Energy-Saving Electrolytic Hydrogen Generation: Ni2P Nanoarray as a High-Performance Non-Noble-Metal Electrocatalyst

It is highly attractive but challenging to develop earth-abundant electrocatalysts for energy-saving electrolytic hydrogen generation. Herein, we report that Ni₂P nanoarrays grown in situ on nickel foam (Ni₂P/NF) behave as a durable high-performance non-noble-metal electrocatalyst for hydrazine oxidation reaction (HzOR) in alkaline media. The replacement of the sluggish anodic oxygen evolution reaction with such the more thermodynamically favorable HzOR enables energy-saving electrochemical hydrogen production with the use of Ni₂P/NF as a bifunctional catalyst for anodic HzOR and cathodic hydrogen evolution reaction. When operated at room temperature, this two-electrode electrolytic system drives 500 mA cm⁻² at a cell voltage as low as 1.0 V with strong long-term electrochemical durability and 100 % Faradaic efficiency for hydrogen evolution in 1.0 m KOH aqueous solution with 0.5 m hydrazine.     

A new approach to anodic substitution reaction using acoustic emulsification

We have developed a novel electrolytic system for anodic substitution reactions using acoustic emulsification. This new system involves the generation of a carbocation by anodic oxidation of a substrate, and then its reaction with a nucleophile droplet formed by ultrasonication. In this system, even if the oxidation potential of the nucleophile is lower than that of the substrate, the substrate was predominantly oxidized to give the corresponding cation intermediate because the nucleophile phase, which was insoluble in the electrolytic medium, was electro-inactive. In addition, the overoxidation of the desired products was considerably suppressed by the extraction of products from the electrolyte solution into the nucleophile phase. As a result, the anodic substitution reaction of several carbamates with allyltrimethylsilane was carried out to provide the corresponding products in good to moderate yields.     

Energy‐Saving Electrolytic Hydrogen Generation: Ni2P Nanoarray as a High‐Performance Non‐Noble‐Metal Electrocatalyst

It is highly attractive but challenging to develop earth‐abundant electrocatalysts for energy‐saving electrolytic hydrogen generation. Herein, we report that Ni₂P nanoarrays grown in situ on nickel foam (Ni₂P/NF) behave as a durable high‐performance non‐noble‐metal electrocatalyst for hydrazine oxidation reaction (HzOR) in alkaline media. The replacement of the sluggish anodic oxygen evolution reaction with such the more thermodynamically favorable HzOR enables energy‐saving electrochemical hydrogen production with the use of Ni₂P/NF as a bifunctional catalyst for anodic HzOR and cathodic hydrogen evolution reaction. When operated at room temperature, this two‐electrode electrolytic system drives 500 mA cm⁻² at a cell voltage as low as 1.0 V with strong long‐term electrochemical durability and 100 % Faradaic efficiency for hydrogen evolution in 1.0 m KOH aqueous solution with 0.5 m hydrazine.     

Phase analysis of platinum-mercury and platinum-lead electrolytic deposits

By means of X-ray diffraction, the phase composition of electrolytic deposits obtained during simultaneous electrodeposition of platinum with lead, and of platinum with mercury, on glassy carbon was investigated. Formation of dispersed platinum (D≈65–110 ?) in both binary system cases, of a solid solution of platinum-lead and of the intermetallic compound PtHg₄ was proved. During the anodic scan up to a potential of +0.75 V in 0.1 M HCl, the compound PtHg₄ undergoes partial oxidation; electrolytic platinum is resistant to oxidation under these conditions. Electronic Publication     

Accelerating H2 Evolution by Anodic Semi-dehydrogenation of Tetrahydroisoquinolines in Water over Co3O4 Nanoribbon Arrays Decorated Nickel Foam

