Hydrogen peroxide can be produced electrochemically by selective oxygen reduction reaction or selective water oxidation reaction in various electrolytes. A very promising, sustainable, and efficient ...method to produce hydrogen peroxide is the so-called electrochemical “lab-on-a-chip” technology, where microfluidic electrochemical flow cells can be used. The main advantage of such a system is “on demand” and “on site” production. If these systems are to be commercialized, suitable electrocatalysts (anode and cathode), sensors, and a device design must be developed and interconnected. Such technology could then eventually be deployed in an industrial environment with internal/external numbering-up approach.
•The characteristics of microfluidic devices and its benefits as energy converters for H2O2 electrosynthesis are discussed.•The low cost of microfluidic devices fabrication is an attractive factor for on-site application on H2O2 electrosynthesis.•Due to its compact and flexible design, microfluidic electrochemical flow cells may be coupled with in-line detectors.•The aim of H2O2 electrosynthesis in microreactors is to bring on-site production directly to the consumer.
In order to reduce the sample consumption and waste generation for electrochemical purposes, a screen-printed electrode (SPE) used for electrodeposition of bismuth film (SPE-BiFE) and a thermostated ...electrochemical flow cell (EFC) were developed. The SPE-BiFE with the EFC was employed to determine Cd2+ and Pb2+ ions in natural, wastewater and tap water samples by square-wave anodic stripping voltammetry (SWASV). For this, the flow-batch analysis (FBA) approach based on solenoid micro-pumps and three-way valves was developed to carry out a fully automated procedure with temperature control. Furthermore, the FBA and the SWASV parameters were optimized, on line simultaneous determination of Cd2+ and Pb2+ ions was performed and two analytical curves were linearly acquired in the concentration ranges from 6.30 to 75.6µgL−1 and from 3.20 to 38.4µgL−1, respectively. Moreover, limits of detection of 0.60µgL−1 and 0.10µgL−1 for Cd2+ and Pb2+, respectively, were obtained. Studies of precision for the same SPE-BiFE and repeatability for five built SPE-BiFE were carried out for Cd2+ and Pb2+ ion measurements and RSD of 4.1% and 2.9% (n=3) with repeatabilities (n=5) of 6.5% and 8.0% were respectively obtained for both analytes. Besides, a low consumption of 700µL of reagents and a sampling frequency of 13h−1 were acquired. Simplicity, fast response, accuracy, high portability, robustness and suitability for in loco analyses are the main features of the proposed electroanalytical method.
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•An electrochemical system with a minimal handling of solutions and low toxicity.•An efficient thermostated control was performed for in loco measurements.•An automated system to perform on line and ex situ electrodeposition of bismuth.•The flow system was used to prepare analytical curves, standard addition, recovery.•Low waste generation and bismuth were in agreement with the green chemistry.
•Electrochemistry (EC) with capillary electrophoresis-mass spectrometry (CE-MS).•On-line coupling of EC with CE-MS is possible.•EC is a means to enable CE-MS studies of neutral ...compounds.•Electrochemical flow cell with screen-printed electrodes can be coupled directly to MS.
Hyphenated techniques have become an important tool in modern analytical research. Among detection techniques, mass spectrometry (MS) plays a dominant role, but efficient analyte separation prior to MS detection is usually desirable, as it provides the basis for reliable qualitative and quantitative determination. However, electrochemical methods offer very versatile approaches for selective sample pretreatment or analyte conversion. This review summarizes recent instrumental analytical developments, which resulted in a special kind of a hyphenated system: electrochemistry-capillary electrophoresis-MS (EC-CE-MS). We discuss the analytical characteristics of this approach and compare them with those of other techniques coupling EC with separation techniques and MS.
Anodes based on substoichiometric titanium oxide (Ti4O7) are among the most effective for the anodic oxidation of organic pollutants in aqueous solutions. Such electrodes can be made in the form of ...semipermeable porous structures called reactive electrochemical membranes (REMs). Recent work has shown that REMs with large pore sizes (0.5–2 mm) are highly efficient (comparable or superior to boron-doped diamond (BDD) anodes) and can be used to oxidize a wide range of contaminants. In this work, for the first time, a Ti4O7 particle anode (with a granule size of 1–3 mm and forming pores of 0.2–1 mm) was used for the oxidation of benzoic, maleic and oxalic acids and hydroquinone in aqueous solutions with an initial COD of 600 mg/L. The results demonstrated that a high instantaneous current efficiency (ICE) of about 40% and a high removal degree of more than 99% can be achieved. The Ti4O7 anode showed good stability after 108 operating hours at 36 mA/cm2.
