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The flow field is a crucial component of proton exchange membrane electrolyzer cell (PEMEC), significantly impacting cell performance and distribution uniformity. This study introduces a modified flow field structure, named the Modified Interdigitated-jet hole Flow Field (MIJFF), based on the interdigitated-jet hole flow field with added under-rib holes. The goal is to increase water supply to the porous electrode and facilitate gas discharge from the diffusion layer, thereby improving under-rib mass transfer and enhancing the uniformity of current density. Three control groups are compared: a single-path serpentine flow field, an interdigitated flow field, and an interdigitated-jet hole flow field. A two-phase, muti-dimensional model is developed to simulate different flow field structures, which are then validated through the experimental approaches. Results indicate that the MIJFF, with added under-rib holes, can better improve under-rib mass transfer, provide water supply and allow timely gas expulsion, avoiding unevenness and performance degradation due to local gas accumulation. Furthermore, the introduction of under-rib holes further increases vertical flow velocity. Compared to the control groups, applying MIJFF to the anode improves liquid saturation, current density and temperature distribution uniformity by 19.65 %, 36.24 % and 37.64 %, respectively, while increasing vertical flow velocity in the channel by 60.6 %. • Comprehensive 3D two-phase multi-channel PEM electrolyzer model. • A modified flow field is proposed with the introduction of under-rib holes. • The MIJFF improves mass transfer and increases vertical flow rate by 60.6 %. • The MIJFF enhances current density uniformity by 36.24 %. [ABSTRACT FROM AUTHOR]

The mesoporous structure of the porous carbon electrodes could promote the in-pore diffusion of electrolyte ions. However, the effect of large mesopores with pore sizes larger than 20 nm in the microporous carbons on the diffusion of different electrolyte ions remains unclear. Herein, porous carbon electrodes with mesopores sizes of 23 nm and 40 nm, respectively, are prepared using the ZnO as a hard template. The electrochemical behavior of porous carbon electrodes with large mesopores and microporous carbon electrodes in different sulfate electrolytes are studied and compared. Electrochemical impedance spectroscopy (EIS) tests demonstrate that the wide and short diffusion path provided by large mesopores can reduce the hindrance of multivalent metal cations and SO 4 2−, thus significantly improving the diffusion efficiency of the multivalent metal sulfate cations. Due to the small size and low valence of monovalent metal ions, it is difficult for large mesopores to promote the diffusion of monovalent metal sulfate ions. Therefore, the large mesopores have little impact on the diffusion of monovalent metal ions, whereas they significantly enhance the diffusion of multivalent metal ions. [Display omitted] • Mesoporous channels are built by ZnO hard templates. • Mesoporous channels significantly improve the rate performance. • The effect of the addition of mesoporous channels on electrochemical behavior. • The short diffusion path is favorable for ion diffusion. [ABSTRACT FROM AUTHOR]

Bubble management in electrocatalysis is very important for reducing overpotential of hydrogen evolution reaction. In this paper, a pore structure model of an aligned porous electrode is established, and the effect of pore size and pore length on bubble transport is studied using the phase field method. The entire transport process of the bubble can be divided into two stages: the motion of bubbles inside pores and the detachment from the pores. The results show that increasing pore size can significantly increase the velocity of the bubble within the pore. Regarding the detachment process of bubble from pores, the movement velocity of the bubble is accelerated due to the different Laplace pressure of the bubble in the inner and outer parts of the pore. However, the pressure gradient decreases with an increase in pore size, resulting in weakened acceleration effect. These two effects are contradictory, and the final effect of the pore size on the bubble transport is related to the pore length. The shorter pore length and smaller pore size strengthen the promotion of the detachment process to bubble transport. In addition, the simulation results provide explanations for electrochemical measurements and bubble visualizations. • The bubble diameter is affected by the pore size and thickness of the electrode. • The transport process of bubbles is studied by using the phase field method. • The simulation results explain the phenomena observed in the experiment. [ABSTRACT FROM AUTHOR]

The Electrochemical impedance spectroscopy (EIS) of three novel cathode channels designs square, boot, and triangular for open cathode polymer electrolyte cathode fuel cell stacks are analyzed. Fundamental mechanisms such as oxygen reduction reaction, proton conductivity, bulk resistance of stack, capacitance and structure features of the porous carbon electrode etc. are investigated with the help of Nyquist/Bode plots and Randles circuit. Operational parameters including airflow rate, current, H 2 gas condition (humidified and dry), and stack temperature are studied focused on understanding the trend of high and low frequency resistance. The minimum resistance and temperature mapping for cross-section designs at different operating conditions is utilized for parametric optimization. Overall, it is recommended to operate the stacks at minimum resistance obtained just before the peak power density and its corresponding temperature ∼40 ° C. Finally, a data-driven hybrid model integrating EIS and artificial intelligence is presented with root mean square error of ∼0.98. • EIS analysis of different cross-section cathode channels is carried out. • OC-PEMFC stack thermal mapping is studied to understand interdependent parameters. • Lowest frequency resistance is utilized for parametric optimization. • Hybrid EIS-AI random forest regression model is used to understand stack operation. [ABSTRACT FROM AUTHOR]

[Display omitted] • Porous Si particles were synthesized from Al–Si alloy powder through acid etching. • Silicide formation and pore refinement contribute to excellent rate characteristics. • Optimized porous Si electrodes exhibited high capacity and cycle characteristics. • Proposed method demonstrates scalability on an industrial scale. [ABSTRACT FROM AUTHOR]

We present a Hybrid Multiphase Porous Electrode Theory (Hybrid-MPET) model that accurately predicts the performance of Medtronic's implantable medical device battery lithium/carbon monofluoride (C F x) - silver vanadium oxide (SVO) under both low-rate background monitoring and high-rate pulsing currents. The distinct properties of multiple active materials are reflected by parameterizing their thermodynamics, kinetics, and mass transport properties separately. Diffusion limitations of Li + in SVO are used to explain cell voltage transient behavior during pulse and post-pulse relaxation. We also introduce change in cathode electronic conductivity, Li metal anode surface morphology, and film resistance buildup to capture evolution of cell internal resistance throughout multi-year electrical tests. We share our insights on how the Li + redistribution process between active materials can restore pulse capability of the hybrid electrode, allow C F x to indirectly contribute to capacity release during pulsing, and affect the operation protocols and design principles of batteries with other hybrid electrodes. We also discuss additional complexities in porous electrode model parameterization and electrochemical characterization techniques due to parallel reactions and solid diffusion pathways across active materials. We hope our models can complement future experimental research and accelerate development of multi-active material electrodes with targeted performance. • Hybrid-MPET model of Medtronic's high-rate Li/CF x -SVO battery is presented. • Separate material properties, diffusion limitation, and aging are accounted for. • Model prediction accuracy is validated on large battery dataset. • Cell pulse capability restoration is explained by Li＋ redistribution across materials. • Li＋ redistribution impact on general cell operation and design principles are discussed. [ABSTRACT FROM AUTHOR]

