Showing papers on "Urea published in 2020"
TL;DR: An electrocatalyst consisting of PdCu alloy nanoparticles on TiO2 nanosheets has been shown to directly couple N2 and CO2 in H2O to produce urea under ambient conditions.
Abstract: The use of nitrogen fertilizers has been estimated to have supported 27% of the world’s population over the past century. Urea (CO(NH2)2) is conventionally synthesized through two consecutive industrial processes, N2 + H2 → NH3 followed by NH3 + CO2 → urea. Both reactions operate under harsh conditions and consume more than 2% of the world’s energy. Urea synthesis consumes approximately 80% of the NH3 produced globally. Here we directly coupled N2 and CO2 in H2O to produce urea under ambient conditions. The process was carried out using an electrocatalyst consisting of PdCu alloy nanoparticles on TiO2 nanosheets. This coupling reaction occurs through the formation of C–N bonds via the thermodynamically spontaneous reaction between *N=N* and CO. Products were identified and quantified using isotope labelling and the mechanism investigated using isotope-labelled operando synchrotron-radiation Fourier transform infrared spectroscopy. A high rate of urea formation of 3.36 mmol g–1 h–1 and corresponding Faradic efficiency of 8.92% were measured at –0.4 V versus reversible hydrogen electrode. Conventionally, urea is synthesized via two consecutive processes, N2 + H2 → NH3 followed by NH3 + CO2. Now, an electrocatalyst consisting of PdCu alloy nanoparticles on TiO2 nanosheets has been shown to directly couple N2 and CO2 in H2O to produce urea under ambient conditions.
209 citations
TL;DR: This study suggested that N in the Bio-MUC was shown slow releasing in water but maize growth promoting in soil, relative to conventional urea, and biochar from agro-wastes could be used for blending urea as combined organo/mineral urea to replace mineral urea so to reduce N use and impacts on global Nr.
125 citations
TL;DR: Mechanistic insights show that Te-doping not only optimizes the CO2/CO adsorption but also promotes NH3 production, fully meeting the requirements of urea synthesis.
Abstract: The renewable electricity-driven reduction of carbon dioxide (CO2RR) is a promising technology for carbon utilization. However, it is still a challenge to broaden the application of CO2RR. Herein, we report a Te-doped Pd nanocrystals (Te-Pd NCs) for promoting urea synthesis by coupling CO2RR with electrochemical reduction of nitrite. The electrochemical synthesis of urea has been achieved with nearly 12.2% Faraday efficiency (FE) and 88.7% N atom efficiency (NE) at -1.1 V versus reversible hydrogen electrode (vs RHE), much higher than those of pure Pd NCs (4.2% FE and 21.8% NE). Significantly, an FE of ∼10.2% and an NE of ∼82.3% for urea solution production via an optimized flow cell system have been realized, where a solution with up to 0.95 wt % of urea has been obtained. Mechanistic insights show that Te-doping not only optimizes the CO2/CO adsorption but also promotes NH3 production, fully meeting the requirements of urea synthesis.
