Constant Potential Electrolysis Research Articles

Electrodeposition behaviour of samarium in 1,3-dimethyl-2-imidazolidone solvent

Abstract The present study investigates the electrochemistry spectroscopy of Sm(III), and electrodeposition of samarium metal in neutral ligand-based ionic liquid (solvate ionic liquid). Mixture consisted of a samarium precursor (either samarium triflate or samarium nitrate hexahydrate) in the solvate ionic liquid, 1.3-dimethyl-2-imidazolidone (DMI). FT-IR analysis of Sm(III)-DMI electrolytes indicates that Sm3+ ion coordinates with DMI through carbonyl group (C=O); the band splits into two with emergence of new peak at 1630 cm−1 and 1649 cm−1 for the triflate and nitrate solutions, respectively. Raman spectroscopy also confirms the solvation of Sm(III) with DMI through oxygen atom of the carbonyl group. Voltametric behaviour of Sm(III) ion indicates two-step reduction mechanism via Sm(III)/Sm(II) at ca. −2.0 V and Sm(II)/Sm(0) at ca. −3.0 V vs. Ag/Ag+ for both samarium(III)-containing electrolytes. Diffusion coefficient value of Sm(III) was determined to be 2.185 × 10−6 cm2/s and 2.418 × 10−8 cm2/s for triflate and nitrate electrolytes, respectively. Electrodeposition of samarium was achieved through constant potential electrolysis using copper substrate as the working electrode which yielded compact deposits from triflate-DMI and non-uniform granular deposit from nitrate-DMI electrolyte. Ex situ X-ray photoelectron spectroscopy analysis of the as-deposited samples revealed the presence of metallic Sm (1081 eV) co-existing with its oxide form (1083 eV).

Mechanistic Insights into Electrocatalytic Hydrogen Evolution by an Exceptionally Stable Cobalt Complex.

Co(aPPy) is one of the most stable and active molecular first-row transition-metal catalysts for proton reduction reported to date. Understanding the origin of its high performance via mechanistic studies could aid in developing even better catalysts. In this work, the catalytic mechanism of Co(aPPy) was electrochemically probed, in both organic solvents and water. We found that different mechanisms can occur depending on the solvent and the acidity of the medium. In organic solvent with a strong acid as the proton source, catalysis initiates directly after a single-electron reduction of CoII to CoI, whereas in the presence of a weaker acid, the cobalt center needs to be reduced twice before catalysis occurs. In the aqueous phase, we found drastically different electrochemical behavior, where the Co(aPPy) complex was found to be a precatalyst to a different electrocatalytic species. We propose that in this active catalyst, the pyridine ring has dissociated and acts as a proton relay at pH ≤ 5, which opens up a fast protonation pathway of the CoI intermediate and results in a high catalytic activity. Furthermore, we determined with constant potential bulk electrolysis that the catalyst is most stable at pH 3. The catalyst thus functions optimally at low pH in an aqueous environment, where the pyridine acts as a proton shuttle and where the high acidity also prevents catalyst deactivation.

RhCuBi Trimetallenes with Composition Segregation Coupled Crystalline‐Amorphous Heterostructure Toward Ethanol Electrooxidation

AbstractThe inefficiency of Pt and Pd benchmark catalysts in achieving complete ethanol oxidation, coupled with their inherent susceptibility to poisoning, poses a significant obstacle to the advancement of direct ethanol fuel cells. In this study, the development of self‐supported and ultrathin RhCuBi trimetallenes, demonstrating exceptional performance in ethanol electrooxidation through segregation and interface engineering is presented. The distinctive RhBi‐rich crystalline/RhCu‐rich amorphous heterostructure of RhCuBi trimetallenes creates a wealth of highly active interfacial sites for the ethanol oxidation reaction (EOR). This results in an impressive 43.3% Faradaic efficiency for the C1 pathway and a peak mass activity of 1.11 A mgRh−1 at 0.68 V versus reversible hydrogen electrode. Moreover, RhCuBi trimetallenes retain 60% of their initial mass activity after 8.5 h of constant potential electrolysis, outperforming commercial Pd and Pt catalysts (<3%). In/ex situ infrared spectroscopy directly reveals the generated C1 products and the key CH3CO* intermediates for EOR on RhCuBi trimetallenes. Theoretical calculations confirm that the RhBi alloy, particularly the lattice‐stretched crystalline/amorphous interfacial sites, facilitates the adsorption/activation of ethanol and the dehydrogenation of CH3CO* toward the C1 pathway of EOR. This breakthrough offers promising prospects for enhancing the efficiency and stability of ethanol electrooxidation in fuel cell applications.

