Showing papers on "Supporting electrolyte published in 2020"

Translating batch electrochemistry to single-pass continuous flow conditions: an organic chemist’s guide

Abstract: The recent renaissance of electrochemical methods for organic synthesis has also attracted increased interest towards flow electrochemistry as the most suitable scale-up strategy. Many electrochemical methods using flow cells are based on recirculation of the electrolyte solution. However, single-pass processing is very attractive as it permits integration of the electrochemical reaction with other synthetic or purification steps in a continuous stream. Translation of batch electrochemical procedures to single-pass continuous flow cells can be challenging to beginners in the field. Using the electrochemical methoxylation of 4-methylanisole as model, this paper provides newcomers to the field with an overview of the factors that need to be considered to develop a flow electrochemical process, including advantages and disadvantages of operating in galvanostatic and potentiostatic mode in small scale reactions, and the effect of the interelectrode gap, supporting electrolyte concentration and pressure on the reaction performance. A comparison of the reaction efficiency in batch and flow is also presented.

Electrochemical preparation of Cu/Cu2O-Cu(BDC) metal-organic framework electrodes for photoelectrocatalytic reduction of CO2

Abstract: Thin films of the metal-organic framework (MOF) Cu(BDC) were electrochemically grown by anodic deposition of the ligand 1,4-benzenedicarboxylate (1,4-BDC) on metallic copper to form Cu/Cu2O-Cu(BDC) electrode. The construction of the electrode was optimized by investigating parameters such as current density, time of anodization, and temperature that directly affect its stability and photoactivity. The best performing electrode was prepared when a current density of 2.5 mA cm−2 was applied for 6.5 min at 110 °C. A methanol concentration of 234 μmol L-1 was produced from the photoelectron reduction of CO2 under UV–vis irradiation for 3 h, an applied potential of +0.10 V, and 0.1 mol L-1 aqueous sodium sulfate solution saturated with CO2 as supporting electrolyte. The rate of CO2 reduction to methanol was found to be ∼20 times that obtained using Cu/Cu2O electrode alone presumably due to preconcentration of dissolved CO2 in the MOF. The capture of CO2 in the MOF surface and/or cavities was confirmed by ATR and DRIFT spectroscopy.

Metal-free electrochemical fluorodecarboxylation of aryloxyacetic acids to fluoromethyl aryl ethers

Abstract: Electrochemical decarboxylation of aryloxyacetic acids followed by fluorination provides easy access to fluoromethyl aryl ethers. This electrochemical fluorodecarboxylation offers a sustainable approach with electric current as traceless oxidant. Using Et3N·5HF as fluoride source and as supporting electrolyte, this simple electrosynthesis affords various fluoromethoxyarenes in yields up to 85%.

A Universal Electrolyte Formulation for the Electrodeposition of Pristine Carbon and Polypyrrole Composites for Supercapacitors.

Abstract: Electrodeposition of conducting polymer-carbon composites from an electrolyte precursor solution is a facile one-step approach to fabricate device-ready electrodes for energy storage. A key challenge in this approach is the dispersion of the carbon nanomaterials with the aqueous precursor solution with previous approaches either heavily oxidizing the carbon nanomaterials or using high concentrations of anionic surfactants as dopants. However, the former reduces the electrical conductivity of carbon, while the latter reduces the ionic mobility of the conducting polymer due to the large anion size. Herein, for the first time we present a quaternary electrolyte formulation for the fabrication of pristine carbon and polypyrrole (PPy) composites that does not sacrifice either electron or ion mobility. The electrolyte uses lithium perchlorate (20 mM) as a supporting electrolyte and dopant, sodium dodecylbenzenesulfonate at a very low concentration (1.43 mM) as a surfactant, together with pristine carbon nanomaterials and pyrrole monomers. The order of magnitude difference between the concentration of the dopant and surfactant ion allows the as-deposited PPy to be doped predominantly by small-sized and mobile perchlorate anions. Composites of PPy with carbon black, carbon nanotubes, and electrochemical exfoliated graphene (EEG) have been successfully prepared using this new quaternary electrolyte. The as-fabricated PPy/EEG composite electrodes showed a specific capacitance of 348.8 F g-1 with a high rate capability (190.7 F g-1 at 71 A g-1). Supercapacitor devices based on the PPy/EEG composite electrodes exhibit a high rate behavior up to 500 mV s-1 and a long cycle life of 5000 cycles.