In this work, a dual-templating pyrolysis strategy is successfully developed to synthesize a highly crumpled graphene (N-TRPG-800). The achievement of the graphene is based on the carbonization of the d (+)-glucosamine hydrochloride and the spatial confinement effect of the graphitic carbon nitride (g-C 3 N 4) in the presence of zinc nanoparticles (Zn NPs). During the pyrolysis process, the d (+)-glucosamine hydrochloride first polymerizes into the layers of g-C 3 N 4 , which is derived from melamine. Afterwards, a further increase in pyrolysis temperature leads to the decomposition of g-C 3 N 4 and the generation of reducing NH 3 gas, which eventually resulting in the formation of 2D ultrathin structure and high heteroatoms doping degree. Simultaneously, the volatilization of the Zn NPs also plays a key role in the pore formation and the hierarchical structure generation. As a result, the as-synthesized graphene sheets simultaneously possesses hierarchical porous structure, high heteroatoms-doped degree, and large specific surface area (506 m2 g−1). Electrochemical measurements show that the N-TRPG-800 exhibits an ultrahigh supercapacitance of 471 F g−1 at 0.2 A g−1 in a three-electrode mode, approaching the theoretical capacitance of 550 F g−1 of graphene, which is superior to that of the state-of-the-art heteroatom-doped porous carbons in literature. A facile dual-templating strategy has been developed to synthesize a highly crumpled graphene sheets with hierarchical structure, high heteroatoms-doping degree, large surface area, and high pore volumes, which exhibits good supercapacitive performance as an electrode material for supercapacitors. [Display omitted] • A dual-templating strategy was developed to synthesize hierarchically porous graphene. • The sample has porous structure, high heteroatom-doping level, and large surface area. • The optimal graphene displays an ultrahigh supercapacitance of 471 F g−1 at 0.2 A g−1 • The formation process of the porous graphene was elucidated and explained in detailed. [ABSTRACT FROM AUTHOR]

The supercooled water characteristics in porous electrodes, affect the proton exchange membrane fuel cell (PEMFC) cold starting. This study analyzed the uneven substrate geometry, specifically, the influence of the contact angle and substrate angle on the solidification nucleation rate. For a given temperature, the nucleation rate decreases with increasing contact angle, with less effect as the contact angle exceeds 150°. Experiments observing the freezing of supercooled water in a detached catalyst layer confirmed this result. The simulation also showed that the nucleation rate decreases exponentially with increasing substrate angle: at the 15 K supercooling, with substrate angles increasing by 20°, nucleation rates have a difference of about 10−11 times. Thus, the effect of the substrate geometry cannot be ignored during the freezing of supercooled water in a porous electrode. • A new method to calculate supercooled water icing process in the pore structure. • The substrate angle affects strongly in supercooled water simulation. • Nucleation rate is influenced less at large contact angles. [ABSTRACT FROM AUTHOR]

Designing porous and flexible electrodes with excellent electrochemical properties is crucial to fabricate high-performance flexible supercapacitors. Conductive polymer-based electrospun fibers are expected to be an ideal material for constructing flexible electrodes due to the enormous specific surface area, unique pore structure and inherent flexibility. However, the exploration of such electrospun fibers with facile preparation methods and high areal capacitance remains challenging. Herein, a novel polyetherimide@polyaniline core-shell fibrous membranes (PEI@PANI CFMs) is fabricated via simply coaxial electrospinning and 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) secondary doping. With the aid of polyetherimide, highly concentrated emeraldine base polyaniline (EB-PANI) can be perfectly wrapped on the surface of fibers without any spinning assistants, ensuring the well-developed pore structures, superior hydrophilicity, good electrical conductivity and outstanding mechanical flexibility. Benefiting from the synergistic effect of structure and constituents, such flexible PEI@PANI CFMs as electrode materials can provide more accessible electrochemical active sites and decrease the ion diffusion resistance. Therefore, the PEI@PANI CFMs present outstanding areal capacitance of 1159.9 mF cm−2 and remarkable energy density of 46.91 μW h cm−2 in the electrodes and symmetric supercapacitors, demonstrating great potential for applications in flexible energy storage field. This fabrication strategy provides a simple and practicable way to manufacture polyaniline-based fibrous membranes for high-performance flexible electrode materials. [Display omitted] • PEI@PANI CFMs were firstly developed by coaxial electrospinning with high density PANI solution. • Continuous PANI shell without spinning assistants enabled high redox activity after AMPS doping. • PEI@PANI CFMs showed unique 3D network pore structure, superior hydrophilicity and flexibility. • PEI@PANI CFMs as electrode exhibited 1159.9 mF cm−2 area specific capacitance at 1 mA cm−2. • The symmetric device delivered remarkable energy density of 46.91 μW h cm−2 at 0.23 mW cm−2 [ABSTRACT FROM AUTHOR]

The lattice Boltzmann method (LBM) plays an important role in the study of the internal flow behavior at the pore-scale inside the electrodes of solid oxide fuel cells (SOFCs). Porosity, tortuosity, and particle size have a remarkable effect on gas transport and electrocatalytic processes, determining the performance of cells when SOFCs are applied in electric power generation, energy storage systems, and industrial production in recent years. However, these pore-scale transport progresses are not well characterized in the numerical studies of conventional computational fluid dynamics (CFD), thus modeling with LBM at the pore-scale is an effective tool for simulating gas transport and electrochemical reactions in electrodes. It overcomes the drawbacks of experimental techniques that do not characterize these processes accurately enough and detail the distribution of important variables. In this review, the methodology and process of electrode pore-scale modeling are presented, along with the application and current studies of LBM for diffusion, electrochemical reactions, and ion migration in SOFC porous electrodes. Important results are discussed. Finally, future perspectives on pore-scale studies of porous electrodes are given. This in-depth review intends to provide ideas for the development and further application of LBM in porous SOFC electrodes. • Different electrode reconstruction methods are classified into six categories. • The modeling process and application fields of LB method are reviewed. • A detailed transfer process analysis of SOFC inside using the LB method is presented. • The future prospects of LB modeling and reconstruction methods are discussed. [ABSTRACT FROM AUTHOR]

The design optimization of lithium-ion battery (LIB) electrode microstructures is key to improving the rate capability of the batteries. In this work, two-dimensional heterogeneous electrodes with different microstructures, which are generated based on particle packing model proposed in our previous work, are investigated for their rate performance. In order to quantify the influence of the tortuosity of the microstructure in a straightforward manner, a topological tessellation-based method is proposed to estimate the tortuosity. As an example, the rate capability of NMC111 electrode is studied with different microstructures. Specifically, we analyze the two competing factors that influence performance of electrodes: the solid-state Li diffusion in particles and Li diffusion the pore phase. The results show that for the electrodes with the same particle size and different porosity, the tortuosity is the key to the rate performance. For the electrodes with the same porosity and different particle sizes, the diffusion of Li ions in the particles has the greatest impact on the rate performance. Based on the above study, gradient electrodes are designed with different particle sizes and porosity compositions. The results show that better performance can be achieved through gradient designs for different usage scenarios. [Display omitted] • The heterogeneous electrodes with different microstructures are generated. • A new method for tortuosity estimation of porous structures is proposed. • Two competing factors that influence performance of electrodes were analyzed. • The gradient electrodes with well performance are designed. [ABSTRACT FROM AUTHOR]

We report on the exploration of the operational boundaries of tubular proton ceramic electrochemical reactors with BaZr 0.8 Ce 0.1 Y 0.1 O 3-δ (BZCY81) electrolyte and Ni-BCZY cermet electrodes under DC current, with the objective to identify and parameterize the processes that limit the performance during operation at high current densities. Electrochemical impedance spectroscopy (EIS), distribution of relaxation time analysis, voltammetry combined with EIS, and gas chromatographic analysis of gas conversion reveal distinct regions of operation, characterized by different polarization resistances and Faraday efficiencies. The results show that the performance of the cell at high current densities is limited by gas diffusivity in the porous electrode, onset of steam electrolysis, and consequent dehydration and p-type electronic leakage conduction in the electrolyte. These limitations are considered representative of actual cell performance under restrictive operational conditions and key to commercialization of proton ceramic electrochemical reactors for sustainable hydrogen production. • EIS, DRT, voltammetry, and gas chromatography analysis of tubular proton ceramics. • Different operational regions identify under DC operation. • Gas diffusivity, onset of steam electrolysis, and electronic conduction. • Indication of enforced p-type conductivity under reducing conditions. [ABSTRACT FROM AUTHOR]