Perchlorate decomposition on rhodium nanoclusters supported on copper crystallite (RhxCu) electrode in an electrodialysis-assisted bipolar electro-reduction system (ED-ER)

Perchlorate (ClO4−) contamination in the aquatic environments presents challenges for remediation due to its high solubility and chemical inertness. A bimetallic RhxCu/Ti was synthesized by incorporating rhodium (Rh) nanoclusters onto the copper crystallites on a titanium mesh substrate for electro-reduction of perchlorate ions. Characterization, which included voltammetry, Raman spectroscopy, and constant potential electrolysis, elucidated the reduction mechanism of perchlorate. A reversible phase transition of Rh(0)⇌ Rh(II) was found to be an effective electron mediator of adsorbed ClO4−, where the neighboring Cu sites were responsible for hydrogenation of chlorinated intermediates. The dispersity of Rh clusters was influenced by the Rh-to-Cu ratio, thereby enhancing the electrochemical reactivity. The bimetallic electrode with around 30 % Rh coverage, i.e., Rh0.3Cu/Ti, possessed superior removal and faradaic efficiency within a potential range of −0.6 V to −0.8 V (vs. Ag/AgCl, at pH 3), which were 95 % and 78 %, respectively. The electro-reduction (ER) and the associated electrodialysis (ED) divided using ion exchange membrane were demonstrated for the treatment of perchlorate wastewater. The electrical field applied by the ED unit drove the migration of ClO4− ions to the surfaces of Rh0.3Cu/Ti cathode, further improving the removal efficiency of perchlorate and lowering energy consumption.

Electrodeposition Behavior of Al-Au Alloys in AlCl3-NaCl-KCl-Aucl Molten Salt

Quartz Crystal Microbalance (QCM) has been used as a highly sensitive mass sensor. This study aims to form porous gold thin films on QCM elements and apply them to highly sensitive gas sensors by attaching selective media. Physical vapor deposition and chemical etching are known methods for forming porous Au thin films. In this study, the electrochemical formation of porous gold films in AlCl3-NaCl-KCl molten salts containing AuCl was investigated. There are few reports about electrodeposition and dissolution potentials of Au in the molten salt electrolyte. As a first step in this study, voltammogram measurements and constant potential electrolysis were performed in the electrolyte, and electrodeposition potentials of Au and Al-Au alloys were discussed.An electrolyte in this study is a mixture of 61 mol% AlCl3- 26 mol% NaCl- 13 mol% KCl molten salt. The mixture salt was melted at 443 K and AuCl was added to the molten salt. A glassy carbon plate (GC) and a pure Al wire were used as the working electrode and reference electrode, respectively. The GC plate and Au mesh were used as the counter electrode for voltammogram measurement and constant potential electrolysis, respectively. Voltammogram measurements were carried out at potential range from -0.1 to 2.4 V vs. Al/Al(Ⅲ). Constant potential electrolysis was performed in the range from -0.2 to 0.3 V with an electric charge density of 40 C cm-2. The electrodeposits were observed by scanning electron microscopy (SEM) and determined the composition of Al and Au by energy dispersive X-ray spectroscopy (EDS).Au ions concentration in the electrolyte was 2.5 mmol dm-3. In voltammogram measurements, a small cathodic current was observed at about 0.8 V, then gradually increased from 0.2 V. In the potential lower than 0 V, a drastical increase of cathodic current was observed, which was attributed to Al electrodeposition. When the potential was reversed, large anodic current flowed from 0 V and a small current peak was also observed at 0.2 V. These were considered to correspond to the dissolution of Al and Al-Au alloys, respectively. Furthermore, a relatively large anodic current peak was observed at about 2 V, which was expected to be due to the dissolution of Au. From the results of constant potential electrolysis, the Au concentration in the electrodeposits at -0.1 V and -0.2 V was less than 1 at%. At 0 V, the Au concentration in the electrodeposit increased sharply to 84 at%, and at 0.3 V it increased moderately to 89 at%. From SEM observation, the morphology of the electrodeposits at -0.1 V and -0.2 V was dense, while that at potentials more than 0 V was sponge-like.AcknowledgementsThis work was supported by JST SICORP and JPMJSC2108.

