Urea Synthesis Research Articles

Urea synthesis by Plasmon-Assisted N2 and CO2 co-electrolysis onto heterojunctions decorated with silver nanoparticles

Urea synthesis by Plasmon-Assisted N2 and CO2 co-electrolysis onto heterojunctions decorated with silver nanoparticles

L-Arginine and immune modulation: A pharmacological perspective on inflammation and autoimmune disorders.

L-Arginine and immune modulation: A pharmacological perspective on inflammation and autoimmune disorders.

Selective coreduction of CO2 and NO3− for urea synthesis via electrochemical pathway modulated by p-block metal-doped copper oxides

Selective coreduction of CO2 and NO3− for urea synthesis via electrochemical pathway modulated by p-block metal-doped copper oxides

Insight into Photocatalytic C─N Coupling for Urea Synthesis on Ru Single Atom Modified CeO2

AbstractCurrently, the production of urea by photochemical routes holds significant potential. However, photocatalytic urea synthesis is significantly limited by the co‐sorption and activation of CO2, H2O, and N2 as well as C─N coupling process. Herein, Ru1 (single atom)/CeO2‐VO (containing oxygen vacancies) is synthesized by a room‐temperature photochemical strategy. Benefiting from the synergistic effect of Ce3+‐VO and single atoms, Ru1/CeO2‐VO nanosheets delivered the highest urea yield rate of 13.73 µmol g−1 h−1. Ultrafast transient absorption spectroscopy demonstrated that the localized asymmetric structure formed by oxygen vacancies and Ru single atoms on CeO2 can generate a stronger locally polarized electric field, thereby extending the photogenerated carrier lifetime. Experimental and theoretical calculations showed that Ru site promoted N2 adsorption and optimized water dissociation, which ensured the formation of N‐containing intermediates and the supply of protons to synthesize urea. The Ce‐ VO site activated CO2 to generate *CO, and the formed *CO migrated from the site to the adjacent Ru‐VO site. Further, the synergistic action of the dual sites promotes *CO couples with *NNH to form *NCONH, eventually converting to urea. Accordingly, this work sheds insight into the design of dual sites for effective photocatalytic C─N bond coupling to synthesize urea.

Patient-specific effects of metformin on the hepatic metabolism in adolescents with metabolic dysfunction-associated steatotic liver disease (MASLD).

Metformin is a commonly prescribed antidiabetic drug that inhibits hepatic glucose production (HGP). Recent studies examining the use of metformin for the treatment of children with metabolic dysfunction-associated steatotic liver disease (MASLD) showed controversial results. To evaluate the patient-specific impact of metformin on hepatic glucose, lipid, amino acid, and energy metabolism in a cohort of 70 paediatric patients with biopsy-proven MASH. We parametrized our mathematical model HEPATOKIN1 of liver metabolism with patient-specific proteomics data of liver enzyme abundances and simulated metformin-induced diurnal changes of a large panel of metabolic functions. On average, a single dose (250mg) of metformin reduced diurnal HGP by 19%. Based on a Z-score of 1, 15% of patients were classified as low responders or high responders. During elevated metformin plasma levels within four after metformin ingestion, energy metabolism, cytosolic and mitochondrial redox potential, urea synthesis and ketone body synthesis were reduced by 10-30%, but averaged over 24h, these metabolic side effects were not significant. In particular, there was no significant impact of metformin on hepatic fat storage. Baseline lactate and insulin activity at 90min after glucose challenge (OGTT) correlated significantly with the reduction in HGP and may serve as predictors of effective therapy. On a daily average, metformin selectively affects hepatic glucose production, glycogen storage and lactate uptake, while numerous other metabolic functions are significantly altered only for several hours after administration of the drug. Our method provides a patient-specific analysis of the potential effects of metformin therapy on central hepatic metabolism and may therefore help guide the physician's therapeutic decision.

In Situ Tailored Frustrated Lewis Pairs on Asymmetric Bi─Ov─In Motifs Domino-Direct High-Efficiency Urea Electrosynthesis.

