Mo_(2)P Monolayer as a Superior Electrocatalyst for Urea Synthesis from Nitrogen and Carbon Dioxide Fixation:A Computational Study

Urea synthesis through the simultaneous electrocatalytic reduction of N_(2)and CO_(2)molecules under ambient conditions holds great promises as a sustainable alternative to its industrial production,in which the development of stable,highly efficient,and highly selective catalysts to boost the chemisorption,activation,and coupling of inert N_(2)and CO_(2)molecules remains rather challenging.Herein,by means of density functional theory computations,we proposed a new class of two-dimensional nanomaterials,namely,transition-metal phosphide monolayers(TM_(2)P,TM=Ti,Fe,Zr,Mo,and W),as the potential electrocatalysts for urea production.Our results showed that these TM_(2)P materials exhibit outstanding stability and excellent metallic properties.Interestingly,the Mo_(2)P monolayer was screened out as the best catalyst for urea synthesis due to its small kinetic energy barrier(0.35 eV)for C-N coupling,low limiting potential(-0.39 V),and significant suppressing effects on the competing side reactions.The outstanding catalytic activity of the Mo_(2)P monolayer can be ascribed to its optimal adsorption strength with the key^(*)NCON species due to its moderate positive charges on the Mo active sites.Our findings not only propose a novel catalyst with high-efficiency and high-selectivity for urea production but also further widen the potential applications of metal phosphides in electrocatalysis.

Balancing sub‐reaction activity to boost electrocatalytic urea synthesis using a metal‐free electrocatalyst

Electrocatalytic urea synthesis via coupling of nitrate with CO_(2)is considered as a promising alternative to the industrial urea synthetic process.However,the requirement of sub-reaction(NO_(3)RR and CO_(2)RR)activities for efficient urea synthesis is not clear and the related reaction mechanisms remain obscure.Here,the construction,breaking,and rebuilding of the sub-reaction activity balance would be accompanied by the corresponding regulation in urea synthesis,and the balance of sub-reaction activities was proven to play a vital role in efficient urea synthesis.With rational design,a urea yield rate of 610.6 mg h−1 gcat.−1 was realized on the N-doped carbon electrocatalyst,superior to that of noble-metal electrocatalysts.Based on the operando SRFTIR measurements,we proposed that urea synthesis arises from the coupling of^(*)NO and^(*)CO to generate the key intermediate of^(*)OCNO.This work provides new insights and guidelines into urea synthesis from the aspect of activity balance.

Electrochemical urea synthesis by co-reduction of CO_(2) and nitrate with Fe^(Ⅱ)-Fe^(Ⅲ)OOH@BiVO_(4) heterostructures

Traditional urea synthesis under harsh conditions is usually associated with high energy input and has aroused severe environmental concerns.Electrocatalytic C-N coupling by converting nitrate and CO_(2) into urea under ambient conditions represents a promising alternative process.But it was still limited by the strong competition between nitrate electrochemical reduction(NO_(3)ER) and CO_(2) electrochemical reduction(CO_(2)ER).Here,Fe^(Ⅱ)-Fe~ⅢOOH@BiVO_(4)-n heterostructures are constructed through hydrothermal synthesis and exhibited superior performance toward urea electrosynthesis with NO_(3)~-and CO_(2) as feedstocks.The optimized urea yield and Faradaic efficiency over Fe^(Ⅱ)-Fe~ⅢOOH@BiVO_(4)-2 can reach13.8 mmol h^(-1) g^(-1) and 11.5% at-0.8 V vs.reversible hydrogen electrode,which is much higher than that of bare FeOOH(3.2 mmol h^(-1) g^(-1) and 1.3%),pristine BiVO_(4)(2.0 mmol h^(-1) g^(-1) and 5.4%),and the other Fe^(Ⅱ)-Fe~ⅢOOH@BiVO_(4)-n(n=1,3,5) heterostructures.Systematic experiments have verified that BiVO_(4)and FeOOH are subreaction active sites towards simultaneous CO_(2)ER and NO_(3)ER,respectively,achieving co-activation of CO_(2) and NO_(3)~-on Fe^(Ⅱ)-Fe~ⅢOOH@BiVO_(4)-2.Moreover,the urea synthesis via the ^(*)CO and NO*intermediates and C-N coupling was confirmed by the in situ Fourier transform infrared spectroscopy.This work not only alleviates the CO_(2) emission and nitrate pollution but also presents an efficient catalyst for synergistic catalysis towards sustainable urea synthesis.