Hierarchical flower-like SrHPO 4 electrodes for the photoelectrochemical degradation of Rhodamine B

Abstract: SrHPO4 films were deposited on fluorine doped tin oxide coated glass (FTO) substrate by cathodic electrodeposition method for photoelectrocatalytic (PEC) oxidation of Rhodamine B (RhB). The as-prepared films were characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR), scanning electron microscopy (SEM) coupled with energy-dispersive X-ray spectroscopy system (EDXS) and atomic force microscope (AFM). The effect of different parameters on the RhB electrochemical degradation, including supporting electrolyte type and concentration, current density, pH, and initial dye concentration, is studied. The most efficient conditions were found to be a current density of 10 mA cm−2, NaCl as a supporting electrolyte with a concentration of 0.1 M and a neutral medium which is favorable for HClO oxidizing species generation. Compared to photocatalysis and electrocatalysis, the photoanode displayed more superior photoelectrodegradation efficiency. Indeed, 94.5% removal of RhB (10 mg/L) in 12 min is obtained. This good efficiency is due to the synergetic effect induced by combining electrodegradation with UV-light energy. The reached electrocatalytic performance of SrHPO4 makes it a new promising photoanode for the treatment of wastewaters contaminated by organic pollutants.

Metal-Organic-Framework FeBDC-Derived Fe3O4 for Non-Enzymatic Electrochemical Detection of Glucose

Abstract: Present-day science indicates that developing sensors with excellent sensitivity and selectivity for detecting early signs of diseases is highly desirable. Electrochemical sensors offer a method for detecting diseases that are simpler, faster, and more accurate than conventional laboratory analysis methods. Primarily, exploiting non-noble-metal nanomaterials with excellent conductivity and large surface area is still an area of active research due to its highly sensitive and selective catalysts for electrochemical detection in enzyme-free sensors. In this research, we successfully fabricate Metal-Organic Framework (MOF) FeBDC-derived Fe3O4 for non-enzymatic electrochemical detection of glucose. FeBDC synthesis was carried out using the solvothermal method. FeCl2.4H2O and Benzene-1,4-dicarboxylic acid (H2BDC) are used as precursors to form FeBDC. The materials were further characterized utilizing X-ray Powder Diffraction (XRD), Scanning Electron Microscopy (SEM), and Fourier-Transform Infrared Spectroscopy (FTIR). The resulting MOF yields good crystallinity and micro-rod like morphology. Electrochemical properties were tested using Cyclic Voltammetry (CV) and Differential Pulse Voltammetry (DPV) with a 0.1 M of Phosphate Buffer Saline (PBS pH 7.4) solution as the supporting electrolyte. The measurement results show the reduction and oxidation peaks in the CV curve of FeBDC, as well as Fe3O4. Pyrolysis of FeBDC to Fe3O4 increases the peak of oxidation and reduction currents. The Fe3O4 sample obtained has a sensitivity of 4.67 µA mM-1.cm-2, a linear range between 0.0 to 9.0 mM, and a glucose detection limit of 15.70 µM.

Electrochemical Synthesis of Carbazoles by Dehydrogenative Coupling Reaction

Abstract: A constant current protocol, employing undivided cells, a remarkably low supporting electrolyte concentration, inexpensive electrode materials, and a straightforward precursor synthesis enabling a novel access to N-protected carbazoles by anodic N,C bond formation using directly generated amidyl radicals is reported. Scalability of the reaction is demonstrated and an easy deblocking of the benzoyl protecting group is presented.

