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This study proposes the synthesis of SnO 2 /Ti 3 C 2 T x composites on porous graphene electrodes (PGEs) for high-performance humidity sensors. In the heterojunction structure of SnO 2 /Ti 3 C 2 T x composites, SnO 2 nanoparticles prevented the layered structure of Ti 3 C 2 T x to collapse and restack. Moreover, the high specific surface area of the SnO 2 /Ti 3 C 2 T x composites provided more adsorption sites that improved their response. Porous graphene was fabricated by a fiber laser-induced process on the polyimide film as an electrode layer for flexible humidity sensors. The characteristics of the SnO 2 /Ti 3 C 2 T x composites and PGEs were examined and investigated. SnO 2 /Ti 3 C 2 T x composites were drop-cast on PGEs to fabricate the humidity sensor. Furthermore, the response of humidity sensors was tested in various RHs. The performance of the proposed humidity sensor demonstrated a wide detection range of 11–97 % RH, low hysteresis of 2.8 % RH, low response/recovery times of 14/49 s, high sensitivity of 862.19 kΩ/%RH, excellent long-time stability and repeatability, and good flexibility. In the future, the proposed sensor can be widely applied in human respiration monitoring, non-contact switch, and detection of volatile organic compounds. [ABSTRACT FROM AUTHOR]

This study examines the use of surface-modified biochar as a porous electrode material for the capacitive deionization removal of chloride and fluoride ions. Incorporation of titanium dioxide and amine groups on biochar aims to increase surface-active sites, facilitate salt ion diffusion, and improve charge efficiency and cation/anion selectivity in asymmetric capacitive deionization. Titania, amine, and activated biochar are denoted as TB, AmB, and AcB, respectively. Physical and electrochemical characterizations were performed to investigate the surface properties of fabricated materials. At the optimum TiO2 loading of 5% (TB-05), the specific capacitance of TB-05 electrode was improved by 35% at scan rate of 1 mV s–1 in comparison to the AcB electrode, despite a decrease in the specific surface area. Three different asymmetric capacitive deionization cell designs—AmB||TB-05, AcB||TB-05, and AmB||AcB—and two symmetrical cell designs—AcB||AcB and TB-05||TB-05 (anode||cathode)—were tested. A symmetric cell design TB-05||TB-05 had a NaCl removal capacity of 8.51 mg g−1, a 42% improvement in comparison to a symmetric AcB cell (6.01 mg g−1). Further, an asymmetric cell AmB||TB-05 showed 67% charge efficiency improvement over symmetric AcB cell, likely due to a reduced co-ion effect. For fluoride removal, a symmetric TB-05 cell showed a removal capacity of 3.51 mg g−1. This study promotes simple surface-modification methods to make inexpensive commercial biochar into a sustainable, and efficient electrode material available for a scale-up asymmetric capacitive deionization. [ABSTRACT FROM AUTHOR]

All-solid-state batteries (ASSBs) with adequately selected cathode materials exhibit a higher energy density and better safety than conventional lithium-ion batteries (LIBs). Ni-rich layered cathodes are benchmark materials for traditional LIBs owing to their high energy density. Recent studies have highlighted the advantages of using crack-free, single-crystalline cathode materials in ASSBs. In this study, a scalable infiltration sheet-type process was used to fabricate composite electrodes with different cathode-material morphologies for ASSBs. Typically, crack-free single-crystalline materials exhibit better retention performance and lower rate capability (i.e., slower kinetics in charge‒discharge processes) than polycrystalline cathode materials. Li6PS5Cl-infiltrated polycrystalline electrodes showed excellent retention performance and rate capability. Galvanostatic intermittent titration technique analysis and transmission electron microscopy of the single-crystalline electrode confirmed severe polarization and the presence of a rock-salt-structure layer in the cathode particles; these results indicated side reactions within the layered structure of the material. In contrast, composite electrodes consisting of polycrystalline cathode materials infiltrated with the solid electrolyte Li6PS5Cl showed excellent electrochemical performance owing to intimate electrode–electrolyte interfacial contact. The result from this study confirmed the critical influence of interface engineering and material morphology on the overall performance and stability of ASSBs and could facilitate the development of high-performance ASSBs in the future. This study introduces a technique for utilizing conventional lithium-ion battery electrodes in all-solid-state batteries. By infiltrating a solid electrolyte solution into the porous electrode, the effects based on the morphology of the active material were investigated. In poly-crystalline materials, high coverage and the formation of a thin side reaction layer were observed. Consequently, the infiltration process also confirmed the superior performance of poly-crystalline materials. [ABSTRACT FROM AUTHOR]

The current goals for implementing the hydrogen economy have highlighted a need to further optimize water‐splitting technologies for clean hydrogen production. Proton exchange membrane water electrolysis (PEMWE) is a leading technology, but further optimizations of anode materials including the porous transport layer (PTL) and the adjacent catalyst layer (CL) are required to increase overall cell performance and reduce cost. This literature review describes advances in PTL development and characterization, highlighting early PTL characterization work and most common methods including capillary flow porometry and mercury intrusion porometry, optical imaging, neutron and x‐ray radiography, and x‐ray computed tomography. The article also discusses PTL protective coatings and their characterizations, focusing on platinum group metal (PGM)‐based coatings, alternative non‐PGM‐based coatings, post‐treated PTLs, and investigations into thin PGM‐based coatings. Furthermore, it highlights the integration of the PTL and the adjacent CL along with associated characterization challenges. Lastly, this review discusses future developments in the characterization needed to improve PEMWE's performance and long‐term durability are discussed. [ABSTRACT FROM AUTHOR]