Magnesium oxide templated porous carbon (MgOC) is a promising material as an enzyme electrode platform. Herein, a flavin adenine dinucleotide-dependent glucose dehydrogenase (FAD-GDH) and thionine were immobilized using a crosslinker, and the applicability of MgOC with various pore sizes as a platform was investigated. Among the pores of MgOC, the novel designed FAD-GDH/thionine network generated a 1.1 mA cm−2 catalytic current at 100 nm pore size, demonstrating a significantly improved glucose supply and a thin redox composite layer was formed within the nanostructured material. At low loading, the catalytic current is independent of the pore size; however, at high loading, a varied catalytic current is achieved for the different MgOC pore sizes. Further, the stability was improved of porous platform compared to the glassy carbon (GC) electrode. Additionally, a glucose/O 2 biofuel cell is constructed with FAD-GDH/thionine on porous MgOC and non-porous GC as an anode, and mediated bilirubin oxidase as a cathode. A remarkably high electricity generation efficiency (0.23 mW cm−2 μg−1 of FAD-GDH) is shown on a porous electrode platform than non-porous and a previously reported immobilized FAD-GDH-based anode. These results demonstrate the potential of porous MgOC as an anode for a novel FAD-GDH/thionine network toward electricity generation. • Effectively immobilized FAD-GDH and thionine via crosslinker on porous electrode platform. • Literature focuses on the effects of pore size and tuning of various loadings of redox network. • The porous electrode promotes higher performance and stability than non-porous electrode. • Redox network/porous electrode platform identified as an anode for highest power efficiency. [ABSTRACT FROM AUTHOR]

Commercialized implementations of anion exchange membrane water electrolysis (AEMWE) require stable operation at high current density. To achieve this, ohmic, electrochemical and concentration polarizations are supposed to be exceedingly suppressed. Among all crucial materials, porous electrodes with catalyst coatings extensively affect the above polarizations, which are highly sensitive to specific mechanical pressure for cell assembly. However, the imposed mechanical pressure and its effects on cell performance are rarely reported in AEMWE cells. Here, quantitative characterizations of mechanical pressure and its effects on i) physical properties of catalyst coated electrodes and ii) corresponding single-cell performance are comprehensively investigated. First, the imposed mechanical pressure on membrane electrode assembly (MEA) is controlled by different total thickness gaps between anode/cathode and poly-tetra-fluoroethylene (PTFE) gaskets (Δd = 0, 100, 200, 300 μm). Second, the above resulted distributions of mechanical pressure are quantitatively studied by a mechanical pressure tracking method. Third, the influence of the mechanical pressure on the physical properties of the electrodes and cell performance are demonstrated. It is proved that the mechanical pressure of ca. 0.5 MPa is comprehensively beneficial for suppressing internal resistance (R Ω) and charge transfer resistance (R ct), with slightly increased mass diffusion resistance (R md) and hydrogen crossover. This study unveils the intrinsic effects of mechanical pressure on cell performance and provides critical insights into baseline benchmarking and single-cell even stack optimization. [Display omitted] • Dependence of cell mechanics, mass transport, wettability over contact pressure. • Electrochemical performance and internal resistance in the pressure range 0–6 MPa. • 0.5 MPa is optimal contact pressure to suppress R Ω /R ct and relieve R md. • Membrane thickness (≥50 μm) favorable to prevent membrane damage. • Pre-assembly and gradually increased mechanical pressure are esential for mounting. [ABSTRACT FROM AUTHOR]

A quantitative measurement of wettability between the porous electrode and the electrolyte in lithium-ion batteries can greatly improve our understanding of wetting behavior. Although the wetting balance method is widely used to measure the electrolyte transport rate in the porous electrodes, it suffers from several drawbacks and has limited accuracy. We here presented a combined experimental and theoretical investigation of the dynamics of electrolyte imbibition through electrodes. We proposed a novel method to accurately measure the electrolyte imbibition rate. Excellent agreement between the experimental data and the developed analytical model is obtained. The coefficient of penetrance (COP) and the solid permeability coefficient (SPC) are identified as important parameters, i.e., the electrolyte with higher COP value wets faster into an electrode, whereas for an electrolyte, the electrode with higher SPC value is more amenable to be impregnated. The effect of electrolyte salt concentration and electrolyte solvent has been studied in detail. The result suggests that increasing salt concentration adversely influences electrolyte wetting rate, whereas switching from EC-DEC system to EC-EMC system improves electrolyte wetting rate. In addition, for the electrolytes tested in this study, the imbibition into the uncalendered graphite anode is much faster than that into the uncalendered NMC532 cathode. Image 1 • Experimental and theoretical study on electrolyte imbibition through electrodes. • A novel method to accurately measure the electrolyte imbibition rate is proposed. • Increasing salt concentration adversely influences electrolyte wetting rate. • Switching from EC-DEC system to EC-EMC system improves electrolyte wetting rate. • Imbibition into the graphite anode is much faster than that into the NMC532 cathode. [ABSTRACT FROM AUTHOR]

This paper presents a methodology for understanding the phenomena that occur inside an actual electrode in a flow battery. We reconstruct the 3D microstructure of an electrode based on the real microstructure morphology to model the effect of mesopores on the electrode's electrochemical performance. In various reconstructed electrode structures, the presence of mesopores on carbon fibers has been shown to improve the performance compared to an electrode with no pores on the carbon fibers. This provides valuable insight for the preparation of a carbon electrode for a flow battery. In other words, the activity of carbon fibers with mesopores should be considered when preparing carbon paper, which will probably significantly improve the electrode performance. In addition, unlike the homogenous models in previous reports, simulation results showed the electrolyte flow and current density distribution in the pores and gap bridging pores. The pore interconnectivity and accessibility could be determined, which will provide significant guidance for electrode preparation to guarantee the utilization of a specific surface area. The approach proposed in this work sheds light on the phenomena inside the microstructure and provides detailed geometries for building the relationship between the structure and performance. • 3D microstructure of an actual electrode in a flow battery was reconstructed. • The previously existing homogenous models were improved. • The phenomena occurring inside an actual electrode was exhibited. • Carbon fibers constructing mesopores can improve electrode performance. • We provide valuable insight for the carbon electrode preparation. [ABSTRACT FROM AUTHOR]

At the core of redox flow reactors, the design of the flow field geometry –which distributes the liquid electrolyte through the porous electrodes– and the porous electrode microstructure –which provides surfaces for electrochemical reactions– determines the performance of the system. To date, these two components have been engineered in isolation and their interdependence, although critical, is largely overlooked. Here, we systematically investigate the interaction between state-of-the-art electrode microstructures (a paper and a cloth) and prevailing flow field geometries (flow through, serpentine and four variations of interdigitated). We employ a suite of microscopic, fluid dynamics, and electrochemical diagnostics to elucidate structure-property-performance relationships. We find that interdigitated flow fields in combination with paper electrodes –which features a uniform microstructure with unimodal pore size distribution– and flow-through configurations combined with cloth electrodes –which have a hierarchical microstructure with bimodal pore size distribution– provide the most favorable trade-off between hydraulic and electrochemical performance. Our analysis evidences the importance of carrying out the co-design of flow fields and electrode microstructures in tandem. [Display omitted] • Coupled influence of electrodes and flow field geometries on reactor performance. • Woven electrodes perform best with flow through geometries. • Non-woven electrodes perform best with interdigitated designs. • Flow fields and electrodes must be designed in tandem. [ABSTRACT FROM AUTHOR]

