Total Current Efficiency Research Articles

Properties of ternary NiFeW alloy coating by jet electrodeposition

In this paper, ternary NiFeW alloy coatings were prepared by jet electrodeposition, and the effects of lord salt concentration, jet speed, current density and temperature on the properties of the coatings, including the composition, microhardness, surface morphology, structure and corrosion resistance, were investigated. Results reveal that the deposition rate reaches a maximum value of 27.30 $$\upmu \hbox {m}\hbox { h}^{-1}$$ , and the total current efficiency is above 85%. The maximum microhardness is 605 HV, and the wear and corrosion resistance values of the alloy coating are good. Moreover, the ternary NiFeW alloy coating is smooth and bright, and it presents a dense cellular growth. The alloy plating is nanocrystalline and has face-centered cubic structure.

Treatment of reverse-osmosis concentrate of printing and dyeing wastewater by electro-oxidation process with controlled oxidation-reduction potential (ORP)

Reverse osmosis concentrate (ROC) of printing and dyeing wastewater remains as a daunting environmental issue, which is characterized by high salinity, chemical oxygen demand (COD), chroma and low biodegradability. In this study electro-oxidation process (PbO2/Ti electrode) coupled with oxidation-reduction potential (ORP) online monitor was applied to treat such a ROC effluent. The results show that with the increase of specific electrical charge (Qsp), the removal efficiencies of COD, TN and chroma increased significantly at the incipience and then reached a gentle stage; the optimal total current efficiency (12.04 kWh m−3) was obtained with the current density of 10 mA cm−2 (Qsp, 3.0 Ah L−1). Meanwhile, some inorganic ions can be simultaneously removed to varying degrees. FTIR analyses indicated that the macromolecular organics were decomposed into smaller molecules. A multi-parameter linear relationship between ORP and Qsp, COD and Cl− concentration was established, which can quantitatively reflect the effect of current density, chloride ion concentration, pollutants and reaction time on the performance of the electro-oxidation system. As compared to a traditional constant-current system, the constant-ORP system developed in this study (through the back-propagation neural network [BPN] model with ORP monitoring) approximately reduced the energy cost by 24–29%. The present work is expected to provide a potential alternative in optimizing the electro-oxidation process.

Nutrient recovery from wastewater through pilot scale electrodialysis

Nutrient recovery performance utilising an electrodialysis (ED) process was quantified in a 30-cell pair pilot reactor with a 7.2 m2 effective membrane area, utilising domestic anaerobic digester supernatant, which had been passed through a centrifuge as a feed source (centrate). A concentrated product (NH4-N 7100 ± 300 mg/L and K 2490 ± 40 mg/L) could be achieved by concentrating nutrient ions from the centrate wastewater dilute feed stream to the product stream using the ED process. The average total current efficiency for all major cations over the experimental period was 76 ± 2% (NH4-N transport 40%, K transport 14%). The electrode power consumption was 4.9 ± 1.5 kWh/kgN, averaged across the three replicate trials. This value is lower than competing technologies for NH4-N removal and production, and far lower than previous ED lab trials, demonstrating the importance of pilot testing. No significant variation in starting flux densities and cell resistance voltage for subsequent replicate treatments indicated effective cleaning procedures and operational sustainability at treatment durations of several days. This study demonstrates that ED is an economically promising technology for the recovery of nutrients from wastewater.

Fullerene Mediated Electrosynthesis of Silver Nanoparticles in Toluene-DMF

Using C60 and C70 fullerenes as mediators, efficient mediated electrosynthesis of silver nanoparticles (AgNP) in toluene-DMF/ 0.1 M Bu4NBF4 medium was carried out by reduction of Ag+ at the potentials of the fullerene radical anions generation. Synthesis was performed in the absence and in the presence of poly(N-vinylpyrrolidone) (PVP) in the cathodic compartment of a diaphragm-separated cell by addition of Ag+ as AgNO3 into solution and in a single compartment cell by in situ generation of Ag+ by dissolution of an Ag-anode during electrolysis. In all cases, Ag+ ions are quantitatively reduced upon consumption of the theoretical amount of electricity; the generated metal is quantitatively obtained in solution bulk in the form of spherical NP with sizes in the range from 11 ± 2 to 24 ± 9 nm. In electrolysis in a single compartment cell, dispersion of the Ag-anode occurs along with its dissolution and the total current efficiency of AgNP is 131 ÷ 163%. In the presence of PVP, individual AgNP are stabilized in the PVP shell. The isolated Ag/PVP nanocomposite is deposited on a solid support both in individual form and as three-component Ag/PVP/fullerene nanocomposite. In the absence of PVP, the Ag/fullerene nanocomposite is obtained.