Recent advances in 3D printing have enabled the manufacture of porous electrodes which cannot be machined using traditional methods. With micron-scale precision, the pore structure of an electrode can now be designed for optimal energy efficiency, and a 3D printed electrode is not limited to a single uniform porosity. As these electrodes scale in size, however, the total number of possible pore designs can be intractable; choosing an appropriate pore distribution manually can be a complex task. To address this challenge, we adopt an inverse design approach. Using physics-based models, the electrode structure is optimized to minimize power losses in a flow reactor. The computer-generated structure is then printed and benchmarked against homogeneous porosity electrodes. We show how an optimized electrode decreases the power requirements by 16% compared to the best-case homogeneous porosity. Future work could apply this approach to flow batteries, electrolyzers, and fuel cells to accelerate their design and implementation. [ABSTRACT FROM AUTHOR]

An electrical double‐layer capacitor (EDLC) comprises two porous electrodes sandwiching an electrolyte‐permeable separator, which prevents the electrodes from short‐circuiting. While previous studies have mainly focused on electrolyte and electrode properties of EDLCs, the device configuration in terms of electrode and separator sizes received less attention, with separators often simplistically modelled as infinitely large reservoirs of ions. Herein, we investigate how the relationship between electrode and separator thicknesses impacts EDLC charging. We find that the assumption of bulk reservoir holds only under specific conditions. Moreover, we identify a tradeoff between stored energy density and pressure variations within the separator, potentially jeopardizing the EDLC durability. We also explore the influence of ionic liquid additives on EDLC charging. While prior research has shown that trace amounts of uncharged additives with strong electrode affinity can significantly enhance energy storage, we observe this effect as negligible for electrodes and separators of comparable sizes. Instead, we show how to optimize EDLC performance by fine‐tuning the concentration of additives and separator‐to‐electrode size ratio to maximize stored energy density. [ABSTRACT FROM AUTHOR]

In polymer membrane fuel cells (PEMFC), the pore microstructure and the effective diffusion coefficient ( D eff ) of the catalytic layer have a significant impact on the overall performance of the fuel cell. In this work, numerical methods to simulate PEMFC catalytic layers were used to study the effect of isotropy ( I xy ) on the D eff . The proposed methodology studies reconstructed systems by Simulated Annealing imaging with different surface fractions of microstructures composed by two diffusive phases: agglomerates and pores. The D eff is determined numerically by the Finite Volume Method solved for Fick's First Law of Diffusion. The results show that the proposed methodology can effectively quantify the effect of isotropy on the D eff for both diffusion phases. Two trends were obtained in the magnitude of the D eff concerning the change in isotropy: (1) an analytical equation is proposed in this article for D eff ≥ 5 % D 0 and (2) numerical solutions are determined for D eff < 5 % D 0. In our analytical equation are both a lineal and a logarithmic sweep. When the surface fraction is ∅ = 50%, the D eff decreases more linearly than ∅ = 10 % at the beginning of the isotropy change, which indicates that small changes in isotropy in the particulate material modify it drastically; under these conditions the diffusion coefficient in the pore is predominant. (3) When the surface fraction is less than 50%, the D eff decreases more exponentially at the beginning and more linearly at the end of the isotropy change, which shows that small isotropy changes in the bar-aligned material drastically alter it. In this trend, diffusion in the agglomerate is less affected by isotropy. The proposed methodology can be used as a design tool to improve the mass transport in porous PEMFC electrodes. [ABSTRACT FROM AUTHOR]

[Display omitted] Supercapacitors have the advantages of fast charging and discharging speeds, high power density, long cycle life, and wide operating temperature range. They are widely used in portable electronic equipment, rail transit, industry, military, aerospace, and other fields. The design and preparation of low-cost, high-performance electrode materials still pose a bottleneck that hinders the development of supercapacitors. In this paper, coal was used as the raw material, and the coal-based porous carbon electrode material was constructed using the iodine intercalation-assisted activation method and used for supercapacitors. The CK-700 electrode exhibits excellent charge storage performance in a 6 M potassium hydroxide (KOH) electrolyte, with a maximum specific capacitance of 350 F/g at a current density of 0.5 A/g. In addition, it has an excellent rate performance (310 F/g at 1 A/g) and cycle stability (capacitance retention up to 91.7 % after 30000 cycles). This work provides a method for realizing high-quality, high-yield and low-cost preparation of coal-based porous carbon, and an idea for improving the performance of supercapacitors. [ABSTRACT FROM AUTHOR]

Symmetrical solid oxide cells (SSOCs) are very useful for energy generation and conversion. To fabricate the electrode of SSOC, it is very time‐consuming to use the conventional approach. In this work, we design and develop a novel method, extreme heat treatment (EHT), to rapidly fabricate electrodes for SSOC. We show that by using the EHT method, the electrode can be fabricated in seconds (the fastest method to date), benefiting from enhanced reaction kinetics. The EHT‐fabricated electrode presents a porous structure and good adhesion with the electrolyte. In contrast, tens of hours are needed to prepare the electrode by the conventional approach, and the prepared electrode exhibits a dense structure with a larger particle size due to the lengthy treatment. The EHT‐fabricated electrode shows desirable electrochemical performance. Moreover, we show that the electrocatalytic activity of the perovskite electrode can be tuned by the vigorous approach of fast exsolution, deriving from the increased active sites for enhancing the electrochemical reactions. At 900 °C, a promising peak power density of 966 mW cm−2 is reached. Our work exploits a new territory to fabricate and develop advanced electrodes for SSOCs in a rapid and high‐throughput manner. [ABSTRACT FROM AUTHOR]

