Urea Production Research Articles

Fundamentals and Rational Design of Heterogeneous C‐N Coupling Electrocatalysts for Urea Synthesis at Ambient Conditions

AbstractElectrocatalytic C‐N coupling reaction is regarded as a promising strategy for achieving clean and sustainable urea production by coreducing CO2 and nitrogen species, thus contributing to carbon neutrality and the artificial nitrogen cycle. However, restricted by the sluggish adsorption of reactants, competitive side reactions, and multistep reaction pathways, the electrochemical urea production suffers from a low urea yield rate and low selectivity so far. In order to comprehensively improve urea synthesis performance, it is crucial to develop highly efficient catalysts for electrochemical C‐N coupling. In this article, the catalyst‐designing strategies, C‐N coupling mechanisms, and fundamental research methods are reviewed. For the coreduction of CO2 and different nitrogen species, several prevailing reaction mechanisms are discussed. With the aim of establishing the standard research system, the fundamentals of electrocatalytic urea synthesis research are introduced. The most important catalyst‐designing strategies for boosting the electrocatalytic urea production are discussed, including heteroatom doping, vacancy engineering, crystal facet regulation, atom‐scale modulation, alloying and heterostructure construction. Finally, the challenges and perspectives are proposed for future industrial applications of electrochemical urea production by C‐N coupling.

Characteristics of N Transformation of Humic Acid Urea in Different Circle Layers of the Fertisphere: A Simulated Experiment

Due to its broad yield-increasing effect and low cost, humic acid urea (HAU) has become one of the leading modified fertilizers worldwide. The fertisphere is the primary space where urea (U) granules participate in the soil nitrogen cycle, forming a nutrient concentration gradient centered on the point of fertilization. The closer the circle layers to the urea granule in the fertisphere, the higher the nitrogen concentration. However, HAU in this microregion remains poorly understood. The differences in the transformation process from the inside to outside circle layers of the U and HAU fertispheres were simulated and studied using soil incubation experiments under 20, 10, 2, 1, and 0.2 g kg−1 nitrogen inputs. The 20 and 10 g kg−1 inputs represent the layers closest to the urea granule. Within the first seven days, HAU treatment showed higher concentrations of soil ammonia-N content than U treatment within the two layers closest to the fertilizer core, while exhibiting lower concentrations under the farthest two layers. Under 2 g kg−1 nitrogen input, the nitrate nitrogen under the HAU treatment was significantly higher than that in the U treatment, indicating a higher nitrification rate. During the 42-day incubation period, soil mineral nitrogen content under the HAU treatment was higher than that for the U treatment in the two closest circles. On the 42nd day, the residual urea-N under the HAU treatment was significantly higher than that for the U treatment when the nitrogen input was higher than 1 g kg−1. The effect of higher fertilizer preservation and supply capacity of HAU in Fluvo-aquic soil was achieved by changing the urease activity and nitrification rate in fertisphere ranges closer to the fertilizer core. An improved understanding of the high-efficiency mechanism of HAU in the fertisphere process will contribute to the development of new-generation high-efficiency urea products.

Efficient Solar Driven Upgrading of N2 to Urea Through Photoredox Reactions on Pt Cluster/TiO2

AbstractSynthetic nitrogen fertilizers, such as urea, are instrumental in augmenting agricultural output and addressing the demands of a growing population. Nevertheless, conventional urea production heavily relies on energy‐intensive processes. In this study, an environmentally friendly photocatalytic method is proposed for directly and selectively synthesizing urea from nitrogen (N2) and methanol (CH3OH using a Pt cluster‐decorated TiO2 catalyst (Pt cluster/TiO2). Remarkably, the Pt cluster/TiO2 exhibits outstanding urea synthesis performance with a rate of 105.68 µmol g−1 h−1 and N‐selectivity of 97.29 ± 0.79%, representing the highest level of photocatalytic urea synthesis from N2. Further analysis with density functional theory (DFT) calculation reveals that the “σ–π*” donor–acceptor interaction occurred between Pt clusters and N2, efficiently reducing the N2 hydrogenation barrier. EPR experiments demonstrate that photogenerated electrons (e−) and hole (h+) are synchronously consumed through N2 reduction and CH3OH oxidation, thereby accelerating urea synthesis. The crucial step of C─N coupling is initiated by the reaction between *NH─NH and *CHO intermediate, facilitated by the low energy barrier on Pt cluster/TiO2. This work suggests an mild route of urea production and provides profound insights into the underlying chemistry of the C─N coupling reaction, which can guide the sustainable synthesis of essential indispensable chemicals.