Mineralization of organic pollutants by anodic oxidation using reactive electrochemical membrane synthesized from carbothermal reduction of TiO2.

Reactive Electrochemical Membrane (REM) prepared from carbothermal reduction of TiO2 is used for the mineralization of biorefractory pollutants during filtration operation. The mixture of Ti4O7 and Ti5O9 Magnéli phases ensures the high reactivity of the membrane for organic compound oxidation through •OH mediated oxidation and direct electron transfer. In cross-flow filtration mode, convection-enhanced mass transport of pollutants can be achieved from the high membrane permeability (3300 LMH bar-1). Mineralization efficiency of oxalic acid, paracetamol and phenol was assessed as regards to current density, transmembrane pressure and feed concentration. Unprecedented high removal rates of total organic carbon and mineralization current efficiency were achieved after a single passage through the REM, e.g. 47 g m-2 h-1 - 72% and 6.7 g m-2 h-1 - 47% for oxalic acid and paracetamol, respectively, at 15 mA cm-2. However, two mechanisms have to be considered for optimization of the process. When the TOC flux is too high with respect to the current density, aromatic compounds polymerize in the REM layer where only direct electron transfer occurs. This phenomenon decreases the oxidation efficiency and/or increases REM fouling. Besides, O2 bubbles sweeping at high permeate flux promotes O2 gas generation, with adverse effect on oxidation efficiency.

An environmentally friendly electrochemical reactor for the degradation of organic pollutants in the total absence of a liquid electrolyte: A case study using diclofenac as a model pollutant

In order to fabricate an environmentally friendly electrochemical reactor for the degradation of organic pollutants in the total absence of a liquid electrolyte, fluid-permeable anodes (FPAs) composed of mixed oxide-covered mesh electrodes (MOMEs) containing cobalt and nickel, denoted as MOME-Ni(x)Co(1−x)Oy where x=0.9, 0.8 and 0.3, were prepared by thermal decomposition using the slow cooling rate method on a stainless-steel fine-mesh support. The electrochemical degradation of diclofenac (model pollutant) in electrolyte-free water was carried out in batch mode using a solid polymer electrolyte (SPE) electrochemical reactor. For the different MOME compositions, their properties were investigated as a function of the initial drug concentration (IDC) and the electric current density (j). The effects of IDC and j on the degradation of diclofenac were quite similar according to analyses performed using UV–vis and HPLC techniques, wherein it was verified for the different MOMEs that the degradation rate of diclofenac increased with increasing j and IDC. The electrode composition (Ni percentage) exerted only a minor influence on the degradation of diclofenac. On the other hand, a strong influence of j and IDC on the degradation was verified. It was also verified that an increase in IDC resulted in higher values of total current efficiency (TCE) measured for the combustion reaction. Taking into account that the lowest values of the electrical energy per order (EEO) were obtained for MOME-Ni(0.3)Co(0.7)Oy, it was concluded that the best overall performance for the electrochemical degradation of diclofenac in electrolyte-free water was achieved using this electrode composition.

Effects of Sodium Hypophosphite on the Behaviors of Electrodeposited NiWP Alloy Coatings

In this paper, ternary NiWP alloy coatings were prepared by electrodeposition, and the effects of sodium hypophosphite (NaH2PO2) concentration on the properties of the coatings, including the deposition rate, current efficiency, composition, surface morphology, corrosion resistance, and microhardness, were investigated. Results reveal that the deposition rate and current efficiency are mainly dependent on the NaH2PO2 concentration in the plating bath. The deposition rate reaches a maximum value of 8.70 μm/h with a NaH2PO2 concentration of 10 g/L, whereas the total current efficiency decreases from 33.10 to 27.80%. As the concentration of NaH2PO2 increases, the grain size of the obtained coatings gradually decreases. Moreover, when the NaH2PO2 concentration is 6 g/L, the NiWP alloy coatings possess a microhardness value of 663.7 HV.