Electrochemical Reduction from CO2 to CH4 By Electrodeposited Cu/L-Histidine Hybrid Materials

The electrochemical reduction technology of carbon dioxide (CO2) is attracting attention due to it can convert CO2 into a useful resource with zero emissions by using surplus electricity and renewable energy. For achieving efficient electrolytic reduction of CO2, the development of a high active electrocatalysts is required. Copper (Cu) is the only metal that is capable of electrochemically converting CO2 to hydrocarbons, but the high overpotential of hydrocarbon formation and the low selectivity of the reduction products have been problems. One of the solutions to these problems is the hybridization of metal and organic materials, in which the metal serves as the CO2 reduction reaction sites and the organic material stabilizes the intermediates [1]. In the present study, we have demonstrated electrochemical reduction of CO2 by electrodeposited Cu loading L-Histidine (L-His) which is expecting stabilization of CO2 reductive intermediates hybrids.The electrodeposited Cu/L-His hybrids was obtained by a constant current electrolysis at -1.0~-4.5 mA cm-2 for 1 C cm-2 from the aqueous solutions containing 10 mmol dm-3, CuSO4･5H2O, 0.1 mol dm-3 Na2SO4, and 0.5~20 mmol dm-3 L-His in a three-electrode cell with carbon paper (CP) as the working electrode, platinum wire as the counter electrode, and Ag/AgCl as the reference electrode. The pH of electrolytic bath was controlled between 1.10 and 4.07 by adding H2SO4. The electrochemical reduction of CO2 has been carried out by a constant potential electrolysis at -1.27 V vs. RHE of 0.5 mol dm-3 KHCO3 aqueous solutions saturated with CO2. The amount of reductive gas products was quantified by GC-MS and GC-TCD.The changing the color from pale blue to deep blue was observed by adding L-His into electrolytic bath containing Na2SO4 and CuSO4･5H2O. As increasing concentration of L-His, absorption peak measured by UV-Vis was shifting from around 800 nm originated [Cu(H2O)4]2+ to around 630 nm. The shift was not observed above Cu2+ : L-His = 1 : 2 for molar concentration ratio, therefore, it was considered that Cu2+ and L-His form a complex of [Cu(L-His)2]2+ in aqueous solution. Thus, electrodeposition of Cu/L-His has been tried from Cu2+ : L-His = 1 : 2 aqueous solutions but electrodeposited Cu/L-His cannot achieve. As decreasing pH of electrolytic bath with fixing Cu2+ : L-His = 1 : 2, the absorption peak originated [Cu(L-His)2]2+ was shifting to [Cu(H2O)4]2+ absorption peak. Below pH = 1.7, the absorption peak had been shifted to [Cu(H2O)4]2+ completely and the precipitate was obtained in this condition. The hybridization Cu and L-His was confirmed by Raman spectra. Not only Cu, L-His peaks but also new peak originated L-His adsorbs to Cu were observed. CP has fiber like structure but electrodeposited Cu and Cu/L-His were precipitated such coating CP fiber. The particle size of Cu/L-His hybrids was more homogeneous, and the particles were more densely packed together compared to the pure Cu. However, changing diffraction patterns and peak broadening due to loading organic components in XRD were not observed.The electrochemical reductive reaction of CO2 on ED Cu has been conducted and the faradic efficiency (FE) of CO2 reductive gas product were calculated (Figure). Electrodeposited Cu (ED Cu) showed dramatically improvement of FE from CO2 to CH4 compared to copper foil (Cu foil). Furthermore, the L-His loading electrodeposited Cu (ED Cu/L-His) was more improved than ED Cu. Worthy of a special mention, the amount of hydrogen generation was reduced dramatically by introducing L-His. It can be considered that a reaction field was formed in which the CO2 reduction reaction preferentially takes place over hydrogen evolution. As increasing the concentration of L-His between 0.5~20 mmol dm-3, the FE from CO2 to CH4 goes high until 1.0 mmol dm-3 and then goes down, therefore, it can be observed that high L-His loading inhibits CO2 electrochemical reduction.[1] S. Jia et al., Angew. Chem. Int. Ed. 2021, 60, 10977–10982. Figure 1