The green urea synthesis via co-electrolysis of waste nitrate and CO2 is alluring but challenging, especially with insufficient selectivity caused by thermodynamic differences and kinetic mismatch between multi-step conversion processes. Here, a domino effect-oriented electrosynthesis strategy is showcased to steer cascade reactions in upgrading nitrate and CO2 toward urea of high selectivity on Bi-doped In2O3 with asymmetric oxygen vacancies (Ov). The conventionally arbitrary reaction mode can be vectored and re-customized by stable and cumulative *NH2 intermediates in situ derived from priority nitrate reduction reaction, which not only form surface frustrated Lewis pairs (SFLPs, Bi─Ov─In─NH2) with Bi Lewis acid sites to synergistically adsorb and activate CO2 but also provide more opportunities for sluggish C─N coupling, delivering an unprecedented urea Faradic efficiency of 80.2% and an impressive urea yield of 2.38 × 103µg h-1 mgcat. -1 at -0.4V versus RHE. The atomically dispersed Bi sites promote the protonation of *NO to form nucleophilic *NH2 intermediates, which can be stabilized in the electrophilic region mediated by asymmetric Ov, permitting two nucleophilic attacks to complete the C─N coupling. The domino modeling protocol via positioning a specific intermediate in situ tailors the parallel conversion process and may guide selectivity control of electrosynthesis.

Activity-Selectivity Trends in Electrochemical Urea Synthesis: Co-Reduction of CO2 and Nitrates Over Single-Site Catalysts.

Electrochemical co-reduction of carbon dioxide and nitrates (CO2NO3RR) holds promise for sustainable urea production. However, the sluggish kinetics of the sixteen-electron transfer and unclear mechanistic understanding strongly impede its development. Here, combined experimental and computational approaches are employed to screen a series of metal phthalocyanine as model catalysts (MPcs, M = Zn, Co, Ni, Cu, and Fe) to uncover the activity-selectivity trends in electrochemical CO2NO3RR. Thetheoretical simulations reveal that the thermodynamics of urea synthesis is significantly influenced by key intermediates, where the enhanced adsorption of *HOOCNO, coupled with reduced adsorptions of *N and *COOH, and moderate adsorption of *H2O, can significantly promote the urea production. ΔG*HOOCNO-ΔG*N-ΔG*COOH+ΔG*H2O as a potential descriptor is proposed for predicting the efficiency of CO2NO3RR toward urea formation. The findings provide systematic guidance for the future design of high-efficiency catalysts for urea electrosynthesis, addressing a crucial need for sustainable nitrogen fixation.

Theory-Guide Design of Integrative Catalytic Pairs for Urea Synthesis from Nitrate and Carbon Dioxide.

Electrochemical coreduction of carbon dioxide and nitrate offers a sustainable pathway to synthesize value-added urea from greenhouse gas and nitrogen-containing waste; however, challenges remain in designing efficient catalysts. Based on the concept of "integrative catalytic pairs (ICPs)", a catalyst for urea synthesis is designed by introducing heteroatoms (B and C) into M-N-C, where a single transition metal is dispersed on N-doped carbon material. Using a two-step theoretical screening strategy, Ni-N3B is identified as a promising catalyst for urea synthesis, with a low limiting potential (-0.43 V) and a small kinetic barrier for C-N coupling (0.74 eV) due to the electronic regulation effects and the synergy of Ni and B function for enhancing NO3- activation and facilitating C-N coupling between gaseous CO2 and *NH intermediate. Under the guidance of these theoretical results, our further experimental validation demonstrates that the synthesized Ni-N3B catalyst achieves a Faradaic efficiency of 51.92% and a urea yield rate of 32.30 mmol h-1 g-1 at -0.6 V vs RHE. Our work not only identifies an efficient urea synthesis catalyst without relying on trial-and-error methods but also inspires further exploration of ICPs-based catalysts in electrocatalysis.

Amorphization Induces High-Density Undercoordinated Indium Sites for Enhanced Electrocatalytic Urea Synthesis

Amorphization Induces High-Density Undercoordinated Indium Sites for Enhanced Electrocatalytic Urea Synthesis

Physiological and Transcriptome Analyses of Gill and Hepatopancreas of Potamocorbula ustulata Under Ammonia Exposure