Fast charging of lithium-ion battery accounting for both charging time and battery degradation is key to modern electric vehicles. The challenges of fast charging optimization are (i) the high dimensionality of the space of possible charging protocols while the experiment budget is often limited; and (ii) the limited quantitative description of battery capacity fade mechanisms. This article proposes a data-driven multi-objective charging approach to minimize charging time while maximizing battery cycle life, in which a Chebyshev scalarization technique is used to transform the multi-objective optimization problem into a group of single objective problems, and a constrained Bayesian optimization (BO) is then utilized to effectively explore the parameter space of charging current as well as handle the constraint of charging voltage. Moreover, continuous-varied-current charging protocols are introduced into the proposed charging optimization approach by the utilization of polynomial expansion technique. The effectiveness of the proposed charging approach is demonstrated on a porous electrode theory-based battery simulator. The results show that the proposed constrained BO-based approach possesses superior charging performance and higher sample efficiency, compared with the state-of-the-art baselines including constrained optimization by linear approximations (COBYLA) and covariance matrix adaptation evolutionary strategy (CMA-ES). In addition, the increase in the charging performance and its uncertainty with an increasing number of degrees of freedom used in charging protocols is discussed. • A method is proposed to minimize charging time while maximizing battery lifetime. • A constrained Bayesian optimization is utilized to explore the parameter space. • The method is sample-efficient and does not require first-principles models. • The convergence rate of method in fast-charging optimization is quantified. [ABSTRACT FROM AUTHOR]

Solar-driven thermally regenerative electrochemical (STREC) device is a promising pathway for efficient green electricity production. The potential of this device is enabled by its full solar spectrum absorption, low fabrication cost, as well as scalability in design. We propose a continuous operation STREC device with its potential assessed by a comprehensive thermodynamic model-based analysis under various device designs, material choices, and operation conditions. The understanding was then used for the optimization and operation strategies of the proposed STREC device. The highest contribution to the total heat loss is found to be the radiative heat loss of the hot cell and the sensible heat loss due to electrolyte cycling, which is dictated by the temperature differences. Concentration overpotentials take the most proportion of the electrical loss induced by the inefficient mass transfer in porous electrodes. The results reveal that STREC device with the solar absorbing and reacting multifunctional electrode can reach a solar-to-electricity efficiency of 12.67% under an optimized condition which is promising to compete with existing solar electricity production technologies. The model developed in this study also offers a fast evaluation platform for material screening, device design, and operational condition optimization. • Solar driven thermally regenerative device for electricity production is proposed. • Detailed model is developed for comprehensive performance analysis of the STREC. • Conversion efficiency can achieve 12% with a relative Carnot efficiency of 90%. [ABSTRACT FROM AUTHOR]

High-performance metal supported solid oxide fuel cells (MS-SOFC) with an integrated high entropy alloy (HEA) internal reforming catalyst (IRC) are demonstrated for transportation applications using ethanol and methanol as fuels. Addition of the HEA IRC dramatically improves cell performance and stability when using ethanol/water blend fuel. Absence of carbon deposition predicted by thermodynamic calculations is confirmed by Raman spectroscopy analysis of posttest anodes. Optimal catalyst processing (deposition technique, loading, firing temperature) and cell operation conditions (flow rates, temperature, fuel compositions) are explored. Infiltrated HEA reforming catalyst provides a highly porous structure and low catalyst loading (6 mg cm−2). The designed structure and catalysts achieve small mass transport resistances in the fuel electrode (26.2 s m−1) and oxygen electrode (41.6 s m−1). The best ethanol concentration (60:40 v% ethanol: water) provides 0.83 W cm−1 at 700 °C, without carbon deposition. The ethanol-fueled MS-SOFC is operated for 500 h, including five thermal cycles. Cell evolution is similar to that reported previously for hydrogen fuel; nickel aggregation and chromia deposition were the major observed changes, and carbon formation can be avoided even after long-term operation. • ⁃Ethanol fueled MS-SOFCs reached a Pmax of 0.83 W cm−2 at 700 °C. • ⁃Addition of internal reforming HEA catalyst improves cell performance by 34%. • ⁃An HEA-anode based DIR-SOFC maintains stable and carbon resistant operation for 500 h. • ⁃Infiltrated porous electrodes demonstrate low mass transport resistance. [ABSTRACT FROM AUTHOR]

Reaction-rate distribution inside porous electrodes influences the overall performance of Li-ion batteries. The design parameters greatly determine the reaction-rate distribution. Therefore, investigating the relationship between the design parameters and the reaction-rate distribution is vital for improving battery performance. In the present paper, the reaction-rate and current-density distributions are analytically derived across porous electrodes at a short time scale with a Tafel approximation of the Butler-Volmer equation. Three sets of solutions are obtained based on applied currents and design parameters of porous electrodes. In all three sets of solutions, the effective ionic and electronic conductivities are found to shift the reaction from the current-collector to the separator interface. The applied current also influences the reaction-rate and current-density distribution. High C-rates increase the nonuniformity of reaction-rate distribution and the non-linearity of the current distribution. In contrast, low C-rates benefit the uniformity of reaction and linearity of current density. • Analytical investigation on reaction-rate and current distributions in porous electrode. • Three sets of solutions for different currents and electrode design parameters. • Effective conductivities and currents shift reaction-rate and current distributions. [ABSTRACT FROM AUTHOR]

Micro-supercapacitor (MSC) electrodes prepared by chemical vapor deposition (CVD) possess high potential as on-chip integrated micro-power sources for future microdevices. In this study, porous graphene/SiC composite films are grown using laser CVD. A double-layer specific capacitance up to 219.3 mF/cm2 is achieved at 10 mV/s, which is 26 times higher than those of the electrodes prepared by CVD with the same energy storage mechanism reported in literatures. After 20000 charge-discharge cycles at room temperature (20 °C) and variable temperatures (0–60 °C), the electrode exhibits robust cycling stability with 99.9% and 109.6% capacitance retention, respectively. Subsequently, it is revealed that the abundance of graphene on the SiC porous skeleton plays a key role in promoting the capacitance enhancement. The strong structure of SiC as well as the strong adhesion between graphene and SiC guarantee the excellent cycling stability. Evidently, the preparation of graphene/SiC porous composite films as MSC electrodes is a highly promising route for fabricating high-performance and reliable on-chip power sources for future miniaturized devices. • Graphene/SiC film with high electrochemical performance has been prepared. • The controlling mechanism of the performance have been revealed in detail. • This study provides a highly promising route for fabricating on-chip power source. [ABSTRACT FROM AUTHOR]

This study addresses the degradation mechanisms of porous fuel electrode from an electrode (Ni/YSZ) and an electrolyte (Ni/CGO)-supported cell operated for long-term in steam electrolysis mode. Using a nanobeam, spatially resolved X-ray fluorescence and X-ray absorption spectroscopy are combined to acquire high-resolution compositional maps and to probe intra-granular changes with the evolution of the Ni chemical state. This experimental work highlights oxidized states of nickel (i.e. NiO/Ni(OH) 2 species) in the case of Ni/CGO while for Ni/YSZ the chemical state is metallic. In both types of fuel electrodes, the Ni depletion occurs and the depletion length is reduced to around 1 μm in the case of Ni/CGO after 23,000 h in contrast to around 4 μm in the case of Ni/YSZ after 6100 h. In the case of Ni/CGO, the coating of Ni particles by the diffusion of Gd and Ce from the CGO contact layer prevents the Ni migration while in the case of Ni/YSZ the Ni migration is not suppressed. These results are in accordance with in-situ impedance data where the main difference observed between Ni/YSZ and Ni/CGO fuel electrodes is a deactivation of the fuel electrode as non-ohmic losses for Ni/YSZ in contrast to Ni/CGO. • Large 2D nano-X-ray Fluorescence maps with high spatial resolution. • Spatially resolved Ni K-edge nano-X-ray absorption near edge spectroscopy. • NI chemical state is metallic in Ni/YSZ and presence of oxidized species in Ni/CGO. • 4 μm Ni depletion in Ni/YSZ (6,100 h) and 1 μm in Ni/CGO (23,000 h). • Ni particles Coating by cerium and gadolinium in Ni/CGO prevents the Ni migration. [ABSTRACT FROM AUTHOR]