Environmental Impact Assessment of Rice–Wheat Rotation Considering Annual Nitrogen Application Rate

Rice–wheat rotation is a widely adopted multiple-cropping system in the Yangtze River Basin, China. Nitrogen (N) fertilizer is a key factor in regulating crop yield; however, only a few studies have considered the impact of annual N application on the yield, environmental impacts, and economic profits of rice–wheat rotation systems. In this study, a field experiment was conducted in the Jiangsu Province from 2020 to 2022. The rice and wheat seasons included six and five N fertilizer application rates, respectively (Rice: 0, 180, 240, 300, 360, and 420 kg N ha−1; Wheat: 0, 180, 240, 300, and 360 kg N ha−1), combined to form a total of 30 treatments. Life-cycle assessment was used to evaluate the environmental impacts of rice–wheat rotation under different N application treatments, using area, yield, and economic profit as functional units. Ten environmental impact categories were selected, including global warming. The results showed that grain yield did not consistently increase with an increase in N application, and the annual yield was the highest when 300 and 240 kg N ha−1 (R300W240 treatment) was applied in the rice and wheat seasons, respectively. The area-based weighting index of the R300W240 treatment ranked 20th among the 30 treatments, while the yield- and profit-based weighting indices were the lowest among the 30 treatments, decreasing by 14.9% and 28.7%, respectively, compared to the other treatments. The R300W240 treatment was the optimal annual N application strategy for rice–wheat rotation. Among the 10 environmental impacts considered, urea production contributed significantly to over eight environmental impacts, whereas the pollutant losses caused by its application contributed significantly to six environmental impacts. These findings reveal the dependence of the rice–wheat rotation system on the unsustainable use of N fertilizer and indicate that N fertilizer management practices should be further optimized to improve the environmental sustainability of grain production in the future.

The industry transformation from fossil fuels to hydrogen will reorganize value chains: Big picture and case studies for Germany

In many industries, low-carbon hydrogen will substitute fossil fuels in the course of the transformation to climate neutrality. This paper contributes to understanding this transformation. This paper provides an overview of energy- and emission-intensive industry sectors with great potential to defossilize their production processes with hydrogen. An assessment of future hydrogen demand for various defossilization strategies in Germany that rely on hydrogen as a feedstock or as an energy carrier to a different extent in the sectors steel, chemicals, cement, lime, glass, as well as pulp and paper is carried out. Results indicate that aggregate industrial hydrogen demand in those industries would range between 197 TWh and 298 TWh if production did not relocate abroad for any industry sector. The range for hydrogen demand is mainly due to differences in the extent of hydrogen utilization as compared to alternative transformation paths for example based on electrification. The attractiveness of production abroad is then assessed based on the prospective comparative cost advantage of relocating parts of the value chain to excellent production sites for low-carbon hydrogen. Case studies are provided for the steel industry, as well as the chemical industry with ethylene production through methanol and the production of urea on the basis of ammonia. The energy cost of the respective value chains in Germany is then compared to the case of value chains partly located in regions with excellent conditions for renewable energies and hydrogen production. The results illustrate, that at least for some processes – as ammonia production – relocation to those favorable regions may occur due to substantial comparative cost advantages.

Effects of a second iron-dextran injection administered to piglets during lactation on differential gene expression in liver and duodenum at weaning.

