The electrodeposition of aluminium is demonstrated using a eutectic mixture of aluminium chloride and urea. The mixture is shown to be conducting through the formation of both cationic (AlCl
2
·urea
...n
+
) and anionic (AlCl
4
−
) species and electrodeposition is achieved through the cationic species. The use of a biphasic system with the ionic liquid and a protective hydrocarbon layer allows metal deposition to be carried out in an environment with ambient moisture without the need for a glove box. A direct comparison is made between the AlCl
3
:urea and imidazolium chloride:AlCl
3
systems and the differences in speciation and mass transport manifest themselves in different deposit morphologies. Brighteners which work in the chloroaluminate system such as toluene and LiCl are shown to be ineffective in the urea based system and the reasons for these differences are ascribed to the mechanism of the anodic reaction which is rate limiting.
The electrodeposition of aluminium is demonstrated using a eutectic mixture of aluminium chloride and urea and the use of a protective alkane layer enable aluminium to be deposited under ambient conditions.
Polyaniline itself can be converted to its conductive form from its insulating form by applying an oxidising potential in which polyaniline is converted to its positive charge state. Anions in the ...target solution are driven into the positively charged polymer film by electrostatic force, and this process is reversed when a reduction potential is applied. Consequently, interfacial processes of polyaniline modified electrode make it viable to remove undesirable ions from the target solution. During this process, polyaniline operates as an ion-exchanger by directing specific ions at definite potentials, which is the principle of the electrochemically switched ion-exchange technique. Therefore, polyaniline can be employed as a convenient material to perform as a new ion-exchanger modified film in an acidic environment. On the other hand, an abrupt decrease in the electroactivity of polyaniline at elevated pH values restricts its use in such practical applications. To overcome this problem, copolymerization of aniline and o-toluidine is expedient as it will be able to enhance the electrochemical properties of polyaniline. Hence, several copolymers were synthesised in the presence of different aniline and o-toluidine feedstock ratios. It was found that the surface coverage value of a representative poly(aniline-co-o-toluidine) copolymer film was 139.7 nmol cm−2 compared with 76 nmol cm−2 for pure Pani under identical conditions. In addition, the redox cycling in monomer-free NaF solutions showed that the poly(aniline-co-o-toluidine) film exhibited excellent reversibility between redox reactions at pH 6.60. These outcomes clearly illustrate the contribution of o-toluidine to the electrochemical properties of polyaniline at raised pH medium.
The speciation of metals in solution controls their reactivity, and this is extremely pertinent in the area of metal salts dissolved in ionic liquids. In the current study, the speciation of 25 metal ...salts is investigated in four deep eutectic solvents (DESs) and five imidazolium-based ionic liquids using extended X-ray absorption fine structure. It is shown that in diol-based DESs MI ions form MCl2− and MCl32– complexes, while all MII ions form MCl42– complexes, with the exception of NiII, which exhibits a very unusual coordination by glycol molecules. This was also found in the X-ray crystal structure of the compound Ni(phen)2(eg)Cl2·2eg (eg = ethylene glycol). In a urea-based DES, either pure chloro or chloro–oxo coordination is observed. In C6mimCl pure chloro complexation is also observed, but coordination numbers are smaller (typically 3), which can be explained by the long alkyl chain of the cation. In C2mimSCN metal ions are entirely coordinated by thiocyanate, either through the N or the S atom, depending on the hardness of the metal ion according to the hard-soft acid-base principle. With weaker coordinating anions, mixed coordination between solvent and solute anions is observed. The effect of hydrate or added water on speciation is insignificant for the diol-based DESs and small in other liquids with intermediate or strong ligands. One of the main findings of this study is that, with respect to metal speciation, there is no fundamental difference between deep eutectic solvents and classic ionic liquids.
Alternating anodic and cathodic current pulses have been applied to a metal powder on an electrode surface to fuse the particles together. It is shown that homogeneous films can be electroformed with ...different morphologies depending on the size of the powder and the experimental conditions.
This article describes the electroplating of ZnNi alloy from a modified deep eutectic solvent (DES), a mixture of choline chloride (ChCl) and ethylene glycol (EG) commonly known by its commercial ...name Ethaline. In this study the Ethaline was modified with propylene carbonate (PC) to decrease the solution viscosity. Boric acid was also used as an additive to improve surface finish and adhesion. The modifications were shown to increase the reduction rate of metal ions through improved mass transport and also to improve the quality of finish (morphology and interfacial adhesion) of the coating. We demonstrate that it is possible to produce dense, thick and adherent coatings of a γ-phase ZnNi alloy with 81–85% Zn on mild steel substrates using either potentiostatic deposition or controlled current pulse-plating techniques. Mild steel is a typical substrate for a sacrificial anti-corrosion coating used in many applications where the alloy serves to protect the steel from corrosion in harsh environments.
•Electroplating of ZnNi alloy from a modified deep eutectic solvent (DES) has been demonstrated.•Dense, thick and adherent coatings of a γ-phase ZnNi alloy on mild steel were produced.•Electrolyte modifications increased mass transport and have improved the quality of finish.•Corrosion analysis showed that the ZnNi alloy works well as a sacrificial layer for mild steel.
