Electrochemical synthesis of trimetallic nickel-iron-copper nanoparticles via potential-cycling for high current density anion exchange membrane water-splitting applications

Hydrogen is known for its elevated energy density and environmental compatibility and is a promising alternative to fossil fuels.Alkaline water electrolysis utilizing renewable energy sources has emerged as a means to obtain high-purity hydrogen.Nevertheless,electrocatalysts used in the process are fabricated using conventional wet chemical synthesis methods,such as sol-gel,hydrothermal,or surfactantassisted approaches,which often necessitate intricate pretreatment procedures and are vulnerable to post-treatment contamination.Therefore,this study introduces a streamlined and environmentally conscious one-step potential-cycling approach to generate a highly efficient trimetallic nickel-iron-copper electrocatalyst in situ on nickel foam.The synthesized material exhibited remarkable performance,requiring a mere 476 mV to drive electrochemical water splitting at 100 mA cm^(-2)current density in alkaline solution.Furthermore,this material was integrated into an anion exchange membrane watersplitting device and achieved an exceptionally high current density of 1 A cm^(-2)at a low cell voltage of2.13 V,outperforming the noble-metal benchmark(2.51 V).Additionally,ex situ characterizations were employed to detect transformations in the active sites during the catalytic process,revealing the structural transformations and providing inspiration for further design of electrocatalysts.

In situ electrochemical synthesis of MOF-5 and its application in improving photocatalytic activity of BiOBr

Metal-organic frameworks（MOFs） are important functional materials. MOF-5（IL）（Zn4O（BDC）3（BDC=1,4-benzenedicarboxylate） was in situ synthesized by the electrochemical method using a tunable ionic liquid（IL）, 1-butyl-3-methylimidazolium chloride, as template. The crystallization of distinctly spherical MOF-5（IL） synthsized in ionic liquid by the electrochemical method is attributed to π-π stacking effect, ionic bond, and coordination bond. The analysis results show that the product MOF-5（IL） exhibits better crystallinity and higher thermal stability than MOF-5 generated using the solvothermal method. The cyclic voltammetry reveals that the electrosynthesis reaction is irreversible and controlled by the diffusion. The experiments on methylorange degradation show that the unique structure characteristics of MOF-5（IL） can enhance the photocatalytic ability of Bi OBr. Therefore, MOFs can replace noble metals to improve the photocatalytic properties of bismuth oxyhalide.

Electrochemical synthesis of ammonia in molten salts

Ammonia is important feedstock for both fertilizer production and carbon-free liquid fuel.Many techniques for ammonia formation have been developed,hoping to replace the industrial energy-intensive Haber-Bosch route.Electrochemical synthesis of ammonia in molten salts is one promising alternative method due to the strong solubility of N3- ions,a wide potential window of molten salt electrolytes and tunable electrode reactions.Generally,electrochemical synthesis of ammonia in molten salts begins with the electro-cleavage of N2/hydrogen sources on electrode surfaces,followed by diffusion of N3^-/H^+-containing ions towards each other for NH3 formation.Therefore,the hydrogen sources and molten salt composition will greatly affect the reactions on electrodes and ions diffusion in electrolytes,being critical factors determining the faradaic efficiency and formation rate for ammonia synthesis.This report summarizes the selection criteria for hydrogen sources,the reaction characteristics in various molten salt systems,and the preliminary explorations on the scaling-up synthesis of ammonia in molten salt.The formation rate and faradaic efficiency for ammonia synthesis are discussed in detail based on different hydrogen sources,various molten salt systems,changed electrolysis conditions as well as diverse catalysts.Electrochemical synthesis of ammonia might be further enhanced by optimizing the molten salt composition,using electrocatalysts with well-defined composition and microstructure,and innovation of novel reaction mechanism.

Hydrothermal Synthesis,Crystal Structure and Electrochemical Properties of Complex Cu(α-Furacrylic acid)_2(phen)

The title complex （C26H18CuN206, Mr= 517.96） has been synthesized by the reaction of α-furanacrylic acid with 1,10-phenanthroline （phen） in the solvent mixture of water and methanol. Crystal data： monoclinic, space group C2/c with a = 2.2927（4）, b = 1.01248（18）, c = 1.05061（18） nm, β = 111.188（3）°, V= 2.274（7） nm^3, Dc = 1.513 g/cm^3, Z = 4, F（000） = 1060,μ = 1.007mm^-1, R = 0.0320 and ωR = 0.0781. The crystal structural analysis shows that the copper atom is coordinated with four oxygen atoms from two α-furacrylic acids and two nitrogen atoms from 1,10-phenanthroline, giving a distorted octahedral coordination geometry. The result of electrochemical analysis shows that the electron transfer in the electrode reaction is quasi-reversible.

