Effect Of Electrode Geometry Research Articles

Shape Matters: Understanding the Effect of Electrode Geometry on Cell Resistance and Chemo-Mechanical Stress

Rechargeable batteries that incorporate shaped three-dimensional electrodes have been shown to have increased power and energy densities when compared to a conventional geometry, i.e. a planar cathode and anode that sandwich an electrolyte. Electrodes can be shaped to enable a higher active material loading, while keeping ion transport distances small. However, the relationship between electrical and mechanical performance of shaped electrodes remains poorly understood. Many electrode designs have been explored, where the electrodes are individually shaped or intertwined, and advances in manufacturing and shape/topology optimization have made such designs a reality. Here, we explore sinusoidal half cells and interdigitated full cells. First, we use a simple electrostatics model to understand the cell resistance as a function of shape. We focus on low-temperature conditions, where the electrolyte conductivity decreases relative to that of the electrode; here, LiPF6 EC:DMC electrolyte and MnO2 electrode are considered. Next, we use a chemo-mechanics model to examine the stress that arises due to intercalation-driven volume expansion. We show that shaped electrodes provide a significant reduction in resistance in low-temperature conditions, however, they exhibit unfavorable stress concentrations. Overall, we find that the fully interdigitated electrodes may provide the best balance with respect to this resistance-stress trade-off.

Optimizing the Electrode Geometry of an In-Plane Unimorph Piezoelectric Microactuator for Maximum Deflection

Piezoelectric microactuators have been widely used for actuation, sensing, and energy harvesting. While out-of-plane piezoelectric configurations are well established, both in-plane deflection and asymmetric electrode placement have been underexplored in terms of actuation efficiency. This study explores the impact of asymmetric electrode geometry on the performance of slender unimorph actuators that deflect in-plane, where actuator length is much larger than width or thickness. After validating the finite element modeling method against experimental data, the geometric parameters of the proposed unimorph model are manipulated to explore the effect of different electrode geometries and layer thicknesses on actuation efficiency. Four key findings were that (1) the fringing field within the piezoelectric material plays a measurable role in performance, (2) symmetry in electrode placement is generally nonoptimal, (3) optimal electrode geometry is independent of scale, and (4) the smaller the ratio of width to thickness, the larger the deflection. The findings contribute to the development of efficient design strategies that optimize the performance of planar actuators for potential implications for microelectromechanical systems (MEMS). To aid designers of piezoelectric unimorph actuators in determining the optimal electrode geometry, three types of parameterized figures and two types of simulation apps are provided.

Coupled Eulerian–Lagrangian model prediction of neural tissue strain during microelectrode insertion

Objective.Implanted neural microelectrodes are an important tool for recording from and stimulating the cerebral cortex. The performance of chronically implanted devices, however, is often hindered by the development of a reactive tissue response. Previous computational models have investigated brain strain from micromotions of neural electrodes after they have been inserted, to investigate design parameters that might minimize triggers to the reactive tissue response. However, these models ignore tissue damage created during device insertion, an important contributing factor to the severity of inflammation. The objective of this study was to evaluate the effect of electrode geometry, insertion speed, and surface friction on brain tissue strain during insertion.Approach. Using a coupled Eulerian-Lagrangian approach, we developed a 3D finite element model (FEM) that simulates the dynamic insertion of a neural microelectrode in brain tissue. Geometry was varied to investigate tip bluntness, cross-sectional shape, and shank thickness. Insertion velocities were varied from 1 to 8 m s-1. Friction was varied from frictionless to 0.4. Tissue strain and potential microvasculature hemorrhage radius were evaluated for brain regions along the electrode shank and near its tip.Main results. Sharper tips resulted in higher mean max principal strains near the tip except for the bluntest tip on the square cross-section electrode, which exhibited high compressive strain values due to stress concentrations at the corners. The potential vascular damage radius around the electrode was primarily a function of the shank diameter, with smaller shank diameters resulting in smaller distributions of radial strain around the electrode. However, the square shank interaction with the tip taper length caused unique strain distributions that increased the damage radius in some cases. Faster insertion velocities created more strain near the tip but less strain along the shank. Increased friction between the brain and electrode created more strain near the electrode tip and along the shank, but frictionless interactions resulted in increased tearing of brain tissue near the tip.Significance. These results demonstrate the first dynamic FEM study of neural electrode insertion, identifying design factors that can reduce tissue strain and potentially mitigate initial reactive tissue responses due to traumatic microelectrode array insertion.