Excessive ammonia accumulation poses a significant threat to aquatic species. Potamocorbula ustulata, known for its burrowing behavior and high population density, may experience elevated ammonia levels in its environment. However, its ammonia stress response mechanisms remain unclear. This study investigates the physiological and molecular responses of P. ustulata to acute ammonia exposure. Antioxidant enzyme activity was significantly altered in the gills and hepatopancreas, with GS, GDH, and ARG levels markedly increasing in the hepatopancreas. Transcriptome analysis revealed that after 24 h of exposure, differentially expressed genes (DEGs) were enriched in apoptosis and inflammation-related pathways (MAPK, NF-kB, NOD-like receptor signaling). By 96 h, DEGs in the gills were associated with nitrogen metabolism and transport, while those in the hepatopancreas were linked to oxidative phosphorylation and amino acid metabolism. Key ammonia transport and excretion genes, including V-type H+-ATPase, Ammonium transporter Rh, and Na+/K+-ATPase, were significantly upregulated in the gills, while glutamine synthetase and glutamate dehydrogenase were upregulated in the hepatopancreas (p < 0.05). These findings suggest that ammonia stress disrupts antioxidant defense, triggers inflammation and apoptosis, and enhances ammonia tolerance through excretion, glutamine conversion, and urea synthesis. This study provides insights into the molecular mechanisms underlying ammonia tolerance in bivalves.

Construction of highly vascularized hepatic spheroids of primary hepatocytes via pro-angiogenic strategy in vitro

Primary hepatocytes are widely recognized for their ability to accurately represent thein vivohepatocyte phenotype. However, traditional avascular primary hepatocyte culture models are limited by inadequate mass transfer, which leads to a rapid decline in hepatocyte function and survival. To address these challenges, vascularization of hepatic spheroids is crucial for enhancing oxygen and nutrient supply, thereby enabling the construction of larger and more complex hepatic tissuesin vitro. In this study, we achieved vascularization of hepatic spheroids containing freshly isolated primary hepatocytes by incorporating fibroblasts as a source of paracrine factors to induce angiogenesis. Multicellular spheroids composed of primary hepatocytes and fibroblasts were formed in non-adhesive concave wells, and one of the spheroids was subsequently embedded in a fibrin-collagen hydrogel within a microfluidic device. Endothelial cells were then seeded onto adjacent microfluidic channels. They formed microvascular networks that extended toward and penetrated the hepatic spheroid. The vascularized hepatic spheroid closely mimicked hepatic sinusoids, with hepatocytes in close contact with microvessels. Moreover, the vascularized spheroid exhibited significantly enhanced hepatic function, specifically albumin secretion and urea synthesis. Our findings provide insights into the establishment of highly vascularized hepatic spheroidsin vitro, which is crucial for constructing scalable hepatic tissues in the context of biofabrication.

Recent innovations in urea synthesis via electrochemical C-N coupling reaction: insights and perspectives

Recent innovations in urea synthesis via electrochemical C-N coupling reaction: insights and perspectives

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 CO2 emissions. Electrocatalytic urea synthesis under ambient conditions via CN coupling from CO2 and 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 CN coupling reaction for electrocatalytic urea synthesis. Furthermore, this review explores future prospects for industrial CN coupling, considering potential nitrogen and carbon sources and examining alternative CN coupling products, such as amides and amines.

Balancing Intermediates Formation on Atomically Pd‐Bridged Cu/Cu2O Interfaces for Kinetics‐Matching Electrocatalytic C─N Coupling Reaction

AbstractThe electrochemical C─N coupling of CO2 and nitrogenous species provides a promising approach for synthesizing valuable chemicals such as urea, amides, and other C─N compounds. However, the unbalanced formation of C‐ and N‐intermediates results in slow C─N coupling kinetics. Herein, we report an atomically Pd‐bridged Cu/Cu2O (Pd1–Cu/Cu2O) catalyst, synthesized through the in situ electrochemical reconstruction of Pd1–Cu2Te nanosheets. This catalyst features Pd–Cu dual sites that significantly enhance C─N coupling both thermodynamically and kinetically. The reconstructed Pd1–Cu/Cu2O achieves a urea yield rate of 31.8 mmol h−1 gcat.−1 and a Faradaic efficiency (FE) of 42.2%, along with excellent stability over 100 h. In situ spectroscopic examinations and theoretical calculations disclose that the Pd–Cu dual sites on Pd1–Cu/Cu2O modulate the reduction kinetics of CO2 and NO3−, balance the formation of crucial *CO and *NH2 intermediates, and lower the energy barrier for C─N coupling, thereby facilitating urea synthesis. Furthermore, the Pd1–Cu/Cu2O enables the unprecedented C─N coupling of aniline with CO, resulting in a remarkable acetanilide yield rate of 1021.2 mmol h−1 gcat.−1 with an FE of 23.7%. This heteroatom bridging strategy offers a new pathway for designing efficient electrocatalyst for the synthesis of C─N coupled compounds.