Six female littermate piglets were used in an experiment to evaluate the mRNA expression in tissues from piglets given one or two 1mL injections of iron dextran (200mg Fe/mL). All piglets in the litter were administered the first 1mL injection < 24h after birth. On day 7, piglets were paired by weight (mean body weight = 1.72 ± 0.13kg) and one piglet from each pair was randomly selected as control (CON) and the other received a second injection (+Fe). At weaning on day 22, each piglet was anesthetized, and samples of liver and duodenum were taken from the anesthetized piglets and preserved until mRNA extraction. differential gene expression data were analyzed with a fold change cutoff (FC) of |1.2| P < 0.05. Pathway analysis was conducted with Z-score cutoff of P < 0.05. In the duodenum 435 genes were significantly changed with a FC ≥ |1.2| P < 0.05. In the duodenum, Claudin 1 and Claudin 2 were inversely affected by + Fe. Claudin 1 (CLDN1) plays a key role in cell-to-cell adhesion in the epithelial cell sheets and was upregulated (FC = 4.48, P = 0.0423). Claudin 2 (CLDN2) is expressed in cation leaky epithelia, especially during disease or inflammation and was downregulated (FC = -1.41, P = 0.0097). In the liver, 362 genes were expressed with a FC ≥ |1.2| P < 0.05. The gene most affected by a second dose of 200mg Fe was hepcidin antimicrobial peptide (HAMP) with a FC of 40.8. HAMP is a liver-produced hormone that is the main circulating regulator of Fe absorption and distribution across tissues. It also controls the major flows of Fe into plasma by promoting endocytosis and degradation of ferroportin (SLC4A1). This leads to the retention of Fe in Fe-exporting cells and decreased flow of Fe into plasma. Gene expression related to metabolic pathway changes in the duodenum and liver provides evidence for the improved feed conversion and growth rates in piglets given two iron injections preweaning with contemporary pigs in a companion study. In the duodenum, there is a downregulation of gene clusters associated with gluconeogenesis (P < 0.05). Concurrently, there was a decrease in the mRNA expression of genes for enzymes required for urea production in the liver (P < 0.05). These observations suggest that there may be less need for gluconeogenesis, and possibly less urea production from deaminated amino acids. The genomic and pathway analyses provided empirical evidence linking gene expression with phenotypic observations of piglet health and growth improvements.

Efficient C-N coupling for urea electrosynthesis on defective Co3O4 with dual-functional sites.

Urea electrosynthesis under ambient conditions is emerging as a promising alternative to conventional synthetic protocols. However, the weak binding of reactants/intermediates on the catalyst surface induces multiple competing pathways, hindering efficient urea production. Herein, we report the synthesis of defective Co3O4 catalysts that integrate dual-functional sites for urea production from CO2 and nitrite. Regulating the reactant adsorption capacity on defective Co3O4 catalysts can efficiently control the competing reaction pathways. The urea yield rate of 3361 mg h-1 gcat-1 was achieved with a corresponding faradaic efficiency (FE) of 26.3% and 100% carbon selectivity at a potential of -0.7 V vs. the reversible hydrogen electrode. Both experimental and theoretical investigations reveal that the introduction of oxygen vacancies efficiently triggers the formation of well-matched adsorption/activation sites, optimizing the adsorption of reactants/intermediates while decreasing the C-N coupling reaction energy. This work offers new insights into the development of dual-functional catalysts based on non-noble transition metal oxides with oxygen vacancies, enabling the efficient electrosynthesis of essential C-N fine chemicals.

Boosting urea synthesis in simulated flue gas electroreduction by adjusting W–W electronic properties

Porous catalyst with dual catalytic sites realizes efficient electrocatalytic production of urea from flue gas via adjusting W–W electronic properties.

Electrochemical urea production using carbon dioxide and nitrate: state of the art and perspectives

The minireview highlights recent developments in designing electrocatalysts for the co-reduction of CO2 and nitrates into urea. It also discusses advanced detection methods for intermediates and final products, as well as future research prospects.