Analysis of The Effect of Aluminum Electrode Geometry on The Removal of Polyethylene Microbeads Using The Electrocoagulation Method in Greywater

Abstract: The increasing use of cosmetics and personal care products containing small-sized and low-density microbeads will disrupt the aquatic environment because they are difficult to remove in wastewater treatment plants (WWTPs). Electrocoagulation (EC) is an effective technology for removing microbeads from greywater. This research aims to develop an effective cylindrical electrode geometry design in the EC process to reduce electrode passivation, as evidenced by the removal of polyethylene (PE) microbeads from greywater, reduced energy consumption, and the analysis of the EC kinetics model. Experiments were carried out on batch and continuous systems using artificial greywater with an initial concentration of 0.5 g/L. Variations made in the batch system are the geometry of the cylindrical electrode without holes (ESTB), a cylindrical electrode with holes (ESB), a cylindrical electrode with anode with holes, and a cathode with no holes (ESB-A), a cylindrical electrode with cathode, with holes and anode with no holes (ESB-K), and plate electrode (EP). The variations carried out in the continuous system were flow rates of 60, 70, 80, and 90 mL/minute using the best electrode geometry design obtained from the batch system. The best removal efficiency of PE microbeads in a batch system was 98.44% in ESB-K geometry and saved 75% energy consumption compared to EP. The best removal efficiency of PE microbeads in a continuous system was 79.76% at a flow rate of 60 mL/minute. The kinetic model of the EC reaction which corresponds to the removal process of PE microbeads is a first-order reaction. Future research should focus on optimizing the design of continuous reactors so that they can be applied to tertiary processing in domestic WWTPs and industrial WWTPs.Abstrak: Meningkatnya penggunaan kosmetik dan produk perawatan pribadi (CPCP) yang mengandung microbeads berukuran kecil dan berkepadatan rendah akan mengganggu lingkungan perairan karena sulit disisihkan di instalasi pengolahan air limbah (IPAL). Elektrokoagulasi adalah teknologi yang efektif untuk menyisihkan microbeads dari greywater. Penelitian ini bertujuan untuk mengembangkan desain geometri elektroda silinder yang efektif pada proses elektrokoagulasi untuk mengurangi pasivasi elektroda yang dibuktikan dari penyisihan microbeads polyethylene dari greywater dan pengurangan konsumsi energi yang digunakan dan menganalisis model kinetika elektrokoagukasi. Eksperimen dilakukan pada sistem batch dan kontinu menggunakan greywater artifisial dengan konsentrasi awal 0,5 g/L. Variasi yang dilakukan pada sistem batch adalah geometri elektroda silinder tidak berlubang (ESTB), elektroda silinder berlubang (ESB), elektroda silinder anoda berlubang dan katoda tidak berlubang (ESB-A), elektroda silinder katoda berlubang dan anoda tidak berlubang (ESB-K), dan elektroda pelat (EP). Variasi yang dilakukan pada sistem kontinu adalah laju alir 60, 70, 80, dan 90 mL/menit menggunakan desain geometri elektroda terbaik yang diperoleh dari sistem batch. Efisiensi penyisihan microbeads polyethylene terbaik pada sistem batch sebesar 98,44% pada geometri ESB-K dan menghemat 75% konsumsi energi dibandingkan EP. Efisiensi penyisihan microbeads polyethylene terbaik pada sistem kontinu sebesar 79,76% pada laju alir 60 mL/menit. Model kinetika reaksi elektrokoagulasi yang sesuai dengan proses penyisihan microbeads polyethylene adalah reaksi orde satu. Penelitian selanjutnya harus berfokus pada optimalisasi desain reaktor kontinu, sehingga dapat diterapkan pada pengolahan tersier di IPAL domestik maupun IPAL industri.