Study on superoxide and hydroxyl radicals generated in indirect electrochemical oxidation by chemiluminescence and UV-Visible spectra

The generation and transformation of radicals on the cathode of indirect electrochemical oxidation were studied by chemilumines- cence(CL)and UV-Visible spectra in the reactor with a salt bridge that connected the separated chambers.The CL intensity of 4×10^(-9)mol/L luminol on the cathode with bubbling oxygen was about seven times that of the intensity without it,which was because of the generation of reactive oxygen species(ROS).The existence of ROS,especially the generation of the superoxide radical,coul...

Electrochemical Synthesis of Polythiophene in an Ionic Liquid

Polythiophene (PTh) was prepared by the direct electrochemical synthesis in an ionic liquid ([BMIM]PF6) containing 0.1 mol/L thiophene by cyclic voltammetry, constant potential and constant current techniques. It is found that smooth and bluegreen PTh films can be obtained at a potential of ca. +1.75 V ( vs. Ag/AgCl ) or a current of ca. 1.5 mA cm-2 in the ionic liquid.

Hydrothermal Synthesis, Crystal Structure and Electrochemical Properties of the Complex Cu(o-Methylbenzoic acid)_2(2,2′-bipy)·(H_2O)

The title complex （C26H24CuN2O5, Mr = 508.01） has been synthesized by o-methylbenzoic acid, 2,2＇-bipyridine （bipy） and copper perchlorate in the mixed solvent of water and methanol. It crystallizes in orthorhombic, space group P212121 with a = 0.70814（10）, b = 1.6953（3）, c = 1.9539（3） nm, V= 2.3457（6） nm^3, De= 1.439 g/cm^3, Z = 4,μ = 0.971 mm^-1, F（000） = 1052, R = 0.0432 and wR = 0.0860. The structural determination shows that the copper atom is coordinated by three oxygen atoms from two o-methylbenzoic acids and one water molecule together with two nitrogen atoms from 2,2＇-bipyridine, giving a distorted square-pyramidal coordination geometry. The cyclic voltammetric behavior of the complex is also discussed.

Effects of alkaline cations (M^+= Li^+, Na^+, K^+, Cs^+) on the electrochemical synthesis of polyaniline in nitric acid electrolyte

The effects of alkaline cations （M^＋ = Li^＋, Na^＋, K^＋, Cs^＋）on the electrochemical synthesis of polyaniline were carfled out under cyclovoltammetric conditions using nitrates of Li^＋, Na^＋, K^＋, and Cs^＋ as the supporting electrolytes. The results show that the oxidation potentials of aniline in the electrolytes decrease as the protonation extent of aniline decreases from the fast scan, which is caused by the decrease of the ionic radius of alkaline metal ions at the same concentration of alkaline cations. With the scan number increasing, the deposit charge Q as the characteristic growth function also depends on the protonation of aniline, and it increases with the ionic radius of alkaline cations increasing. SEM images show the effect of alkaline cations on the morphology of polyaniline. It is clear that the ionic mobility of alkaline cations is further lower than that of W. Alkaline cations and counter-ions were the species responsible for the enhancement of Pani electrosynthesis. Therefore, this is exactly what SEM images show： a relatively rough fibrous structure in the case of Pani-H^＋ suggesting a sponge-like structure and a highly orderly fiber-like structure in the case of Pani-M^＋.