The effects of process parameters on the electroless plating of ionic polymer–metal composites (IPMCs) were studied in this work. Specifically, the NaBH4 reduction of platinum onto Nafion-117 was characterised. The effects of the concurrent variation of NaBH4 concentration, stir time and temperature on surface resistance were studied through a full factorial design. The three-factor three-level factorial design resulted in 27 runs. Surface resistance was measured using a four-point probe. A regression model with an R2 value of 97.45% was obtained. Surface resistance was found to decrease with increasing stir time (20 to 60 min) and temperature (20 to 60 °C). These responses were attributed to increased platinisation rates, resulting in more uniform electrode deposition, confirmed by scanning electron microscopy (SEM) and energy-dispersive X-ray (EDAX) analysis. Surface resistance decreased, going from 1% to 5% NaBH4 concentration, but increased from 5% to 10% concentration. This behaviour was attributed to surface morphology: increased grain size inducing porous electrodes, in line with findings in the literature. The maximum tip displacement, measured through a computer vision system, as well as the maximum blocking force, measured through an analytical balance setup, were obtained for all 27 samples. The varying results were discussed with regards to surface and cross-sectional SEMs, alongside EDAX analysis. [ABSTRACT FROM AUTHOR]

Miniaturized energy storage devices, such as electrostatic nanocapacitors and electrochemical micro-supercapacitors (MSCs), are important components in on-chip energy supply systems, facilitating the development of autonomous microelectronic devices with enhanced performance and efficiency. The performance of the on-chip energy storage devices heavily relies on the electrode materials, necessitating continuous advancements in material design and synthesis. This review provides an overview of recent developments in electrode materials for on-chip MSCs and electrostatic (micro-/nano-) capacitors, focusing on enhancing energy density, power density, and device stability. The review begins by discussing the fundamental requirements for electrode materials in MSCs, including high specific surface area, good conductivity, and excellent electrochemical stability. Subsequently, various categories of electrode materials are evaluated in terms of their charge storage mechanisms, electrochemical performance, and compatibility with on-chip fabrication processes. Furthermore, recent strategies to enhance the performance of electrode materials are discussed, including nanostructuring, doping, heteroatom incorporation, hybridization with other capacitive materials, and electrode configurations. [ABSTRACT FROM AUTHOR]

Abstract Recent advances in 3D printing have enabled the manufacture of porous electrodes which cannot be machined using traditional methods. With micron-scale precision, the pore structure of an electrode can now be designed for optimal energy efficiency, and a 3D printed electrode is not limited to a single uniform porosity. As these electrodes scale in size, however, the total number of possible pore designs can be intractable; choosing an appropriate pore distribution manually can be a complex task. To address this challenge, we adopt an inverse design approach. Using physics-based models, the electrode structure is optimized to minimize power losses in a flow reactor. The computer-generated structure is then printed and benchmarked against homogeneous porosity electrodes. We show how an optimized electrode decreases the power requirements by 16% compared to the best-case homogeneous porosity. Future work could apply this approach to flow batteries, electrolyzers, and fuel cells to accelerate their design and implementation.

[Display omitted] • Rattan is converted to 3D current collector via a facile and cost-effective strategy. • The CR owns hierarchical structure, directional channels, and superior stability. • 3D MnO 2 cathode with a large mass loading of 10 mg cm−2 is successfully constructed. • Interfacial charge transfer kinetics can be significantly improved by 3D structure. • The cathode offers substantial areal capacity of 3.65 mAh cm−2 and good cyclability. Aqueous zinc-ion batteries (AZIBs) have emerged as prospective candidates for wide-scale energy storage, benefiting from their exceptional reliability and budget-friendliness. To tackle the challenge of limited energy density of AZIBs, it is pivotal to explore cathodes with substantial mass loadings. In this study, rattan is converted into a three-dimensional (3D) current collector with directional channels, high compressive strength, good electrolyte affinity, and superior electrochemical stability through a process involving ultraviolet light irradiation-assisted delignification followed by high-temperature carbonization. Using this current collector and a straightforward slurry pasting method, a 3D MnO 2 cathode featuring substantial loading amount of 10 mg cm−2 for active material can be constructed. This cathode's rich channel structure allows the carbon nanotube/MnO 2 composite material to establish full contact with the electrolyte, significantly facilitating interfacial charge transfer. The optimized cathode achieves an outstanding areal capacity of 3.65 mAh cm−2 at 0.1 A/g and sustains 1.52 mAh cm−2 at 1 A/g. Besides, the capacity retention remains at 60.2 % after 1000 cycles, even under such large mass loading. Notably, the fabrication procedure of the 3D cathode is simple, and the associated costs are relatively low compared to other 3D cathodes for AZIBs. These findings present an effective strategy for developing cost-effective and high-performance electrodes with large areal capacities, advancing energy storage technologies. [ABSTRACT FROM AUTHOR]

A porous electrode material consisting of NiCo2O4/RGO with an approximate diameter of 200 nm has been successfully fabricated. This promising porous material was derived from ZIF-67/RGO (zeolitic imidazolate framework-67 crystals doped with reduced graphene oxide sheets) through an ion exchange and etching process using Ni(NO3)2·6H2O followed by a thermal reaction. The composition was analyzed using spectroscopic and morphological techniques. The obtained porous and hollow structure of NiCo2O4/RGO contains rich active sites. Additionally, its improved performance and stability were demonstrated using potassium ferricyanide (K3[Fe(CN)]6) (PFC) and sodium hydroxide (NaOH) as an electrolyte. NiCo2O4/RGO in NaOH/PFC exhibited a maximum estimated specific capacitance of 212.5 F g−1 at 0.5 A g−1 and demonstrated excellent retention value reaching 91.7% after applying 10,000 cycles at 20 A g−1. This symmetric supercapacitor achieved an outstanding energy density (Ed) of 75.54 Wh kg−1 at a power density (Pd) of 1.6 kW kg−1 at 0.5 A g−1. Surprisingly, there is a 2.5-fold enhancement in Ed (from 32.44 to 75.54 Wh kg−1) of NiCo2O4/RGO through the addition of 0.3 M PFC into 3 M NaOH. The results indicate that the NiCo2O4/RGO electrode could be ideal for supercapacitors. [ABSTRACT FROM AUTHOR]