Effects of droplet volume, electrode geometry, and surface tension on the threshold actuation voltage of a droplet on coplanar electrodes

Actuation voltage is critical for droplet motion on coplanar electrodes via electrowetting on dielectric. In this study, we derive an electromechanical model including threshold actuation voltage, as well as liquid (surface tension, droplet volume, electrical conductivity) and device parameters (electrode width, applied frequency, relative permittivity, and thickness of materials) on a one-plate structure. In addition, the effects of the three most important parameters (droplet volume, electrode geometry, and surface tension) on the threshold actuation voltage of the droplet on coplanar electrodes were investigated experimentally. The effects of electrode geometry, surface tension, and droplet volume on liquid actuation voltage can also be successfully explained based on the theoretical model. This study covers a wide range of droplet volume and surface tension for liquid actuation voltage. Different solutions—DI water, NaCl solution, and water–ethanol mixtures—are used to verify the threshold actuation voltage of liquids in our model. The model’s results are in good agreement with experimental results. Our findings can be utilized to obtain the threshold actuation voltage for various solutions on coplanar electrodes.

Effect of the electrode geometry on the performance of a batch electrochemical reactor used for Cr(VI) removal

The efficient removal of hexavalent chromium from aqueous media is a problem that has found a solution by electrochemical methods. In this work, the effect of electrode geometry on the performance of a stirred tank electrochemical reactor designed for this purpose is evaluated. Two electrode configurations are evaluated: static rings (SR) and electro baffles (EB). The electrodes installed in the batch reactor are static, so the stirring is done with a system of two impellers, whose distance between them is also a variable studied. Five cases are assessed. The evaluation of the cases contemplates experimental tests of Cr(VI) reduction to know its effect on the reaction rate and energy consumption. Computational fluid dynamics analysis is also performed to assess the hydrodynamic environment inside the reactor and relate it to experimental performance. The results show that the electrode geometry affects the Cr(VI) reduction rate as it promotes the process to be controlled by mass transfer. The hydrodynamic analysis shows that the process requires two aspects: an efficient circulation of the fluid inside the tank and homogeneous flow conditions in the vicinity of the electrode surface.

The Effect of Electrode Geometry and Pre-heating Treatment on Resistance Spot Welding Strength

Resistance spot welding (RSW) is one of the most significant and common metal joining methods used in industries. The present paper discusses the comparative performance of resistance spot welding electrodes of nontraditional design with the traditional one of 8 mm contact diameter in welding a 1.5 mm thick low carbon steel sheet used in automobile structural bodies and bridges. The modified electrode tip surface center was machined to have three different holes of 2, 3, and 4 mm depth and three different diameters of 2, 4, and 6 mm producing nine different hollow electrode dimensions. As well as the influence of pre-heating temperature on the mechanical properties of the weld joint was investigated by considering the other main parameters of welding time, current, and force are constant. The shear tensile test and torsion test examinations are carried out to investigate the mechanical properties. Also, to interrupt the results, a macrograph examination was conducted to determine the nugget size formation. The results show that the increase or decrease in the strength of the weld joint is greatly influenced by the proper selection of the modified electrode geometries. Also, the results indicated that the maximum improvement in shear tensile strength and torsional strength is about 140% and 150% compared to the traditional one. Furthermore, pre-heating processes helped decrease the contact resistance at the faying surfaces and improve the weld tensile strength and torsional strength to about 141% and 171% at 200 oC. Moreover, improvement may be achieved by slightly increasing pre-heating temperatures

Determining effects of induction electrode geometry on charging efficiency of droplets in pesticide electrostatic spraying applications

