Nanoengineering Metal–Organic Frameworks and Derivatives for Electrosynthesis of Ammonia

Electrocatalytic synthesis under mild conditions has become increasingly important as one of the practical alternatives for industrial applications,especially for the green ammonia(NH_(3))industry.A properly engineered electrocatalyst plays a vital role in the realization of superior catalytic performance.Among various types of promising nanomaterials,metal–organic frameworks(MOFs)are competitive candidates for developing efficient electrocatalytic NH_(3) synthesis from simple nitrogen-containing molecules or ions,such as N_(2) and NO_(3)^(−).In this review,recent advances in the development of electrocatalysts derived from MOFs for the electrosynthesis of NH_(3) are collected,categorized,and discussed,including their application in the N_(2) reduction reaction(NRR)and the NO_(3)^(−)reduction reaction(NO3RR).Firstly,the fundamental principles are illustrated,such as plausible mechanisms of NH_(3) generation from N_(2) and NO_(3)^(−),the apparatus of corresponding electrocatalysis,parameters for evaluation of reaction efficiency,and detection methods of yielding NH_(3).Then,the electrocatalysts for NRR processes are discussed in detail,including pristine MOFs,MOF-hybrids,MOF-derived N-doped porous carbons,single atomic catalysts from pyrolysis of MOFs,and other MOF-related materials.Subsequently,MOF-related NO3RR processes are also listed and discussed.Finally,the existing challenges and prospects for the rational design and fabrication of electrocatalysts from MOFs for electrochemical NH_(3) synthesis are presented,such as the evolution of investigation methods with artificial intelligence,innovation in synthetic methods of MOF-related catalysts,advancement of characterization techniques,and extended electrocatalytic reactions.

Apparent Kinetics for Electrosynthesis Process of Chromic Acid

A new green technique for producing chromic acid via an electrosynthesis method was studied.The kinetic experiments were carried out on the direct electrosynthesis reaction of chromic acid from sodium dichromate in a self-made electrosynthesis reactor with a multiple-unit metal oxides combination anode,a stainless steel cathode,and a reinforcing combination Nafion 324 cation exchange membrane.The apparent kinetic data were experimentally measured at different reaction time under different reaction conditions by relating many essential cell processes and their interaction,as well as their synergistic effect to the whole electrochemical synthesis process.The results show that the electrosynthesis reaction process follows a quasi-first-order reaction kinetic characteristic.The apparent kinetic model of the electrosynthesis reaction was established,and kinetic parameters were calculated.

Electrosynthesis of hierarchical NiLa-layered double hydroxide electrode for efficient oxygen evolution reaction

Oxygen evolution reaction(OER) is a key process for electrochemical water splitting due to its intrinsic large overpotential. Recently, layered double hydroxides(LDHs), especially Ni Fe-LDH, have been regarded as highly performed electrocatalysts for OER in alkaline condition. Here we first present a new class of Ni La-LDH electrocatalyst synthesized by an electrochemical process for efficient water splitting. The as-prepared NiL a-LDH nanosheet arrays(NSAs) give remarkable electrochemical activity and durability under alkaline environments, with a low overpotential of 209 mV for OER to deliver a current density of 10 mA cm^-2, surpassing most of previous reported LDHs eletrocatalysts. The presence of NiLa-LDH in this work extends the studies about LDHs-based electrocatalysts, which will benefit the development of electrochemical energy storage and conversion systems.

Advanced electrosynthesis of hydrogen peroxide on oxidized carbon electrocatalyst

Hydrogen peroxide(H2O2)is one of the 100 most important chemicals involved in multiple chemical processes including paper and textile manufacturing,waste degradation,and pharmaceutical production[1].Compared with the current industrial process to produce H2O2 following the anthraquinone oxidation/reduction method,electrochemical reduction of oxygen to H2O2 through a two-electron pathway constitutes an environmental friendly alternative route[2-4].Unfortunately,the electrogeneration of H2O2 from two-electron reduction of oxygen feedstock is kinetically sluggish and therefore requires electrocatalysts with high reactivity,high selectivity,and good stability[5,6].

