The limiting aspects in the voltammetric response of 3D printed electrodes is thoroughly investigated with numerical simulations and new 3D printed electrode designs. Severe diffusion limitations, ...resulting from a recessed electrode geometry, is found in a commonly used 3D printed electrode and electrochemical cell design, impeding the investigation of electron transfer kinetics at these electrodes by classical methods, such as Nicholson's, widely used on this and similarly mass transport-limited designs. A new 3D printed electrode design, an inlaid disk (non-recessed) geometry, is used to investigate the voltammetric response of printed electrodes in bulk solution, i.e., without mass transport limitations. At this condition, it is clear that the voltammetric response is limited by contact resistance, arising from the printed material low electrical conductivity. Gold modified electrodes, deliberately designed with different contact resistances, highlight the resistive behavior, with quasi-reversible voltammetric profiles. This contrasts with the common assumption of a voltammetric response limited by finite electron kinetics. Electron transfer rate constants (k0) and transfer coefficients (α) for electrodes with and without surface modifications are calculated from experimental data using a modified Butler-Volmer equation, incorporating ohmic losses. The reported k0 and α values are independent of electrode geometry or printing parameters, unlike the observable rate constant usually reported for 3D printed electrodes. By accounting for contact resistance and finite electron transfer kinetics, cathodic and anodic peak potentials and currents of voltammograms recorded with 3D printed electrodes are predicted before printing, allowing electrode designs to be optimized in the virtual space.
Display omitted
Ultra-violet (UV) photosensors are commonly used for environmental monitoring and space applications to measure UV radiation in order to mitigate its negative effects. This work investigates the ...effect of the spacing between the electrodes on the performance and response of UV photosensors. First, ZnO nanorods are thermally grown on a glass substrate with transparent interdigitated electrodes. The surface topography and morphology are characterized using advanced microscopy techniques. The optical properties are explored using UV-Vis and photoluminescence analyses. I-t and I-V measurements in the dark and under UV radiation are carried out to reveal the photosensor characteristics at electrode spacings of 50, 75, 100, 125, and 150 µm. The best photosensor performance is observed at a spacing of 75 µm under a bias voltage of +7 V. The photosensor has a responsivity of 5.06478 mAW−1, photosensitivity of 0.58002 %, gain of 1.0058, rise time of 0.533 s, and decay time of 0.474 s. Regardless of the performance of the photosensors, this study gives an insight into the role of the electrode geometry, including the electrode gap and measurement path, which could be helpful in designing UV photosensors and optimizing their performance.
Display omitted
•ITO electrodes with an IDE structure and gap widths of 50, 75, 100, 125, and 150 µm are coated with ZnO nanorods using CBD.•The morphological, optical, and electrical properties of the ZnO NRs as a photosensor device are analyzed and discussed.•The role of the electrode, including the gap width and measurement path, on the photosensor performance is investigated.•The Photosensor with a gap width of 75 µm showed a photocurrent of 34.4 µA and responsivity of 5.065 mA/W at +7 V bias.
Effects of electrode geometry on emulsion dehydration efficiency.
Display omitted
•Three novel electrode geometries were designed.•The effects of the electrode geometries were analyzed using ...macroscopic experiments.•Experimental results were compared with those of electric field simulation.•There was close agreement between the simulation results and the experimental data.
The complicated nature of current wet crude oil requires a further upgrade of electrical dehydration technology that can satisfy the latest processing criteria. This study investigated the dehydration efficiency of a dispersed phase of distilled water in a continuous phase of conduction oil in electric fields created by three proposed electrodes. The electric field distribution was created and analyzed using COMSOL Multiphysics software and the level-set method. The results show that the electric fields created by our proposed electrodes can aid the dehydration process by optimizing the electric field distribution and the electropolymerization behaviors. Furthermore, the results indicate that the non-uniform fields formed by the proposed electrodes can lead to acceleration in the movement of water droplets as well as a facilitated sedimentation stage. A water film created by a copper mesh electrode can induce a droplet–interface coalescence, and the geometry of a grid electrode can promote a two-phase oil and water movement. These results could provide insights for the future design of the best electrode geometry for efficient electrocoalescence.
Electrodes are basic components of C4D (capacitively coupled contactless conductivity detection) sensors, and different electrode structures (the configuration pattern or the electrode geometry) can ...lead to different measurement results. In this work, the effects of electrode geometry of radial configuration on the measurement performance of C4D sensors are investigated. Two geometrical parameters, the electrode length and the electrode angle, are considered. A FEM (finite element method) model based on the C4D method is developed. With the FEM model, corresponding simulation results of conductivity measurement with different electrode geometry are obtained. Meanwhile, practical experiments of conductivity measurement are also conducted. According to the simulation results and experimental results, the optimal electrode geometry of the C4D sensor with radial configuration is discussed and proposed. The recommended electrode length is 5–10 times of the pipe inner diameter and the recommended electrode angle is 120–160°.