Anodic Dissolution Behavior of Al Alloys Containing Al6Fe or β-AlFeSi in EmImCl–AlCl3 Electrolyte During Electrorefining

To produce over 99.9% of high-purity Al from Al alloys containing Al6Fe or β-AlFeSi through electrorefining, their anodic dissolution and cathodic electrodeposition characteristics should be clarified. In this study, the anodic dissolution and cathodic electrodeposition behavior of Al–Fe binary and Al–Fe–Si ternary alloys were investigated in an EmImCl–AlCl3 ionic liquid electrolyte at 323 K. Anodic polarization measurements, constant potential electrolysis, X-ray diffraction (XRD), scanning electron microscopy (SEM), field-emission SEM (FE-SEM), and energy dispersive spectroscopy (EDS) were used to study the anode and electrodeposits on the cathode. Constant potential electrolysis showed that Fe dissolved from Al6Fe in the Al–Fe anode at 0.7 V vs Al/Al(III) and from β-AlFeSi in the Al–Fe–Si anode at 1.4 V and was co-deposited with Al on the cathode. Notably, Si did not dissolve from β-AlFeSi at either potential. A combination of controlled anodic dissolution potential and the use of the Al alloy containing β-AlFeSi further suppressed the dissolution and cathodic co-deposition of Fe, affording high-purity Al on the cathode. This suggests that Al alloys with intermetallic compounds that are less likely to dissolve Fe at the anode are optimal for obtaining over 99.9% of high-purity Al from Al alloys containing Fe in the electrorefining method.

Electrochemical Behavior and Reduction of in LiCl-KCl Molten Salt

In this work, we explored the electrochemical behavior and reduction process of uranyl ions in molten LiCl-KCl eutectic at 773 K. Cyclic voltammetry (CV) and square wave voltammetry (SWV) results showed that the reduction of ions on the inert W electrode was a three-step process: (1) (2) and (3) Electrolysis experiments further confirmed this reduction mechanism that ions were reduced to UO2 on the molybdenum electrode by applying a constant potential of −1.00 V vs Ag/AgCl and subsequently to uranium metal at a more negative potential of −2.35 V vs Ag/AgCl. In addition, ions could be thoroughly reduced to uranium metal through a 4-h constant current electrolysis at −18 mA cm−2. Electronic absorption spectroscopy (EAS) and inductively coupled plasma optical emission spectroscopy (ICP-OES) respectively illustrated that the oxidation state of uranium was unchanged and uranium concentration gradually decreased during the electrolysis. Finally, X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to characterize the phase composition and microstructure of deposited products. Nano-sized UO2 and U metal particles were successfully obtained by constant potential and current electrolysis. The results of this work further reveal the electrochemical behavior and reduction mechanism of ions in molten LiCl-KCl, providing a guiding ideology for the pyrochemical reprocessing of oxide spent fuels.