Small cavities on a sliding surface can improve lubrication performance, which has been verified by many researchers. Electrochemical machining (ECM) is an effective way to fabricate this kind of ...small cavities on a large scale. When the diameter and the removal volume for the cavities are specified, it is still required to efficiently determine the appropriate machining parameters. This paper presents a machine vision based control system for an ECM variant: the scanning micro electrochemical flow cell (SMEFC). The aim of this system is to control the diameter of the cavity in real-time. With the assistance of machine vision, fast acquisition of the machining parameters for the specified diameter and the specified removal volume is possible. The system configuration is first explained in detail, including hardware and software configuration and the image processing algorithms. The latter are based on the Shi-Tomasi corner detector and are used for feedback control, stability and symmetry evaluation of the electrolyte droplet. For convenience, all of these functions have been integrated into a self-developed unified G-code interface. Furthermore, the theoretical explanation for controlling the machining process by vacuum gap (VG) tuning has been investigated through a two-phase flow simulation model, which revealed how the VG influences the shear rate and the pressure difference near the meniscus. Finally, a case study shows how to use the proposed strategy to get suitable machining parameters for a cavity with a diameter of 900 μm and a target removal volume of 0.03 mm3. This demonstrates the availability of a deterministic removal strategy.
This article elaborates on the design and optimization of a specialized flow cell for the measurement of direct conversion of pressure into electrical energy (Electrokinetic Energy Conversion, EKEC) ...which has been presented in Østedgaard-Munck et al. (2017) 1. Two main flow cell parameters have been monitored and optimized: A) the hydraulic pressure profile on each side of the membrane introduced by pumps recirculating the electrolyte solution through the flow fields and B) the electrical resistance between the current collectors across the combined flow cell. The latter parameter has been measured using four-point Electrochemical Impedance spectroscopy (EIS) for different flow rates and concentrations. The total cell resistance consists of contributions from different components: the membrane (Rmem), anode charge transfer (RA), cathode charge transfer (RC), and ion diffusion in the porous electrodes (RD).
The intrinsic membrane properties of Nafion 117 has been investigated experimentally in LiI/I2 solutions with concentrations ranging between 0.06 and 0.96M and used to identify the preferred LiI/I2 solution concentration. This was achieved by measuring the solution uptake, internal solution concentration and ion exchange capacity. The membrane properties were further used to calculate the transport coefficients and electrokinetic Figure of merit in terms of the Uniform potential and Space charge models. Special attention has been put on the streaming potential coefficient which is an intrinsic property.
► The microporous membrane electrode was prepared by sputtering of platinum onto the track-etched membrane filter. ► A new dual-electrode flow sensor has been fabricated by piling these electrodes. ► ...The electrolysis is performed when the sample solution flows through the membrane electrode. ► In this case, the sample solution surely flows through the pores of the membrane filters. ► Because of the highly efficient electrolysis at each electrode, collection efficiency values as high as 100% were obtained.
A new dual-electrode flow sensor has been fabricated by piling the microporous membrane electrodes which have 7–10μm thickness. The electrode was prepared by sputtering of platinum onto both sides of the membrane filter which contain a smooth flat surface as well as cylindrical pores with uniform diameters. The electrolysis is performed when the sample solution flows through the membrane electrode, and a generated analyte on the first working electrode is instantaneously transported to the surface of second working electrode which is located at the downstream of the first one. In this case, the sample solution surely flows through the pores of the membrane filters. As the result, highly efficient electrolysis was achieved at each electrode, and the collection efficiency values as high as 100% were obtained in the wide range of flow rate. Good responses to the injections of sample solutions were also confirmed in the FIA system.
A novel electrochemical flow cell system that can be programmed to set arbitrary conditions for flow velocity and concentration has been developed. The system includes an electrochemical flow cell ...and solution supply devices. The flow cell is a coaxial cylindrical pipe and a working electrode is arranged on the inner shaft. The working electrode protrudes from the inner shaft for stable measurement. The solution supply device can continuously change the flow rate and concentration of the solution to be supplied to the flow cell. Using the measurement system, current can be measured under continuous changes of the flow velocity and of the concentration in a wide range. Therefore, it is possible to evaluate the concentration dependence and flow velocity dependence of an electrode reaction efficiently with great detail. To verify the developed system, the diffusion-limited current is measured under continuous change of the copper ion concentration in the copper sulfate aqueous solution. The measured current was compared with the numerical solution of the diffusion-limited current for annular flow. Results of the comparison demonstrate that the developed system works as designed.
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