Exploration of earth-abundant transition metals (Fe, Co, Ni) doped on W18O49 system as electrocatalysts for urea productiont

The conversion of inert N2 and CO2 into urea by electrocatalytic technology not only reduces the cost of urea synthesis in future, but also alleviates the environmental pollution problem caused by carbon emission in traditional industrial production. However, facing downside factors such as strong competitive reactions and unclear reaction mechanism, the design of high-performance urea catalysts is imminent. This study demonstrates that W18O49 system doped heteronuclear metals (TM = Fe, Co, Ni) can effectively solve the problem of competitive adsorption between N2 and CO2 and realize the co-adsorption of N2 and CO2 at diverse sites. Their theoretical limiting voltages for urea production on TM-W18O49 (TM = Fe, Co, Ni) systems are −0.46 V, −0.42 V and −0.52 V, respectively. The results are all lower than that of the contrastive voltage in pristine W18O49 system (-0.91 V), further indicating the rationality and necessity of single-atom doped strategy for the co-reduction of two molecules. Specially, Co-W18O49 can theoretically inhibit the side reactions of NRR, CO2RR, and HER, which deserve future experimental exploration in future. The study suggests that doping heteronuclear metal into transition metal oxides is a feasible scheme to solve competitive adsorption and improve catalytic performance.

Mild and scalable synthesis of a high performance CrFeCoNiRu0.05 high entropy nano-alloy/carbon electrocatalyst for efficient urea production with a chelate-based ionic liquid

We firstly reported synthesis of CrFeCoNiRu0.5 high-entropy alloy nanoparticles using an ionic liquid. The CrFeCoNiRu0.5 high-entropy alloy provides exceptionally high electrocatalytic activity for green urea synthesis.

Theoretical study on the synthesis of urea by series electrocatalysis of lithium main group embedded in COF structure

Replacement of the Harber-Bosch process for urea production by electrochemical reduction is an attractive alternative that reduces chemical energy consumption, reduces environmental pollution and improves efficiency. Among them, the method of electrochemical coupling of N2 and CO2 to produce urea has been widely used, but the inertness of nitrogen and nitrogen bond and high dissociation energy make it difficult to activate N2. Meanwhile, the method of synthesis of urea by NO3RR came into being. Nitrate in sewage is more abundant and convenient than nitrogen raw material, and more importantly, the dissociation energy of NO bond is much lower than that of NN. In this study, the transition metal embedded lithium COF catalyst was taken as an example, and the optimal electrocatalyst was selected through screening and synthesis energy barrier comparison to study the mechanism of urea synthesis. We studied the NRR and NO3RR paths, respectively, and found that the NRR synthesis of urea was optimal on the LiTaS-Pc VPPs catalyst, with a limiting potential value of −0.57V, and the NO3RR synthesis of urea was optimal on the LiVS-Pc VPPs catalyst, with a limiting potential value of −0.39V. It is found that NO3RR on the lithium catalyst is relatively better, and the required limit potential value is lower. In addition, the advantage of choosing lithium metal doping as catalyst in our study is that HER can be well inhibited, and the desorption of urea is easier than that of transition metal doping (taking molybdenum as an example). This study points out the direction for the electrocatalytic synthesis mechanism of urea, and provides a new idea for the selection of catalysts, paving the way for the future production of urea.

Investigation of Iron Based Di-Atomic Catalysts to Identify Active Sites for Coupled Reduction Reactions of CO2 and N2