Long-term open circuit microbial electrosynthesis system promotes methanogenesis

Microbial electrosynthesis(MES) can potentially provide a mean for storing renewable energy surpluses as chemical energy. However, the fluctuating nature of these energy sources may represent a threat to MES, as the microbial communities that develop on the biocathode rely on the continuous existence of a polarized electrode. This work assesses how MES performance, product generation and microbial community evolution are affected by a long-period(6 weeks) power off(open circuit). Acetogenic and H2-producing bacteria activity recovered after reconnection. However, few days later syntrophic acetate oxidation bacteria and H2-consuming methanogens became dominant, producing CH4 as the main product, via electromethanogenesis and the syntrophic interaction between eubacterial and archaeal communities which consume both the acetic acid and the hydrogen present in the cathode environment. Thus,the system proved to be resilient to a long-term power interruption in terms of electroactivity. At the same time, these results demonstrated that the system could be extensively affected in both end product generation and microbial communities.

Recent developments in electrosynthesis of nitriles and electrocatalytic cyanations

Nitrile compounds are a class of high-value chemicals and versatile intermediates which can easily be transformed into a variety of useful products bearing functional groups such as carboxyl, carbamoyl, aminomethyl, ketyl and heterocyclic derivatives. Various thermal catalytic cyanation procedures have been devised and scaled up industrially while developing alternative methods are actively pursued. The access to these classes of molecules electrochemically offers greener alternatives to their preparation. The development of electrochemical synthesis of cyano-containing compounds under mild conditions with low energy consumption will imminently become indispensable approaches for industrial production of nitriles. The electrochemical cyanation presents many challenges from the toxicity of cyanide to the development of catalysts and the design of electrochemical cells. Electrochemical cyanation reaction offers promise to conveniently accessing nitriles but still requires efficient electro-catalysts, safe protocols and scale up considerations. This review discusses recent progress in the field of electrochemical synthesis of nitrile compounds placing emphasis on electro-synthetic and electro-catalytic mechanism aspects while making reference to original works to highlight the progress in this area.

Carbon Dioxide Fixation Method for Electrosynthesis of Benzoic Acid from Chlorobenzene

Carbon dioxide fixation technique was developed as an alternative dechlorination method of chlorobenzenes. Electrolysis of chlorobenzene was carried out in a one-compartment cell fitted with an aluminium anode and a platinum cathode. Electrolysis in N, N-dimethylformamide （DMF） solution containing 0.1 M of tetrapropylammonium bromide （TPAB） at 0 ℃, 100 ml/min of CO2 flow rate and 120 mA/cm^2 of current density was found to be the optimum conditions of this electrocarboxylation, which gave 72% yield of benzoic acid from chlorobenzene. These conditions were then applied to 1,2-dichlorobenzene and 1,3-dichlorobenzene in order to convert them to their corrcsponding benzoic acids.

Study on the Recycling of Mediator in Indirect Electrosynthesis of Benzaldehyde

This paper has studied the recycling of the oxidation mediator Mn(Ⅲ)/Mn(Ⅱ) and sulfuric acid solution in process of indirect electrosynthesis of benzaldehyde. Experimental resalts show that mis recycling may be realized When electrolysis and synthetic reaction are carried out in the same concentration of 60% H2SO4 separately, then there will be no waste discharged, energy consumption will be decreased and almost no current efficiency will be lossed during recycling process. The optimun current efficiency is 76%, yield of benzaldehyde is 64%.

Highly selective electrosynthesis of 3,4-dihydroisoquinoline accompanied with hydrogen production over three-dimensional hollow CoNi-based microarray electrocatalysts

Electrocatalytic oxidation reaction of biomass-based derivatives is an excellent candidate to replace water oxidation for obtaining both value-added products and hydrogen(H_(2)),but the exploration of competent electrocatalysts is still highly challenging.Herein,two new types of three-dimensional self-supported hollow microarrays containing CoNi layered double hydroxide(CoNi-LDH)and N-doped carbon nanosheets decorated with CoNi alloyed nanoparticles(CoNi-NC)on carbon cloth(CC)are prepared,which are further used as efficient electrocatalysts for tetrahydroisoquinoline(THIQ)electrooxidation and hydrogen evolution reaction(HER),respectively.We demonstrate that the Co-modulated electronic environment for Ni(II)/Ni(Ⅲ)redox-looping in CoNi-LDH is the main factor to boost the selectivity of 3,4-dihydroisoquinoline(DHIQ)for the indirect electrooxidation process of THIQ.Density functional theory(DFT)calculations reveal that the Ni(Ⅲ)/Co(Ⅲ)dual sites of CoNi-LDH exhibit enhanced adsorption for THIQ but poorer adsorption for DHIQ compared to pure Co(Ⅲ)or Ni(Ⅲ).Therefore,the Ni(Ⅲ)/Co(Ⅲ)dual sites can effectively inhibit the peroxidation of DHIQ to isoquinoline(IQ)over CoNi-LDH,thus improving the selectivity of DHIQ to nearly 100%,much higher than that of its pure Ni counterpart.Moreover,CC@CoNi-NC can deliver high HER activity with low overpotential(40 mV@10 mA·cm^(-2))and high exchange current density(3.08 mA·cm^(-2)).Impressively,the assembled flow-cell device with CC@CoNi-LDH anode and CC@CoNi-NC cathode only requires low cell voltage and electricity consumption of 1.6 V and 3.50 kWh per cubic meter of H_(2)(@25 mA·cm^(-2)).