Highlights: A blade-coated composite paste, composed of a compressible 3D carbon skeleton, PEDOT:PSS, and CNTs, can naturally dry to form a porous electrode on paper with a micro- and nano-structured surface. The all-paper pressure sensor demonstrated an ultrahigh sensitivity of 1014 kPa−1, a wide responsive range up to 300 kPa, and an ultralow operating voltage of 0.01 V. The sensor showcased superior detection capability, ranging from subtle wrist pulses and robust finger taps to large-area spatial force. Flexible and wearable pressure sensors hold immense promise for health monitoring, covering disease detection and postoperative rehabilitation. Developing pressure sensors with high sensitivity, wide detection range, and cost-effectiveness is paramount. By leveraging paper for its sustainability, biocompatibility, and inherent porous structure, herein, a solution-processed all-paper resistive pressure sensor is designed with outstanding performance. A ternary composite paste, comprising a compressible 3D carbon skeleton, conductive polymer poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate), and cohesive carbon nanotubes, is blade-coated on paper and naturally dried to form the porous composite electrode with hierachical micro- and nano-structured surface. Combined with screen-printed Cu electrodes in submillimeter finger widths on rough paper, this creates a multiscale hierarchical contact interface between electrodes, significantly enhancing sensitivity (1014 kPa−1) and expanding the detection range (up to 300 kPa) of as-resulted all-paper pressure sensor with low detection limit and power consumption. Its versatility ranges from subtle wrist pulses, robust finger taps, to large-area spatial force detection, highlighting its intricate submillimeter-micrometer-nanometer hierarchical interface and nanometer porosity in the composite electrode. Ultimately, this all-paper resistive pressure sensor, with its superior sensing capabilities, large-scale fabrication potential, and cost-effectiveness, paves the way for next-generation wearable electronics, ushering in an era of advanced, sustainable technological solutions. [ABSTRACT FROM AUTHOR]

Synopsis: This study presents a thiocyanogen-modulated alkali activation strategy for preparing N, S co-doped lignin hierarchical porous carbon (NSLHPC). Thiocyanate acts as a surface modulation mediator to introduce nitrogen and sulfur heteroatoms via oxygen replacement reaction. NSLHPC exhibits excellent electrochemical performance and long cycling lifespan in both symmetric supercapacitors and zinc-ion hybrid capacitors. [Display omitted] • Thiocyanogen-modulated alkali activation strategy for the preparation of NSLHPC. • Oxygen replacement reaction between KSCN and lignin carbon for N, S co-doping. • NSLHPC exhibits an impressive SSA of 2705.3 m2/g and a pore volume of 3.27 cm3/g. • NSLHPC presents remarkable electrochemical performance in aqueous supercapacitors. • DFT calculations reveal that N, S co-doping reduces the adsorption energy barrier of Zn2+. Constructing heteroatom-doped porous carbons with distinct charge storage properties is significant for high-energy–density supercapacitors, yet it remains a formidable challenge. Herein, we employed a thiocyanogen-modulated alkali activation strategy to synthesize N and S co-doped lignin hierarchical porous carbon (NSLHPC). In this process, thiocyanogen serves as a surface modulation mediator to substitute oxygen with nitrogen and sulfur species, while the combination of KOH activation and MgO template generates numerous nanopores within the carbon structure. The three-dimensional interconnected nanosheet architecture facilitates rapid ion transfer and enhances accessibility to active sites. Density functional theory (DFT) calculations demonstrate that introducing N and S heteroatoms through oxygen substitution reduces the adsorption energy barrier of Zn2+. Consequently, the optimized NSLHPC exhibits a remarkable specific capacitance of 438F/g at 0.5 A/g in 6 M KOH, delivering an energy density of 10.4 Wh/kg in the symmetric supercapacitor and an impressive energy density of 104.9 Wh/kg in the zinc-ion hybrid capacitor. The NSLHPC cathode also shows an excellent lifespan with capacitance retention of 99.0 % and Columbic efficiency of 100 % over 10,000 cycles. This study presents innovative strategies for engineering high-performance porous carbon electrode materials by emphasizing pore structure modulation and N, S co-doping as crucial approaches. [ABSTRACT FROM AUTHOR]

Designing and optimizing the pore structure of porous carbon electrodes is essential for diverse energy storage systems. In this study, an innovative approach spray phase‐inversion strategy was developed for the rapid and efficient fabrication of controlled porous carbon aerogel. Moreover, the aggregation structure of polyacrylonitrile is controlled by adjusting the Hansen's solubility parameter, thereby regulating the electrode material structure. Furthermore, the theoretical analysis of the spray phase‐inversion process revealed that this regulation process is jointly regulated by solvent hydrodynamic diameter and phase‐inversion kinetics. Through optimization, a novel porous carbon material was obtained that exhibited excellent performance as an electrode material. When utilized in supercapacitors for energy storage, it demonstrated a high specific capacitance of 373.1 F g−1 in a 6 M KOH electrolyte solution. Simultaneously, it has been observed that the preparation strategy for porous electrodes offers notable advantages in terms of excellent designability, broad universality, simplicity, and high efficiency, thereby holding promise for large‐scale fabrication of diverse porous electrode materials and various types of electrodes for diverse energy storage applications. [ABSTRACT FROM AUTHOR]