Urea is a valuable chemical feed stock that is commonly used in fertilizers and other industrial applications, including for the production of plastics and resins. Conventionally, industrial urea is produced through the reaction of ammonia and carbon dioxide under high pressure and temperature, resulting in intensive energy inputs and inefficiencies. In contrast, electrochemical synthesis of urea under mild conditions has been shown to be possible by coupled electrochemical reduction of CO2 (CO2RR) and N2 (NRR)1. While finding active and efficient catalysts remains a major challenge, rational design can be advanced by identification of the favourable atomic arrangements that facilitate C-N bond formation. For this purpose, carbon-supported and nitrogen-coordinated metal single atom catalysts (SACs) are a promising class of electrocatalysts2. Given their well-defined atomic structure, these material systems are valuable model systems for identifying active sites for specific reactions.Cu and Ni are well-known as efficient CO2RR catalysts3,4, whereas Fe-based catalysts are traditionally used for N2 fixation to produce NH3 via the thermochemical Haber-Bosch method5. This background knowledge served as motivation for fabrication of two types of di-atomic catalysts (DACs), containing Cu-Fe and Ni-Fe components anchored in an electrochemically inert carbon framework. A wet-chemical method was used for synthesizing these materials. While no crystalline metallic reflections were observed in X-ray diffraction patterns, X-ray photoelectron spectroscopy confirmed the presence of constituent metals along with lattice N, O, and C. The X-ray absorption near edge structure (XANES) measurements of Fe, Ni and Cu edges show significantly different spectra when compared to corresponding metal foils and oxides. Importantly, a nitrogen-coordinated ‘single atom’ morphology with inter-metal interactions is confirmed by extended X-ray absorption fine structure (EXAFS). Electrochemical reduction reactions in the presence of CO2 and N2 showed formation of 2e- CO2RR products, with CO dominant for the case of Ni-Fe DACs. In contrast, for the case of Cu-Fe DACs, formic acid generation was significantly more pronounced than CO. For the case of isolated NRR, NH3 was observed for both DACs. The production of urea, however, was only observed for Cu-Fe DACs. While mechanistic investigations are underway, the primary difference in these activities is hypothesized to be due to formation of different intermediates and reaction paths followed during CO2RR. Previous studies6 have suggested that the choice of reaction path, CO2→*OCHO→formic acid or CO2→*COOH→CO, could be dependent on oxophilicity of the reaction site. Our observations indicate that C-N coupling is promoted by oxophilic CO2RR catalysts. Since the direct identification of active sites for coupled CO2RR and NRR has rarely been reported using simple ‘single atom’ based catalyst systems, our work opens up a new direction for designing catalysts capable of C-N coupling for the efficient generation of the valuable chemical, urea, under ambient conditions.References Chen, C., Zhu, X., Wen, X., Zhou, Y., Zhou, L., Li, H., Tao, L., Li, Q., Du, S., Liu, T. and Yan, D., Nat. Chem. 12, 717–724 (2020).Chen, Y., Ji, S., Chen, C., Peng, Q., Wang, D. and Li, Y., Joule 2, 1242–1264, (2018).Ferri, M., Delafontaine, L., Guo, S., Asset, T., Cristiani, P., Campisi, S., Gervasini, A. and Atanassov, P., ACS Energy Lett. 7, 2304–2310, (2022).Leverett, J., Yuwono, J.A., Kumar, P., Tran-Phu, T., Qu, J., Cairney, J., Wang, X., Simonov, A.N., Hocking, R.K., Johannessen, B. and Dai, L., ACS Energy Lett. 7, 920–928 (2022).Fuller, J., An, Q., Fortunelli, A. and Goddard III, W.A., Acc. Chem. Res. 55, 1124–1134 (2022).Feaster, J.T., Shi, C., Cave, E.R., Hatsukade, T., Abram, D.N., Kuhl, K.P., Hahn, C., Nørskov, J.K. and Jaramillo, T.F., ACS Catal. 7, 4822–4827 (2017).

Electrocatalytic Urea Synthesis via C-N Coupling from CO2 and Nitrogenous Species.