Hydrothermal Synthesis and Electrochemical Properties of Complex Cu(CH_3C_6H_4COOH)_2(2,2′-bipy)·(H_2O)

The title complex has been synthesized by 4-methylbenzoic acid and 2,2′-bipyridine （bipy） in the mixed solvent of water and methanol. It crystallizes in the triclinic system, space group P1^- with a = 0.7047（3）, b = 1.1217（5）, c = 1.6718（7） nm, α = 103.826（7）, β = 90.772（6）, γ = 104.195（6）°, C26H25CuN2O5.50, Mr = 517.02, V = 1.2404（9） nm^3, Dc = 1.384 g/cm^3, Z = 2, F（000） = 536,μ（MoKα） = 0.921 mm^-1, R = 0.0782 and wR = 0.2172. Structural analysis shows that the copper atom is coordinated with three oxygen atoms from two 4-methylbenzoic acids and one water molecule together with two nitrogen atoms from 2,2＇-bipyridine, giving a distorted square-pyramid coordination geometry. The cyclic voltametric behavior of the complex has also been described.

Shape control technology during electrochemical synthesis of gold nanoparticles

Gold nanoparticles with different shapes and sizes were prepared by adding gold precursor （HAuC14） to an electrolyzed aqueous solution of poly（N-vinylpyrrolidone） （PVP） and KN03, which indicates the good reducing capacity of the PVP-containing solution after being treated by electrolysis. Using a catholyte and an anolyte as the reducing agents for HAuC14,＇ respectively, most gold nanoparticles were spherical particles in the former case but plate-like particles in the latter case. The change in the pH value of electrolytes caused by the electrolysis of water would be the origin of the differences in shape and morphology of gold nanoparticles. A hypothesis of the H＋ or OH- catalyzed PVP degradation mechanism was proposed to interpret why the pH value played a key role in determining the shape or morphology of gold nanoparticles. These experiments open up a new method for effectively controlling the shape and morphology of metal nanoparticles by using electrochemical methods.

Electrochemical synthesis of catalytic materials for energy catalysis

Electrocatalysis is a process dealing with electrochemical reactions in the interconversion of chemical energy and electrical energy.Precise synthesis of catalytically active nanostructures is one of the key challenges that hinder the practical application of many important energy‐related electrocatalytic reactions.Compared with conventional wet‐chemical,solid‐state and vapor deposition synthesis,electrochemical synthesis is a simple,fast,cost‐effective and precisely controllable method for the preparation of highly efficient catalytic materials.In this review,we summarize recent progress in the electrochemical synthesis of catalytic materials such as single atoms,spherical and shaped nanoparticles,nanosheets,nanowires,core‐shell nanostructures,layered nanomaterials,dendritic nanostructures,hierarchically porous nanostructures as well as composite nanostructures.Fundamental aspects of electrochemical synthesis and several main electrochemical synthesis methods are discussed.Structure‐performance correlations between electrochemically synthesized catalysts and their unique electrocatalytic properties are exemplified using selected examples.We offer the reader with a basic guide to the synthesis of highly efficient catalysts using electrochemical methods,and we propose some research challenges and future opportunities in this field.

Hydrothermal Synthesis,Crystal Structure and Electrochemical Properties of the Copper(II) Complex [Cu_4O_4(phen)_4(ClC_6H_4COO)_2(H_2O)_2]·(H_2O)_3

The title complex of copper（Ⅱ） with m-chlorobenzoic acid, 1,10-phenanthroline （phen） and copper perchlorate has been synthesized and characterized in the solvent mixture of water and methanol. Crystal data for this complex： triclinic, space group PI^-, a = 1.06853（12）, b = 1.30740（16）, c = 1.49546（17） nm, α= 101.791（2）,β = 103.413（2）, γ = 105.815（2）°, V= 1.8736（4） nm^3, Mr = 904.67, Dc = 1.604 g/cm^3, Z = 2,/7（000） = 924,μ = 1.34 mm^-1, GOOF = 1.049, the final R = 0.0324 and wR = 0.0797. The structure analysis shows that a chair-like structure [Cu4O4] is defined by three quadrilaterals shaped by four copper and four oxygen atoms, and every copper ion is coordinated by three oxygen atoms from three wate： molecules and two nitrogen atoms from one 1,10-phenanthroline molecule, giving a distorted square-pyramidal coordination geometry. The CV analysis results indicate that the electron transfer in the electrode reaction is quasi-reversible.