Thermo‐electrochemical cells (TECs) provide a new potential for self‐powered devices by converting heat energy into electricity. However, challenges still remain in the fabrication of flexible and tough gel electrolytes and their compatibility with redox actives; otherwise, contact problems exist between electrolytes and electrodes during stretching or twisting. Here, a novel robust and neutral hydrogel with outstanding stretchability was developed via double‐network of crosslinked carboxymethyl chitosan and polyacrylamide, which accommodated both n‐type (Fe2+/Fe3+) and p‐type ([Fe(CN)6]3−/[Fe(CN)6]4−) redox couples and maintained stretchability (>300%) and recoverability (95% compression). Moreover, poly(3,4‐ethylenedioxythiophene):poly(styrene sulfonate) textile electrodes with porous structure are integrated into gel electrolytes that avoid contact issues and effectively boost the Pmax of n‐ and p‐type thermocell by 76% and 26%, respectively. The optimized thermocell exhibits a quick current density response and is continually fully operational under deformations, which satisfies the working conditions of wearable devices. Multiple thermocells (four pairs) are effectively connected in alternating single n‐ and p‐type cells in series and outputted nearly 74.3 mV at ΔT = 10°C. The wearable device is manufactured into a soft‐pack thermocells to successfully harvest human body heat and illuminate an LED, demonstrating the potential of the actual application of the thermocell devices. [ABSTRACT FROM AUTHOR]

The presented paper characterized the molten salt-modified Ni electrode with excellent catalytic activity towards alkaline urea electrooxidation reaction. The electrodes were modified by electrodeposition of Al from molten salt electrolytes containing NaCl-KCl-AlF3 at a temperature of 750 °C and applied potential of −1.9 V. The porous surface was obtained by anodic polarization with a potential of −0.4 V until the anodic current was equal to 0 mAcm−2. The prepared deposits' structure, surface morphology, and composition were analyzed using scanning electron microscopy (SEM) and X-ray diffraction (XRD). Anodic polarization was applied to assess the electrocatalytic activity and elucidate the urea electrooxidation mechanism in 1 M KOH + 0.33 M urea solution. The nanocrystalline structure, fine grain size, and microcracks on the surface of the studied electrodes contributed to their notably high electrochemically active surface area (ECSA). The cyclic voltammetry in the non-Faradaic regions of the samples shows that molten salt modification can increase the double layer capacitance of bare Ni plates by around ten times, from 0.29 mFcm−2 to 2.16 mFcm−2. Polarization of the electrodes in urea-containing KOH solution with potential of +1.52 V shows a significant difference in catalytic performance. For the bare nickel sample, the registered current density from the urea electrooxidation reaction was around +1 mAcm−2, and for the molten salt-modified one, it was +38 mAcm−2, which indicates the fact that the molten salt surface treatment can be a promising tool in tailoring the electrochemical properties of materials. [ABSTRACT FROM AUTHOR]

Two-layer microfluidic devices with porous membranes have been widely used in bioapplications such as microphysiological systems (MPS). Porous electrodes, instead of membranes, have recently been incorporated into devices for electrochemical cell analysis. Generally, microfluidic channels are prepared using soft lithography and assembled into two-layer microfluidic devices. In addition to soft lithography, three-dimensional (3D) printing has been widely used for the direct fabrication of microfluidic devices because of its high flexibility. However, this technique has not yet been applied to the fabrication of two-layer microfluidic devices with porous electrodes. This paper proposes a novel fabrication process for this type of device. In brief, Pluronic F-127 ink was three-dimensionally printed in the form of sacrificial layers. A porous Au electrode, fabricated by sputtering Au on track-etched polyethylene terephthalate membranes, was placed between the top and bottom sacrificial layers. After covering with polydimethylsiloxane, the sacrificial layers were removed by flushing with a cold solution. To the best of our knowledge, this is the first report on the sacrificial approach-based fabrication of two-layer microfluidic devices with a porous electrode. Furthermore, the device was used for electrochemical assays of serotonin and could successfully measure concentrations up to 5 µM. In the future, this device can be used for MPS applications. [ABSTRACT FROM AUTHOR]

In solid oxide fuel cell (SOFC), sintering of YSZ and NiO powders into porous anode plays a crucial role in determining its overall performance. In this study, a coarse-graining (CG) molecular dynamics (MD) model is developed to capture sintered half-cell composed of porous functional layer with NiO/YSZ particles and dense YSZ ceramic electrolyte layer with applied in anode-supported SOFC. The sintering process is simulated in two stages, i.e., heating process followed by temperature-holding process. This study also explores effects of sintering parameters (e.g., temperature, powder size and material compositions) on structural characteristics, including distribution of sintered triple-phase boundary (TPB) length, porosity, and pore size. It is found that structural properties vary mainly during the heating stage of sintering, while a higher sintering temperature leads to a larger TPB length and a lower porosity, while increasing in diameter ratio of the NiO powders to YSZ powders is advantageous for increasing TPB length, porosity and size pores for promoting electrode electrochemical activity. This work provides a bottom-up approach for potential optimization of SOFC fabrication condition and parameters. [ABSTRACT FROM AUTHOR]

Electrolytic capacitors store larger amounts of energy thanks to their thin dielectric layers and enlarged surface area. However, the benefits of using a liquid electrolyte are at the expense of the possibility of leakage, evaporation, or rupture of the device over time. As a solution, solid electrolytes, such as conductive polymers, substitute the liquid ones decreasing the internal resistance and enlarging the lifetime of these devices. PEDOT:PSS is a widely used conductive polymer in the formation of solid electrolytic capacitors. However, using the enlarged surface of the porous electrodes efficiently requires industrial processes, the efficacy of which has not been explored. In this work, porous aluminium electrodes with dielectric layers of different thicknesses were coated with PEDOT:PSS at different levels of doping in order to study the efficiency of the production of solid electrolytic capacitors in industry. The combination of odd random phase electrochemical impedance spectroscopy (ORP-EIS) with surface characterization techniques (SEM-EDX, GDOES) formed a methodology that allowed the study of both the electrical properties and the level of impregnation for these model systems. All samples consisting of a porous aluminium electrode with an amount of PEDOT:PSS deposited on top resulted in an inefficient degree of penetration between the two electrodes. However, the electrochemical analysis proved that the use of dopants produces systems with the highest capacitive properties. Consequently, the evolution towards better solid electrolytic capacitors does not rely solely on the proper coverage of the porous electrodes, but on the proper electrical properties of the PEDOT:PSS within the pores. [ABSTRACT FROM AUTHOR]