High performance duplex-structured SnO2-Sb-CNT composite anode for bisphenol A removal

Abstract In this study, a duplex-structured SnO2-Sb-CNT composite anode (Ti/SnO2-Sb/SnO2-Sb-CNT) was fabricated using pulse electrodeposition technique. SnO2-Sb-CNT composite composed of 4–5 nm SnO2-Sb particles was synthesized via co-precipitation prior to the electrode preparation and characterized with BET and TEM. Characterization of Ti/SnO2-Sb/SnO2-Sb-CNT by FESEM, EDS, XRD, XPS, LSV, CV and EIS revealed that the novel duplex structured electrode had larger electroactive surface area and lower charge transfer resistance than conventional Ti/SnO2-Sb prepared by thermochemical decomposition, due to its more compact and rough surface. It also improved the electrochemical stability of Ti/SnO2-Sb/SnO2-Sb-CNT with a service lifetime up to 86 h. The oxygen evolution potential (OEP) of Ti/SnO2-Sb/SnO2-Sb-CNT was determined to be 2.2 V (vs Ag/AgCl). Bulk electrolysis of bisphenol A (BPA) was conducted to evaluate the electrocatalytic performance of the electrodes at various current densities (10–40 mA cm−2) and initial pH (3–11) of solution by determination of BPA degradation, total organic carbon (TOC) removal and mineralization current efficiency (MCE). Ti/SnO2-Sb/SnO2-Sb-CNT intended to adsorb more BPA molecules, which may contribute to its high current efficiency for electrochemical oxidation of BPA. The presence of humic acid (HA) could decrease the performance efficiency by inhibiting the adsorption of BPA by Ti/SnO2-Sb/SnO2-Sb-CNT. A mechanism is proposed to illustrate the enhanced degradation of BPA by Ti/SnO2-Sb/SnO2-Sb-CNT by synergistic adsorption and electrochemical oxidation.

Effects of transparent bottom electrode thickness on characteristics of transparent organic light-emitting devices

We conduct both simulation and experiment studies of impacts of simultaneously varying the thicknesses of transparent bottom electrodes and semi-transparent top thin metal electrodes on optical characteristics (e.g., transmission, reflection) and efficiencies of transparent organic light-emitting devices (OLEDs). For the thickness range of both electrodes studied, the total electroluminescent (EL) efficiencies (including both bottom and top emission), EL spectra, and emission patterns remain similar; yet the ratio of top to bottom emission would be modulated by the semi-transparent top metal electrode thickness. The thickness of the transparent bottom electrode has weak effects on the efficiencies of top/bottom/total emission, but it does have definite effects on optical transmission/reflection spectra (e.g. peak/valley wavelengths). Meanwhile, the thickness of semi-transparent top metal electrodes mainly affect magnitudes of the optical transmission/reflection. Transmissive/reflective hues and appearances of the transparent OLEDs can thus be tuned by the thicknesses of bottom/top electrodes. Overall, we demonstrated efficient transparent green phosphorescent OLEDs exhibiting a high peak transmittance of up to 81% and rather high total external quantum efficiencies of up to 21–21.5% (corresponding to a total current efficiency of 80–82 cd/A and total power efficiency of 95–99 l m/W), among the highest (if not the highest) for planar transparent OLEDs using no other optical out-coupling structures. By varying the thicknesses of transparent bottom electrodes and semi-transparent top metal electrodes, the ratio of top to bottom emission, and the transmissive or reflective hues/appearances of transparent OLEDs in the off state can be tuned, yet without sacrificing total EL efficiencies or changing their EL colors/patterns. Such tunable optical characteristics of transparent OLEDs may find some interesting applications.