Synthesis of graphene materials by electrochemical exfoliation: Recent progress and future potential

Synthesis of structurally controlled graphene materials is critical for realizing their practical applications.The electrochemical exfoliation of graphite has emerged as a simple method to produce graphene materials.This review examines research progress in the last 5 years,from 2015 to 2019.Graphene material synthesis methods generally have a trade‐off between increasing production yield and achieving better material property control.The synthesis conditions for synthesizing pristine graphene,graphene oxide(GO),and graphene composites are significantly different.Thus,in this review,we first discuss synthesis methods for graphene materials with high C/O ratios from four aspects:graphite electrodes,equipment engineering,electrolytes,and additional reduction methods.Next,we survey synthesis methods for GO and examine how the pretreatment of the graphite electrodes,electrolytes,and operation parameters,such as applied voltages,electrolyte temperatures,and mechanical forces,affect the quality of GO.Further,we summarize electrochemical exfoliation methods used to dope graphene materials,introduce covalent functional groups,incorporate various nanoparticles,and assembly of graphene architectures.For all synthesis methods,we compare the properties of resulting graphene materials such as C/O ratios,lateral size,layer numbers,and quality characterized by Raman spectroscopy.Lastly,we propose our perspectives on further research.We hope this review stimulates more studies to realize the on‐demand production of graphene materials with desired properties using electrochemical exfoliation methods.

Synthesis and electrochemical properties of polyradical cathode material for lithium second batteries

A stable polyradical, poly (2,2,6,6-tetramethylpiperidinyloxy methacrylate) (PTMA), was synthesized,and its structure was determined by infrared, ultraviolet-visible, and ESR spectroscopy. Cyclic voltammograms ofthe PTMA polyradical electrodes were obtained by using a three-electrode cell at a scan rate of 5 mV/s within a po-tential range of 3.2-4. 0 V. The results show that the shape of oxidation peak is very similar to that of reductionpeak, and oxidation peak current is equal to the corresponding reduction peak current, which suggest that PTMApossesses an excellent reversibility. The difference of the anodic peak potential (Ea,p =3.66 V, vs Li/Li+ ) and ca-thodic peak potential(Ec,p =3.58 V, vs Li/Li+ ) is estimated at 80 mV, which is extremely less than that of the oth-er organic positive materials in lithium second batteries such as organosulfide compounds, leading to a capability forhigh current capability in the charging and discharging process of the battery. The maximum discharge specific ca-pacity of PTMA is 78.4 mA @ h/g at the constant discharge current of 0.3 mA (0.2 C rate), the coulombic efficien-cy is about 95%, and the charging and discharging curves of the batteries have an obvious plateau at 3.65 V and3.56 V, respectively. The discharging specific capacity of the battery decreased is about 2% after 100 cycles. ThePTMA/Li button batteries exhibite an excellent stability.

Synthesis and photophysical and electrochemical properties of new cyclometalated platinum complex containing oxadiazole ligand

A new cyclometalated platinum complex containing 2, 5-bis(naphthalene-1-yl)-1,3,4-oxadiazole ligand was synthesized and characterized. The UV-Vis absorptions and photoluminescent properties of the ligand and its platinum complex were investigated. A characteristic metal-ligand charge transfer absorption peak at 439 nm in the UV spectrum and a strong emission peak at 625 nm in the photoluminescence spectrum were observed for this complex in dichloromethane. Cyclic voltammtry (CV) analysis shows that the EHOMO (energy level of the highest occupied molecular orbital) and ELUMO (energy level of the lowest unoccupied molecular orbital) of the platinum complex are about 、5.69 and 、3.25 eV, respectively, indicating that the oxadiazole-based platinum complex has a potential application in electrophosphorescent devices used as a red-emitting material.

Electrochemical synthesis of alkali-intercalated iron selenide superconductors

Electrochemical method has been used to insert K/Na into FeSe lattice to prepare alkali-intercalated iron selenides at room temperature. Magnetization measurement reveals that KxFe2Se2 and NaxFe2Se2 are superconductive at 31 K and 46 K, respectively. This is the first successful report of obtaining metal-intercalated FeSe-based high-temperature superconductors using electrochemical method. It provides an effective route to synthesize metal-intercalated layered compounds for new superconductor exploration.