Coupling the H₂ evolution reaction in water with thermodynamically favorable organic oxidation reactions is highly desirable, because it can enhance the energy conversion efficiency compared with electrocatalytic water splitting, and produce value-added chemicals instead of O₂ in the anodic reaction. Herein, Co₃O₄ nanoribbon arrays in situ grown on nickel foam (Co₃O₄@NF) was employed as an effective electrocatalyst for the selective oxidation of tetrahydroisoquinolines (THIQs). Various value-added semi-dehydrogenation products including dihydroisoquinolines with electro-deficient or -rich groups could be obtained with moderate yields and faradaic efficiencies. Benefitting from the rich surface active sites of Co₃O₄@NF, a two-electrode (Co₃O₄@NF||Pt) electrolytic system drove a benchmark current density of 10 mA cm⁻² at a cell voltage as low as 1.446 V in 1.0 M KOH aqueous solution containing 0.02 M THIQ, which was reduced by 174 mV in comparison with that of overall water splitting.     

The role of acid catalysis in the electrosynthesis of <Emphasis Type="Italic">N</Emphasis>-(2,5-dimethoxyphenyl)azoles

The influence of the acid components of the medium on the anodic 2,5-dimethoxy-phenylation of various azoles at the nitrogen atom was studied for constant-current electrolysis of the mixture azole—1,4-dimethoxybenzene in an undivided cell. Elimination of azole functions in the key steps of the process can be catalyzed by such electrophilic species as Brønsted (AcOH) and Lewis acids (ZnCl₂) and even the radical cation generated in the anodic oxidation of 1,4-dimethoxybenzene. The data obtained provided evidence for the existence of the arenonium cation as a key reaction intermediate.     

The SON2 mechanism : A non-oxidative reaction that is initiated by electron transfer oxidation

Under oxidizing conditions, aromatic chloro and fluoro compounds undergo what formally are typical nucleophilic substitution reactions with surprising ease. As an example, 4-fluoroanisole is converted the 4-acetoxyanisole by anodic or metal ion oxidative initiation, and the reaction is shown to be a chain process. It is proposed that a mechanism analogous to that of the reductively initiated S_RN1 mechanism operates: The substrate is oxidized to a radical cation by the initiator system, and the radical cation then undergoes ipso attack by the nucleophile. In the third step, the leaving group leaves as a species at the same oxidation level as the nucleophile, giving the radical cation of the product to be formed. A chain transfer step involving this ion and a new substrate molecule then completes the propagation sequence.Previously reported cases of this phenomenon are discussed and the individual steps of the chain reaction are considered in terms of their thermochemistry. It is concluded that the S_ON2 mechanism should be more favoured with easily oxidizable substrates.     

TiO2@C Nanostructured Electrodes for the Anodic Removal of Cocaine

The generalization use of therapeutic and illicit drugs are introducing new several chemical pollutants in water. They have been detected in water and sewage samples worldwide, hence they are considered as emerging pollutants. The increase of water threats has a negative impact on the life quality and human health. Among the illicit drugs, cocaine and derivatives are increasingly present, making efficient detection and elimination of wastewater highly prioritaire. In that sense, the main core of this work is the assessment of a novel cost‐efficient electrochemical method based on substrate electro‐oxidation (EO) using low‐cost anodes based on common graphite modified with TiO₂ nanosized particles incorporated on the surface by assisted microwave deposition. Two different diameters (2 and 5 nm) of nanostructured TiO₂@C anodes were tested for cocaine EO reaction using three different electrolytic solutions (NaCl 50 mM, Na₂SO₄ 50 mM or Na₂SO₄ 100 mM). In all cases, the electrochemical oxidation of cocaine appears to be a combination of hypsochromic and hyperchromic processes. Reaching ca. 90 % degradation after 10 minutes for all electrodes, an enhanced efficiency was especially observed for the system with higher cylindrical diameter and NaCl salt medium. The differential pulse (DP) voltammogram, carried out with all assay solutions after 10 minutes of anodic remediation at both electrodes, exhibited an anodic peak consistent with catechol like compounds.     

