Electrochemical synthesis of melanin-like polyindolequinone

Conducting polymer is a rapidly developing area of research due to its potential in combining the physical properties of polymers with electrical properties previously found only in inorganic systems. These conducting polymers owe their unique properties to a conjugated polymer backbone and become conducting upon oxidation or reduction. Melanin, a biopolymer, possess a conjugated backbone required of a conducting polymer, and has shown properties of an amorphous semiconductor. However, there has not been much study done in this area despite its potential, and this is partially due to the lack of processing methods as melanin is generally synthesised as an intractable powder. Thus, a better synthetic method was required, and a possible solution is the use of electrochemical synthesis. In our previous study we have shown that melanin can be synthesised electrochemically as a free-standing film, which was the first step towards the use of melanin as a bulk material. This project aims to continue from this preliminary work, investigating the various synthetic parameters and possible modifications as well as investigating possible applications for the electrochemically synthesised melanin film

Circuit Synthesis of Electrochemical Supercapacitor Models

This paper is concerned with the synthesis of RC electrical circuits from physics-based supercapacitor models describing conservation and diffusion relationships. The proposed synthesis procedure uses model discretisation, linearisation, balanced model order reduction and passive network synthesis to form the circuits. Circuits with different topologies are synthesized from several physical models. This work will give greater understanding to the physical interpretation of electrical circuits and will enable the development of more generalised circuits, since the synthesized impedance functions are generated by considering the physics, not from experimental fitting which may ignore certain dynamics

High-quality mesoporous graphene particles as high-energy and fast-charging anodes for lithium-ion batteries.

The application of graphene for electrochemical energy storage has received tremendous attention; however, challenges remain in synthesis and other aspects. Here we report the synthesis of high-quality, nitrogen-doped, mesoporous graphene particles through chemical vapor deposition with magnesium-oxide particles as the catalyst and template. Such particles possess excellent structural and electrochemical stability, electronic and ionic conductivity, enabling their use as high-performance anodes with high reversible capacity, outstanding rate performance (e.g., 1,138 mA h g-1 at 0.2 C or 440 mA h g-1 at 60 C with a mass loading of 1 mg cm-2), and excellent cycling stability (e.g., >99% capacity retention for 500 cycles at 2 C with a mass loading of 1 mg cm-2). Interestingly, thick electrodes could be fabricated with high areal capacity and current density (e.g., 6.1 mA h cm-2 at 0.9 mA cm-2), providing an intriguing class of materials for lithium-ion batteries with high energy and power performance

Effect of Thiols for Nitrogen Reduction to Ammonia

Ammonia is an important chemical used for fertilizers and also a potential carbon-free hydrogen storage medium. The Haber-Bosch process is the main production process, which requires large energy- and capital-input. Therefore, it is crucial to develop an alternate scalable synthesis that provides a less energy intensive and more economical route for synthetic ammonia production. In this paper, a 1Fe1Ni film was functionalized with C3OH and C6OH for the electrochemical synthesis of ammonia. This work will provide some insight into how thiol ligands can increase the selectivity of the catalyst for nitrogen reduction reaction and can be improved on to provide a new synthesis for ammonia

Membrane electrochemical reactors (MER) for NADH regeneration in HLADH-catalysed synthesis: comparison of effectiveness

Two membrane electrochemical reactors(MER) were designed and applied to HLADH-catalysed reduction of cyclohexanone to cyclohexanol. The regeneration of the cofactor NADH was ensured electrochemically, using either methyl viologen or a rhodium complex as electrochemical mediator. A semipermeable membrane (dialysis or ultra-filtration) was integrated in the filter-press electrochemical reactor to confine the enzyme(s) as close as possible to the electrode surface. When methyl viologen was used, the transformation ratio of cyclohexanone varied from 0 to 65% depending on the internal arrangement of the reactor. Matching the reactor configuration to the reaction system was essential in this case. With the rhodium complex, the ultra-filtration MER was tested in continuous and recycling configurations. The best conditions led to 100% transformation of 0.1 L volume of 0.1 M cyclohexanone after 70 h with the recycling mode. Finally, the performances of the reactors are discussed with respect to different evaluations of the production yields