Impact of Ag on Electrochemical Recovery of UO2 in Molten LiCl-KCl Salt

To investigate the effect of fission element Ag on the electrochemical recovery of UO2, the electroreduction mechanisms of Ag+ and kinetic property of Ag+/Ag couple were first studied on W electrode by different electrochemical techniques. The electrode reactions of Ag+ and were found to be one-step and two-step reduction processes, respectively. The exchange current density of Ag+/Ag couple was estimated to be 0.0431∼0.0727 A cm−2 in the temperature range of 723∼798 K by LP technique, and its activation energy was evaluated to be 33.91 kJ mol−1. The deposition products obtained by constant potential electrolysis (CPE) were characterized by XRD and SEM-EDS, which showed the formed Ag and UO2 having pine-branch and micron-scale polyhedral structure, respectively. The influence of Ag+ on the electrochemical behavior of and morphology of UO2 were studied. The deposition potential of Ag+ was close to that of to UO2. The changes of Ag+ concentration and scan rate had no effect on the electroreduction mechanism of CPE was conducted, and the result indicated that UO2 and Ag could be co-deposited. The deposited Ag could change the morphology of recovered UO2.

Separation of lanthanides erbium and ytterbium on indium electrodes by modulated potential selective extraction in molten salts and a thermodynamic and kinetic analysis of the process

The main purpose of this paper is to study the extraction and separation of key fragment elements based on the electrolytic refining process of spent fuel dry reprocessing. Firstly, the electrochemical mechanisms of Er(III) and Yb(III) in LiCl-KCl molten salts were investigated on W and In film electrodes with applied cyclic voltammetry (CV), square wave voltammetry (SWV) and open circuit potential (OCP) at 773 K. The results indicated that the reduction behaviour of In(III) and Yb(III) ions were a two-step transfer process and Er(III) ions was a one-step transfer process. Then, the kinetic parameters in electrochemical processes were calculated on an In electrode with different temperatures. The OCP approach was used to determine the equilibrium potential of Er(III)/Er(0) in the temperature range of 773 K∼848 K, and thermodynamic parameters of the In3Er alloy were provided. Based on electrochemical behaviour results, the electrochemical extraction of Er(III) and Yb(III) from LiCl-KCl-ErCl3 molten salts and LiCl-KCl-YbCl3 molten salts at liquid In electrodes was performed by constant potential and constant current electrolysis, respectively. The electrolysis products were determined by X-ray diffraction (XRD), scanning electron microscopy and energy dispersive spectrometry (SEM-EDS), the primary intermetallic compounds generated in the alloys were In3Er and In3Yb. The average extraction rates for Er(III) and Yb(III) were 94.70% and 96.54%, respectively, according to inductively coupled plasma atomic emission spectroscopy (ICP-AES) analysis. Er(III) and Yb(III) were selectively extracted and separated from LiCl-KCl-ErCl3-YbCl3 molten salts by potentiostatic control on the basis of the previously studied Lns (Er and Yb) extraction on In electrodes. The separation rate of Er(III) and Yb(III) by electrochemical selective deposition was 94.21%.

Electrochemical separation of fission element neodymium using plumbum electrode from molten LiCl–KCl based on spent fuel reprocessing

In order to investigate the application prospects for the extraction of fission products neodymium (Nd) by electrolytic refining at active plumbum (Pb) electrodes, the reduction mechanism of Nd(III)/Pb(II) at inert tungsten, and Nd(III) at Pb thin film electrodes was investigated. This work simultaneously presents the results of kinetic and thermodynamic parameter of Pb(II)/Nd(III). The composition of the Pb–Nd alloy compound formed on the activated Pb electrode was determined by X-ray diffraction analysis (XRD) and scanning electron microscopy coupled with energy-dispersive spectroscopy (SEM-EDS), and the thermodynamic parameters of the formed Pb3Nd alloy were calculated: ΔHf0Pb3Nd=−219.92kJmol−1 and ΔSf0Pb3Nd=−47.48Jmol−1K−1. Nd(III) was extracted in the form of Pb–Nd alloy by constant potential electrolysis (PE) in LiCl–KCl melt. Based on the analysis of inductively coupled plasma-atomic emission spectrometry (ICP-AES) results, the average extraction rate of Nd(III) ions at the liquid Pb electrode could reach 99.03%.