Electrochemical oxidation of Reactive Blue 19 on boron-doped diamond anode with different supporting electrolyte

Abstract: In this study, boron-doped diamond film (BDD) electrode with high sp3/sp2 ratio was prepared by hot filament chemical vapor deposition (HFCVD). A systemic electrochemical advanced oxidation processes (EAOPs) study was carried out by using BDD anode and three different supporting electrolyte (Na2SO4, NaCl, and Na2S2O8) to degrade the high volume and high concentration (0.5 L, 100 mg L-1) simulated anthraquinone Reactive Blue 19 (RB-19) dye wastewater. BDD-PS (persulfate) system was used to study the effects of current density, initial pH and solution temperature on decolorization degree and mineralization rate (TOC removal rate) by comparing with other two electrolytes (NaCl and Na2SO4). BDD activated PS could effectively degrade RB-19 in a large pH range (1.5-12), and higher degradation efficiency and lower energy consumption under strong acid and alkali conditions than traditional BDD-EO based on Na2SO4 and NaCl electrolytes. More interestingly, at the temperature of 70 ℃, the TOC removal reached 90% in 30 min and 100% in 60 min, which is apparently higher than that under NaCl and Na2SO4 as electrolytes. Our work indicates BDD-PS technology can effectively degrade organic wastewater, which has the characteristics of efficiently and better pH applicability, and more importantly which can decompose RB-19 with the aid of increase of temperature.

Investigation of electrochemical degradation of Basic Red 13 dye in aqueous solutions based on COD removal: numerical optimization approach

Abstract: The aim of this study was to remove Basic Red 13 dye by electrochemical oxidation with Ti/Pt anodes and to numerically optimize the operating conditions such as current density (5–20 mA/cm2), flow rate (10–50 mL/min), initial pH (2–9) and supporting electrolyte concentration (10–100 mM) by using response surface methodology. Chemical oxygen demand analysis which was chosen as a response was performed according to closed reflux colorimetric method. Also, the effluent chloride levels were analyzed with the argentometric method. Momentary temperature, pH and electrical conductivity readings were taken with a multimeter. Although a number of possible system conditions were obtained with numerical optimization, the system operating conditions with the lowest energy consumption are considered to be optimal. From the quadratic model formed from central composite design in response surface methodology with numerical analysis, the optimum conditions were determined to be 4.38 for initial pH, 19.53 mA/cm2 for current density, 40.78 mL/min for flow rate and 85.57 mM for supporting electrolyte concentration. At these optimum points, chemical oxygen demand removal efficiency was calculated as 99.98% and energy consumption values of the system were calculated as 7.91 kW h/m3 and 0.98 kW h/kgCOD. Under these conditions when an industrial system is operated, the chemical oxygen demand removal yield will be 99.98% and the approximate cost of the system will be $1.25 to treat 1 ton of wastewater.

Gas–liquid–solid reaction system for CO2 electroreduction to formate without using supporting electrolyte

Abstract: The authors of this work would like to acknowledge the financial support from the MINECO through the projects CTQ2016-76231-C2-1-R and CTQ2016-76231-C2-2-R (AEI/FEDER, UE) JSG acknowledges financial support from VITC (Vicerrectorado de Investigacion y Transferencia de Conocimiento) of the University of Alicante (UTALENTO16-02)

Chemical and Electrochemical Recycling of End-Use Poly(ethylene terephthalate) (PET) Plastics in Batch, Microwave and Electrochemical Reactors.

Abstract: This work describes new methods for the chemical recycling of end-use poly(ethylene terephthalate) (PET) in batch, microwave and electrochemical reactors. The reactions are based on basic hydrolysis of the ester moieties in the polymer framework and occur under mild reaction conditions with low-cost reagents. We report end-use PET depolymerization in refluxing methanol with added NaOH with 75% yield of terephthalic acid in batch after 12 h, while yields up to 65% can be observed after only 40 min under microwave irradiation at 85 °C. Using basic conditions produced in the electrochemical reduction of protic solvents, electrolytic experiments have been shown to produce 17% terephthalic acid after 1 h of electrolysis at -2.2 V vs. Ag/AgCl in 50% water/methanol mixtures with NaCl as a supporting electrolyte. The latter method avoids the use of caustic solutions containing high-concentration NaOH at the outset, thus proving the concept for a novel, environmentally benign method for the electrochemical recycling of end-use PET based on low-cost solvents (water and methanol) and reagents (NaCl and electricity).