An oxidative carbon-carbon bond formation system in cycloalkane-based thermomorphic multiphase solution

A selective anodic oxidation system in which a carbocation intermediate is generated exclusively by use of a temperature-controlled multiphase solution to separate the different stages of the reaction from each other and from the products is described. The formation of a thermomorphic middle layer in an electrolytic solution composed of c-Hex and LPC/MeNO2 results in enhanced interaction between aliphatic alkenes and polar unstable cation.     

Investigation of the Anodic Behavior of Al in Room Temperature Ionic Liquid Electrolytes: BMI‐BF4, PP14‐BF4 and BMI‐BF4·PC

The anodic polarization behavior of Al, Ta and Nb foil was investigated in 1‐butyl‐3‐methylimidazolium tetrafluoroborate ionic liquid (BMI‐BF₄). Compared with that of Ta and Nb foil, it showed that a better passive film was formed on Al foil surface after the anodic polarization in BMI‐BF₄, which could resist the potential up to 94.58 V vs. Ag⁺/Ag. Besides, similar anodic behavior of Al foil was observed in N‐methyl‐N‐butylpiperidinium tetrafluoroborate ionic liquid (PP14‐BF₄), which indicated that the anodic polarization behavior of Al foil was independent of the cations of RTIL. In addition, the investigation of anodic polarization behavior of Al foil was carried out in the mixture electrolytes composed of BMI‐BF₄·PC. Differently, two breakdown potential processes of Al foil were presented compared to pure BMI‐BF₄. Further research showed that the passive film on Al foil was mainly composed of AlF₃ and Al₂O₃ after the first breakdown potential process, while the fluoride film increased with continual anodic polarization, which improved the anodic stability of Al foil and resisted higher breakdown potential. The high breakdown potential properties of Al foil in BMI‐BF₄, PP14‐BF₄ and the mixture of BMI‐BF₄·PC during the anodic polarization can be favored for R&D of the high performance electrochemical devices.     

Effects of additives on anodic fluorination in ionic liquid hydrogen fluoride salts

Anodic fluorination of ethyl α-(2-pyrimidylthio)acetate in neat ionic liquid hydrogen fluoride salts (Et₃N–3HF, Et₄NF–4HF, Et₄NF–5HF) was investigated to avoid an anode passivation, which sometimes occurs during anodic fluorination in organic solvent. In order to improve the yield of fluorinated product, polyether having coordination ability to cation and anodic stability was introduced to the reaction system as additives (3%). Furthermore, such additives were found to be also effective for anodic fluorodesulfurization of 4-phenylthio-1,3-dioxolan-2-one in neat ionic liquid system.     

Tetragonal to monoclinic phase transition observed during Zr anodisation

Plasma electrolytic oxidation (PEO) is a coating procedure that utilises anodic oxidation in aqueous electrolytes above the dielectric breakdown voltage to produce oxide coatings that have specific properties. These conditions facilitate oxide formation under localised high temperatures and pressures that originate from short-lived microdischarges at sites over the metal surface and have fast oxide volume expansion. Anodic ZrO₂ films were prepared by subjecting metallic zirconium to PEO in acid solutions (H₂C₂O₄ and H₃PO₄) using a galvanostatic DC regime. The ZrO₂ microstructure was investigated in films that were prepared at different charge densities. During the anodic breakdown, an important change in the amplitude of the voltage oscillations at a specific charge density was observed (i.e., the transition charge density (Q ^T)). We verified that this transition charge is a monotonic function of both the current density and temperature applied during the anodisation, which indicated that Q ^T is an intrinsic response of this system. The oxide morphology and microstructure were characterised using SEM and X-ray diffraction experiments (XRD) techniques. X-ray diffraction analysis revealed that the change in voltage oscillation was correlated with oxide microstructure changes during the breakdown process.     