Sulfurized polyacrylonitrile (SPAN) is a promising cathode material for lithium-sulfur batteries owing to its reversible solid–solid conversion for high-energy-density batteries. However, the sluggish reaction kinetics of SPAN cathodes significantly limit their output capacity, especially at high cycling rates. Herein, a CNT-interpenetrating hierarchically porous SPAN electrode is developed by a simple phase-separation method. Flexible self-supporting SPAN cathodes with fast electron/ion pathways are synthesized without additional binders, and exceptional high-rate cycling performances are obtained even with substantial sulfur loading. For batteries assembled with this special cathode, an impressive initial discharge capacity of 1090 mAh g−1 and a retained capacity of 800 mAh g−1 are obtained after 1000 cycles at 1 C with a sulfur loading of 1.5 mg cm−2. Furthermore, by incorporating V2O5 anchored carbon fiber as an interlayer with adsorption and catalysis function, a high initial capacity of 614.8 mAh g−1 and a notable sustained capacity of 500 mAh g−1 after 500 cycles at 5 C are achieved, with an ultralow decay rate of 0.037% per cycle with a sulfur loading of 1.5 mg cm−2. The feasible construction of flexible SPAN electrodes with enhanced cycling performance enlists the current processing as a promising strategy for novel high-rate lithium-sulfur batteries and other emerging battery electrodes. [ABSTRACT FROM AUTHOR]

The electrochemical performance of microsupercapacitors with graphene electrodes is reduced by the issue of graphene sheets aggregation, which limits electrolyte ions penetration into electrode. Increasing the space between graphene sheets in electrodes facilitates the electrolyte ions penetration, but sacrifices its electronic conductivity which also influences the charge storage ability. The challenging task is to improve the electrodes' electronic conductivity and ionic diffusion simultaneously, boosting the device's electrochemical performance. Herein, we experimentally realize the enhancement of both electronic conductivity and ionic diffusion from 2D graphene nanoribbons assisted graphene electrode with porous layer‐upon‐layer structure, which is tailored by graphene nanoribbons and self‐sacrificial templates ethyl cellulose. The designed electrode‐based device delivers a high areal capacitance of 71 mF cm−2 and areal energy density of 9.83 μWh cm−2, promising rate performance, outstanding cycling stability with 97% capacitance retention after 20 000 cycles, and good mechanical properties. The strategy paves the way for fabricating high‐performance graphene‐based MSCs. [ABSTRACT FROM AUTHOR]

The goal of this research is to fabricate a novel type of highly active porous electrode material, based on stainless steel and dedicated to water electrolyzers. The main novelty of the presented work is the innovative application of the molten salts treatment, which allows the design of a highly developed porous structure, which characterizes significantly higher catalytic activity than untreated steel substrates. The equimolar mixture of NaCl and KCl with 3.5 mol% AlF3 was used as the molten salt. The surface modification procedure includes the deposition of an Al layer with application at the potential of −1.8 V and following dissolution at −0.9 V, to create a porous alloy surface. The cathodic polarization measurements of the prepared porous stainless steel electrodes were measured in a 10 mass% KOH solution. Moreover, the amount of hydrogen generated during constant voltage electrolysis with a hydrogen sensor in situ was also measured. The porous stainless steel alloy showed higher current density at lower potentials in the cathodic polarization compared to untreated stainless steel. The cathodic polarization measurements in alkaline solution showed that the porous 304 stainless steel alloy is an excellent cathode material. [ABSTRACT FROM AUTHOR]

Redox Flow Batteries (RFBs) offer a promising solution for energy storage due to their scalability and long lifespan, making them particularly attractive for integrating renewable energy sources with fluctuating power output. This study investigates the performance of a prototype Zinc-Chlorine Flow Battery (ZCFB) designed for low-cost and readily available electrolytes. The ZCFB utilizes a saltwater electrolyte containing ZnCl2 and NaCl, paired with a mineral spirits catholyte. The electrolyte consists of a 4 M ZnCl2 and a 2 M NaCl solution, both with a pH of 4.55. The anode was a zinc metal electrode, while the cathode comprised a porous carbon electrode on a titanium grid current collector. The cell volume was approximately 4.0 mL, with separate reservoirs for the NaCl/H2O and mineral spirits electrolytes. Experiments were conducted under constant current conditions, with a 0.2 A charging current and a 5 mA discharge current chosen for optimal cell voltage. The study analyzed the relationship between voltage, current, power, and capacity during both charging and discharging cycles. Results from multiple charge/discharge cycles found that the current density of the battery is around 62.658 mA/cm2 with an energy capacity average of 1.2 Wh. These findings can contribute to the development of more efficient and practical ZCFBs, particularly for applications requiring low-cost and readily available electrolytes. [ABSTRACT FROM AUTHOR]

The 3D structure (i.e., microstructure) of porous electrodes governs the performance of emerging electrochemical technologies such as fuel cells, electrolysis, and batteries. Sustaining electrochemical reactions and convective‐diffusive mass transport at high efficiency is complex and motivates the search for sophisticated microstructures with multimodal pore size distributions and pore size gradients. Here a new synthesis route for porous, metallic layers is presented that combines the characteristics of carbon structures (i.e., pore size, porosity) with the properties of metals (i.e., recyclability, conductivity). Building on the method of dynamic hydrogen bubble templating, a novel approach is engineered to manufacture thin, free‐standing layers using an electrochemical flow cell through the introduction of an intermediate layer and optimization of the synthesis parameters. Mechanically stable layers are created with thicknesses ranging from ≈50 to ≈200 µm comprising porous, dendritic structures, arranged to form a vascular network of larger pores with a gradient in radii from ≈5 µm at the bottom and up to ≈36 µm at the top of the material. Using X‐ray tomographic data, the morphology is analyzed, and the diffusive transport through the material as a function of liquid filling is simulated and compared to state‐of‐the‐art carbon fiber‐based electrodes, showing significantly higher mass transfer properties. [ABSTRACT FROM AUTHOR]