At the core of the aluminum (Al) ion battery is the liquid electrolyte, which governs the underlying chemistry. Optimizing the rheological properties of the electrolyte is critical to advance the ...state of the art. In the present work, the chloroaluminate electrolyte is made by reacting AlCl3 with a recently reported acetamidinium chloride (Acet-Cl) salt in an effort to make a more performant liquid electrolyte. Using AlCl3:Acet-Cl as a model electrolyte, we build on our previous work, which established a new method for extracting the ionic conductivity from fitting voltammetric data, and in this contribution, we validate the method across a range of measurement parameters in addition to highlighting the model electrolytes’ conductivity relative to current chloroaluminate liquids. Specifically, our method allows the extraction of both the ionic conductivity and voltammetric data from a single, simple, and routine measurement. To bring these results in the context of current methods, we compare our results to two independent standard conductivity measurement techniques. Several different measurement parameters (potential scan rate, potential excursion, temperature, and composition) are examined. We find that our novel method can resolve similar trends in conductivity to conventional methods, but typically, the values are a factor of two higher. The values from our method, on the other hand, agree closely with literature values reported elsewhere. Importantly, having now established the approach for our new method, we discuss the conductivity of AlCl3:Acet-Cl-based formulations. These electrolytes provide a significant improvement (5–10× higher) over electrolytes made from similar Lewis base salts (e.g., urea or acetamide). The Lewis base salt precursors have a low economic cost compared to state-of-the-art imidazolium-based salts and are non-toxic, which is advantageous for scale-up. Overall, this is a noteworthy step at designing cost-effective and performant liquid electrolytes for Al-ion battery applications.
The electrodeposition of zinc has been studied in two deep eutectic solvents. Unlike the metals studied to date in these liquids, zinc electrodeposition is not mass transport limited and the ...morphology of the deposit differs in the two liquids. This study shows that changing the concentration of solute affects the physical properties of the liquid to different extents although this is found to not effect the morphology of the metal deposited. EXAFS was used to show that the speciation of zinc was the same in both liquids. Double layer capacitance studies showed differences between the two liquids and these are proposed to be due to the adsorption of a species on the electrode which is thought to be chloride. The differences in zinc morphology is attributed to blocking of certain crystal faces leading to deposition of small platelet shaped crystals in the glycol based liquid.
► The effect of additives on the morphology of electrodeposited zinc is demonstrated. ► Two ionic liquids were used for the study. ► The additives brighten the deposit due to double layer changes ► ...Ethylene diamine and ammonia are the most effective additives.
The electrodeposition of metals using ionic liquids has received considerable attention during the last ten years. Recent developments have taken these novel electrolytes from laboratory to commercial scale. One of the factors limiting the development into practical plating systems is the understanding of how brighteners function. In this study we describe the addition of three polar additives and their effect upon the nucleation mechanism of zinc and the resultant morphology. It is shown that the structure of the zinc deposits is controlled by double layer properties and it is proposed that the brightening effect of ethylene diamine and ammonia are caused by their ability to inhibit the adsorption of chloride at the electrode surface. The deposition of most metals using ionic liquids results in apparently amorphous deposits, which tend to be actually nano-crystalline. The additives used in this study produce macro-crystalline deposits, which resemble those obtained from aqueous solutions.
The addition of a simple amide to AlCl(3) causes the formation of a liquid of the form AlCl(2)·nAmide(+) AlCl(4)(-). The material thus produced is liquid over a wide temperature range, is relatively ...insensitive to water and has the properties of an ionic liquid. This ionic liquid is shown to be a suitable medium for the acetylation of ferrocene and the electrodeposition of aluminium and demonstrated that quaternary ammonium cations are not always needed to form ionic liquids.
Electroactive polymers such as polyaniline, polypyrrole and poly(3,4-ethylenedioxythiophene) have many potential applications, but the nature of the electrolyte can be adversely affected on mass ...transport processes – of electronic charge, electroneutrality counter-ions (“charge-balancing”), reactant species, and mobility of polymer segments. In this study, polyaniline (PANI) films have been prepared in deep eutectic solvent (Oxaline, a eutectic mixture of oxalic acid and choline chloride) and acidic aqueous media using cyclic voltammetry associated with the electrochemical quartz crystal microbalance (EQCM). PANI was found to grow in both liquids although the rate of growth was slower in Oxaline than aqueous acid due to the higher viscosity of the former. The results showed that PANI electrodes made in aqueous solutions grow by an autocatalytic mechanism, unlike those in deep eutectic solvents (DESs). The stability and durability of some films was examined in DESs and aqueous solutions at 25 °C and 50 °C. The results showed the mobile species are different when cycled in the DES compared to aqueous media. For films grown in different media but cycled in aqueous acid, the anion (HSO4−) was found to dominate the mobile species. However, the mass behaviour of PANI electrodes (deposited from aqueous/Oxaline-DES) in DESs (Ethaline) at 50 °C was most strongly associated with cation (Ch+) egress (i.e., mass decrease) during the oxidation reaction and cation (Ch+) ingress (i.e., mass increase) during the reduction reaction. In addition, the results showed that temperature plays an important role in increasing the rate of diffusion and the stability of mass change in viscous ionic liquids.
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