ConspectusIndustrial urea synthesis consists of the Haber-Bosch process to produce ammonia and the subsequent Bosch-Meiser process to produce urea. Compared to the conventional energy-intensive urea synthetic protocol, electrocatalytic C-N coupling from CO2 and nitrogenous species emerges as a promising alternative to construct a C-N bond under ambient conditions and to realize the direct synthesis of high-value urea products via skipping the intermediate step of ammonia production. The main challenges for electrocatalytic C-N coupling lie in the intrinsic inertness of molecules and the competition with parallel side reactions. In this Account, we give an overview of our recent progress toward electrocatalytic C-N coupling from CO2 and nitrogenous species toward urea synthesis.To begin, we present the direct transformation of dinitrogen (N2) to the C-N bond by coelectrolysis, verifying the feasibility of direct urea synthesis from N2 and CO2 under ambient conditions. In contrast to the highly endothermic step of proton coupling in conventional N2 reduction, the N2 activation and construction of the C-N bond arise from a thermodynamic spontaneous reaction between CO (derived from CO2 reduction) and *N═N* (the asterisks represent the adsorption sites), and the crucial *NCON* species mediates the interconversion of N2, CO2, and urea. Based on theoretical guidance, the effect of N2 adsorption configurations on C-N coupling is investigated on the model catalysts with defined active site structure, revealing that the side-on adsorption rather than the end-on one favors C-N coupling and urea synthesis.Electrocatalytic C-N coupling of CO2 and nitrate (NO3-) is also an effective pathway to achieve direct urea synthesis. We summarize our progress in the C-N coupling of CO2 and NO3-, from the aspects of modulating intermediate species adsorption and reaction paths, monitoring irreversible and reversible reconstruction of active sites, and precisely constructing active sites to match activities and to boost the electrocatalytic urea synthesis. In each case, in situ electrochemical technologies and density functional theory (DFT) calculations are carried out to unveil the microscopic mechanisms for the promotion of C-N coupling and the enhancement of urea synthesis activity. In the last section, we put forward the limitations, challenges, and perspectives in these two coupling systems for further development of electrocatalytic urea synthesis.

Determination of the heat transfer coefficient between pellets and air during the modernization of a pelletizing tower based on industrial research

The object of research is the heat transfer coefficient between pellets and air flow in industrial granulation towers. The problem lies in the difficulty of optimizing the heat transfer process. As a result of experiments and analysis, it was shown that each granulating tower for the production of mineral fertilizers has unique properties that significantly affect the efficiency of heat transfer. There are general mathematical models, but for accurate modeling and optimization of heat transfer, the unique characteristics of each production must be taken into account. The results showed that creating an accurate mathematical model for each specific fertilizer production is a difficult task due to the large number of unmeasured or difficult to reconcile factors. The method of calculating the heat transfer coefficient for the granulator tower obtained in the course of the work derives from a set of researches on the production of mineral fertilizers. This approach is based on the analysis of technical parameters and granulation composition of the product. The developed method makes it possible to reliably ensure the operating conditions of the device during modernization and changes in production volumes. These results are important for both practical and theoretical purposes. They can be used to accurately predict the operating conditions of equipment during modification and productivity growth. According to the research results, this approach allows obtaining fairly reliable data for forecasting the thermodynamic conditions of the tower equipment in the event of its modernization and transition of the granulation tower to the production of an increased amount of products. The specified method was tested in calculations of production modernization at urea production plants (Indian Farmers Fertilizer Cooperative (Iffco), India), Rustavi Azot LLC (Georgia), Grodno Azot LLC (Republic of Belarus) and others. This method has proven to be quite reliable in predicting the possible need for an additional amount of air supplied to the tower and forming requirements for the operating parameters of rotary vibrating granulators in the event of a significant increase in the load on the float in the tower and an increase in the amount of products planned for release.

FeOOH with Low Spin State Iron as Electron Acceptors for High Yield Rate Electrosynthesis of Urea from Nitrate and Carbon Dioxide.

Co electroreduction of carbon dioxide and nitrate to synthesize urea provides an alternative strategy to high energy-consumption traditional methods. However, the complexity of the reaction mechanism and the high energy barrier of nitrate reduction result in a diminished production of urea. Herein, a convenient electrodeposition technique to prepare the FeOOH with low spin state iron that increases the yield rate of urea efficiently is employed. According to soft X-ray Absorption Spectroscopy and theoretical calculations, the unique configuration of low spin state iron as electron acceptors can effectively induce electron pair transfer from the occupied σ orbitals of intermediate * NO to empty d orbitals of iron. This σ→d donation mechanism leads to a reduction in the energy barrier associated with the rate-determining step (* NOOH→* NO+* OH), hence augmenting the urea generation. The low spin state iron presents a high urea yield rate of 512µgh-1 cm-2 , representing approximately two times compared to the medium spin state iron. The key intermediates (* NH2 and * CO) in the formation of C─N bond are detected with in situ Fourier transform infrared spectroscopy. The coupling of * NH2 and * CO contributes to the formation of * CONH2 , which subsequently endures multi-step proton-coupled electron transfer to generate urea.