Aligned porous electrodes with different pore sizes and thicknesses are prepared by freezing casting method, and the effect of the electrode thickness and pore size on hydrogen evolution reaction (HER) performance and bubble removal capability are experimentally studied. The results show that the pore size and thickness of the aligned porous electrodes have a significant impact on the HER performance by affecting the electrochemical active surface area (ECSA) and bubble transport process. The influence of pore sizes and electrode thicknesses on HER performance are different with current density. In the region of low current density, the effect of electrode thickness on electrochemical performance is more significant than that of pore size. While at high current density pore size becomes a limiting factor for electrochemical performance. Additionally, the Δζ γ is proposed to evaluate the bubble removal capability, and a small Δζ γ indicates the good bubble removal efficiency. [Display omitted] • The thickness and pore size of aligned porous electrodes affect the HER performance. • The pore size is the limited factor affecting HER performance at high current density. • A method based on Tafel formula is proposed to evaluate the bubble removal capability of electrodes. [ABSTRACT FROM AUTHOR]

As a result of different extraction methods, CNCs bear different surface groups with different degrees of substitution (DS), which may affect the electrode properties when incorporated as the reinforcing template in conducting polymer electrodes. After depositing polypyrrole (PPy) electrodes with different CNCs as dopants, we found that the PPy/CNCs electrode structure and electrochemical performance were sensitive to the DS of CNCs sulfate groups, while variation in the DS of carboxylates did not have any significant effect. PPy/CNCs electrodes deposited with carboxylated CNCs and a low sulfate group DS showed a porous and interconnected structure, while PPy/CNCs electrodes deposited with carboxylated CNCs with a high sulfate DS had a dense structure. Higher areal capacitance, higher rate capability, and smaller resistance were achieved with PPy/CNCs electrodes deposited using CNCs bearing carboxylates and a low DS of sulfate groups on CNCs. Cycling studies showed that porous electrodes reduced their charge storage capacity over 3000 cycles, however, dense PPy electrodes prepared using high-sulfate DS CNCs increased their charge storage capacity by 715% (from 0.15 to 1.07 F cm−2) over the first 1200 cycles showing opening of the structure and better electrolyte perfusion. This capacitance then stayed constant for at least another 1700 cycles. [Display omitted] • CNC surface groups directly affect PPy templating during electrode formation. • CNCs with low amount of surface sulfate groups lead to desirable porous electrodes. • CNCs with high amount of surface sulfate groups lead to dense electrodes. • Amount of carboxylate groups do not have an effect on the final structure. • Cycling of dense CNC-PPy electrodes increases capacitance by over 700%. [ABSTRACT FROM AUTHOR]

Fast charging is a desirable feature for lithium-ion batteries. Charging at high currents, however, can damage the battery and accelerate aging processes. Fast charging protocols are typically computed by solving an optimization in which the cost function and constraints encode the conflicting requirements of safety and speed. A key element of the optimization is the choice of the dynamic model of the battery, with an inherent tradeoff between model accuracy and computational complexity. An oversimplified model may result in unreliable protocols, whereas a complex model may result in an optimization that is too computationally expensive to be suitable for real-time applications. This article describes an approach for embedding a complex battery model into charging optimization while having low computational cost. Multiphase Porous Electrode Theory is used to provide an accurate description of batteries characterized by multiphase materials, and the optimization is solved by transformation into mixed discrete-continuous simulation of a set of Differential–Algebraic Equations. The methodology is applied to an MPET model of commercially available Lithium Iron Phosphate batteries. Protocols based on a variety of operational constraints are computed to assess both the effectiveness of the approach, and the advantages and disadvantages of the charging protocols. • Fast charging protocols designed for multiphase batteries. • Computationally efficient protocol design by solving as a hybrid simulation. • Protocols designed for commercial lithium-ion batteries. • Protocols minimize charging time, subject to safety and operational constraints. • First such analysis based on Multiphase Porous Electrode Theory. [ABSTRACT FROM AUTHOR]

The twelve-electron carbon dioxide reduction reaction (12 e – CO 2 RR) constitutes a sustainable alternative to steam cracking for the production of ethylene (C 2 H 4), the world's most coveted organic compound. State-of-the-art gas diffusion electrodes (GDEs), while exhibiting promising faradaic efficiencies for C 2 H 4 electrosynthesis, suffer from poor long-term stability, particularly at elevated applied currents, due to catalyst delamination and flooding of the diffusion layer. Herein, through the development and optimisation of a novel, facile and flexible spray-printing method, hydrophobic porous carbon and copper electrodes with different architectures are obtained readily by using suspensions consisting of two fugitive solvents, which provide larger surface areas for the three-phase boundary and improve the hydrophobicity/flooding tolerance of the electrodes, due to their increased surface roughness and binder (PVDF) content. These structures, with pore sizes as low as 60 μm, transform the surfaces from incomplete wetting to highly hydrophobic, and can be employed as gas-diffusion, microporous or supportive layers, in addition to acting as a supporting substrate for the copper-based catalyst. These layers are spray-printed in a stacked assembly upon polymer film and carbon paper substrates, and ultimately result in an extended duration of enhanced C 2 H 4 production at applied currents of up to 200 mA cm−2 via multiple configurations. Through layer-by-layer spray-printing with a hydrophobic microporous layer and porous catalyst support, this inventive approach can efficiently control the hydrophobicity of the GDE, and extends the cathode operation time by a factor of 6, with a maximum faradaic efficiency of 52% attained, and an average of >30% maintained over 12 h of continuous electrolysis, demonstrating the versatility of this technique for engineering highly durable GDEs for selective CO 2 reduction toward multi-carbon (C 2+) commodities, energy storage devices and other electrochemical applications. Prolonging electrochemical CO 2 conversion to ethylene : A novel and versatile layer-by-layer spray-printing method incorporating a hydrophobic microporous layer and porous catalyst support, enables the efficient modulation of the GDE's hydrophobicity, extending the cathode's permanence by a factor of 6, and attaining a maximum 12 e – CO 2 RR faradaic efficiency of 52%, while maintaining >30% for 12 h of electrolysis. [Display omitted] • Comparison of GDE configurations spray-printing, PVD/sputtering, electrodeposition. • Successful incorporation of hydrophobic films to hinder flooding. • Porous electrodes of different layers extended the duration of CO 2 electrolysis. • Layer-by-layer spray-printing for >12 h C 2 H 4 production at 52% faradaic efficiency. • GDE design process for far-reaching applications across batteries and electrocatalysis. [ABSTRACT FROM AUTHOR]

The rapid charging and/or discharging of electrochemical cells can lead to localized depletion of electrolyte concentration. This depletion can significantly impact the system's time dependent resistance. For systems with porous electrodes, electrolyte depletion can limit the rate of charging and increase energy dissipation. Here we propose a theory to control and avoid electrolyte depletion by tailoring the value and spatial distribution of resistance in a porous electrode. We explore the somewhat counterintuitive idea that increasing local spatial resistances of the solid electrode itself leads to improved charging rate and minimal change in energy loss. We analytically derive a simple expression for an electrode matrix resistance profile that leads to highly uniform electrolyte depletion. We use numerical simulations to explore this theory and simulate spatiotemporal dynamics of electrolyte concentration in the case of a supercapacitor with various tailored electrode matrix resistance profiles which avoid localized depletion. This increases charging rate up to ∼ 2 -fold with minimal effect on overall dissipated energy in the system. [ABSTRACT FROM AUTHOR]