This work describes a novel methodology for measuring the potential distribution within the porous copper foam electrode of a zinc‐air/silver hybrid (ZASH) flow battery by using local potential probes. The suitability of dynamic hydrogen electrodes (DHEs) and a quasi‐reference electrode as probes is evaluated, with the latter chosen in view of stability. Liquid and solid‐phase potentials are recorded at varying applied current densities over multiple charge‐discharge cycles. Various zinc structures are found within specific overpotential ranges, with moss‐like structures appearing between 7.8 mV and 13.2 mV and the desired boulder structures in the range of 22 mV to 100 mV. Regardless of the current density, the highest liquid‐phase potentials are always measured in the outermost region of the porous foam near to the separator. In practice, this means that increasing the thickness of the copper foam over about 5 mm does not provide significant performance benefits. Conversely, solid‐phase potentials across the copper foam remain nearly uniform, resulting in negligible effects on local overpotential. The presented technique provides unique insights into the behavior of porous electrodes in electrochemical energy conversion technologies, facilitating the determination of the optimal properties for maximum efficiency, such as electrode thickness. [ABSTRACT FROM AUTHOR]

In this research, a three-dimensional model has been developed in COMSOL Multiphysics software for numerical simulation to assess the high temperature proton exchange membrane fuel cell performance across various parameters. The results of the simulation and the data from experiments correspond closely when the values of the temperature, the thicknesses of the electrode layer and the membrane are 453.15K, 50e-6m and 100e-6m, respectively. Polarization curves at different cell temperatures, operating pressures, different porosities of gas diffusion layer, membrane conductivities, membrane thicknesses and porous electrode thicknesses are examined. The obtained results indicate that the fuel cell performance decreases when the cell runs at temperatures from 393.15K to 453.15K. Moreover, it is found that the cell performance is improved when the gas diffusion layer porosity increases from 0.1 to 0.6. Furthermore, the investigation of the fuel cell thickness membrane effect shows that a thinner membrane of 25e-6m gives the best performance. The simulation using the present developed model can be useful for optimization of the cell design and the operating conditions. [ABSTRACT FROM AUTHOR]

In the current work, we report the binder-free hydrothermal one-pot synthesis of a cobalt oxide hierarchical nanostructure (3O4-HNS) onto a highly conductive carbon fiber substrate (CFS/Co3O4-HNS) as an efficient electrode for energy storage devices. The fabricated electrode and synthesized 3O4-HNS were structurally characterized using SEM, EDAX, XRD, and FTIR techniques. Electrochemical characterization of the fabricated CFS/3O4-HNS electrode was also performed and showed that the electrical double-layer capacitance and pseudo-capacitance mechanisms both play roles in the charge storage of the CFS/3O4-HNS electrode. The obtained results exhibited the electrochemical-specific capacitance of 715 F=g at a current density of 3A=g for the CFE/Co3O4-HNS electrode. The fabricated electrode remains at 96% of its initial capacitance after 3000 cycles, showing the excellent cyclability of the fabricated CFS/3O4 -HNS electrode. These results paved the way for using the proposed facile, one-pot synthesized CFE/3O4 -HNS as an efficient electrode for use in electrochemical energy storage devices. [ABSTRACT FROM AUTHOR]

This research focuses on the rational design of porous enzymatic electrodes, using horseradish peroxidase (HRP) as a model biocatalyst. Our goal was to identify the main obstacles to maximizing biocatalyst utilization within complex porous structures and to assess the impact of various carbon nanomaterials on electrode performance. We evaluated as-synthesized carbon nanomaterials, such as Carbon Aerogel, Coral Carbon, and Carbon Hollow Spheres, against the commercially available Vulcan XC72 carbon nanomaterial. The 3D electrodes were constructed using gelatin as a binder, which was cross-linked with glutaraldehyde. The bioelectrodes were characterized electrochemically in the absence and presence of 3 mM of hydrogen peroxide. The capacitive behavior observed was in accordance with the BET surface area of the materials under study. The catalytic activity towards hydrogen peroxide reduction was partially linked to the capacitive behavior trend in the absence of hydrogen peroxide. Notably, the Coral Carbon electrode demonstrated large capacitive currents but low catalytic currents, an exception to the observed trend. Microscopic analysis of the electrodes indicated suboptimal gelatin distribution in the Coral Carbon electrode. This study also highlighted the challenges in transferring the preparation procedure from one carbon nanomaterial to another, emphasizing the importance of binder quantity, which appears to depend on particle size and quantity and warrants further studies. Under conditions of the present study, Vulcan XC72 with a catalytic current of ca. 300 µA cm−2 in the presence of 3 mM of hydrogen peroxide was found to be the most optimal biocatalyst support. [ABSTRACT FROM AUTHOR]

Electrochemical energy storage devices are vital for renewable energy integration and the deployment of electric vehicles. Ongoing research seeks to create new materials with innovative morphologies capable of delivering high specific capacitance for the next generation of customizable energy devices. Carbon nitride is an excellent candidate for electrochemical energy storage devices; however, it has limitations such as layer stacking, poor electric conductivity, a restricted number of electroactive sites, and static electrochemical reaction rates. This research objective is to make porous structures in carbon nitride nanosheets and integrate them with CuO particles to increase surface area and improve electrochemical performance. The use of thermal heating, acidic treatment, and hydrothermal processes accomplishes this. Along with X-ray diffraction peaks of the CuO phase, a prominent peak (002) at 27.67° indicates the presence of graphitic-structured carbon nitride. TEM images show that CuO particles are evenly attached to the surface of g-C3N4 nanosheets with lattice intervals of 0.336 and 0.232 nm, which are the (002) and (111) orientations of the g-C3N4 and CuO phases, respectively. Adding CuO nanoparticles to porous g-C3N4 nanosheets avoids layer stacking and provides micro- and mesopore channels, increasing the specific surface area (42.60m2 g-1). The CuO@ porous g-C3N4 electrode delivered 817 F g-1 of specific capacitance at 1Ag-1 and admirable capacitance retention (92.3% after 6000 cycles) due to the synergistic impact of its unique composition and structural characteristics. Because of its outstanding electrochemical performance and fascinating discoveries, CuO@ porous g-C3N4 may be employed as a cathode material for high-performance supercapacitors. [ABSTRACT FROM AUTHOR]