This work presents the results of two-dimensional modeling of the effects of non-equilibrium excitation and electrode geometry on H2/air ignition in a nanosecond plasma discharge. A multiscale ...adaptive reduced chemistry solver for plasma assisted combustion (MARCS-PAC) based on PASSKEy discharge modeling package and compressible multi-component reactive flow solver ASURF+ is developed and validated. This model is applied to simulate the impact of non-equilibrium plasma excitation and electrode geometry and heat loss on the dynamics of the discharge from streamer to spark and ignition kernel development in a H2/air mixture with a pair of cylindrical electrodes. The results show that the plasma-generated species (N2(A), N2(B), N2(a′), N2(C), O(1D), O and H) in the spark and afterglow significantly accelerate the ignition kernel development. The increase of discharge voltage at the same total discharge energy promotes the non-equilibrium active species production. It is found that the production of electronically excited species at higher reduced electric field strength is more efficient in enhancing ignition in comparison to the vibrational excitation and heating. Moreover, the 2D simulation clearly reveals that the electric field and active species distribution are highly non-uniform. The streamers are initiated at the sharp outer edges of the negative and positive electrodes by a strong electric field while the electric field is much weaker at the centerline of the electrodes. Furthermore, the simulations reveal that the ignition enhancement is sensitive to the variation of electrode shape, diameter, and gap size due to the changes of electric field distribution and location of streamer formation. A cylindrical electrode produces a larger discharge volume and ignition kernel than the parabolic and spherical electrodes, when the discharge is localized near the axis of the gap. It is found that there is a non-monotonic dependence of ignition kernel size on the electrode diameter and inter-electrode distance. The increase of electrode diameter and gap size above the optimal conditions leads to the reduction of ignition kernel volume, due to the decrease of active species concentration and gas temperature. At a larger electrode surface area and electrode diameter as well as smaller electrode gap size, the heat loss to electrode plays a greater role in reducing the ignition kernel size and slowing ignition kernel development. This work provides insights and guidance to understand the kinetic enhancement of non-equilibrium plasma and the effects of electrode geometries on ignition for the optimization ignitors in advanced engines.
Scanning electrochemical microscopy (SECM) is an emerging electroanalytical sensing technique, used to investigate the electrochemical properties of the sample by ultra‐micro‐electrode(UME) scanning ...probe. UME signal usually is the current, which depends not only on the properties of the evaluated system but also on UME characteristics such as geometry. Variations of UME geometry can decrease accuracy of the measurement, and then correct analysis of the SECM data becomes almost impossible. In the present work, we studied the precision of measurements with three different the most frequent types of defected UME's ((i) recessed‐UME, (ii) outwarded‐UME, (iii) cone‐UME). Measurement results were compared with that obtained with not defected standard‐plane‐UME. Computational experiment was performed with SECM model using diffusion equations with non‐rectangular border conditions to calculate estimated currents for these three types of defected UMEs and to compare them with that for standard‐plane‐UME. In order to test the correctness of the model, computations for recessed‐UME model were compared with data of real‐recessed‐UME experiment.
•2 × 50 μm2 sputtered iridium oxide (SIROF) ultramicro-sized (UM-sized) electrodes in ferrocene in acetonitrile at 5, 50, and 500 mV/s sweep rates form a sigmoidal-shape cyclic voltammogram ...indicating hemispherical diffusion of ferrocene.•4 × 50 μm2 SIROF UM-sized electrodes in PBS have a longer transition time compared to micro-sized electrodes indicating more availability of counterions to UM-sized electrodes.•SIROF UM-sized electrodes in PBS have a higher charge injection capacity (CIC), lower maximum driving voltage per unit current density, and lower specific AC impedance compared to micro-sized electrodes.•Higher perimeter to area ratio (P/A) SIROF electrodes have lower maximum driving voltage per unit current density during pulsing and lower specific AC impedance.•SIROF UM-sized electrodes can present long-term electrochemical stability over 109 current pulses.
Hemispherical transport of electroactive species to ultramicroelectrodes (UME) as opposed to linear transport to regular electrodes, makes them an attractive candidate for a variety of different applications such as sensors and neural electrodes. In this paper, ultramicro-sized (UM-sized) sputtered iridium oxide film (SIROF) electrodes’ cyclic voltammogram in a buffer electrolyte with ionic counterions (phosphate-buffered saline (PBS)) is compared to their cyclic voltammogram in electrolytes with neutral electroactive species (ferrocene in acetonitrile), as they correspond to the use of UMEs as neural electrodes and sensors, respectively. To assess the behavior of SIROF UM-sized electrodes in PBS, their transition time, charge injection capacity (CIC), and specific impedance (voltage per unit current density) is compared to the corresponding quantities in microelectrodes. Moreover, the effect of the perimeter to area ratio (P/A) on the specific impedance and CIC of the UM-sized electrodes is evaluated to provide design guidance for their use as neural electrodes. The stability of SIROF UM-sized coating is assessed by subjecting the electrode to long-term continuous current pulsing and potential cycling. While cyclic voltammograms of SIROF UM-sized electrodes in ferrocene presented a steady-state current at slow sweep rates (< 500 mV/s), such behavior was not observed in PBS. However, the inflection points in the chronopotentiometric curve representing transition time were shorter for micro-sized SIROF electrodes compared to UM-sized electrodes once they were subjected to similar current densities. Also, SIROF UM-sized electrodes presented higher CIC and lower specific impedance compared to microelectrodes. SIROF UM-sized electrodes with larger P/A had lower specific impedance and higher CIC and their electrochemical properties could remain stable under long-term continuous pulsing and cycling.
Advanced high strength steels are usually coated by a zinc layer for an increased resistance against corrosion. During the resistance spot welding of zinc coated steel grades, liquid metal ...embrittlement (LME) may occur. As a result, cracking inside and around the spot weld indentation is observable. The extent of LME cracks is influenced by a variety of different factors. In this study, the impact of the used electrode geometry is investigated over a stepwise varied weld time. A spot welding finite element simulation is used to analyse and explain the observed effects. Results show significant differences especially for highly increased weld times. Based on identical overall dimensions, electrode geometries with a larger working plane allow for longer weld times, while still preventing LME within the investigated material and maintaining accessibility.
PDF