By incorporating all positive design criteria developed to date, to improve on performance and gas purities, a scalable and simplistic Mono-Circular Filter Press (MCFP) reactor has been developed and tested for the Divergent Electrode-Flow-Through (DEFT™) membraneless alkaline electrolysis technology. An improved gas/liquid separation methodology was utilised, which allows for hydrogen and oxygen gas purities of 99.81 and 99.50 vol% respectively, at the optimal flow velocity of 0.075 m s −1 and an electrode gap of 2.5 mm. Circular 30 mm mesh electrodes were utilised, with each electrode pair having its own independant pressurised chamber, with a unique indirect injection mechanism for the electrolyte. By incorporating a gas purge ensures that gas purity is maintained for long operational periods. By utilising a Ni/Ni catalyst combination, a current density of 1.14 A cm −2 at 2.5 VDC was obtained at a flow velocity of 0.075 m s −1 , 60 °C, and an electrode gap of 2.5 mm. In utilising a double layer of mesh, with the same specification, and experimental conditions, a current density of 1.91 A cm −2 at 2.5 VDC was realised, providing evidence for the effectiveness of multi-layered porous electrodes for the DEFT™ principle. Future improvements will focus on reducing the footprint and electrolytic flow velocity for the technology. [ABSTRACT FROM AUTHOR]

The impedances of several electric double layer capacitors are analysed at high frequencies by using the Randles equivalent electric circuit with the semi-infinite Warburg impedance. The Warburg coefficient, the charge transfer resistance, the interfacial capacitance, as well as the geometric resistance of the devices are determined by means of a non-linear least squares fitting. Unlike other previous studies using this circuit, we identify the characteristic frequencies from the zero-pole representation at the limits of the Randles impedance at high and low frequencies. Our study includes the overlapping between the interfacial and porous transport processes in the equivalent series resistance at high frequencies and it additionally considers the frequency at the intersect point between the interfacial and porous regions in the impedance Nyquist plots. Evolution with time of the short-circuit current and the voltage drop in response to a current pulse in supercapacitors are theoretically analysed at the shortest times from numerical inversion of the Laplace transform by using PSpice ® . The numerical results obtained from the Randles impedance and those from the low-frequency Warburg approximation are compared, and the significance of the different time constants is analysed and discussed. [ABSTRACT FROM AUTHOR]

Thin layers of continuous gold have been deposited on the both sides of porous polypropylene films (PPF) via electroless plating method to form a sandwich structure with two conductive surfaces and an intermediate insulating layer (Au/PPF/Au). Then poly (3, 4-ethylenedioxy thiophene) (PEDOT) layers are electrodeposited on the two conductive sides via cyclic voltammetry method to form the sandwich-structured PEDOT-Au/PPF/Au-PEDOT. Gel electrolyte of H 3 PO 4 /polyvinyl alcohol (H 3 PO 4 /PVA) is then added to the sandwich-structured PEDOT-Au/PPF/Au-PEDOT to form the integrated flexible supercapacitor of Au-PEDOT|H 3 PO 4 /PVA|PEDOT-Au. The PEDOT-Au/PPF/Au-PEDOT sandwiched structures are characterized and the capacitive performances of the integrated flexible cells are investigated in detail. The results show that the optimum integrated flexible cell exhibits excellent cycling stability (91.8% capacitance retention after 20000 cycles) and relatively high areal specific capacitance. Furthermore, the cells of Au-PEDOT|H 3 PO 4 /PVA|PEDOT-Au not only exhibit excellent bending endurance (99.1% capacitance retention after 5000 repeated bending cycles), but also can be conveniently connected in series without additional wires. This integrated flexible cell may exhibit potential application in portable electronics. [ABSTRACT FROM AUTHOR]

A simple semi-empirical master curve concept, describing the rate capability of porous insertion electrodes for lithium-ion batteries, is proposed. The model is based on the evaluation of the time constants of lithium diffusion in the liquid electrolyte and the solid active material. This theoretical approach is successfully verified by comprehensive experimental investigations of the rate capability of a large number of porous insertion electrodes with various active materials and design parameters. It turns out, that the rate capability of all investigated electrodes follows a simple master curve governed by the time constant of the rate limiting process. We demonstrate that the master curve concept can be used to determine optimum design criteria meeting specific requirements in terms of maximum gravimetric capacity for a desired rate capability. The model further reveals practical limits of the electrode design, attesting the empirically well-known and inevitable tradeoff between energy and power density. [ABSTRACT FROM AUTHOR]

The intercalation and aging induced volume changes of lithium-ion battery electrodes lead to significant mechanical pressure or volume changes on cell and module level. As the correlation between electrochemical and mechanical performance of lithium ion batteries at nano and macro scale requires a comprehensive and multidisciplinary approach, physical modeling accounting for chemical and mechanical phenomena during operation is very useful for the battery design. Since the introduced fully-coupled physical model requires proper parameterization, this work also focuses on identifying appropriate mathematical representation of compressibility as well as the ionic transport in the porous electrodes and the separator. The ionic transport is characterized by electrochemical impedance spectroscopy (EIS) using symmetric pouch cells comprising LiNi 1/3 Mn 1/3 Co 1/3 O 2 (NMC) cathode, graphite anode and polyethylene separator. The EIS measurements are carried out at various mechanical loads. The observed decrease of the ionic conductivity reveals a significant transport limitation at high pressures. The experimentally obtained data are applied as input to the electrochemical-mechanical model of a prismatic 10 Ah cell. Our computational approach accounts intercalation induced electrode expansion, stress generation caused by mechanical boundaries, compression of the electrodes and the separator, outer expansion of the cell and finally the influence of the ionic transport within the electrolyte. [ABSTRACT FROM AUTHOR]

Microfluidic fuel cells, electrolyzers, and redox flow batteries utilize laminar flow channels to provide reactants, remove products and avoid their crossover. These devices often also employ porous flow-through electrodes as they offer a high surface area for the reaction and excellent mass transfer. The geometrical features of these electrodes and flow channels strongly influence energy efficiency. We derive explicit analytical relations for the optimal flow channel width and porous electrode volumetric surface area from the perspective of energy efficiency. These expressions are verified using a two-dimensional tertiary current distribution and porous electrode flow model in COMSOL and are shown to be able to predict optimal parameters in commonly used flow-through and interdigitated flow fields. The obtained analytical models can dramatically shorten modelling time and expedite the industrial design process. The optimal channel width and pore sizes we obtain, in the order of 100 microns and 1 micron respectively, are much smaller than those often used. This shows that there is a significant room for improvement of energy efficiency in flow cells that can sustain the resulting pressure drop. [Display omitted] • We quantify the energy losses in a membraneless flow-through electrochemical cell. • Butler–Volmer kinetics activation losses add to frictional pumping dissipation. • The associated optimal electrode pore size and gap are found computationally and analytically. • Successful validation with 2D Brinkman Nernst–Planck porous electrode simulations. • Our simple analytical formulas are also found to work for interdigitated flow fields. [ABSTRACT FROM AUTHOR]