Defect engineered electrocatalysts for C-N coupling reactions toward urea synthesis

Urea is extensively used in agriculture and chemical industry,and it is produced on an industrial scale from CO_(2)and Haber-Bosch NH_(3)under relatively high temperature and high pressure conditions,which demands high energy input and generates masses of carbon footprint.The conversion of CO_(2)and N sources(such as NO_(2)^(−),NO_(3)^(−),and N_(2))through electrocatalytic reactions under ambient conditions is a promising alternative to realize efficient urea synthesis.Of note,the design of electrocatalyst is one of the key factors that can improve the efficiency and selectivity of C-N coupling reactions.Defect engineer-ing is an intriguing strategy for regulating the electronic structure and charge density of electrocatalysts,which endows electrocatalysts with excellent physicochemical properties and optimized adsorption en-ergy of the reaction intermediates to reduce the kinetic barriers.In this minireview,recent advances of defect engineered electrocatalysts in urea electrosynthesis from CO_(2)and various N reactants are firstly introduced.Mechanistic discussions of C-N coupling in these advances are presented,with the aim of directing future investigations on improving the urea yield.Finally,the prospects and challenges of de-fect engineered electrocatalysts for urea synthesis are discussed.This overview is expected to provide in-depth understanding of structure-reactivity relationship and shed light on future electrocatalytic C-N coupling reactions.

Recent advances in electrochemical synthesis of urea via C-N coupling

Urea is widely used as fertilizer and is a key substance supporting global food production. However, the traditional industrial synthesis of urea faces the challenges with high energy consumption and serious environmental problems. With the increasing global demand for environmental protection and sustainable development, it is much necessary to develop novel and clean methods for the synthesis of urea.Electrocatalysis provides an efficient and renewable synthesis route that can directly produce urea at room temperature and atmospheric pressure by the coupling of CO_(2) and nitrogenous molecules. In this review, we summarized the most recent advances in electrochemical synthesis of urea via CAN coupling systematically, focusing on the coupling of CO_(2) and different nitrogen sources. And the associated coupling mechanism, catalysts optimization, and electrolyzer design are well discussed. Moreover, the challenges and future directions for electrocatalytic CAN coupling are prospected. This review will provide timely and valuable guidance for others and attract more interests to promote the development of electrochemical synthesis of urea or other valuable chemicals containing CAN bond.

Manganese catalyzed urea and polyurea synthesis using methanol as C1 source

The manganese-catalyzed dehydrogenative coupling between methanol and amines for the synthesis of ureas and polyureas is described. Importantly, catalytic efficiency can be improved by the newly synthesized MACHO ligands. Furthermore, this highly atom-economical protocol demonstrates a broad substrate scope with good functional group tolerance, producing H_(2)as the sole byproduct. Mechanistic studies disclose that formamide is formed through manganese-catalyzed formylation of amine with methanol.Subsequent dehydrogenation affords a transient isocyanate, which is attacked by another equivalent of amine to provide the final product.

Engineering Spin States of Isolated Copper Species in a Metal-Organic Framework Improves Urea Electrosynthesis

The catalytic activities are generally believed to be relevant to the electronic states of their active center, but understanding this relationship is usually difficult. Here, we design two types of catalysts for electrocatalytic urea via a coordination strategy in a metal–organic frameworks: Cu^(Ⅲ)-HHTP and Cu^(Ⅱ)-HHTP. Cu^(Ⅲ)-HHTP exhibits an improved urea production rate of 7.78 mmol h^(−1)g^(−1) and an enhanced Faradaic efficiency of 23.09% at-0.6 V vs. reversible hydrogen electrode, in sharp contrast to Cu^(Ⅱ)-HHTP.Isolated CuⅢspecies with S = 0 spin ground state are demonstrated as the active center in Cu^(Ⅲ)-HHTP, different from Cu^(Ⅱ) with S = 1/2 in Cu^(Ⅱ)-HHTP. We further demonstrate that isolated Cu^(Ⅲ)with an empty dx2-y20orbital in Cu^(Ⅲ)-HHTP experiences a single-electron migration path with a lower energy barrier in the C–N coupling process, while Cu^(Ⅱ)with a single-spin state( d_(x2-y2)^(1)) in Cu^(Ⅱ)-HHTP undergoes a two-electron migration pathway.