Effective synthesis of ethylene urea from CO2 adsorbed cerium doped Mg–Al layered double hydroxide

The steady increase in CO2 levels in the atmosphere is the leading cause of climate change and global warming and is now a global concern. To reduce the impact of CO2, various novel routes have been proposed to capture, utilize, and convert it into valuable chemicals. In this study, a noble Ce-doped Mg–Al layered double hydroxide (Mg–Al LDH) [Mg/Al molar ratio = 3 and Ce/Al molar ratio = 0.1, 0.5, 1.0] were synthesized using co-precipitation and sol–gel method and used as an adsorbent for CO2 gas and later on efficient source of CO2 in the synthesis of ethylene urea (EU). The specific surface area of the Ce-doped Mg–Al LDHs prepared by sol-gel method (96.1–333 m2/g) were higher than co-precipitation method (0.5–10.6 m2/g). Each Ce-doped Mg–Al LDHs were successfully adsorbed CO2, where first desorption occurred at around 50–250 °C temperature. The comparative adsorption of CO2 was observed increase with decreasing the Ce/Al molar ratio. Adsorption of CO2 was found to be 0.05, 0.04, 0.04 mmol/g for co-precipitation method and 0.62, 0.42, 0.37 mmol/g for sol-gel method, where Ce/Al molar ratio was 0.1, 0.5, 1.0 respectively. The EU produced from the reaction between ethylenediamine (EDA) and CO2 adsorbed Ce-doped Mg–Al LDHs, where a comparative amount of EU was observed in the order of Ce/Al molar ratio = 1.0 > 0.5 > 0.1. According to the temperature effect, EU production was increased with an increase in temperature from 120 °C to 160 °C. At 160 °C, the production of EU by co-precipitation method was found to be 0.03, 0.04, 0.07 mmol/g and by sol-gel method was found to be 0.06, 0.07, 0.16 mmol/g, where Ce/Al molar ratio was 0.1, 0.5, 1.0 respectively. A much higher production was found in all the Ce-doped Mg–Al LDHs compared to pristine Mg–Al LDH at all the temperatures. The performance of Ce-doped Mg–Al LDHs synthesized by the sol-gel method was observed to be better than that of the co-precipitation method in terms of both adsorption of CO2 and production of EU. In this study, Ce-doped Mg–Al LDH introduced as a successful CO2 adsorbent, a source of CO2 and an effective promoter in the ethylene urea production.

Sub-lethal impacts of lead poisoning on blood biochemistry, immune function and delta-aminolevulinic acid dehydratase (δ-ALAD) activity in Cape (Gyps coprotheres) and white-backed (G. africanus) Vulture chicks

Although the prevalence of lead poisoning in southern Africa's Gyps vultures is now well-established, its finer physiological effects on these endangered species remain poorly characterised. We evaluated the sub-lethal impact of acute lead exposure on Cape and White-backed Vulture chicks from two breeding colonies in South Africa, by analysing its possible effects on key blood biochemistry parameters, immune function, packed cell volume and δ-aminolevulinic acid dehydratase (δ-ALAD) activity. All 37 White-backed Vulture nestlings sampled displayed elevated lead levels (>10 μg/dL), and seven had blood [Pb] >100 μg/dL. Eight of 28 Cape Vulture nestlings sampled had blood [Pb] exceeding background exposure, with one showing blood [Pb] >100 μg/dL. Delta-aminolevulinic acid dehydratase (δ-ALAD) activity was significantly and negatively related to blood [Pb] in nestlings from both species, with 50% inhibition of the enzyme predicted to occur at blood [Pb] = 52.8 μg/dL (White-backed Vulture) and 18.8 μg/dL (Cape Vulture). Although no significant relationship was found between % packed cell volume (PCV) and blood [Pb], the relatively lower mean PCV of 32.9% in White-backed Vulture chicks, combined with normal serum protein values, is likely indicative of depression or haemolytic anaemia. The leukogram was consistent in both species, although the presence of immature heterophils suggested an inflammatory response in White-backed Vulture chicks with blood [Pb] >100 μg/dL. Values for cholesterol, triglycerides, total serum protein, albumin, globulin, albumin/globulin ratio, alanine aminotransferase (ALT) and gamma-glutamyl transferase (GGT) were consistent with values previously reported. Calcium and phosphorus concentrations suggested no adverse effects on bone metabolism. A significant decrease in urea: uric acid (U:UA) ratio at blood [Pb] >100 μg/dL in White-backed Vulture chicks, brought about by a decrease in urea production, raises the possibility of hepatic abnormality. These results suggest that δ-ALAD activity may serve as a sensitive biomarker of lead toxicity in both species, while highlighting the need to better understand the significant variability in sensitivity that is observed, even between closely related members of the same genus.

