventional Bosch-Meiser method for environmentally friendly urea synthesis. Two-dimensional (2D) materials exhibit significant advantages in electrocatalysis due to their unique ultrathin structure and physicochemical properties as a platform Substrates for atomic modification. Here, this review focuses on the Surface functionalization of 2D electrocatalysts (Oxides, Sulfide, MOFs, Mxene, et al.) through heteroatom doping, defect engineering, and Surface molecule functionalization to enhance the catalyst conductivity, lower the reaction barrier, and improve its cycling stability. Then, we provide a Summary of surface modified 2D electrocatalysts (the single-atom site, synergistic effects of dual-active-sites, et al.) towards C−N coupling reaction of N2 /NOx and CO2 for urea synthesis, analyze the catalysis origins through combination of DFT calculations, which are widely adopted to offer a precise description of the electronic structure of catalysts and the relationship between catalytic activity and catalysts. The reaction mechanisms researches reveals the optimization of reaction pathways by the dynamic evolution of the catalyst surface, providing a new direction for the design of adaptive catalytic materials.Finally, challenges and perspectives in the field are presented.

Electrocatalytic C-N coupling of nitrate and CO2 represents a paradigm shift in sustainable urea synthesis. We demonstrate that amorphous CuOx-coated crystalline Cu nanowires achieve a record-breaking urea yield rate of 0.89 mol h-1 g-1 via novel electrochemical-chemical looping. Mechanistic investigations reveal a three-step catalytic cycle: (i) electro-reductive generation of Cu0 and oxygen vacancies (Ov); (ii) Ov-mediated nitrate activation via oxygen atom insertion, spontaneously yielding nitrogen-bonded nitrite (*NO2) while oxidizing Cu0 to catalytically active Cu+; and (iii) Cu+-catalyzing C-N coupling between *NO2 and CO2 to form urea. This pathway circumvents conventional rate-limiting nitrate reduction step, reducing the electron transfer requirement from 16e- to 12e- for urea synthesis. Notably, direct nitrite utilization fails to generate Cu+ or nitrogen-bonded intermediates, instead forming oxygen-bonded species with markedly reduced C-N coupling activity-a finding that overturns conventional understanding. Our work establishes new fundamental principles for efficient urea synthesis and provides insights into catalyst design and green chemistry.

The electrocatalytic C−N coupling from CO 2 and nitrate emerges as one of the solutions for waste upgrading and urea synthesis. In this work, we constructed electron-deficient Cu sites by the strong metal-polymer semiconductor interaction, to boost efficient and durable urea synthesis. In situ Raman spectroscopy identified the existence of electron-deficient Cu sites and was able to withstand electrochemical reduction conditions. Operando synchrotron-radiation Fourier transform infrared spectroscopy and theoretical calculations disclosed the vital role of electron-deficient Cu in adsorption and C−N coupling of oxygen-containing species. The electron-deficient Cu displayed a high urea yield rate of 255.0 mmol h −1  g −1 at −1.4 V versus the reversible hydrogen electrode and excellent electrochemical durability, superior than that of non-electron-deficient counterpart with conductive carbon material as the support. It can be concluded that the regulation of site electronic structure is more important than the optimization of catalyst conductive properties in the C−N coupling reactions.

Turning the harmful NO into value-added chemicals is a promising alternative to achieve the electrocatalytic NO upgrading and maintain the global N-balance. However, the reaction mechanisms and electrochemical performances and are still needed to be further investigated. Herein, the development of electrochemical NO reduction and oxidation reaction (NORR and NOOR) were respectively summarized. In the NORR part, we summarized the electrocatalytic reaction systems, including directly NORR (NO to NH3/NH2OH) and the C-N coupling reactions with COx for urea, and organic molecules for amino acid, oxime. The reaction mechanisms and design principles of electrocatalysts for different reaction systems were reviewed, combining theoretical calculations and advanced characterization techniques. The NO reaction is also a potential approach to replace others cathodic reduction. Finally, the challenges and outlooks in this fields have been proposed. The electrocatalytic NO reaction not only realizes the efficient green utilization, but also provides guidance for nitrogen economy.

Electrocatalytic C-N coupling from carbon dioxide and nitrate provides a sustainable alternative to the conventional energy-intensive urea synthetic protocol, enabling wastes upgrading and value-added products synthesis. The design of efficient and stable electrocatalysts is vital to promote the development of electrocatalytic urea synthesis. In this work, copper phthalocyanine (CuPc) is adopted as a modeling catalyst toward urea synthesis owing to its accurate and adjustable active configurations. Combining experimental and theoretical studies, it can be observed that the intramolecular Cu-N coordination can be strengthened with optimization in electronic structure by amino substitution (CuPc-Amino) and the electrochemically induced demetallation is efficiently suppressed, serving as the origination of its excellent activity and stability. Compared to that of CuPc (the maximum urea yield rate of 39.9 ± 1.9 mmol h-1 g-1 with 67.4% of decay in 10 test cycles), a high rate of 103.1 ± 5.3 mmol h-1 g-1 and remarkable catalytic durability have been achieved on CuPc-Amino. Isotope-labelling operando electrochemical spectroscopy measurements are performed to disclose reaction mechanisms and validate the C-N coupling processes. This work proposes a unique scheme for the rational design of molecular electrocatalysts for urea synthesis.

Electrocatalytic C-N couplings are promising alternatives to construct C-N bonds and to synthesize vital chemicals, including amine, amide, amino acid, oxime, imine, and nitrile, under ambient conditions. In recent years, the electrocatalytic C-N coupling has attracted a wide range of research interest and has achieved considerable developments. Here, the electrocatalytic C-N coupling is systematically reviewed aiming at reductive cathode and oxidative anode. In the cathodic part, the electrocatalytic coupling reaction systems, the corresponding design principles of electrocatalysts for different reaction systems, the mechanism studies from experimental and theoretical aspects, and the application-oriented electrocatalytic devices for electrocatalytic C-N couplings are summarized. Anodic C-N coupling offers a potential approach to replace the conventional energy-demand synthesis protocols, and is an indispensable part of the green and controllable construction of unsaturated C = N and C equivalent to N bonds. According to the principle that electron transfer is the crucial point in anodic C-N coupling, the anodic coupling reactions are sorted out based on the direct and the indirect C-N coupling paths, respectively. Finally, the challenges and outlooks in this field are proposed. Electrocatalytic C-N coupling is an appealing research topic in electrochemistry and possesses infinite possibilities in the future. The development of electrochemical C-N coupling reactions at cathode and anode is summarized, and the electrocatalytic coupling reaction systems, the catalyst design principle, the reaction mechanisms, and the application oriented electrocatalytic devices are reviewed. image