Electrode properties in the induction charging method, usually used in electrostatic pesticide spraying, can have a significant impact on the charging efficiency. The study aimed to investigate the effect of several specifications of the ring-shaped electrode such as diameter, length, cross-section shape, material, and the number of used electrodes, on the charging efficiency of spray droplets. Also, the effect of insulating the electrode electrically on removing the electric leakage resulting from electrode wetting and increasing the charging efficiency was studied. Results showed that neither the electrode material nor its cross-section shape affects the charging efficiency. Reducing the diameter and increasing the length of the ring-shaped induction electrode improves the charging operation by inducing more electric charges on the liquid jet. However, they cause electrode wetting and later electrical leakage at low values of the electrode voltages. Using more than one electrode to charge the spray droplets can increase charging efficiency. Generally, the insulated electrode with an insulator layer reduces the charging efficiency of spray droplets by about 24∼38% at 1∼6 kV electrode voltage compared with the exposed electrode. Nevertheless, it increases the charging efficiency (by 28% at 16 kV) by allowing the use of high values of the high voltage applied to the induction electrode without facing the electrical leakage between the electrode surface and grounded liquid that causes the earthing of the high voltage electrode and stopping of the charging operation.

Effect of electrode geometry on the flow structure induced by plasma actuators

Pulsed surface arc discharge (PSAD) is one of the essential techniques in flow control. In this paper, the effects of electrode configuration on heat transfer characteristics of PSAD and disturbance characteristics of PSAD on the flow field were investigated by thermal imaging technology and high-speed photography technology. By defining the curvature of curve (COC) of the electrode, we investigated the physical mechanism of the electrode configuration, affecting the PSAD disturbed flow field. The results show that the COC has the optimal solution COCopt. When COC ≤ COCopt, the smaller the COC, the more concentrated the PSAD disturbances to the flow field. When COC > COCopt, the electrode configuration will have an end point effect, resulting in a deviation between the theoretical COC and the real COC. The larger the COC, the stronger the end point effect, and the more concentrated the PSAD disturbances to the flow field. The COC affects the disturbance degree of PSAD to the flow field by distorting the electric field intensity distribution. The change in the electric field intensity causes the fluctuation frequency of the flow field to be inconsistent with the discharge frequency of the PSAD. The stronger the distortion degree of the electric field intensity, the stronger the high-frequency characteristics of the fluctuating frequency of the flow field, and the stronger the high-frequency characteristics of the flow mode of the flow field. In addition, we obtained the value range of COCopt within 0.5–0.7 through theoretical derivation and established a mathematical model of electrode structure's effect on the flow field's flow structure.

Highly Sensitive and Ultra-Responsive Humidity Sensors Based on Graphene Oxide Active Layers and High Surface Area Laser-Induced Graphene Electrodes.

Ultra-sensitive and responsive humidity sensors were fabricated by deposition of graphene oxide (GO) on laser-induced graphene (LIG) electrodes fabricated by a low-cost visible laser scribing tool. The effects of GO layer thickness and electrode geometry were investigated. Sensors comprising 0.33 mg/mL GO drop-deposited on spiral LIG electrodes exhibited high sensitivity up to 1800 pF/% RH at 22 °C, which is higher than previously reported LIG/GO sensors. The high performance was ascribed to the high density of the hydroxyl groups of GO, promoted by post-synthesis sonication treatment, resulting in high water physisorption rates. As a result, the sensors also displayed good stability and short response/recovery times across a wide tested range of 0–97% RH. The fabricated sensors were benchmarked against commercial humidity sensors and displayed comparable performance and stability. Finally, the sensors were integrated with a near-field communication tag to function as a wireless, battery-less humidity sensor platform for easy read-out of environmental humidity values using smartphones.

Effect of gap size of gold interdigitated electrodes on the electrochemical immunosensing of cardiac troponin-I for point-of-care applications

This work describes the effect of electrode geometry on the sensor's performance, towards the fabrication of impedimetric bio-sensor for cardiac troponin-I (CTnI) detection. Herein, development of a novel, Electrochemical Impedance Spectroscopy (EIS) based immunosensor for point-of-care applications is explored using gold coated Interdigitated Electrodes (IDEs). The effect of sensor's geometry and its effect on sensor's performance has not been well characterised in the available literature; the understanding of which would significantly advance bio-sensor design and its performance. Greater control of electrode geometries and inter-electrode spacing will increase the electrode surface area, consequently increasing the charge-transfer resistance and reduce the double-layer capacitance. These, in turn, give rise to improved signal-to-noise ratios, thereby affording greater sensitivity, lower detection limits and faster detection times. IDEs of various gap sizes (5 µm, 10 µm, 50 µm and 75 µm) were investigated for sensing of CTnI within 2 ng/mL-12 ng/mL concentration range. The sensitivity is found to be largely dependent on IDE's gap size: ∼ 50% enhancement is achieved upon decreasing the spacing from 75 µm to 5 µm. The response time of the developed immunosensor was found to be ∼ 10 s with excellent selectivity and performance in spiked serum, which makes it an ideal candidate for point of care applications.

