Effect Of Electrode Microstructure Research Articles

Numerical modeling of ion transport and adsorption in porous media: A pore-scale study for capacitive deionization desalination

A pore-scale model is presented to simulate the dynamic ion transport and adsorption processes in porous electrodes used for capacitive deionization (CDI). The Stokes equation governing water flow is solved using the lattice Boltzmann method and Nernst-Planck equation describing ion transport is solved using the finite volume method. The ion adsorption process is considered at the surface of carbon electrodes. After validation against analytical solutions and published results, the model is used to study the coupled water flow, ion transport and adsorption in both two-dimensional and three-dimensional porous CDI electrodes at the pore scale. The effect of electrode microstructure, electrical potential and flow velocity on the adsorption processes is quantitatively investigated, and the relative importance of various parameters is determined. The presented model can be a powerful numerical tool to quantitatively analyze ion transport and adsorption in porous electrodes, and may provide useful information for the design and optimization of CDI electrodes and operating conditions for desired desalination efficiency, water throughput and cost.

Lattice Boltzmann Simulation of Ion and Electron Transport in Lithium Ion Battery Porous Electrode During Discharge Process

A two dimensional lattice Boltzmann simulation of ion and electron transport within lithium ion battery porous electrode was presented in this study. In the simulation, a LiyC6|LixMn2O4 rocking-chair rechargeable battery structure was employed and the electrode was composed of irregular particles. The effects of electrode micro-structure on the local lithium concentration distribution, electric potential and macroscopic discharge performance were investigated. Results show that smaller particles were lithiated and delithiated at a higher rate during the discharge process. The lithium depletion in anode and the lithium accumulation in cathode were enhanced in the edges and corners for large irregular particles. The particles with lower lithium concentration produced higher local electric potential in the anode. For discharge performance, the porosity of the electrode had significant influence on the achievable capacity.

GPU-Accelerated Pore-Scale Transport Resolved Model for Flow-Assisted Battery Design

Redox flow batteries (RFBs) have emerged as grid-scale energy storage technology used in intermittent renewable energy resource applications due to their decoupled power and energy sizing and long life cycles. However, redox flow batteries suffer from low energy and power densities, which may be resolved by improving electrode design. As such, gaining insight into the effect of the electrode microstructure by using computer simulations is paramount in improving RFB performance. Such design optimization would not be possible through experimental procedure due to cost, time, or availability of materials.Existing volume-averaged models treat the electrode/electrolyte matrix as a homogenous medium of uniform porosity. By contrast, we have developed a pore-scale simulation that distinctly accounts for the separate electrode/electrolyte phases. Our model requires no simplification or assumptions regarding the electrode morphology, and enables us to carry out detailed studies into the effects of the precise electrode microstructure with unprecedented fidelity. A comparison between the two approaches is shown in plots of electrode overpotential in a smooth distribution of a volume averaged model (Fig. 1a) and in a detailed 3D surface distribution of our pore-scale model (Fig. 1b). To simulate our system we use realistic carbon fiber geometry as an input to our simulation. X-ray computed tomography images of carbon fibers (Fig. 2a) are segmented in 2D images and then stacked as a 3D image (Fig. 2b) to create the virtual volume (Fig. 2c) from which we may take a selection of desired porosity. This model may be extended to the treatment of many different flow battery system configurations including all Vanadium, Vanadium/Bromide, and other novel VRB systems.The primary drawback of a pore-scale approach is the high computational resources required. To overcome this challenge, in lieu of a traditional implementation with Message Passing Interface, which uses many central processing units to divide the computational effort of a simulation, as an alternative we employ the use of Graphics Processing Units (GPUs) which have been shown well suited for solving problems in computational fluid dynamics.In this work we present an application using GPUs to increase the speedup of our simulations in order to simulate realistic length and time scales not possible using traditional methods (Fig. 3). Computational techniques for efficiently simulating RFB systems are examined along with the effect of domain size and number of processors on scalability and speedup.

Effect of electrode microstructure on the sensitivity and response time of potentiometric NOx sensors based on stabilized-zirconia and La5/3Sr1/3NiO4–YSZ sensing electrode

The microstructure of a potentiometric NOx sensor’s electrodes considerably affects the sensor performance. In the present paper, nanometric La5/3Sr1/3NiO4 and different YSZ concentrations (5wt%, 10wt% and 20wt%) composite powders were synthesized with microwave-assisted complex-gel auto-combustion method for fabricating NOx sensor electrodes. The sensor electrodes were sintered at 1000°C, 1100°C and 1200°C respectively to obtain a variety of electrode morphology. The electrode porosity decreased with the increased YSZ addition. The sintering temperatures have effect on the porosity and distribution. All the sensors could produce a steady-state response voltage at the lower temperatures. Sensor fabricated with 10wt% YSZ additional composites and sintered at 1000°C exhibited the biggest response to NO at 400°C.