Synthesis of anthraquinone based electroactive polymers: A critical review

Conducting polymers or synthetic monomers have revolutionized the world and are at the heart of scientific research having a scope of vast diverse applications in many technological fields. The conducting and redox polymers have been investigated as energy storage systems because of their better sustainability, ease of synthesis, and environmental compatibility. Owing to the conducting properties of quinones, they gain too much importance among the researchers. Keeping in view the importance and sustainability of conducting polymers, for the first time, this study compiles a detailed overview of synthetic approaches followed by investigations on electrochemical properties and future directions. This study critically examines the synthetic process of simple monomers, substituted monomers, and polymers of anthraquinone (AQ) under the classification of low- and high-molecular-weight AQ–based derivatives, their working principles, and their electrochemical applications, which enable us to explore their novel possible application in automotive, solar cell devices, aircraft aileron, and biomedical equipment. Irrefutably, we confirm that high-molecular-weight polymeric AQ compounds are best in comparison with low-molecular-weight AQ monomers because they have pre-eminent properties over monomeric systems. Because of the significant properties of AQ, polymeric systems are high demanding and have emerged as a hot topic among the researchers these days. In the current scenario, this study is of immense importance because it identifies and discusses the right and sustainable combination and paves the way to utilize these novel materials in different technologies

Highly selective electrochemical hydrogenation of alkynes: Rapid construction of mechanochromic materials

Electrochemical hydrogenation has emerged as an environmentally benign and operationally simple alternative to traditional catalytic reduction of organic compounds. Here, we have disclosed for the first time the electrochemical hydrogenation of alkynes to a library of synthetically important Z-alkenes under mild conditions with great selectivity and efficiency. The deuterium and control experiments of electrochemical hydrogenation suggest that the hydrogen source comes from the solvent, supporting electrolyte, and base. The scanning electron microscopy and x-ray diffraction experiments demonstrate that palladium nanoparticles generated in the electrochemical reaction act as a chemisorbed hydrogen carrier. Moreover, complete reduction of alkynes to saturated alkanes can be achieved through slightly modified conditions. Furthermore, a series of novel mechanofluorochromic materials have been efficiently constructed with this protocol that showed blue-shifted mechanochromism. This discovery represents the first example of cis-olefins-based organic mechanochromic materials

Self-assembly of 3D fennel-like Co3O4 with thirty-six surfaces for high performance supercapacitor

Three-dimensional (3D) fennel-like cobalt oxide (II,III) (Co3O4) particles with thirty-six surfaces on nickel foams were prepared via a simple hydrothermal synthesis method and its growth process was also researched. The crystalline structure and morphology were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), and Raman spectroscopy. The Brunauer-Emmett Teller (BET) analysis revealed that 3D fennel-like Co3O4 particles have high specific surface area. Therefore, the special structure with thirty-six surfaces indicates the good electrochemical performance of the micron-nanometer material as electrode material for supercapacitors. The cyclic voltammetry (CV), galvanostatic charge-discharge, and electrochemical impedance spectroscopy (EIS) were conducted to evaluate the electrochemical performances. Compared with other morphological materials of the similar sizes, the Co3O4 particles on nickel foam exhibit a high specific capacitance of 384.375 F.g(-1) at the current density of 3A.g(-1) and excellent cycling stability of a capacitance retention of 96.54% after 1500 galvanostatic charge-discharge cycles in 6M potassium hydroxide (KOH) electrolyte

Low filled conductive P(VDF-TrFE) composites: Influence of silver particles aspect ratio on percolation threshold from spheres to nanowires

Polymer composites filled with silver nanowires enable the highest value of electrical conductivity known up to now in the case of conductive nanoparticle dispersion with a percolation threshold less than 1 vol%. Silver nanowires with high aspect ratio were elaborated by two types of synthesis: electrochemical deposition in a template and polyol synthesis. For the first time the influence of each kind of nanowires in composites was studied and compared to spherical nanoparticles as reference. The value of percolation threshold and conductivity level above the percolation threshold were measured and compared. These silver nanowires were introduced into poly(vinylidenedifluoride-trifluoroethylene) in comparison to spherical silver nanoparticles. The preparation method modified the effective aspect ratio of nanowires. The low percolation threshold and the microscopy observations confirmed the good dispersion of nanowires in composites. The lowest percolation threshold was determined in the case of the polyol synthesis nanowires (0.63 vol%) in comparison with electrochemical deposited nanowires (2.2 vol%). The level of conductivity above the percolation threshold obtained with each kind of particles is in the same range near 100 S.m− 1. The value of electrical conductivity obtained above the percolation threshold is unusual at this low content of conductive filler and is observed for the first time in a conductive polymer composite