Effect of Coaxial Electrode Geometry on the Electric Field Enhancement Factor for a High Voltage Vacuum Gap

We present an experimental analysis of the change in the electric field enhancement factor with varying gap size and penetration depth (P.D) of cathode into anode for a coaxial vacuum gap, diagnosed using Fowler–Nordheim analysis and optical imaging via scanning electron microscope (SEM) and time integrated Digital single lens reflex camera (DSLR). Data were collected on the Coaxial Gap Breakdown Machine (240 A, 25 kV, 150 ns, ~0.1 Hz). Experiments using five different gap sizes at nine different P.Ds are compared over runs comprising 50 shots for each case. The results show a strong link between enhancement factor and gap size, with P.D and surface topology. For large gap sizes, 150, 330, and 700 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \mathrm {m}$ </tex-math></inline-formula> , the average enhancement factor value increases with increasing P.D. For smaller gap sizes, 50 and 100 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \mathrm {m}$ </tex-math></inline-formula> , the average enhancement factor decreases with P.D. SEM imaging before and after plasma formation for each gap size allows for quantifying surface finish, microprotrusion growth, average blast diameter, and an estimation of the surface area breakdowns occupy. Time integrated DSLR imaging analysis of the gap at each shot allows for a determination of the distribution of breakdowns about the circumference of the gap for each case tested. The Fowler–Nordheim analysis allows for a quantitative analysis of the surface roughness of all gap sizes tested. Results show that for large gap sizes, the gap geometry and increasing area of breakdown is the main cause for increasing average enhancement factor. For small gap sizes, the dominant driving factor for small average enhancement factors—that subsequently decrease with P.D—is significant changes in surface topology due to an increased number of breakdowns.

A droplet-based electricity generator for large-scale raindrop energy harvesting

Droplet-based electricity generator (DEG) has been demonstrated as efficient method to harvest energy from the natural environment. However, the complex structure and low output power density are still two barriers to wide applications. To this end, by making full use of the self-capacitance effect of the upper electrode, a droplet-based electricity generator with a simple open structure (SCE-DEG) was proposed in this paper. The working principle of SCE-DEG and the effects of electrode geometry and droplet parameters (volume, conductivity, and dropping frequency) on its output voltage were analyzed. Compared with the DEG, the upper electrode of SCE-DEG does not need to connect to the lower electrode and the ultra-high instantaneous peak output power (765 W/m2) can still be achieved by self-capacitance effect of the upper electrode. This research provides a reference for the large-scale raindrop energy harvesting.

Modeling of the effects of non-equilibrium excitation and electrode geometry on H2/air ignition in a nanosecond plasma discharge

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.

The application of physics-informed neural networks to hydrodynamic voltammetry.

Electrochemical problems are widely studied in flowing systems since the latter offer improved sensitivity notably for electro-analysis and the possibility of steady-state measurements for fundamental studies even with macro-electrodes. We report the exploratory use of Physics-Informed Neural Networks (PINNs) as potentially simpler, and easier way to implement alternatives to finite difference or finite element simulations to predict the effect of flow and electrode geometry on the currents observed in channel electrodes where the flow is constrained to a rectangular duct with the electrode embedded flush with the wall of the cell. Several problems are addressed including the evaluation of the transport limited current at a micro channel electrode, the transport of material between two adjacent electrodes in a channel flow and the response of an electrode where the electrode reaction follows a preceding chemical reaction. The approach is shown to give quantitative agreement in the limits for which existing solutions are known whilst offering predictions for the case of the previously unexplored CE reaction at a micro channel electrode.