The New Synthesis of Azo Urea from Substituted Semicarbazide

Using N-bromosuccinimide and pyridine as the oxidation system to dehydrogenate aryl substituted semicarbazide to form azo compounds is described for the first time in this paper. Nine azo compounds have been prepared in excellent yield under mild condition. This method only. needs simple instrument and short reaction time.

A review on electrocatalytic CO_(2) conversion via C-C and C-N coupling

Electrochemical C-C and C-N coupling reactions with the conversion of abundant and inexpensive small molecules,such as CO_(2) and nitrogencontaining species,are considered a promising route for increasing the value of CO_(2) reduction products.The development of high-performance catalysts is the key to the both electrocatalytic reactions.In this review,we present a systematic summary of the reaction systems for electrocatalytic CO_(2) reduction,along with the coupling mechanisms of C-C and C-N bonds over outstanding electrocatalytic materials recently developed.The key intermediate species and reaction pathways related to the coupling as well as the catalyst-structure relationship will be also discussed,aiming to provide insights and guidance for designing efficient CO_(2) reduction systems.

Ambient electrosynthesis of urea from carbon dioxide and nitrate over Mo_(2)C nanosheet

Electrocatalytic synthesis of urea through C-N bond formation,converting carbon dioxide(CO_(2))and ni-trate(NO_(3)^(-)),presents a promising,less energy-intensive alternative to industrial urea production process.In this communication,we report the application of Mo_(2)C nanosheets-decorated carbon sheets(Mo_(2)C/C)as a highly efficient electrocatalyst for facilitating C-N coupling in ambient urea electrosynthesis.In CO_(2)-saturated 0.2 mol/L Na_(2)SO_(4)solution containing 0.05 mol/L NO_(3)^(-),the Mo_(2)C/C catalyst achieves an impres-sive urea yield of 579.13μg h^(-1)mg^(-1)with high Faradaic efficiency of 44.80%at-0.5 V versus the reversible hydrogen electrode.Further theoretical calculations reveal that the multiple Mo active sites enhance the formation of^(∗)CO and^(∗)NH_(2)intermediates and facilitate their C-N coupling.This research propels the use of Mo_(2)C-based electrodes in electrocatalysis and accentuates the capabilities of binary metal-based catalysts in C-N coupling reactions.

Synthesis,Crystal Structure and Antifungal Activity of N-((2,6-Difluorophenyl)carbamoyl)-1,3-dimethyl-1H-pyrazole-4-carboxamide

The title compound N-（（2,6-difluorophenyl）carbamoyl）-1,3-dimethyl-1 H-pyrazole-4-carboxamide（C13H12F2N4O2） was synthesized, and its structure was confirmed by ^1H NMR,HRMS and X-ray diffraction. It crystallizes in the monoclinic system, space group P21/c with a = 9.50（2）, b = 10.11（2）, c = 14.07（3） A^°, β = 102.15（3）°, Dc = 1.480 g/cm^3, Z = 4, V = 1320（5） A^°3, the final R = 0.0789 and wR = 0.1860 for 1054 observed reflections with I 〉 2σ（I）. The preliminary biological test shows that the title compound has weak antifungal activities.

Synthesis, Assessment of Biological Activity and Toxicity for N-(<i>β</i>-D-Glycopyranosyl)-Thiosemicarbazides

In the modern science, priority is given for the search of biological active compounds with specific properties. As a result of experimental data, it was found that in the reaction between N-(β-D-glycopyranosyl)-semicarbazide and the Lawesson reagent (2,4-bis(p-methoxyphenyl)-1,3-dithiadiphosphetane 2,4-disulfide) at the ratio 1:1 in pyridine when boiling under reflux in a water bath for 20 - 35 minutes, a new synthetic compound N-(β-D-glycopyranosyl)-thiosemicarbazide is formed. The individuality and structure of the target products were confirmed by 13C NMR spectroscopy, 1H NMR spectroscopy, IR spectroscopy, and elemental analysis. For the synthesized new compounds of N-(β-D-glycopyranosyl)-thiosemicarbazides, the probability of pharmacological and toxic effects were predicted by the computer method in silico. From the synthesized compounds N-(β-D-galactopyranosyl)-thiosemicarbazide, the probability of antibacterial (antibacterial) activity is predicted (Pa/Pi 0.544/0.013). The antibacterial activity of the compound (4) was confirmed in a test for salmonella infection of lambs, salmonellosis of calves, and colipathogenic E. coli serotypes. An experimental study by the in vitro method made it possible to conclude that the new synthetic compound N-(β-D-galactopyranosyl)-thiosemicarbazide in the studied concentrations has a pronounced bactericidal and bacteriostatic effect. The synthetic new compound N-(β-D-glyco- pyranosyl)-thiosemicarbazide is a promising compound for further study.