A Comprehensive Review of Nano-Urea vs. Conventional Urea

Conventional chemical fertilizers, notably urea, have long been employed globally to meet the increasing demands for food production. However, the use of conventional urea has raised environmental concerns, including nitrate leaching, global warming, ozone layer depletion, and groundwater pollution. Additionally, there is an overburden on the government in the form of import expenditure. As the global population grows and arable land diminishes, the demand for chemical fertilizers, particularly nitrogen intensifies. Urea production, responsible for a significant portion of the global nitrogen fertilizer demand, contributes to environmental problems such as greenhouse gas emissions and pollution. Researchers advocate for reducing urea demand through energy-efficient fertilizers to address these issues. Nano-fertilizers, characterized by nano-dimensions and slow-release properties, offer a potential solution. They serve as efficient nutrient carriers, minimizing losses through leaching and emissions. Nano-urea, developed by the Indian Farmers Fertiliser Cooperative (IFFCO), stands out with nanometer-sized particles, prolonged shelf-life, and reduced environmental impact. Its adoption holds promise for sustainable agriculture, reducing agro-chemical use and enhancing soil health. Comparing nano-urea to conventional urea reveals higher efficiency, reduced environmental impact, controlled nutrient supply, and economic benefits. Nano-urea's nanotechnology-based innovations offer a transformative approach to crop nutrition, promoting sustainability, environmental conservation, and increased profitability for farmers. The Indian Agricultural Research Institute's experiment revealed that basal nitrogen application at 75% with prilled urea, full phosphorus and potassium, and nano-urea + nano-Zn sprays achieved yields comparable to 100% N + full P and K doses. Embracing energy-efficient novel fertilizers, such as nano-fertilizers, is crucial for achieving sustainable agriculture and meeting global food demands while mitigating environmental impacts.

Sonochemical‐Assisted Synthesis of Ultrathin NiCu layered Double Hydroxide for Enhanced CN Coupling toward Electrocatalytic Urea Synthesis

The electrocatalytic carbon–nitrogen (CN) coupling, facilitating one‐step urea synthesis under ambient conditions, holds great promise as a viable alternative to conventional protocols. However, developing efficient and low‐cost electrocatalysts for CN coupling remains a great challenge. Herein, a “bottom‐up” strategy is proposed to synthesize multidimensional hybrid materials of ultrathin NiCu layered double hydroxide (LDH) nanosheets on carbon nanofiber (u‐NiCu‐LDH/CNF) through an ultrasonic‐assisted solvothermal method. The NiCu‐LDH nanosheets in the u‐NiCu‐LDH/CNF composite exhibit a significantly thinner morphology compared to NiCu‐LDH/CNF prepared by conventional solvothermal without ultrasonic assistance. Leveraging its large specific surface area and well‐exposed active sites, the u‐NiCu‐LDH/CNF demonstrates dramatically improved electrocatalytic activity in CN coupling for urea production, leading to a satisfactory urea yield rate (19.43 mmol g−1 h−1) and a high Faradaic efficiency (13.95%). Density functional theory calculations reveal that the CN coupling step on the NiCu‐LDH model starts through the reaction between *NO2 and *CO2 intermediates. This spontaneous CN coupling process is beneficial in promoting high levels of urea yield. This work presents a facile approach for preparing 2D ultrathin LDH, showcasing tremendous prospects in electrocatalytic urea synthesis.