111 citations
TL;DR: It is demonstrated that coating urea with ZnO-NPs enhances plant performance and Zn accumulation, thus potentiating field-scale deployment of nano-scale micronutrients and highlighting a key benefit of nanofertilizers: a reduction of nutrient inputs into agriculture without yield penalities
Abstract: Zinc oxide nanoparticles (ZnO-NPs) hold promise as novel fertilizer nutrients for crops. However, their ultra-small size could hinder large-scale field application due to potential for drift, untimely dissolution or aggregation. In this study, urea was coated with ZnO-NPs (1%) or bulk ZnO (2%) and evaluated in wheat (Triticum aestivum L.) in a greenhouse, under drought (40% field moisture capacity; FMC) and non-drought (80% FMC) conditions, in comparison with urea not coated with ZnO (control), and urea with separate ZnO-NP (1%) or bulk ZnO (2%) amendment. Plants were exposed to ≤ 2.17 mg/kg ZnO-NPs and ≤ 4.34 mg/kg bulk-ZnO, indicating exposure to a higher rate of Zn from the bulk ZnO. ZnO-NPs and bulk-ZnO showed similar urea coating efficiencies of 74-75%. Drought significantly (p ≤ 0.05) increased time to panicle initiation, reduced grain yield, and inhibited uptake of Zn, nitrogen (N), and phosphorus (P). Under drought, ZnO-NPs significantly reduced average time to panicle initiation by 5 days, irrespective of coating, and relative to the control. In contrast, bulk ZnO did not affect time to panicle initiation. Compared to the control, grain yield increased significantly, 51 or 39%, with ZnO-NP-coated or uncoated urea. Yield increases from bulk-ZnO-coated or uncoated urea were insignificant, compared to both the control and the ZnO-NP treatments. Plant uptake of Zn increased by 24 or 8% with coated or uncoated ZnO-NPs; and by 78 or 10% with coated or uncoated bulk-ZnO. Under non-drought conditions, Zn treatment did not significantly reduce panicle initiation time, except with uncoated bulk-ZnO. Relative to the control, ZnO-NPs (irrespective of coating) significantly increased grain yield; and coated ZnO-NPs enhanced Zn uptake significantly. Zn fertilization did not significantly affect N and P uptake, regardless of particle size or coating. Collectively, these findings demonstrate that coating urea with ZnO-NPs enhances plant performance and Zn accumulation, thus potentiating field-scale deployment of nano-scale micronutrients. Notably, lower Zn inputs from ZnO-NPs enhanced crop productivity, comparable to higher inputs from bulk-ZnO. This highlights a key benefit of nanofertilizers: a reduction of nutrient inputs into agriculture without yield penalities.
97 citations
TL;DR: Results of high-throughput sequencing revealed bacterial community groups with higher nutrient metabolic cycling ability under BCRNF treatment during harvest stage, and significantly improved soil NO3−, leading to an increase in N uptake by rape and NUE, thereby promoting rape growth and increasing grain yield.
Abstract: Biochar-based controlled release nitrogen fertilizers (BCRNFs) have received increasing attention due to their ability to improve nitrogen-use efficiency (NUE) and increase crop yields. We previously developed a novel BCRNF, but its effects on soil microbes, NUE, and crop yields have not been reported. Therefore, we designed a pot experiment with five randomised treatments: CK (without urea and biochar), B (addition biochar without urea), B + U (biochar mixed urea), Urea (addition urea without biochar), and BCRNF (addition BCRNF), to investigate the effects of BCRNF on nitrifiers and denitrifiers, and how these impact nitrogen supply and NUE. Results of high-throughput sequencing revealed bacterial community groups with higher nutrient metabolic cycling ability under BCRNF treatment during harvest stage. Compared to Urea treatment, BCRNF treatment stimulated nitrification by increasing the copy number of the bacterial amoA gene and reducing nitrous oxide emission by limiting the abundance of nirS and nirK. Eventually, BCRNF successfully enhanced the yield (~ 16.6%) and NUE (~ 58.79%) of rape by slowly releasing N and modulating the abundance of functional microbes through increased soil nitrification and reduced denitrification, as compared with Urea treatment. BCRNF significantly improved soil NO3−, leading to an increase in N uptake by rape and NUE, thereby promoting rape growth and increasing grain yield.
70 citations
08 Jun 2020
TL;DR: Fluorescent carbon dots (N-CDs) were synthesized from ascorbic acid and urea following a green route and were characterized on the basis of analytical, spectroscopic, and microscopic techniques.
Abstract: Fluorescent carbon dots (N-CDs) were synthesized from ascorbic acid and urea following a green route and were characterized on the basis of analytical, spectroscopic, and microscopic techniques. Th...
70 citations
TL;DR: The results highlight the important role of optimizing fertilizer form and N rate as well as straw return to the field in alleviating soil acidification.
68 citations
TL;DR: In this paper, the inclusion complexes (ICs) of environmentally degradable polyester and urea prepared by one-step blending are developed as slow-release urea fertilizers for the first time.
62 citations
TL;DR: The study provides some novel insights into the Ni/Co catalyst design and fabrication with efficient catalytic synergism for electrocatalysis and finds crystal lattice hybridization was found in the interface of Ni/ Co oxide nanoparticles that assembled as a nanorod bundle structure.