Uncovering the Mechanism for Urea Electrochemical Synthesis by Coupling N2 and CO_(2) on Mo2C-MXene

In this work, the catalytic activities of MoC-MXene for the co-synthesis of urea from Nand COare reported by well-defined density functional theory(DFT) method. The calculated results show that the presence of surface functional groups is not conducive to the CO/N(C/N) coupling process in urea synthesis reaction. The exposed MoC on the surface can realize urea synthesis at the limit point of 0.69 eV, but the large transition state energy barrier(1.50 eV)indicates that bare MoC is not a promising urea catalyst. Loading single atoms can improve the urea synthesis performance of bare MoC. The energy barrier of urea synthesis reaction and the transition state energy barrier of C/N coupling reaction have dropped significantly by the atomic loading of Fe and Ti on bare MoC. Moreover, Ti doped MoC exhibits better catalytic selectivity toward urea production, making it an excellent catalyst for urea synthesis. We hope this work can pave the way for the electrochemical synthesis of urea.

Liver-related effects of chronic hepatitis C antiviral treatment

More than five years ago,the treatment of hepatitis C virus infection was revolutionized with the introduction of all-oral direct-acting antiviral(DAA)drugs.They proved highly efficient in curing patients with chronic hepatitis C(CHC),including patients with cirrhosis.The new DAA treatments were alleged to induce significant improvements in clinical outcome and prognosis,but the exact cause of the expected benefit was unclear.Further,little was known about how the underlying liver disease would be affected during and after viral clearance.In this review,we describe and discuss the liver-related effects of the new treatments in regards to both pathophysiological aspects,such as macrophage activation,and the time-dependent effects of therapy,with specific emphasis on inflammation,structural liver changes,and liver function,as these factors are all related to morbidity and mortality in CHC patients.It seems clear that antiviral therapy,especially the achievement of a sustained virologic response has several beneficial effects on liver-related parameters in CHC patients with advanced liver fibrosis or cirrhosis.There seems to be a timedependent effect of DAA therapy with viral clearance and the resolution of liver inflammation followed by more discrete changes in structural liver lesions.These improvements lead to favorable effects on liver function,followed by an improvement in cognitive dysfunction and portal hypertension.Overall,the data provide knowledge on the several beneficial effects of DAA therapy on liverrelated parameters in CHC patients suggesting short-and long-term improvements in the underlying disease with the promise of an improved longterm prognosis.

Metalphthalocyanine frameworks grown on TiO_(2)nanotubes for synergistically and efficiently electrocatalyzing urea production from CO_(2)and nitrate

Electrocatalytic synthesis of urea from CO_(2)and NO_(3)^(-)under ambient conditions provides an appealing alternative to the traditional energy-intensive urea synthetic protocol.Highly active and selective electrocatalysts for efficient urea production are therefore urgently desired owing to the unsatisfactory performance of the thus far reported catalysts.Herein,a phthalocyaninebased(Pc-based)covalent organic framework(COF),namely Co Pc-COF,fabricated from the nucleophilic substitution reaction of hexadecafluorophthalocyaninato cobalt with octahydroxylphthalocyanine cobalt,in situ grew on the surface of multilayered Ti O_(2)nanotubes(NTs),generating the Co Pc-COF@Ti O_(2)NTs composite.Powder X-ray diffraction analysis in combination with electron microscopy measurements discloses the uniform coating of crystalline Co Pc-COF on the multilayered Ti O_(2)NTs in Co Pc-COF@Ti O_(2)NTs.Remarkably,electrochemical tests reveal the superior electrocatalytic activity of Co Pc-COF@Ti O_(2)NTs towards urea production from CO_(2)and NO3-with a record-high yield of 1,205μg h^(-1)cm^(-2)and an outstanding Faraday efficiency of 49%at-0.6 V versus reversible hydrogen electrode due to the significant synergistic catalysis effect.In situ attenuated total reflection infrared spectroscopic investigation and theoretical calculations unveil the efficient C–N coupling reaction between*CO intermediate derived from CO_(2)on Co Pc moieties and*NH2intermediate formed from NO_(3)^(-)on Ti O_(2)NTs during the urea formation process over Co Pc-COF@Ti O_(2)NTs.This work should be helpful towards designing and fabricating high-performance electrocatalysts for sustainable synthesis of urea through efficient synergistic effect of multiactive centers.