Highly efficient electrosynthesis of H_(2)O_(2)in acidic electrolyte on metal-free heteroatoms co-doped carbon nanosheets and simultaneously promoting Fenton process

Recently electrochemical synthesis of H_(2)O_(2)through oxygen reduction reaction(ORR)via 2e^(-)pathway is considered as a green and on-site route.However,it still remains a big challenge for fabricating novel metal-free catalysts under acidic solutions,since it suffers from high overpotential due to the intrinsically week*OOH adsorption.Herein,a co-doped carbon nanosheet(O/N–C)catalyst toward regulating O and N content was synthesized for improving the selectivity and activity of H_(2)O_(2)electrosynthesis process.The O/N–C exhibits outstanding 2e-ORR performance with low onset potential of 0.4 V(vs.RHE)and a selectivity of 92.4%in 0.1 mol/L HClO_(4)solutions.The in situ electrochemical impedance spectroscopy(EIS)tests reveals that the N incorporation contributes to the fast ORR kinetics.The density functional theory(DFT)calculations demonstrate that the binding strength of*OOH was optimized by the co-doping of oxygen and nitrogen at certain content,and the O/N–C–COOH site exhibits a lower theoretical overpotential for H_(2)O_(2)formation than O–C–COOH site.Furthermore,the promoted kinetics for typical organic dye degradation in simultaneous electron-Fenton process on O/N–C catalyst was demonstrated particularly for broadening its environmental application.

Confluence of asymmetric catalysis and electrosynthesis in sustainable chemical transformations

Electrosynthesis has gained widespread recognition for its extraordinary ability to precisely control the redox process.This outstanding capability enables the direct conversion of non-functionalized substrates into reactive intermediates by utilizing easily accessible starting materials, eliminating the need for preliminary functionalization procedures and allowing for unconventional bond activations.

Recent advances in organic electrosynthesis using heterogeneous catalysts modified electrodes

Organic electrosynthesis as an emerging green and advantageous alternative to traditional synthetic methods has achieved remarkable progress in recent years because sustainable electricity can be employed as traceless redox agents. To surmount the over-oxidation/reduction issues of direct electrolysis,mediated or indirect electrochemical processes are attaining remarkable significance and promoting the selectivity of products. Molecular electrocatalysts, benefiting from the easily electronic and steric modulation, suffers from readily degradation issue in most cases. Remarkably, heterogeneous catalysts have drawn more attention due to their high activity, stability, and recyclability. Hence, in this review, the most recent growth of heterogeneous catalysts modified electrodes for organic electrosynthesis were summarized, highlighting structural optimization and electrochemical performance of these materials as well as reaction mechanism. Furthermore, key challenges and future directions in this area were also discussed.

Electrosynthesis of ^(15)N-labeled amino acids from ^(15)N-nitrite and ketonic acids

^(15)N isotope-labeled amino acids(^(15)N-amino acids)are crucial in the fields of biology,medicine,and chemistry.^(15)N-amino acids are conventionally synthesized through microbial fermentation and chemical reductive amination of ketonic acids methodologies,which usually require complicated procedures,high temperatures,or toxic cyanide usage,causing energy and environmental concerns.Here,we report a sustainable pathway to synthesize ^(15)N-amino acids from readily available ^(15)N-nitrite(^(15)NO_(2)-)and biomass-derived ketonic acids under ambient conditions driven by renewable electricity.A mechanistic study demonstrates a ^(15)N-nitrite→^(15)NH_(2)OH→^(15)N-pyruvate oxime→^(15)N-alanine reaction pathway for ^(15)N-alanine synthesis.Moreover,this electrochemical strategy can synthesize six ^(15)N-amino acids with 68%–95%yields.Furthermore,a ^(15)N-labeled drug of ^(15)N-tiopronin,the most commonly used hepatitis treatment drug,is fabricated using ^(15)N-glycine as the building block.Impressively,^(15)N sources can be recycled by the electrooxidation of ^(15)NH4^(+) to ^(15)NO_(2)-with a method economy.This work opens an avenue for the green synthesis of ^(15)N-labeled compounds or drugs.