Abstract: Urea electrolysis has received great attention for the energy-relevant applications, and efficient nanostructured catalysts are required to overcome the sluggish urea oxidation kinetics. Herein, we noticed that the valence state of Ni in the hybrid Ni/Co oxide nanorods can be correlated to the catalytic capability for urea oxidation. Crystal lattice hybridization was found in the interface of Ni/Co oxide nanoparticles that assembled as a nanorod bundle structure. The more or the less of Ni2+/Ni3+ generated lower catalytic ability, and Ni/Co oxide with the optimum content of Ni2+/Ni3+ exhibited the highest catalytic ability for urea oxidation because of the efficient synergism, resulting from the formation of high valence state of Ni species and improved kinetics. A low onset potential of 1.29 V was required for the urea oxidation compared with the high onset potential of 1.52 V for water oxidation; high selectivity for urea oxidation was found in the potential below 1.50 V, and as a promising application for urea-assisted water electrolysis about 190 mV less was required to provide 10 mA cm−2 in the two-electrode system, indicating the energy-efficient nature for hydrogen evolution. The study provides some novel insights into the Ni/Co catalyst design and fabrication with efficient catalytic synergism for electrocatalysis.
60 citations
TL;DR: FeOOH supported on Ni foam enables highly efficient UOR electrocatalysis and can be readily produced through a hydrolysis reaction, representing the best yet reported noble metal-free urea electrolyser.
59 citations
TL;DR: Electrochemical performances suggest that this adopted synthesis route may open a novel avenue for the fabrication of heteroatom-doped carbon electrode materials, especially based on renewable and low-cost cellulose.
Abstract: Using the disulfide bond and carboxyl group in the molecular structure, α-lipoic acid was easily dissolved in the NaOH/urea solution and could be used as a ternary solvent for dissolving cellulose....
TL;DR: In this article, a bio-based slow-release fertilizer (SRF) has been developed using reinforcement of starch-g-poly(acrylic acid-co-acrylamide) superabsorbent polymer with natural char nanoparticles (NCNPs).
Abstract: Loss control of nutrients and water has been considered as a global challenge of agriculture because it faced with concurrent management of these two necessities of crop production. Herein, a bio-based slow-release fertilizer (SRF) has been developed using reinforcement of starch-g-poly(acrylic acid-co-acrylamide) superabsorbent polymer with natural char nanoparticles (NCNPs). Incorporation of urea in the matrix of nano-biocomposite resulted in the efficient SRF formulation with remarkable water absorbency (215.1 g/g). Variables including starch, monomers, cross-linker, and nano-filler dosages were optimized using screening the urea release behavior of samples in various pHs (3–10) and salt solutions (NaCl, CaCl2, and FeCl3). NCNPs acted as physical cross-linker as well as nano-filler and formed H-bondings between the oxygenated groups of the polymer and nanoparticles. Urea release measurements in water indicated a well slow-release property of SRF formulations, 70 % of nitrogen released during 21 days. The release time was prolonged with increasing the amount of NCNPs because the favorable interfacial polymer-filler interactions resulted in slower nitrogen diffusion and consequently, slower release rate at neutral and basic pHs. The water-retention of soils containing two different SRFs (with and without nano-filler) showed that NCNPs could double the water-retention compared with the neat polymer. While nitrate leaching rate in the soil for pure urea was measured to be 591.8 mg/L, the starch-g-poly(acrylic acid-co-acrylamide)/NCNPs/Urea decreased the leaching loss of N up to 49.5 mg/L. The soil burial degradation test indicated that the presence of NCNPs in the network of polymer could facilitate the degradation process of the SRF samples.
TL;DR: In this paper, a new idea for facile and green synthesis of urea-based highly branched polymers (HBPs) using polyamines and urea via deamination.
Abstract: We propose a new idea for facile and green synthesis of urea-based highly branched polymers (HBPs) using polyamines and urea via deamination. More importantly, our strategy is to directly use the s...
TL;DR: In this article, an interlaced rosette-like MoS2/Ni3S 2/NiFe-layered double hydroxide/nickel foam (LDH/NF) was successfully synthesized by a two-step hydrothermal reaction.