Electrocatalytic ammonia synthesis via a proton conducting oxide cell with BaCe0.5Zr0.3Y0.16Zn0.04O3-δ electrolyte membrane

Ceramic membrane cells of BaCe0.5Zr0.3Y0.16Zn0.04O3-δ (BCZYZ) have been developed for electrocatalytic ammonia synthesis. Unlike the high-pressure Haber-Bosch process, an atmospheric synthesis of ammonia was attempted in this work. The membrane cells were fabricated by tape casting and the electrode materials were applied by ion impregnation. The impregnated electrodes comprised NiO/CeO2 composite anode and iron oxide cathode. The formation of ammonia was studied in the range of 400–500°C. The addition of Pd catalyst into the iron oxide cathode enhanced the ammonia formation rate while the addition of Ru improved only the electrochemical performance. The highest ammonia formation rate of 4×10−9mols−1cm−2 was obtained from Pd-modified cell at 450°C. The current efficiency of ammonia formation was in the range of 1–2.5% while that of H2 evolution varied from 0 to 60% depending on applied potentials. The total current efficiency close to 100% was obtained from Pd-modified cell.

Elimination of radiocontrast agent Diatrizoic acid from water by electrochemical advanced oxidation: Kinetics study, mechanism and mineralization pathway

Diatrizoic acid (DIA) is an iodinated X-ray contrast media commonly used in hospitals. It is persistent and recalcitrant in aquatic environments and difficult to biodegrade. Thus, we studied its removal from aquatic medium by two electrochemical advanced oxidation processes: anodic oxidation and electro-Fenton using BDD anode and carbon felt cathode. The effect of two of the most important variables on, i.e., applied current intensity (both processes) and catalyst concentration (electro-Fenton) was assessed to optimize oxidative degradation of DIA and mineralization rate of its aqueous solution. 1000mA current intensity and 0.2mM catalyst (Fe2+) concentration (at pH3) were determined as optimal operating values for its effective removal from water based on the following parameters: concentration decay of DIA, total organic carbon removal rate and mineralization current efficiency. The rate constant for oxidation of DIA by OH was determined using competition kinetics method and found be 3.96×108Lmol−1s−1. Obtained results showed a quick and complete mineralization of DIA solution. In addition, the identification of aromatic intermediates, short-chain carboxylic acids and mineral ions released to the solution during electro-Fenton treatment allowed us proposing a plausible mineralization mechanism of DIA by OH generated in the process. Finally, the toxicity of treated solutions along time was assessed following the luminescence inhibition of the marine bacteria Vibrio fischeri, using Microtox® method.

ITO-free, efficient, and inverted phosphorescent organic light-emitting diodes using a WO3/Ag/WO3 multilayer electrode

We present an indium tin oxide (ITO)-free, bottom-emission inverted phosphorescent organic light-emitting diode (PHOLED) with a maximum luminance of 280,000 cd/m2 at 8 V, total maximum current efficiency of 81.4 cd/A, and external quantum efficiency of 22.4%. The inverted OLED structure is composed of glass/WO3 (30 nm)/Ag (15 nm)/WO3 (5 nm)/BPhen:15wt% CS2CO3 (5 nm)/BPhen (30 nm)/CBP: 8wt% Ir(ppy)3 (10 nm)/TAPC (50 nm)/WO3 (5 nm)/Ag (150 nm) multilayers. In this device structure, the WO3/Ag/WO3 (WAW) multilayer serving as a transparent cathode demonstrates a low sheet resistance (3.5 Ω/sq) and high optical transmittance (approximately 80%) in a visible light range of 400–600 nm; this multilayer was prepared by thermal evaporation to form a relatively smooth morphology of the conductive thin film on the glass substrate. In addition, an electron-only WAW device was subjected to electrical characterization, and the results revealed that this device exhibited a more efficient electron injection property at the WAW/BPhen:CS2CO3 interface than the contact electrode of a standard ITO-based device.