Electrosynthesis of hydroxylamine from nitrate reduction in water

Hydroxylamine(NH_(2)OH),a vital but unstable industrial feedstock,is presently prepared under harsh conditions that cause environmental and energy concerns.Here,we report an electrochemical method to prepare oximes,which serve as precursors for NH_(2)OH after facile hydrolysis.The carbon-supported amorphous Mn electrocatalyst delivers a current density of~100 mA cm^(-2) with a Faradaic efficiency of 40.92%and a yield rate of 0.251 mmol cm^(-2)h^(-1) for formaldoxime(CH_(2)NOH)generation by using nitrate and formaldehyde as reactants.Formaldoxime can be easily released to produce NH_(2)OH via hydrolysis.Impressively,this method exhibits an economic advantage over conventional manufacturing based on techno-economic analysis.A series of control experiments,in situ characterizations,and theoretical simulations unveil the reaction mechanism via the spontaneous reaction between an aldehyde and*NH_(2)OH intermediate derived from nitrate electroreduction.The high activity of Mn originates from its inhibitory effects on the further reduction of key*NH_(2)OH intermediate.This strategy opens a sustainable and green way for NH_(2)OH synthesis under mild conditions using renewable energy.

New microbial electrosynthesis system for methane production from carbon dioxide coupled with oxidation of sulfide to sulfate

Microbial electrosynthesis system (MES) is a promising method that can use carbon dioxide,which is a greenhouse gas,to produce methane which acts as an energy source,without using organic substances.However,this bioelectrical reduction reaction can proceed at a certain high applied voltage when coupled with water oxidation in the anode coated with metallic catalyst.When coupled with the oxidation of HS–to SO_(4)^(2-),methane production is thermodynamically more feasible,thus implying its production at a considerably lower applied voltage.In this study,we demonstrated the possibility of electrotrophic methane production coupled with HS–oxidation in a cost-effective bioanode chamber in the MES without organic substrates at a low applied voltage of 0.2 V.In addition,microbial community analyses of biomass enriched in the bioanode and biocathode were used to reveal the most probable pathway for methane production from HS–oxidation.In the bioanode,electroautotrophic SO_(4)^(2-)production accompanied with electron donation to the electrode is performed mainly by the following two steps:first,incomplete sulfide oxidation to sulfur cycle intermediates (SCI) is performed;then the produced SCI are disproportionated to HS^(–)and SO_(4)^(2-).In the biocathode,methane is produced mainly via H_(2)and acetate by electronaccepting syntrophic bacteria,homoacetogens,and acetoclastic archaea.Here,a new ecofriendly MES with biological H_(2)S removal is established.

Cobalt-iron oxide/black phosphorus nanosheet heterostructure:Electrosynthesis and performance of(photo-)electrocatalytic oxygen evolution

Highly active,stable,and cut-price(photo-)electrocatalysts are desired to overwhelm high energy barriers for anodic oxygen evolution reaction processes.Herein,a heterostructure of cobalt-iron oxide/black phosphorus nanosheets is in-situ synthesized via a facile and novel three-electrode electrolysis method.Bulky black phosphorus is exfoliated into its nanosheets at the cathode while the CoFe oxide is derived directly from the metal wire anode during the electrolysis process.This heterostructure exhibits excellent electrocatalytic oxygen evolution reaction(OER)performance,and the overpotential at 10 mA·cm^(−2)is 51 mV lower than that of the commercial RuO_(2)catalyst.Its superior OER performance stems from the favorable adsorption behavior and an enlarged electrochemical active surface area of the catalyst.To reveal the origin of excellent OER performance from the point of adsorption strength of OH*,methanol oxidation reaction(MOR)test is applied under the identified OER operating conditions.Further introduction of light illumination enhances the OER activity of this heterostructure.The overpotential drops down to 280 mV,benefiting from pronounced photochemical response of black phosphorus nanosheets and iron oxide inside the heterostructure.This work develops a new electrochemical method to construct high performance and light-sensitive heterostructures from black phosphorus nanosheets for the OER.