Simultaneous electrochemical detection of oxygen (O2) and hydrogen peroxide (H2O2) in neutral media

The simultaneous detection of oxygen (O2) and hydrogen peroxide (H2O2) in neutral media was investigated by cyclic voltammetry using a two-working modified glassy carbon (GC) electrode system. Both electrodes were functionalized either by electrodeposited or by chemically-prepared gold nanoparticles (AuNPs). AuNPs electrodeposition was achieved by constant potential electrolysis either at 0.5 or ‐0.5 V/SHE in acidic HAuCl4 solution. Colloidal AuNPs were obtained according four different procedures (type A to D) derived from the classical Turkevich synthesis and further drop-casted on GC. The kinetics of H2O2 oxidation was studied by recording steady-state voltammograms in a deaerated NaCl/NaHCO3 pH 7.4 neutral solution on all the functionalized electrodes and favorably compared to unmodified GC and bare gold electrodes. Both Koutecky-Levich and Tafel treatment of the current-potential curves showed that the highest anodic transfer coefficient αn (0.78 ± 0.14) was obtained with the electrodeposited AuNPs/GC electrode using the most cathodic deposition potential of ‐0.5 V which provided the highest average number of nanoparticles per square micrometer (555 ± 49 µm-2) of very little average size (25 ± 12 nm) NPs. The simultaneous detection and quantification of O2 and H2O2 was achieved only with electrodes functionalized using D-type Turkevich synthesis. In this case H2O2 was detected at the anode while current corresponding to O2 reduction was selectively recorded at a potential close to ‐0.3 V without interference from H2O2.

Cathodic Processes in Uranium Containing Molybdate Melts

Cathodic processes in Li2MoO4–K2MoO4–MoO3 and K2MoO4–MoO3 melts containing added UO2MoO4 were investigated at 550–800 °C using cyclic voltammetry, cathodic polarization and bulk electrolysis. Cathodic reduction of molybdate melts (not containing uranium) resulted in formation of molybdenum dioxide. Products of the cathodic reactions in the melts containing uranium molybdate predominantly consisted of crystalline uranium oxides (mostly UO2 and U4O9) and MoO2. Minor products formed included other uranium oxides (U3O8, U13O34), mixed uranium-molybdenum oxides (U1.5Mo10O32, Mo2UO8) and molybdates (provisionally attributed to K2U(MoO4)3). Effect of temperature, cathodic current density 0.05–1 A cm−2), excess MoO3 concentration (30–50 mol%) on the composition of the cathodic reaction products were analyzed. Oxygen-to-uranium atomic ratio (oxygen coefficient) for primary uranium oxide phases was determined and varied from 1.963 to 2.161 for UO2±x and from 2.209 to 2.287 for U4O9±y. The effect of the electrolysis regime on the composition of the cathodic product was also considered. Constant-current and constant-potential electrolysis, as well pulsed-current, pulsed-potential and pulsed-reversed-current electrolysis were investigated with varying the parameters of alternating pulses (duration, current density or potential). Chemical and phase composition of the products produced by bulk electrolysis was fully characterized.

Determination of antibiotics by amperometry using nortropine N-oxyl, a highly active nitroxyl radical.