Cation exchange extraction of neptunium(V) and protactinium(V) from molten nitrate salt

Cu-di-(2-ethylhexyl)phosphate was used as the cation exchange extractant from molten nitrate salt. IR absorption spectra of di-(2-ethylhexyl)phosphoric acid and Cu-di-(2-ethylhexyl)phosphate were compared and it was proved that the acidic form of the extractant is not Cu-di-(2-ethylhexyl)-phosphate. Using LiNO₃−NH₄NO₃ eutectic melt, it was shown that the back-extraction of Cu²⁺ is a cation exchange reaction. Np(V) and Pa(V) were extracted by Cu-di-(2-ethylhexyl)phosphate from LiNO₃−NaNO₃−KNO₃ eutectic melt. The distribution ratio of Np(V) was greater than that of Pa(V) on the contrary of their distribution ratios in the aqueous extraction system. A possible cation exchange extraction reaction was proposed for the extraction of Np(V).     

Electrochemical Cross-Dehydrogenative Coupling between Phenols and β-Dicarbonyl Compounds: Facile Construction of Benzofurans

Preparative electrochemical synthesis is an ideal method for establishing green, sustainable processes. The major benefits of an electro-organic strategy over that of conventional chemical synthesis are the avoidance of reagent waste and mild reaction conditions. Here, an intermolecular cross-dehydrogenative coupling between phenols and β-dicarbonyl compounds has been developed to build various benzofurans under undivided electrolytic conditions. Neither transition metals nor external chemical oxidants are required to facilitate the dehydrogenation and dehydration processes. The key factor in success was the use of nBu₄NBF₄ as the electrolyte and hexafluoroisopropanol as the solvent, which play key roles in the cyclocondensation step. This electrolysis is scalable and can be used as a key step in drug synthesis. On the basis of several experimental results, the mechanism, particularly of the remarkable anodic oxidation and cyclization process, was illustrated.     

Carbon Nanotube Immobilized Electrode Using Amphiphilic Phospholipid Polymer with Anti‐fouling and Dispersion Property for Electrochemical Analysis

A carbon nanotube (CNT)‐modified electrode was fabricated by dropping a dispersion of multi‐walled CNTs in water‐soluble and amphiphilic phospholipid polymer with both dispersing ability and anti‐biofouling property onto a Au electrode. A poly(2‐methacryloyloxyethyl phosphorylcholine‐co‐n‐butyl methacrylate) (PMB) composed from 50 mol% of 2‐methacryloxylethyl phosphorylcholine and 50 mol% of n‐butyl methacrylate (PMB50) was used as dispersing reagent for CNTs. The dispersion of water‐insoluble material by PMB50 and its antifouling effects in electrochemical analysis were investigated. The CNT‐modified electrode showed an anodic peak potential that was shifted negatively and an increase in the current value for the electrolytic oxidation of nicotinamide adenine dinucleotide. In addition, the charge on PMB50 did not inhibit the electrochemical reaction of the redox compounds K₃[Fe(CN)₆], [Ru(NH₃)₆]Cl₃, and hydroxymethylferrocene. Cyclic voltammetry of K₃[Fe(CN)₆] in 4 % bovine serum albumin (BSA) using a bare Au electrode, the anodic peak current was reduced to 47 % of that without BSA. In contrast, the antifouling effect of the PMB50‐coated electrode meant that the current was only reduced to 70 % of that without BSA.     

Electrochemical iodofluorination of electron-deficient olefins

Electron-deficient olefins like α,β-unsaturated ester, amide, and phosphonate reacted with iodonium cation species generated by the anodic oxidation of iodide anion in Et₃N-5HF/CH₃NO₂ to form corresponding iodofluorinated compounds in good to moderate yields. The reaction proceeds at room temperature under air atmosphere and constant current conditions. The iodofluorinated products were shown to be useful fluorine-containing building blocks.     