TL;DR: In this article, Co-doped α-Ni(OH) 2 hybrid films with unique ultrafine nanoparticles assembled network structure are constructed as efficient bifunctional electrocatalysts for urea-assisted water electrolysis.
TL;DR: Solid-state 2H NMR revealed that the high conductivity was attributed to the strengthening of the hydrogen bonds between guest H2O induced by hydrogen bonds in the interface between H2 O and the polarized coordinated urea.
Abstract: Highly stable superprotonic conductivity (>10-2 S cm-1) has been achieved through the unprecedented solvent-free-coordinative urea insertion in MOF-74 [M2(dobdc), M = Ni2+, Mg2+; dobdc = 2,5-dioxido-1,4-benzenedicarboxylate] without an acidic moiety. The urea is bound to open metal sites and alters the void volume and surface functionality, which triggers a significant change in proton conductivity and diffusion mechanism. Solid-state 2H NMR revealed that the high conductivity was attributed to the strengthening of the hydrogen bonds between guest H2O induced by hydrogen bonds in the interface between H2O and the polarized coordinated urea.
TL;DR: Winter wheat grown on a sandy soil in the UK was treated with urea fertilizer with the urease inhibitor N-(n-butyl) thiophosphoric triamide (NBPT), the nitrification inhibitor dicyandiamide (DCD), the effects on soil microbial community diversity, the abundance of genes involved in nitrification and crop yields and net N recovery were compared.
Abstract: Inhibitors of urease and ammonia monooxygenase can limit the rate of conversion of urea to ammonia and ammonia to nitrate, respectively, potentially improving N fertilizer use efficiency and reducing gaseous losses. Winter wheat grown on a sandy soil in the UK was treated with urea fertilizer with the urease inhibitor N-(n-butyl) thiophosphoric triamide (NBPT), the nitrification inhibitor dicyandiamide (DCD) or a combination of both. The effects on soil microbial community diversity, the abundance of genes involved in nitrification and crop yields and net N recovery were compared. The only significant effect on N-cycle genes was a transient reduction in bacterial ammonia monooxygenase abundance following DCD application. However, overall crop yields and net N recovery were significantly lower in the urea treatments compared with an equivalent application of ammonium nitrate fertilizer, and significantly less for urea with DCD than the other urea treatments.
TL;DR: In this paper, the authors compared the influence of three nitrification inhibitors, namely dicyandiamide (DCD), NP and NBPT, on rice growth, the fate of urea nitrogen (N), and the abundances and activities of ammonia oxidizers and denitrifiers.
TL;DR: In this paper, the effect of the fitting method, urea concentration and polarized potential on the impedance behavior are deeply studied to understand more about the anodic process of urea, which can be interpreted via the adsorption of intermediates at the surface of the electroactive catalyst.
TL;DR: The analysis indicates that the low removal was a consequence of Cu2+ complexation with the ammonia resulting from the hydrolysis of urea, indicating that it is necessary to design a sequential process that decouples bacterial growth and copper precipitation, thereby decreasing the urea requirement.
TL;DR: In this paper, the authors examined the magnesium ions effect on carbonate crystal polymorph when Ca( CH 3 COO)2/urea acts as cementation solution in microbially induced carbonate precipitation (MICP) process.
TL;DR: In this article, the adsorption mechanism of urea, creatinine, and uric acid on spherical activated carbon was investigated and it was shown that the interaction among urea molecules, such as hydrogen bonding, induced multilayer adaption.
01 Nov 2020
TL;DR: In this article, the effects of reaction temperature, urea peroxide concentration, liquid-gas ratio (L/G), SO2 concentration, and urea concentration in UREO solutions on NO removal were investigated.
TL;DR: Evaluating the effect of different NH4+-based nitrogen on soil nitrification depended on the impact of the fertilizers on soil pH, and nitrification played an important role in NO emissions, but not in N2O emissions, decoupled crop N preference and the form of N available in spite of increasing soil pH.
TL;DR: In this paper, the authors investigated the nitrogen release pattern of urea-impregnated biochar (UB), hydrochar (UH), UZ, and U-HAP in water and a calcareous waterlogged soil.