Nitroxyl radical compounds oxidize hydroxy groups and some amino groups upon application of an electric potential. The resulting anodic current depends on the concentration of these functional groups in solution. Thus, it is possible to quantify compounds containing these functional groups by electrochemical methods. Cyclic voltammetry has been used to evaluate the catalytic activity of nitroxyl radicals, and the ability of such radicals to sense biological and other compounds. In this study, we evaluated a method for quantifying compounds using constant-potential electrolysis (amperometry) of nitroxyl radicals for application in flow injection analysis and high-performance liquid chromatography as an electrochemical detector. When amperometry was performed using 2,2,6,6-tetramethylpiperidine 1-oxyl, a common nitroxyl radical compound, little change was observed even with 100mM glucose due to its low reactivity in neutral aqueous solutions. In contrast, 2-azaadamantane N-oxyl and nortropine N-oxyl, which are highly active nitroxyl radicals, showed a concentration-dependent response in neutral aqueous solution. Responses of 33.8 and 125.9 μA, respectively, were observed. By recognition of hydroxy and amino groups, we have succeeded in the electrochemical detection of some drugs by amperometry. Streptomycin, an aminoglycoside antibiotic, was quantifiable in the range of 30-1000µM.

Clarification of the anodic dissolution behavior of metallurgical structures during electrorefining of Al-Mn alloys in a 1-ethyl-3-methyl-imidazolium chloride-AlCl3 ionic liquid

Recycling Al is crucial to reduce the energy and environmental costs of Al manufacturing; however, the reclamation efficiency of high-quality Al from Al alloys is limited by the co-deposition of impurities during the electrorefining process. To address this issue, the anodic dissolution behavior of metallurgical structures within various Al-Mn binary alloys in 1-ethyl-3-methyl-imidazolium chloride-AlCl3 ionic liquid was investigated. During the constant-potential electrolysis of Al-1.5%Mn cast and cold-rolled plate alloys, an enriched layer derived from Mn solid solution was formed at an electrorefining potential of 0.2 V; this was attributed to preferential dissolution of Al in the matrix phase, followed by Mn accumulation at the Al surface. Furthermore, dissolution of the Al-Mn-Fe and Al-Mn intermetallic compounds occurred at 0.6 and 1.0 V, respectively; thus, the dissolution behavior of Mn in the Al-Mn alloys differed between the Mn solid solution in the matrix phase and the Mn-containing intermetallic compounds. These results indicate that by controlling the microstructure of the Al-Mn alloy and the applied anodic potential, the dissolution of Mn into the 1-ethyl-3-methyl-imidazolium chloride-AlCl3 electrolyte can be suppressed, thus preventing its co-deposition with Al on the cathode. This development is therefore anticipated to inform the development of electrorefining processes to obtain high-quality recycled Al for numerous manufacturing applications.

Electrolytic reduction of Gd2O3-ZnO in NaCl-CaCl2 Molten Salt

The electrochemical behaviors of Gd2O3, ZnO and Gd2O3-ZnO in NaCl-CaCl2 molten salt was studied by cyclic voltammetry and square wave voltammetry, and the corresponding constant potential electrolysis and XRD analysis indicated that the reduction processes were in agreement with the process that 3PI (metal∣oxide∣electrolyte three-phase interline) expanded with time from surface to interior of the cathode. Moreover, the addition of ZnO could promote the electrochemical reduction of Gd2O3. According to the electrochemical behavior (CV) and the characterization (XRD and SEM-EDS) of electrolytic product, the intermetallic compounds, GdZn12, Gd2Zn17 and Gd13Zn58, were generated during the electrolysis of Gd2O3-ZnO cathode without dendritic deposits.

Pulsed Nitrate-to-Ammonia Electroreduction Facilitated by Tandem Catalysis of Nitrite Intermediates

Electroreduction of nitrate to ammonia offers a promising pathway for nutrient recycling and recovery from wastewater with energy and environmental sustainability. There have been considerable efforts on the regulation of reaction pathways to facilitate nitrate-to-ammonia conversion over the competing hydrogen evolution reaction but only with limited success. Here, we report a Cu single-atom gel (Cu SAG) electrocatalyst that produces NH3 from both nitrate and nitrite under neutral conditions. Given the unique mechanism of NO2- activation on Cu SAGs with spatial confinement and strengthened kinetics, a pulse electrolysis strategy is presented to cascade the accumulation and conversion of NO2- intermediates during NO3- reduction with the prohibited competition from the hydrogen evolution reaction, thus substantially enhancing the Faradaic efficiency and the yield rate for ammonia production compared with constant potential electrolysis. This work underlines the cooperative approach of the pulse electrolysis and SAGs with three-dimensional (3D) framework structures for highly efficient nitrate-to-ammonia conversion enabled by tandem catalysis of unfavorable intermediates.