Microstructure and reactivity effects on the performance of Nd2NiO4+δ oxygen electrode on Ce0.9Gd0.1O1.95 electrolyte

Abstract The effect of electrode microstructure on the electrochemical behavior of symmetrical Nd2NiO4+δ/Ce0.9Gd0.1O1.95/Nd2NiO4+δ cells was studied by Electrochemical Impedance Spectroscopy as a function of temperature (500

Effects of Electrode Microstructure on Intermediate Temperature Solid Oxide Fuel Cell Performance

Abstract In this study, the effects of electrode microstructure and electrolyte parameters on intermediate temperature solid oxide fuel cell (ITSOFC) performance were investigated using a one-dimensional solid oxide fuel cell model from the Pacific Northwest National Laboratory (PNNL). The activation overpotential was investigated through the exchange current density term, which is dependent on the cathode activation energy, the cathode porosity, and the pore size and grain size at the cathode triple phase boundary. The cathode pore size, grain size, and porosity were not integrated in the PNNL model, therefore, an analytical solution for exchange current density from Deng and Petric (2005, “Geometric Modeling of the Triple-Phase Boundary in Solid Oxide Fuel Cells,” J. Power Sources, 140, pp. 297–303) was utilized to optimize their effects on performance. Through parametric evaluation and optimization of the electrode microstructure parameters, the activation overpotential was decreased by 29% and the overall ITSOFC maximum power density was increased by almost 400% from the benchmark PNNL case. The effects and importance of electrode microstructure parameters on ITSOFC performance were defined. Optimization of such parameters will be the key in creating viable ITSOFC systems. Although this was deemed successful for this project, future research should be focused on numerically quantifying and modeling the electrode microstructure in two- and three-dimensions for more accurate results, as the electrode microstructure may be highly multidimensional in nature.

Effect of Electrode Microstructure through Particle-Scale Modeling of LiMn2O4 Electrode

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Effect of electrode microstructure on gas-phase diffusion in solid oxide fuel cells

The relation between electrode microstructure and gas diffusion has been investigated with different morphologies of Pt electrodes by using AC impedance techniques. The measurements were carried out at temperatures of 873–1273 K and oxygen partial pressure (P O 2 ) of 0.01–1 atm. Gas-phase diffusion was observed only for high-performance electrodes at the high-temperature (1073–1273 K) and low-oxygen-partial-pressure regions (<0.1 atm P O 2 ). Considering the physical and electrochemical characteristics of impedance arcs, it was found that the arc at the frequency of below 1 Hz was related to gas conversion resistance, while the arc at the frequency of around 10 Hz represented pore diffusion resistance through the current-collecting part. For a thick electrode with a low porosity, however, gas diffusion resistance through pores of an electrode was observed at a frequency of around 100 Hz. From the results of a comparison of electrode performances with different electrode microstructures, electrochemical reaction sites (ERS) are supposed to be located at the peripheral line of Pt and YSZ as well as the Pt/YSZ interfaces where reaction gas can easily diffuse.

Characteristics of cathodic polarization at Pt/YSZ interface without the effect of electrode microstructure

The characteristics of cathodic polarization at the Pt/yttria stabilized zirconia (YSZ) interface have been evaluated with different electrode microstructures by ac impedance analysis. The measurements were carried out at the temperatures of 873–1273 K and oxygen partial pressure ( P O 2 ) in the range of 0.01–1 atm. From the results of impedance analysis, it was found that gas phase diffusion can be involved in two different ways, such as boundary-layer diffusion and pore diffusion. When the gas phase diffusion was effectively eliminated from the total electrode resistance ( R el), we observed the same dependences of temperature and oxygen partial pressure regardless of their different electrode microstructures. In the high temperature (1073–1273 K) and low oxygen partial pressure regions (<0.01 atm P O 2 ), the cathode reactions included two major reactions: gas phase diffusion and direct adsorption reaction. In direct adsorption reaction oxygen molecules are directly adsorbed from the gas phase and dissociate on oxygen vacancies, which are located at the triple phase boundaries (TPB). In the low temperature (<973 K) and high oxygen partial pressure region (∼1 atm P O 2 ), the cathode reaction is dominated by the dissociation of oxygen molecules at the Pt/YSZ interface.

The Effect of Electrode Microstructure on Cathodic Polarization

The Effect of Electrode Microstructure on Cathodic Polarization

Effect of electrode microstructure on leakage current in lead–lanthanum–zirconate–titanate multilayer capacitors

Lead–lanthanum–zirconate–titanate (PLZT) multilayer capacitors involving platinum bottom electrodes have been fabricated on a silicon nitride/silicon (SiN/Si) substrate system. Leakage current characteristics show strong dependence on the processing temperature of the bottom electrode. A drop in leakage current by five orders of magnitude has been observed for capacitor with platinum electrode deposited at room temperature. Scanning tunneling microscopy (STM) studies reveal significant differences in the microstructure of platinum films deposited at different substrate temperatures. Based on STM results, a correlation between the microstructure of the bottom electrode, space layer at PLZT/Pt interface, and the nucleation of PLZT has been suggested to explain this new observation.