Treatment of landfill leachate using electrochemically assisted UV/chlorine process: Effect of operating conditions, molecular weight distribution and fluorescence EEM-PARAFAC analysis

Leachate, a highly polluted wastewater, is generated from landfill containing complex compositions which have great impact on the environment. The advanced treatment of biochemically treated landfill leachate using electrochemically assisted UV/chlorine process (UEC) in a flow reactor was investigated. The effects of pH and current density on COD and NH3-N removal by UEC process were evaluated. At the pH value of 5.0, current density of 60mA/cm2, the removal efficiencies for COD and NH3-N were observed as 77% and 87%, respectively. The electrochemical process alone (EC) could obtain relatively high NH3-N removal but very low COD removal, compared with which, the UEC process significantly promoted the removal efficiency of COD while that of NH3-N increased to a very limited extent. Most of NH3-N was converted into N2 and little nitrogen compounds and chloramines were remained in the leachate after 8h treatment. Moreover, the variations of active chlorine and chloride ions were monitored in the EC and UEC systems, and a possible mechanism was proposed for the UEC process. The in situ electro-generated active chlorine and photo-generated radical species should be responsible for the efficient degradation of landfill leachate. The total energy consumption and current efficiency were 216.5 (kWh/kg COD) and 17.5%, respectively, for 8h treatment. In addition, the molecular weight (MW) percentage distribution analysis and PARAFAC analysis of excitation emission matrix (EEM) fluorescence spectroscopy indicated that the organic matters in the leachate were significantly degraded into the fractions with small molecular weight.

High-Performance Hybrid White Organic Light-Emitting Diodes Utilizing a Mixed Interlayer as the Universal Carrier Switch**Supported by the National Natural Science Foundation of China under Grant No 61076066, and the Innovation Project of Science and Technology Plan Projects of Shaanxi Province under Grant No 2011KTCQ01-09.

A new interlayer is successfully used to be a universal carrier switch, developing high-performance hybrid white organic light-emitting diodes (WOLEDs). By dint of this interlayer, the two-color hybrid WOLED shows a maximum total current efficiency (CE) and power efficiency (PE) of 48.1 cd/A and 37.6 lm/W, respectively, while the three-color hybrid WOLED shows a maximum total CE and PE of 33.8 cd/A and 25.7 lm/W, respectively. The color rendering index of the three-color hybrid WOLEDs are ≥75, which is already a sufficient level for many commercial lighting applications. In addition, both the two-color and three-color hybrid WOLEDs show low efficiency roll-off and stable color. Furthermore, devices with the new interlayer show much higher performance than devices with the most commonly used 4,4-N,N-dicarbazolebiphenyl and N,N'-di(naphthalene-1-yl)-N,N'-diphenyl-benzidine interlayers.

High efficiency yellow organic light-emitting diodes with optimized barrier layers

High efficiency Iridium (III) bis (4-phenylthieno [3,2-c] pyridinato-N,C2′) acetylacetonate (PO-01) based yellow organic light-emitting devices are fabricated by employing multiple emission layers. The efficiency of the device using 4,4′,4″-tris(N-carbazolyl) triphenylamine (TCTA) as potential barrier layer (PBL) outperforms those devices based on other PBLs and detailed analysis is carried out to reveal the mechanisms. A forward-viewing current efficiency (CE) of 65.21cd/A, which corresponds to a maximum total CE of 110.85cd/A is achieved at 335.8cd/m2 in the optimized device without any outcoupling enhancement structures.

Efficient single-emitting layer hybrid white organic light-emitting diodes with low efficiency roll-off, stable color and extremely high luminance

An efficient single-emitting layer hybrid white organic light-emitting diode (WOLED) was developed, simultaneously fulfilling low efficiency roll-off, stable color and extreme luminance. At the practical luminance of 1000cd/m2, a total current efficiency of 42.8cd/A and power efficiency of 19.2lm/W are achieved, maintaining as high as 40.5cd/A and 15.5lm/W even at 5000cd/m2. Besides, a slight color variation [(0.025, 0.011)] and extreme luminance (∼106cd/m2) are obtained. The working mechanism is unveiled and it is demonstrated that the triplet-exciton-confining ability of electron transport layers plays a more vital role in device performances, particularly for the lifetime.