Cost evaluation and sensitivity analysis of the alkaline zinc-iron flow battery system for large-scale energy storage applications

Alkaline zinc-iron flow batteries attract great interest for remarkable energy density, high safety, environmentally benign. However, comprehensive cost evaluation and sensitivity analysis of this technology are still absent. In this work, a cost model for a 0.1 MW/0.8 MWh alkaline zinc-iron flow battery system is presented, and a capital cost under the U.S. Department of Energy's target cost of 150 $ per kWh is achieved. Besides, the effects of electrode geometry, operating conditions, and membrane types on the system cost are investigated. The results illustrate that a low flow rate and thin electrodes with high porosity contribute to low capital costs under low current densities. Furthermore, the porous polybenzimidazole (PBI) membrane is more cost-effective than Nafion 212 membrane. This work provides an integrated estimation for the zinc-iron flow battery system, demonstrating its tremendous potential for grid-level energy storage applications.

Investigation of the Effects of Electrode Geometry on the Performance of C4D Sensor with Radial Configuration.

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°.

Finite Element Method Study of Nanostructured Metal Oxide Based on NiO for Nonenzymatic Urea Sensors

Urea electrooxidation has attracted increasing attention because urea is an essential biomarker for diagnosing kidney conditions. Most urea sensors are based on the enzyme; however, enzyme-based sensors have a moderately complicated assembling method [1] due to poor stability. Different from the bulk diffusion of urea in the enzymatic urea oxidation [2], the nonenzymatic urea oxidation has reactions between the reductive and oxidative at the electrode surface [3]. Moreover, in order to use nonenzymatic urea sensors in a biomedical application area, high conductivity and catalytic activities are required. Therefore, a study of nonenzymatic urea sensor on a nanostructured electrode is of substantial interest.For urea detection, various metal oxides, such as ZnO [4], CuO [5], and NiO [6], have been broadly proposed. Practically, NiO catalysts were studied extensively for urea electrooxidation due to successful long-term operation [7]. Typical nonenzymatic catalysts for urea electrooxidation mainly focused on designing new nanostructures and maximizing their catalytic ability. However, quantitative models integrating the physical, chemical, and geometrical design properties still need improvement to develop sensor devices. The urea reaction occurs on the surface of nanostructured metal oxide. Thus, the effect of electrode geometry on the electrochemical reactions is motivated to explore urea sensors application.In the present study, we studied three different NiO structures such as nanorods, nanoflakes, and nanoparticles, for the nonenzymatic electrochemical sensor. Additionally, we developed a new analytical model to understand the nonenzymatic urea sensor using the finite element method. To further adjust the model, the morphology and the composition of the NiO catalysts were investigated using transmission electron microscopy, scanning electron microscopy, and X-ray photoelectron spectroscopy. The NiO catalysts showed remarkable electrochemical achievement with acceptable linear sensitivity and selectivity to urea electrooxidation. Comprehensive information of the modeling concerning NiO as a catalyst in the nonenzymatic urea sensor will be given.References FATEMA, Kamrun Nahar, et al. “New Design of Active Material Based on YInWO4-G-SiO2 for a Urea Sensor and High Performance for Nonenzymatic Electrical Sensitivity.” ACS Biomaterials Science & Engineering, 2020.Debata, Suryakanti, et al. "Design of CdV2O4-V6O13 micro flowers for non-enzymatic electrochemical detection of urea." In AIP Conference Proceedings, vol. 2115, no. 1, p. 030058. AIP Publishing LLC, 2019.YOON, Jaesik, et al. “Silver-Nanoparticle-Decorated NiOOH Nanorods for Electrocatalytic Urea Sensing.” ACS Applied Nano Materials, 2020, 3.8: 7651-7658.YOON, Jaesik, et al. “Ag/ZnO Catalysts with Different ZnO Nanostructures for Non‐enzymatic Detection of Urea.” Electroanalysis, 2019, 31.1: 17-21.Goda, M. A., et al. “Enhanced Electrocatalytic Oxidation of Urea at CuOx-NiOx Nanoparticle-Based Binary Catalyst Modified Polyaniline/GC Electrodes.” Journal of The Electrochemical Society, 2020 167(6), 064522.Tyagi, Manisha, et al. "NiO nanoparticle-based urea biosensor." Biosensors and Bioelectronics 2013, 41:110-115.BARAKAT, Nasser AM, et al. “Influence of nitrogen doping on the electrocatalytic activity of Ni-incorporated carbon nanofibers toward urea oxidation.” International Journal of Hydrogen Energy, 2017, 42.34: 21741-21750.