The potentiality of mixed conducting oxides as electrodes in rechargeable oxygen ion batteries is exemplified by impedance measurements and galvanostatic cycling. Porous La 0.6 Sr 0.4 CoO 3 − δ (LSC) thin film electrodes were prepared on yttria-stabilized zirconia electrolytes with a dense ZrO 2 blocking layer on top to prevent oxygen exchange with the measurement atmosphere. Half cell measurements performed between 350 and 460 °C revealed electrode capacities up to 135 mAh/cm3. Measured charge/voltage curves are compared with those reconstructed from chemical capacitance values and with model calculations. Two different storage mechanisms were identified: At low potentials (< 0.05 V vs. 1 bar O 2), mainly oxygen vacancies become filled during charging. At higher potentials, however, O 2 gas formation (> 500 bar at potentials > 0.1 V) in closed pores dominates charge/voltage characteristics, which can be described by calculations based on a real gas model. Moreover, full oxygen ion batteries were investigated, where such a porous LSC electrode served as cathode and a dense La 0.9 Sr 0.1 CrO 3 − δ (LSCr) film was used as anode. Owing to the much lower reducibility of LSCr, a cell voltage of 1.2 V was obtained at 460 °C with electrode related capacities and energy densities up to 100 mAh/cm3 and 53 mWh/cm3, respectively. [Display omitted] • Porous La 0.6 Sr 0.4 CoO 3 − δ electrodes were tested in rechargeable oxygen ion batteries. • A ZrO 2 blocking layer was used to prevent oxygen exchange with the atmosphere. • Half cell measurements revealed electrode capacities up to 135 mAh/cm3. • Two different charge storage mechanisms were identified. • Full cells were tested with La 0.6 Sr 0.4 CoO 3 − δ cathodes and La 0.9 Sr 0.1 CrO 3 − δ anodes. [ABSTRACT FROM AUTHOR]

Porous electrode theory (PET) is widely used to model battery dynamics by describing electrochemical kinetics and transport in solid particles and electrolyte. Standard PET models rely on black-box descriptions of the thermodynamics of active materials, typically obtained by fitting an open-circuit potential which does not allow for a consistent description of phase-separating materials. Multiphase PET (MPET) was recently developed to describe batteries using white- or gray-box descriptions of the thermodynamics with additional parameters that need to be estimated from experimental data. This work analyzes the identifiability of parameters in the MPET model, including the standard kinetics and diffusion parameters, as well as MPET-specific parameters for the free energy of active materials. Based on synthetic discharge data, both linearized and nonlinear identifiability analyses are performed for an MPET model of a commercial Lithium Iron Phosphate/Graphite battery, which identify which model parameters are not identifiable and which are identifiable only with large uncertainty. The identifiable parameters control phase separation, reaction kinetics, and electrolyte transport, but not solid diffusion, consistent with rate limitation by intercalation reactions at low rates and by electrolyte diffusion at high rates. The article also proposes approaches for reducing parameter identifiability issues. • First identifiability analysis for Multiphase Porous Electrode Theory-based models. • The analysis is carried out for discharge data from a lithium iron phosphate battery. • The analysis identifies which parameters cannot be estimated from the data. • The lack of identifiability is explained in terms of the battery physics. • Approaches are proposed for removing the lack of parameter identifiability. [ABSTRACT FROM AUTHOR]

A novel hybrid model consisting of two models, (1) a freshly developed porous electrode model and (2) a planar electrode model, is proposed for the soluble lead redox flow battery (SLRFB). The model accounts for simultaneous variations in ionic concentrations and potential fields in the electrolyte. It also accounts for variations in porosity, conductivity, and specific surface area at the porous anode due to the deposition/dissolution of the solids. The developed model is consistent with the solid ′ s deposition/dissolution mechanism. Hence, the choice of the model among the two for the simulation of a particular charge or discharge cycle follows naturally. Predictions of the model are validated using experimental data available in the literature. The model predictions suggest that the porous nature of the anode not only controls almost every feature of the battery characteristics but also governs the overall cycle life of the battery. Based on the insights developed using the model predictions, a necessary condition is derived for the battery operating procedure to achieve longer cycle life. • A hybrid approach of modeling based on porous electrode theory is developed. • The porous nature of the anode controls every feature of the battery characteristics. • The growth in the thickness of the anode determines the cycle life of the battery. [ABSTRACT FROM AUTHOR]

Uniform flow distribution through the porous electrodes in a flow battery cell is very important for reducing Ohmic and mass transport polarization. A segmented cell approach can be used to obtain in-situ information on flow behaviour, through the local voltage or current mapping. Lateral flow of current within the thick felts in the flow battery can hamper the interpretation of the data. In this study, a new method of segmenting a conventional flow cell is introduced, which for the first time, splits up both the porous felt as well as the current collector. This dual segmentation results in higher resolution and distinct separation of voltages between flow inlet to outlet. To study the flow behavior for an undivided felt, monitoring the OCV is found to be a reliable method, instead of voltage or current mapping during charging and discharging. Our approach to segmentation is simple and applicable to any size of the cell. [ABSTRACT FROM AUTHOR]

One approach to creating physics-based reduced-order models (ROMs) of battery-cell dynamics requires first generating linearized Laplace-domain transfer functions of all cell internal electrochemical variables of interest. Then, the resulting infinite-dimensional transfer functions can be reduced by various means in order to find an approximate low-dimensional model. These methods include Padé approximation or the Discrete-Time Realization algorithm. In a previous article, Lee and colleagues developed a transfer function of the electrolyte concentration for a porous-electrode pseudo-two-dimensional lithium-ion cell model. Their approach used separation of variables and Sturm–Liouville theory to compute an infinite-series solution to the transfer function, which they then truncated to a finite number of terms for reasons of practicality. Here, we instead use a variation-of-parameters approach to arrive at a different representation of the identical solution that does not require a series expansion. The primary benefits of the new approach are speed of computation of the transfer function and the removal of the requirement to approximate the transfer function by truncating the number of terms evaluated. Results show that the speedup of the new method can be more than 3800. [ABSTRACT FROM AUTHOR]

Thin-film BaZr 0.2 Ce 0.7 Y 0.1 O 3−δ (BZCY) is a promising electrolyte material for intermediate-temperature solid oxide fuel cells. However, a major drawback is its poor adhesion to porous electrodes. For achieving a high adhesion of thin BZCY films to anodes, a mixed electrolyte containing La 0.80 Sr 0.20 Ga 0.80 Mg 0.20 O 3−δ (LSGM) and BZCY is deposited onto a porous NiO–BZCYYb anode, followed by the deposition of a 4 μm-thick BZCY electrolyte layer over the mixed electrolyte layer by e-beam vapor deposition. The formation of a fully dense and well-adhered BZCY layer is confirmed. The prepared cell exhibits excellent potential for achieving high power densities with various fuels. The maximum power densities of a single cell are 1.21, 0.93, and 0.76 W cm −2 at 650 °C with hydrogen, methane, and biogas, respectively. Furthermore, the maximum power densities are 0.26, 0.12, and 0.21 W cm −2 at 500 °C with hydrogen, methane, and biogas, respectively. The ionic conductivities of the electrolyte layer are 1.2 × 10 −2 S cm −1 and 3.1 × 10 −3 S cm −1 at 650 and 500 °C respectively, with an activation energy of 0.46 eV. [ABSTRACT FROM AUTHOR]

Engineering porous heteroatom-doped carbon nanomaterials with remarkable capacitive performance is highly attractive. Herein, a simple and smart method has been developed to synthesize phosphorus (P) doped carbon with hierarchical porous structure derived from lignocellulose. Hierarchically porous P doped carbon is readily obtained by the pyrolysis of lignocellulose immersed in ZnCl 2 /NaH 2 PO 4 aqueous solution, and exhibits excellent capacitive properties. The as-obtained P doped porous carbon delivers a significant capacitance of 133 F g −1 (146 mF cm −2 ) at a high current density of 10 A g −1 with outstanding rate performance. Furthermore, the P doped carbon electrode yields a long-term cycling durability with more than 97.9% capacitance retention after 10000 cycles as well. A symmetric supercapacitor with a maximum energy density of 4.7 Wh kg −1 is also demonstrated based on these P doped carbon electrodes. [ABSTRACT FROM AUTHOR]