Boosting Electrocatalytic Urea Production via Promoting Asymmetric C–N Coupling

Electrocatalytic C–N coupling shows great potential in direct and sustainable urea synthesis.However,the mechanism of interaction between catalytic sites and intermediate species is currently unclear,and exploring corresponding strategies to boost urea synthesis is urgent.Herein,we demonstrated that a multihole structure could preserve the Cu^(+)component of Cu_(2)O spheres under electrochemical reduction conditions.An in situ formed Cu^(0)–Cu^(+)site thermodynamically and kinetically promoted the asymmetric coupling process of^(*)CO and^(*)NO,thereby boosting the urea production.The impressive urea yield rates of 29.2 and 114.0 mmol h^(−1)g^(−1)were realized for electrochemical coupling of CO_(2)with nitrate and nitrite,respectively.The multihole-Cu_(2)O exhibits both superior activity and long-term stability compared to the electrocatalysts with a reconstructed Cu^(0)-dominated surface.This work provides insights into the identification and design of the active site for C–N coupling and urea synthesis.

Urea combustion synthesis of LiNi_(0.5)Mn_(1.5)O_4 as a cathode material for lithium ion batteries

LiNi0.5Mn1.5O4 was synthesized by combustion synthesis （UCS） using urea as fuel. X-ray diffraction and scanning electron microscope measurements showed that the spinel structure LiNio.sMnl.504 with the space group Fd3m was formed during urea combustion. Both structure and particle size could be adjusted by the amount of urea and the heat treatment temperature used in the UCS. For the LiNi0.5Mn1.5O4 sample prepared with a urea/Li molar ratio of 0.57 and a heat treatment temperature of 900℃, the particle-size distribution fell in a narrow range of 1-2 Dm. Electrochemical tests indicated that this LiNi0.sMnl.504 sample delivered a discharge capacity of 133.6 mAh/g with a capacity retention rate of 99.6% after 20 cycles at 0.5 C.

CO_(2)和NO_(3)^(-)偶联在富氧空位的Ru掺杂CeO_(2)纳米棒上高效电催化合成尿素

利用可再生能源驱动的电催化C-N偶联来合成尿素可以取代高能耗、高污染的工业生产尿素过程.然而,同时提高尿素收率和相应的法拉第效率,目前仍面临挑战.在此,我们设计了富氧空位的Ru掺杂CeO_(2)电催化剂用于高效电化学合成尿素.通过调节Ru的比例,发现最佳掺杂量为5%,该Ru-CeO_(2)电催化剂在电压为-0.7 V vs.RHE时能提供20.2 mmol h^(-1)g^(-1)的高尿素产率和20.1%法拉第效率,优于大多数已报道的催化剂.实验结果表明,Ru掺杂和氧空位的协同效应优化了反应物的吸附和活化,增强了C-N偶联的动力学,并显著提高了电化学合成尿素的效率.本工作将为开发高效合成尿素的先进C-N偶联电催化剂提供借鉴.

Carbon dioxide:a renewable feedstock for the synthesis of fine and bulk chemicals

The syntheses of carbon dioxide(CO_(2))based industrially important chemicals have gained considerable interest in view of the sustainable chemistry and“green chemistry”concepts.In this review,recent developments in the chemical fixation of CO_(2)to valuable chemicals are discussed.The synthesis of five-member cyclic carbonates via,cycloaddition of CO_(2)to epoxides is one of the promising reactions replacing the existing poisonous phosgene-based synthetic route.This review focuses on the synthesis of cyclic carbonates,vinyl carbamates,and quinazoline-2,4(1H,3H)-diones via reaction of CO_(2)and epoxide,amines/phenyl acetylene,2-aminobenzinitrile and other chemicals.Direct synthesis of dimethyl carbonate,1,3-disubstituted urea and 2-oxazolidinones/2-imidazolidinones have limitations at present because of the reaction equilibrium and chemical inertness of CO_(2).The preferred alternatives for their synthesis like transesterification of ethylene carbonate with methanol,transamination of ethylene carbonate with primary amine and transamination reaction of ethylene carbonate with diamines/β-aminoalcohols are discussed.These methodologies offer marked improvements for greener chemical fixation of CO_(2)in to industrially important chemicals.