Electrochemically Generated Copper(I)‐Catalyzed Click Chemistry: Triazole Synthesis and Insights into Their Photophysical Properties

AbstractHerein, we report the electro‐click (e‐CLICK) reaction via electrochemically generated copper(I) catalytic species. The reaction worked under constant potential electrolysis (−0.25 V) with copper(II) nitrate and 2,2′‐bipyridine serving as pre‐catalyst and ligand respectively. The reaction accommodates electronically different organic azides and terminal alkynes to afford 1,2,3‐triazoles in good synthetic yields with excellent 1,4‐regioselectivity. Compared to traditional click chemistry, the developed e‐CLICK methodology avoids the use of external reducing agents such as sodium ascorbate. Absorptive properties of selected triazole products were assessed by UV‐visible electronic spectra. Triazole (3 e) was further applied for the spectrophotometric detection of Co2+ and Cu2+ species.

Molten Oxide Electrolysis Using Copper-Containing Carbon-Saturated Molten Iron Anode

This study focused on the use of molten oxide electrolysis (MOE) as a low-cost, clean, continuous separation method suitable for incorporation into actual steelmaking processes. We discussed interfacial behavior from molten iron to slag by anodic polarization of the copper-containing carbon-saturated molten iron (metal phase)–molten oxide (slag phase) interface and investigate the operating mechanism of MOE. The basic constant potential electrolysis between the metal phase (Fe-10 wt% Cu-5.0 wt% C) and slag phase (27 wt% CaO-27 wt% SiO2−45 wt% Al2O3−1.0 wt% CaS) by maintaining 1–2 V vs Pt at 1773 K in an Ar atmosphere is described. When polarized, a high concentration of dispersed Cu-rich phase was detected locally near the metal–slag interface but not in the phase center of the metal. At the metal–slag interface, the energies of the Fe-rich and Cu-rich phase–slag interfaces decreased due to electric capillarity, and the Cu-rich phase distributed near the interface.

The role of zinc sulfide in the electrochemical extraction of molybdenum

The main form of molybdenum in nature is molybdenum sulfide. It also exists in iron ore magnetic separation tailings together with zinc sulfide. Considering separating and extracting molybdenum and zinc, a large amount of SO2 is released and environmental pollution is caused by high energy consumption for the traditional pyrometallurgy process. This research proposes a novel process to achieve efficient extraction and separation of molybdenum and zinc through co-desulfurization of MoS2-ZnS in molten salt. It was found that the sulfur in MoS2 and ZnS could be effectively removed and collected as solid sulfur by constant potential electrolysis in molten NaCl-KCl at 750 °C. Furthermore, electrochemical testing showed that the decomposition of MoS2 was carried out in two steps, ZnS was reduced in one step, and the decomposition voltage of ZnS was smaller than that of MoS2. Zinc was obtained at the first stage, and the MoS2 or its intermediate compounds were wrapped around by liquid zinc. The substitution reaction, 2Zn + MoS2 = Mo + 2ZnS, was able to promote the decomposition of MoS2 in the electrolysis process. Zinc sulfide was then formed in the second stage, and it can be electrolyzed to metallic zinc again for reduction of MoS2. Zn/ZnS played the role of a reducing agent in the process of MoS2-ZnS co-desulfurization, which facilitated the process of desulfurization, and enabled the reduction of MoS2 at a smaller voltage while zinc could be reused. In this work, molybdenum metal containing zinc was extracted at a cell voltage of 2.7 V. Metallic zinc and molybdenum were separated and purified in the final stage by vacuum distillation.