Platinum-decorated graphene aerogel as a porous electrode for flow-through direct methanol microfluidic fuel cell is introduced. Ultra-fine platinum nanoparticles with size ranged from diameter 1.5 nm–3 nm are evenly anchored on the graphene nanosheets without agglomeration. The electrode is characterized by scanning electron microscopy, transmission electron microscopy and energy-dispersive X-ray spectroscopy. Catalytic activity is confirmed by cyclic voltammetry. The electroactive surface area and catalytic activity of platinum on graphene oxide (Pt/GO) are much larger than commercial platinum on carbon black (Pt/C). A counterflow microfluidic fuel cell is designed for contrasting the cell performance between flow-over type and flow-through type electrodes using Pt/C on carbon paper and Pt/GO, respectively. The Pt/GO electrode shows 358% increment in specific power compared with Pt/C anode. Apart from catalytic activity, the effect of porous electrode conductivity to cell performance is also studied. The conductivity of the porous electrode should be further enhanced to achieve higher cell performance. [ABSTRACT FROM AUTHOR]

A new method to accelerate pore-scale simulation of porous electrodes is presented. The method combines the macroscopic approach with pore-scale simulation by decomposing a physical quantity into macroscopic and local variations. The multiscale method is applied to the potential equation in pore-scale simulation of a Proton Exchange Membrane Fuel Cell (PEMFC) catalyst layer, and validated with the conventional approach for pore-scale simulation. Results show that the multiscale scheme substantially reduces the computational cost without sacrificing accuracy. [ABSTRACT FROM AUTHOR]

Variants of SNNV (Sr 0.2 Na 0.8 Nb 1−x V x O 3 , X = 0.1–0.3) ceramic oxides were synthesized via wet chemical method. SNNVs show high electronic conductivity of >100 S/cm when reduced in hydrogen at a relatively low temperature of 650 °C. In particular, 30% V-doped SNNV exhibited the highest conductivity of 300 S/cm at 450 °C. In order to investigate the fuel cell performance, Gd 0.1 Ce 0.9 O 2−δ (GDC) based electrolyte-supported fuel cells were prepared to study the anode characteristics. Sr 0.2 Na 0.8 Nb 0.9 V 0.1 O 3 (SNNV10)-GDC composite was used as an anode and La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3−δ (LSCF)–GDC as a cathode. Both electrodes were porous and sintered at 1050 °C for 2 h in air. The anode side of the fuel cell was infiltrated with 10 wt% GDC/Ni-GDC precursor to activate the anode for fuel oxidation. I-V characteristics were determined in gas conditions such as dry/humidified hydrogen and methane at 650 °C. With the infiltration Ni-GDC, peak power density (PPD) of 280 mW/cm 2 and 220 mW/cm 2 in dry H 2 and CH 4 , respectively, were obtained at 650 °C, which is higher than GDC alone as infiltrate. The high resistances in the humidified conditions are attributed to the lower conductivity of SNNV10 in high P O2 atmospheres. [ABSTRACT FROM AUTHOR]

A low-temperature process for fabricating porous ZnO films on plastic, indium tin oxide-coated polyethylene naphthalate substrates is developed for their use in dye-sensitized solar cells. A special attention is paid to modification of microscopic morphologies for enhancing interparticle connection. ZnO films having two kinds of macroscopic morphologies (flower-like particles and densely packed nanoparticles) are fabricated at temperatures below the heatproof temperature of the substrate, and subsequently immersed in mixed solvents composed of water and ethanol at 90 °C. The immersion leads to the growth of constituting ZnO particles and also the evolution of interparticle connection, depending on solvent compositions. The cell performance is largely improved especially in a short-circuit current density and a power conversion efficiency. The immersion effect is more remarkable for the cell using the densely packed ZnO film, with a 62% increase in the current density and an 84% increase in the conversion efficiency. In consequence, our plastic N719-sensitized ZnO cell shows the conversion efficiency as high as 4.1%. [ABSTRACT FROM AUTHOR]

This study aims to develop a correlation equation between a porous electrode structure and the effective conductivity so as to design an optimal structure for a thick electrode layer of a high-capacity battery. We carried out a three-dimensional reconstruction of a lithium cobalt oxide and graphite electrode based on the cross-sectional images obtained via focused ion beam-scanning electron microscopy (FIB-SEM). The Li ion and electron conductivities are evaluated based on the effective conductive path determined from simulation and these values are compared with the experimental results obtained by electrochemical impedance spectroscopy carries out with a symmetric cell and the direct conductivity measurement under compression. Moreover, the amount of binder and the diameter of the active material particles are increased and decreased numerically using an actual reconstructed electrode structure, and the effect of those structures on the effective conductivity is examined. The most dominant factors that degrade ionic conductivity are the binder distribution and the particle morphology, respectively, in the cathode and anode, and a correlation equation with the function of porosity is obtained. These values are compared with those obtained by theoretical model equations, and the difference between the current effective ionic conductivity and the physical limiting value is determined. [ABSTRACT FROM AUTHOR]

The Pseudo Two Dimensional (P2D) porous electrode model is less preferred for real time calculations due to the high computational expense and complexity in obtaining the wide range of electro-chemical parameters despite of its superior accuracy. This paper presents a finite volume based method for re-parametrising the P2D model for any cell chemistry with uncertainty in determining precise electrochemical parameters. The re-parametrisation is achieved by solving a quadratic form of the Butler-Volmer equation and modifying the anode open circuit voltage based on experimental values. Thus the only experimental result, needed to re-parametrise the cell, reduces to the measurement of discharge voltage for any C-rate. The proposed method is validated against the 1C discharge data and an actual drive cycle of a NCR18650BD battery with NCA chemistry when driving in an urban environment with frequent accelerations and regenerative braking events. The error limit of the present model is compared with the electro-chemical prediction of Li y CoO 2 battery and found to be superior to the accuracy of the model presented in the literature. [ABSTRACT FROM AUTHOR]

Improving the overall energy efficiency by reducing pumping power and improving flow distribution of electrolyte, is a major challenge for developers of flow batteries. The use of suitable channels can improve flow distribution through the electrodes and reduce flow resistance, hence reducing the energy consumption of the pumps. Although several studies of vanadium redox flow battery have proposed the use of bipolar plates with flow channels, similar to fuel cell designs, this paper presents the use of flow channels in the porous electrode as an alternative approach. Four types of electrodes with channels: rectangular open channel, interdigitated open cut channel, interdigitated circular poked channel and cross poked circular channels, are studied and compared with a conventional electrode without channels. Our study shows that interdigitated open channels can improve the overall energy efficiency up to 2.7% due to improvement in flow distribution and pump power reduction while interdigitated poked channel can improve up to 2.5% due to improvement in flow distribution. [ABSTRACT FROM AUTHOR]

Hierarchically porous graphene nanosheets co-doped with nitrogen and sulfur are synthesized via a simple hydrothermal method, followed by a pore activation step. Pore architectures are controlled by varying the ratio of chemical activation agents to graphene, and its influence on the capacitive performance is evaluated. The electric double layer capacitor (EDLC) assembled with optimized dual-doped graphene delivers a high specific capacitance of 146.6 F g −1 at a current density of 0.8 A g −1 , which is higher than that of cells with un-doped and single-heteroatom doped graphene. The EDLC with dual-doped graphene electrodes exhibits stable cycling performance with a capacitance retention of 94.5% after 25,000 cycles at a current density of 3.2 A g −1 . Such a good performance can be attributed to synergistic effects due to co-doping of the graphene nanosheets and the presence of hierarchical porous structures. [ABSTRACT FROM AUTHOR]