Balancing Intermediates Formation on Atomically Pd-Bridged Cu/Cu2O Interfaces for Kinetics-Matching Electrocatalytic C─N Coupling Reaction.

The electrochemical C─N coupling of CO2 and nitrogenous species provides a promising approach for synthesizing valuable chemicals such as urea, amides, and other C─N compounds. However, the unbalanced formation of C- and N-intermediates results in slow C─N coupling kinetics. Herein, we report an atomically Pd-bridged Cu/Cu2O (Pd1-Cu/Cu2O) catalyst, synthesized through the in situ electrochemical reconstruction of Pd1-Cu2Te nanosheets. This catalyst features Pd-Cu dual sites that significantly enhance C─N coupling both thermodynamically and kinetically. The reconstructed Pd1-Cu/Cu2O achieves a urea yield rate of 31.8mmol h-1 gcat. -1 and a Faradaic efficiency (FE) of 42.2%, along with excellent stability over 100h. In situ spectroscopic examinations and theoretical calculations disclose that the Pd-Cu dual sites on Pd1-Cu/Cu2O modulate the reduction kinetics of CO2 and NO3 -, balance the formation of crucial *CO and *NH2 intermediates, and lower the energy barrier for C─N coupling, thereby facilitating urea synthesis. Furthermore, the Pd1-Cu/Cu2O enables the unprecedented C─N coupling of aniline with CO, resulting in a remarkable acetanilide yield rate of 1021.2mmol h-1 gcat. -1 with an FE of 23.7%. This heteroatom bridging strategy offers a new pathway for designing efficient electrocatalyst for the synthesis of C─N coupled compounds.

Surface engineering on bulk Cu2O for efficient electrosynthesis of urea

Electrochemical urea synthesis has recently emerged as a fascinating energy-efficient alternative route, while it remains challenging to achieve simultaneously high production rate and Faradaic efficiency. Herein, we realize an energy-favorable electrochemical C-N coupling path through CO2 and NO3− co-reduction at the heterointerfaces of Cu/Cu2O microparticles, generated by in-situ electrochemical engineering on bulk Cu2O. We achieve urea production rate of 632.1 μg h−1mgcat.−1 with a corresponding Faradaic efficiency of 42.3% at −0.3 V (versus RHE) under ambient conditions. Operando synchrotron radiation-Fourier transform infrared spectroscopy, along with theoretical calculations, reveals the coupling of intermediates NOH* and CO* at the heterointerfaces, benefiting from the modified electronic structure. This work provides a practical route for catalyst design and insights into urea electrosynthesis systems.

Electrode-Electrolyte Engineering and In Situ Spectroscopy for Urea Electrosynthesis from Carbon Dioxide and Nitrate Co-Reduction.

The biogeochemical cycles of carbon and nitrogen are globally disturbed due to the intensive use of fossil fuels and fertilizers, which is reflected by the accumulation of carbon dioxide in the atmosphere and nitrate in water streams. The co-electroreduction of carbon dioxide and nitrate is a promising low-carbon alternative for urea synthesis that would help to reestablish both carbon and nitrogen cycles. This Perspective highlights the importance of rational catalyst and electrolyte engineering to enable electrochemical urea synthesis. Although the field has gained significant attention over the past few years, fundamental research under well-defined conditions remains underexplored. We highlight the importance of investigating structure-sensitivity and electrolyte effects on electrochemical C-N coupling through complementary in situ spectroscopy and online techniques. Model studies, including in situ surface-sensitive investigations, will be crucial to understand the molecular mechanisms and thus to rationally design more efficient systems for urea electrosynthesis, paving the way for their scalable and industrial applications.

A multi-site Ru-Cu/CeO2 photocatalyst for boosting C-N coupling toward urea synthesis.

A multi-site Ru-Cu/CeO2 photocatalyst for boosting C-N coupling toward urea synthesis.

Shape-dependency activity of Nanostructured α-Mn2O3 in direct synthesis of ethylene urea from CO2

Shape-dependency activity of Nanostructured α-Mn2O3 in direct synthesis of ethylene urea from CO2

Multi-orbital electronic coupling mediated by integrating multiple-metal hybridizations at ultrafast heating accumulation for efficient electrochemical urea synthesis

Multi-orbital electronic coupling mediated by integrating multiple-metal hybridizations at ultrafast heating accumulation for efficient electrochemical urea synthesis