Coupling functional anodes with natural air-diffused cathodes enables highly efficient hydrogen peroxide electrosynthesis

Electrosynthesis of hydrogen peroxide(H_(2)O_(2))is a decentralized production method with excellent application prospects.Coupling anodes with cathodes can achieve highly efficient electrosynthesis of hydrogen peroxide.In this study,we prepared an anode for H_(2)O_(2) electrosynthesis via the two-electron water oxidation reaction(2e-WOR)by modifying carbon fiber paper with self-assembling monolayers.In addition,a natural air-diffused cathode loaded with polytetrafluoroethylene/carbon black using carbon cloth as substrate was prepared to combine with the modified anode to produce H_(2)O_(2) simultaneously.The total current efficiency of the anode and cathode reached 152.9%,and the H_(2)O_(2) production rate was as high as 38μmol/min at 2.8 V vs.reversible hydrogen electrodes(RHE)in a Nafion 117 membrane-separated electrolyzer.This work reported a novel carbon-based 2e-WOR catalyst and laid a theoretical foundation for the simultaneous electrosynthesis of H_(2)O_(2) with an anode and cathode.

Metal, iodine and oxidant-free electrosynthesis of substituted indoles from 1-(2-aminophenyl)alcohols

A green and straightforward electrosynthesis of substituted indoles has been developed through dehydration and intramolecular dehydrogenative C–N bond-forming radical cross-coupling from 1-(2-aminophenyl)alcohols under metal,iodine and oxidant-free conditions.This electrochemical indole synthesis strategy has an excellent functional group,water and air tolerance.And,a possible cyclization process was proposed based on the radicaltrapping,intermediate verification,cyclic voltammetry,EPR and control experiments.

Comprehensive understanding of the thriving electrocatalytic nitrate/nitrite reduction to ammonia under ambient conditions

Ammonia(NH_(3))is a multifunctional compound that is an important feedstock for the agricultural and pharmaceutical industries and attractive energy storage medium.At present,NH_(3)synthesis is highly dependent on the conventional Haber–Bosch process that operates under harsh conditions,which consumes large quantities of fossil fuels and releases a large amount of carbon dioxide.As an alternative,electrosynthesis is a prospective method for producing NH_(3)under normal temperature and pressure conditions.Although electrocatalytic nitrogen reduction to ammonia has attracted considerable attentions,the low solubility of N_(2)and high N≡N cracking energy render the achievements of high NH_(3) yield rate and Faradaic efficiency difficult.Nitrate and nitrite(NO_(x)^(-))are common N-containing pollutants.Due to their high solubilities and low dissociation energy of N=O,NO_(x)^(-)−are ideal raw materials for NH_(3) production.Therefore,electrocatalytic NO_(x)^(-)−reduction to NH_(3)(eNO_(x)RR)is a prospective strategy to simultaneously realise environmental protection and NH_(3) synthesis.This review offers a comprehensive understanding of the thriving eNO_(x)RR under ambient conditions.At first,the popular theory and mechanism of eNO_(x)RR and a summary of the measurement system and evaluation criteria are introduced.Thereafter,various strategies for developing NO_(x)−reduction catalysts are systematically presented and discussed.Finally,the challenges and possible prospects of electrocatalytic NO_(x)^(-1) reduction are outlined to facilitate energy-saving and environmentally friendly large-scale synthesis of NH_(3) in the future.

Electrosynthesis of Co3O4 and Co（OH）2 ultrathin nanosheet arrays for efficient electrocatalytic water splitting in alkaline and neutral media

The dimensional confinement endows ultrathin nanosheets with unique physical and chemical properties, which have been widely studied for the purpose of developing active electrocatalysts for water splitting. Ultrathin nanosheets are generally synthesized by chemical vapor deposition, exfoliation, or surfactant- assisted synthesis, which either require special equipment and reaction conditions, or is limited by the low yields and the difficulty in controlling the lateral size and structure of the nanosheets. In addition, achieving a high loading of ultrathin nanosheets on the electrodes without compromising their catalytic activity still remains a challenge. Herein, we report a simple electrodeposition method for preparing C0304 and Co（OH）2 ultrathin nanosheet arrays （UNA） without using templates or surfactants. The obtained arrays exhibit high activity for oxygen and hydrogen evolution reactions, in both alkaline and neutral media. The electrolyzer based on Co304 and Co（OH）2 UNA shows superior activity and stability than that based on IrO2 and Pt/C, which demonstrates the potential of the present electrodeposition method for developing active and stable electrocatalysts for water splitting.