TL;DR: It was found that the Ni@C had a higher residual carbon content and a higher specific surface area than NiO@C, thus exhibiting an enhanced electrochemical performance for urea oxidation, and showed that the highly porous carbon-supported Ni catalysts derived from Ni-based metal–organic framework can be used for Urea oxidation and as an efficient anode material for u Andrea fuel cells.
Abstract: Highly porous self-assembled nanostructured Ni@C and NiO@C were synthesized via calcination of a Ni-based metal–organic framework. The morphology, structure, and composition of as synthesized Ni@C and NiO@C were characterized by SEM, FIB-SEM, TEM, and XRD. The electro-catalytic activity of the Ni@C and NiO@C catalysts towards urea oxidation was investigated using cyclic voltammetry. It was found that the Ni@C had a higher residual carbon content and a higher specific surface area than NiO@C, thus exhibiting an enhanced electrochemical performance for urea oxidation. A direct urea fuel cell with Ni@C as an anode catalyst featured an excellent maximum power density of 13.8 mW cm−2 with 0.33 M urea solution in 1 M KOH as fuel and humidified air as oxidant at 50 °C, additionally showing excellent stability during continuous 20-h operation. Thus, this work showed that the highly porous carbon-supported Ni catalysts derived from Ni-based metal–organic framework can be used for urea oxidation and as an efficient anode material for urea fuel cells.
Abstract: By introducing exogenous nitrogen during biomass pyrolysis under nitrogen-rich conditions, high-value nitrogen-containing products, i.e., nitrogen-rich char and oil may be produced. Based on the cogeneration of high-value nitrogen products from biomass, biomass nitrogen-enriched pyrolysis was performed in a fixed bed with different sources and contents of ammonia. The yields, composition and characteristics of the products were investigated. Moreover, the formation mechanism of N-containing species was explored in depth for the pyrolysis and catalytic pyrolysis with HZSM-5 and Zn/HZSM-5 catalysts via elemental analysis, XPS, FTIR and BET. The results showed that ammonia impregnation could promote a Maillard reaction, reduce the content of small aldehydes and ketones, and produce a nitrogen-enriched bio-oil. The contents of N-containing species and phenolic substances in the pyrolysis oil of biomass impregnated with 10% urea reached 15.66% and 56.69%, respectively. Moreover, the nitrogen on the coke surface after pretreatment was mainly composed of C N, C N and N COO functional groups. The bio-char generated abundant pyridinic-N, pyrrolic-N, quaternary-N, and pyridone-N oxides. The presence of urea introduced many alkaline N-containing functional groups on the surface of the bio-char and promoted the transformation of nitrogen from amides and imides to heterocyclic nitrogen with higher thermal stability. Furthermore, Zn was an excellent catalyst for the Maillard reaction, and the Zn/HZSM-5 catalyst had a higher selectivity for aromatic hydrocarbons (96.98% for biomass and 86.48% for urea/biomass) and N-containing heterocyclic compounds, such as indoles (6.16% for biomass and 13.51% for urea/biomass). Additionally, the coke content decreased, and the catalyst deactivation decreased.
TL;DR: In this article, a glassy carbon electrode was electrochemically modified with Fe3O4/MWCNT/PANI-Nafion nanocomposite film.
Abstract: The present study describes the electrochemical biosensing technique for detection of urea in milk samples. The glassy carbon electrode was electrochemically modified with Fe3O4/MWCNT/PANI-Nafion nanocomposite film. Purified bacterial urease enzyme was immobilized on to the nanocomposite film modified electrode with the help of glutaraldehyde as a cross linker. The characterization of enzyme modified electrode was done by scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy analysis. Various electrochemical techniques such as cyclic voltammetry (CV), differential pulse voltammetry (DPV) and chronoamperometry (CA) have been studied against the known concentrations of urea in buffer medium. A good linear range 1.0–25.0 mM with detection limit 67 µM was achieved for urea concentration. The developed biosensor showed rapid response and good storage stability of 60 days. The developed method was able to detect urea in milk and the results were validated with the standard addition method.
TL;DR: It was found that incorporation of urea and CNFs in the hybrid structure generating compact hydrogel networks with high crosslink density leading to lower absorption with and without pressure, whereas, incorporation of Urea in the structure resulted in a more extended network with higher absorption capacity than hybrid structure.