Keto complexes from the oxidation of η6-xanthene or thioxanthene-η5-cyclopentadienyliron cation and some reactions of the fluorenone and xanthone complexes

Ligand exchange between xanthene and ferrocene gave the η⁶-xanthene-η⁵-cyclopentadienyliron cation which was oxidized in situ with KMnO₄ to give the η⁶-xanthone-η⁵-cyclopentadienyliron cation (III). Similar oxidation of the η⁶-thioxanthene-η⁶-cyclopentadienyliron cation gave a mixture of the thioxanthone complex IV and the corresponding complexed sulfone V. III and the η⁶-fluorenone-η⁵-cyclopentadienyliron cation (VI) were utilized as reactants in the synthesis of new complexes via reactions with a number of reagents. Stereospecific exo-addition to give complexed endo-alcohols were observed in the reaction of III with NaBH₄, NaBD₄ or CH₃Li, and in the reaction of VI with CH₃Li, the anion of acetonitrile, the anion of nitromethane or the phenylacetylide anion. Ring opening reactions to give complexed o,o′-disubstituted benzophenones were observed when III was treated with the anion of acetonitrile, the anion of nitromethane, methylamine, cyclohexylamine, benzylamine or pyrrolidine.     

Kinetics of electrochemical reactions on the Ag(Hg)/Ag4RbI5 interface

The electrochemical behaviour of the Ag(Hg)/Ag₄RbI₅ interface is investigated by a potentiostatic pulse method. It is found that the rate-determining step of the electrode reaction is electron transfer with an exchange current density of 68 mA cm^–2 and a transfer coefficient of approximately 0.45. The order of the electrochemical reaction for silver oxidation is estimated from polarization investigations of silver amalgam in various concentrations. From this it is deduced that the mercury is ionized and is implanted in the electrolyte together with silver under anodic polarization: 15Ag+85Hg–100e^–→15Ag⁺+85Hg⁺. From comparison of the electrochemical behaviour of the Ag(Hg)/Ag₄RbI₅ and Ag/Ag₄RbI₅ interfaces it is concluded that the rate of anodic silver dissolution on the Ag/Ag₄RbI₅ interface is limited by crystallization effects. Electronic Publication     

Über die anodische oxidation von hydrazinderivaten an platin im sauren elektrolyten I. Phenylhydrazin

The investigation of the anodic oxidation of phenylhydrazine at smooth platinum in acid solutions by the triangular voltage scan method, by controlled potential electrolysis and by potential step measurements yields the following results:(1) The overall-reaction yields 4 electrons per PH-molecule.(2) Within the PH-oxidation an inhibiting intermediate is developed, whose further reaction is limited, and which can be reduced by hydrogen.(3) The kinetics of the oxidation reaction are determined by a 1-electron step. The anodic reaction orders of phenylhydrazine and H⁺-ions are z_PH = 0.4 and z_H⁺ = ?0.8, respectively.These results are interpreted by means of a reaction mechanism. The kinetics of the oxidation are explained with the aid of the Temkin adsorption isotherm.     

Electrochemical generation of stable carbocation-tetrafluoroborate salts and the cation-anion interactions in their solid state structures

The electrochemical generation of stable carbocations, among other heterocyclic products, by a unique electrochemical process involving the anodic oxidation of aryl-substituted ketene imines is described. The electrochemical oxidation undergoes an unusual multiannulation process to form these types of products by intermolecular cyclization. The X-ray crystal structures of two carbocation tetrafluoroborate salts,4c and4d, of which the latter is solvated by CH₂Cl₂, are presented. We have observed that one of the B-F bonds in4c is relatively long with respect to the other three similar in length B-F bonds, while in the solvated salt (4d·CH₂Cl₂), one of the B-F bonds is particularly short relative to its congeners. In both cases, the exceptional B-F bonds are oriented toward the positive center of the carbocation. These phenomena are compared with other known X-ray structures of organic tetrafluoroborate salts and discussed.