A photo-assisted electrochemical-based demonstrator for green ammonia synthesis

Bridging laboratory research and practical utilization is of crucial importance for the development of green ammonia synthetic technologies. A decentralized photo-assisted electrochemical-based demonstrator has been proposed for green ammonia synthesis from renewable electricity, air and water, where well-known defect-laden WO_(3) is used as the working electrode, and a commercially available PV panel supplies renewable electricity. In this demonstrator, defect-laden WO_(3) exhibits the optimum electrochemical NH_(3) formation rate(4.51 × 10^(-12)mol s^(-1)cm^(-2)) in 0.1 M K_(2)SO_(4)in a photovoltaic electrochemical(PV-EC) system. A system-level energy and cost analysis was conducted to investigate its economic viability and a general evaluation tool for system performance and cost estimation was proposed. This advance enables the possibility of integrating the small-scale green ammonia demonstrator into a stand-alone farm system.

Synthesis and electrochemical properties of 2,6-bis(6-aryl-[1,2,4]- triazolo[3,4-b][1,3,4]-thiadiazole-3-yl)pyridines

By the condensation of 2,6-bis（4-amino-5-mercapto-[1,2,4]-triazoles-2）pyridine with aromatic acid in the presence of phosphorus oxychloride. Compounds of 2,6-bis（6-aryl-[1,2,4]-triazolo[3,4-b][1,3,4]-thiadiazole-3-yl）pyridines were synthesized. Their structures were confirmed by IR, ^1H NMR spectroscopies and elemental analysis. Their electrochemical behavior and cyclic voltammogram also were be studied. The results showed that they have high ionization potentials and good affinity.

Enhanced performance in the direct electrocatalytic synthesis of ammonia from N2 and H2O by an in-situ electrochemical activation of CNT-supported iron oxide nanoparticles

The direct electrocatalytic synthesis of ammonia from N2 and H2O by using renewable energy sources and ambient pressure/temperature operations is a breakthrough technology,which can reduce by over 90%the greenhouse gas emissions of this chemical and energy storage process.We report here an in-situ electrochemical activation method to prepare Fe2O3-CNT(iron oxide on carbon nanotubes)electrocatalysts for the direct ammonia synthesis from N2 and H2O.The in-situ electrochemical activation leads to a large increase of the ammonia formation rate and Faradaic efficiency which reach the surprising high values of 41.6μg mgcat^−1 h^−1 and 17%,respectively,for an in-situ activation of 3 h,among the highest values reported so far for non-precious metal catalysts that use a continuous-flow polymer-electrolytemembrane cell and gas-phase operations for the ammonia synthesis hemicell.The electrocatalyst was stable at least 12 h at the working conditions.Tests by switching N2 to Ar evidence that ammonia was formed from the gas-phase nitrogen.The analysis of the changes of reactivity and of the electrocatalyst characteristics as a function of the time of activation indicates a linear relationship between the ammonia formation rate and a specific XPS(X-ray-photoelectron spectroscopy)oxygen signal related to O2−in iron-oxide species.This results together with characterization data by TEM and XRD suggest that the iron species active in the direct and selective synthesis of ammonia is a maghemite-type iron oxide,and this transformation from the initial hematite is responsible for the in-situ enhancement of 3-4 times of the TOF(turnover frequency)and NH3 Faradaic efficiency.This transformation is likely related to the stabilization of the maghemite species at CNT defect sites,although for longer times of preactivation a sintering occurs with a loss of performances.

Overview of emerging catalytic materials for electrochemical green ammonia synthesis and process

The concept of“green-ammonia-zero-carbon emission”is an emerging research topic in the global community and many countries driving toward decarbonizing a diversity of applications dependent on fossil fuels.In light of this,electrochemical nitrogen reduction reaction(ENRR)received great attention at ambient conditions.The low efficiency(%)and ammonia(NH_(3))production rates are two major challenges in making a sustainable future.Besides,hydrogen evolution reaction is another crucial factor for realizing this NH_(3)synthesis to meet the large-scale commercial demand.Herein,the(i)importance of NH_(3)as an energy carrier for the next future,(ii)discussion with ENRR theory and the fundamental mechanism,(iii)device configuration and types of electrolytic systems for NH_(3)synthesis including key metrics,(iv)then moving into rising electrocatalysts for ENRR such as single-atom catalysts(SACs),MXenes,and metal–organic frameworks that were scientifically summarized,and(v)finally,the current technical contests and future perceptions are discussed.Hence,this review aims to give insightful direction and a fresh motivation toward ENRR and the development of advanced electrocatalysts in terms of cost,efficiency,and technologically large scale for the synthesis of green NH_(3).