Electro-oxidation of nitrophenol by ruthenium oxide coated titanium electrode: Parametric, kinetic and mechanistic study

Present study investigates mechanism of electrochemical (EC) oxidative degradation of p-nitrophenol (PNP) by ruthenium oxide coated titanium (Ti/RuO2) electrode. First, the process proficiency was determined in terms of chemical oxygen demand (COD), total organic carbon (TOC), current efficiency (CE) and specific energy consumption (SEC) under different experiment conditions of initial pH (pHo), current density (j), electrolyte concentration (m) and initial PNP concentration (Co). Maximum COD and TOC removal efficiencies of 98.9% and 81.9%, respectively, were obtained at j=168.9A/m2, pHo=5.5, Co=100mg/L and m=300mg/L with SEC of 535.7kWh/kg COD. PNP degradation mechanism has also been proposed on the basis of identification of intermediates by gas chromatograph coupled with mass spectrometry (GC/MS). Various intermediates such as quinine, benzoquinone, organic acids and small mineralization products were obtained during the EC treatment of PNP. PNP was found to be oxidized by both direct (hydroxyl radical generated via water electrolysis on anode surface) and indirect (via mediators, hypochlorous acid and active chlorine generated during chlorine oxidation in solution) EC oxidation. Kinetics of EC oxidation was represented by pseudo-first order kinetic model.

Simplified hybrid white organic light-emitting diodes with efficiency/efficiency roll-off/color rendering index/color-stability trade-off

A high-performance hybrid white organic light-emitting diode (WOLED) based on a simple structure has been developed. The resulting device exhibits a maximum total current efficiency and power efficiency of 35.7 cd/A and 30.6 lm/W, respectively. Even at a high luminance of 1000 cd/m2, a current efficiency of 32.0 cd/A and a power efficiency of 19.4 lm/W are obtained, suggesting that the device exhibits a low efficiency roll-off. Besides, the device shows excellent color-stability during a wide range of luminance and a high color rendering index (CRI) of 83 is obtained. Moreover, the origin of the superior properties is explored comprehensively. Such achieved results demonstrate that high efficiency, low efficiency roll-off, stable color and high CRI can be simultaneously realized in a simplified hybrid WOLEDs. (© 2014 WILEY-VCH Verlag GmbH &Co. KGaA, Weinheim)

Electrochemical synthesis of diacetone-2-keto-L-gulonic

The electrochemical oxidation of technological-grade diacetone-L-sorbose to diacetone-2-keto-L-gulonic acid by the preparative electrolysis in alkaline media is studied. The effect of various technological parameters, namely, the cathode material, the temperature, the sodium hydroxide concentration, the current density, and the cell design, on the yield of discetone-2-keto-L-gulonic acid is considered. For the electrosynthesis of diacetone-2-keto-L-gulonic acid on the anode made of Kh18N10T stainless steel, the conditions are found that provide its total substance yield and current efficiency over all stages of oxidation and isolation from solution at the level of 88.5 and 37.5–38.0%, respectively.

Anodic Oxidation as Green Alternative for Removing Diethyl Phthalate from Wastewater Using Pb/PbO2and Ti/SnO2Anodes

AbstractThe electrochemical oxidation (EO) of diethyl phthalate (DEP) in aqueous solution was studied at Pb/PbO2and Ti/SnO2anode materials under galvanostatic‐experimental conditions. Results obtained clearly demonstrated that the anode plays a significant role for the optimization of the oxidation process, deciding the mechanisms and by‐products formed. DEP and by‐products of oxidation were also analyzed during various stages of the electrolysis reaction by HPLC and GC/MS techniques. Before the analysis by GC/MS technique, the samples were treated by solid phase microextraction (SPME) in order to concentrate the compounds from the reaction solution and identify all electrolysis intermediates. Current efficiencies (instantaneous current efficiency; ICE and total current efficiency; TCE) achieved during EO experiments were dependent on anode used and current density (20–40 mA cm−2) at 40°C. The results obtained demonstrated that the environmental electrochemical methods can be a feasible alternative for the wastewater treatment containing hazardous phthalates.