Single Stage Reactors for Electrifying Bio-Methanation

As a combined solution for minimizing CO2 emissions and meeting global energy demands, upgrading CO2 to produce renewable natural gas is an emerging technology to utilize and store renewable energy. When this process is performed by efficient and product selective biocatalysts, conventional and energy intense thermal methanation technologies can be replaced by bio-methanation technology. The bio-methanogenesis process is typically performed with hydrogen produced externally in electrolyzers, but is severely limited by poor mass transport and solubility issues of molecular hydrogen. A system where both electrolysis and microbial conversion are combined in a single reactor helps overcome these problems. However, despite the outstanding opportunities of in-situ electro-bio-methanogenesis, there are challenges of electrified bioreactors that must be overcome, including microbial tolerance and enhancing the kinetics of in-situ hydrogen evolution. Thus, developments to achieve the balance between both biochemical and electrochemical requirements will allow these reactors to achieve optimum performance. The developments include maintaining physiological pH, effective separation of anode and cathode, improving charge transfer kinetics and reducing internal resistance.We have used our advanced manufacturing capabilities to design and fabricate components for developing electro-bioreactors from 0.1 W scale in sluggish H-cells to MW scale stacks of flow cell CO2 electrolyzers. This allows us to achieve the balance between both biochemical and electrochemical requirements mentioned above. In this study, we show how utilization of high surface area porous 3D electrodes can support maintaining biocompatible conditions near the vicinity of hydrogen evolving electrode at effective rates of electrolysis, while improving both efficiency and productivity of microbial methanogenesis. We have conducted studies to understand the effect of electrode geometry and surface area on energy efficiency and microbial health. Finally, we demonstrate the ability to produce pipeline-quality methane (>97% CH4) from CO2 for an extended period.

Effects of Fractal Electrode Geometry in Charge Injection Capacity of TiN Microelectrodes.

Microelectrodes are basic tools for investigating small-scale brain dynamics. Noble metals such as gold (Au), platinum (Pt), and iridium oxide (IrOx) have been used as an electrode material because of their biocompatibility and good charge transfer capability. Their main charge transfer mechanism is the Faradaic process with redox reactions. Unfortunately, the decrease in electrode size accelerates the irreversible electrochemical dissolution during electrical stimulation due to increased current density. The dissolution can be prevented by alternating the electrode material to capacitive charge injection materials such as titanium nitride (TiN). However, electrical conductivity of TiN is relatively lower than the noble metals, which results in a lower charge injection capability. Therefore, there is a need to increase the charge injection limit of TiN electrodes for a high-performing neurostimulation. Our previous work suggested that the Vicseck fractal design can increase the charge injection limit of the microelectrodes. In this work, the effects of the fractal design in capacitive charge injection material were experimentally investigated by using TiN microelectrodes with circular and fractal designs. We measured the cyclic voltammetry, electrochemical impedance spectroscopy, and voltage transients. In addition, the charge injection limits of theses microelectrodes were estimated to quantify the effects of planar geometry on TiN microelectrodes. Despite our previous results showing superior charge injection capability of fractal Pt microelectrodes, the TiN showed no significant improvements due to the fractal geometry. This may be because the increase in charge injection capability of fractal microelectrodes is due to increased Faradaic charge injection process, which is minimized for TiN materials. Thus, our data suggests that the material as well as the geometry of the microelectrodes play key roles in optimizing stimulation microelectrode performance.Clinical relevance-As with the Faradaic charge injection-dominant materials, the capacitive charge injection materials could also benefit from additional investigation to fully characterize effects of electrode geometry for improved neurostimulation performance.