Three-dimensional (3D) printed batteries are considered a special class of energy storage devices that allow flexible control of the electrode structure on a microscopic scale, which is crucial to improving the energy density of miniaturized devices. In this study, lithium iron phosphate (LFP) porous electrodes were prepared by 3D printing technology. The results showed that with the increase of LFP content from 20 wt% to 60 wt%, the apparent viscosity of printing slurry at the same shear rate gradually increased, and the yield stress rose from 203 Pa to 1187 Pa. The rheological property and printability of the slurry show that the printing slurry of 40 wt% LFP has excellent conformal property and self-supporting property. Due to the porous skeleton shortening the transfer distance of ions and electrons and enhancing the efficiency of the electrode reaction, the rate performances and cycle stability of LFP batteries were improved. The 3D-printed battery containing an active material loading of 15.9 mg cm−2 achieved a specific capacity of 121.7 mA h g−1 at 0.5C after 200 cycles and coulombic efficiency higher than 99.7 %, and the LFP battery had an energy density of 350 W h kg−1. These results suggest that 3D printing is an effective strategy for developing batteries with high active material loadings and energy densities at micro sizes. [ABSTRACT FROM AUTHOR]

Wearable long-term monitoring applications are becoming more and more popular in both the consumer and the medical market. In wearable ECG monitoring, the data quality depends on the properties of the electrodes and on how they interface with the skin. Dry electrodes do not require any action from the user. They usually do not irritate the skin, and they provide sufficiently high-quality data for ECG monitoring purposes during low-intensity user activity. We investigated prospective motion artifact–resistant dry electrode materials for wearable ECG monitoring. The tested materials were (1) porous: conductive polymer, conductive silver fabric; and (2) solid: stainless steel, silver, and platinum. ECG was acquired from test subjects in a 10-min continuous settling test and in a 48-h intermittent long-term test. In the settling test, the electrodes were stationary, whereas both stationary and controlled motion artifact tests were included in the long-term test. The signal-to-noise ratio (SNR) was used as the figure of merit to quantify the results. Skin–electrode interface impedance was measured to quantify its effect on the ECG, as well as to leverage the dry electrode ECG amplifier design. The SNR of all electrode types increased during the settling test. In the long-term test, the SNR was generally elevated further. The introduction of electrode movement reduced the SNR markedly. Solid electrodes had a higher SNR and lower skin–electrode impedance than porous electrodes. In the stationary testing, stainless steel showed the highest SNR, followed by platinum, silver, conductive polymer, and conductive fabric. In the movement testing, the order was platinum, stainless steel, silver, conductive polymer, and conductive fabric. [ABSTRACT FROM AUTHOR]

Next-generation polymer electrolyte fuel cells (PEFCs) require an integral design of the porous structure of electrodes at different scales to improve performance and enlarge durability while reducing cost. One of today's biggest challenges is the stable, high-performance operation at low Pt loading due to the detrimental effect of the local oxygen transport resistance caused by ionomer around catalyst sites. Hindered local oxygen transport arises from sluggish kinetics at the local reaction environment, that comprises adsorption at (wet) ionomer and Pt interfaces, and diffusivity of gas species in ionomer and water. Diverse factors affect oxygen transport, including operating conditions (relative humidity, temperature, and pressure), ionomer content and morphology, ionomer heterogeneity, porosity of carbon support, catalyst dispersity, and flooding. To attain performance and durability targets, it is essential to maximize the oxygen utilization of the catalyst layer by implementing enhanced membrane electrode assembly architectures. This involves employing advanced catalyst layer preparation techniques, including electrospraying, to generate optimized highly porous morphologies. Furthermore, achieving these targets necessitates the development of new materials with tailored properties, such as high permeability and porous ionomers, among other innovative strategies. [ABSTRACT FROM AUTHOR]

In this study, the performance of a zero-gap flow-through reactor with three-dimensional (3D) porous Ti/RuO2-TiO2@Pt anodes was systematically investigated for the electrocatalytic oxidation of phenolic wastewater, considering phenol and 4-nitrophenol (4-NP) as the target pollutants. The optimum parameters for the electrochemical oxidation of phenol and 4-NP were examined. For phenol degradation, at an initial concentration of 50 mg/L, initial pH of 7, NaCl concentration of 10.0 g/L, current density of 10 mA/cm2, and retention time of 30 min, the degradation efficiency achieved was 95.05%, with an energy consumption of 15.39 kWh/kg; meanwhile, for 4-NP, the degradation efficiency was 98.42% and energy consumption was 19.21 kWh/kg (at an initial concentration of 40 mg/L, initial pH of 3, NaCl concentration of 10.0 g/L, current density of 10 mA/cm2, and retention time of 30 min). The electrocatalytic oxidation of phenol and 4-NP conformed to the pseudo-first-order kinetics model, and the k values were 0.2562 min−1 and 0.1736 min−1, respectively, which are 1.7 and 3.6-times higher than those of a conventional electrolyzer. Liquid chromatography–mass spectrometry (LC–MS) was used to verify the intermediates formed during the degradation of phenol or 4-NP and a possible degradation pathway was provided. The extremely narrow electrode distance and the flow-through configuration of the zero-gap flow-through reactor were thought to be essential for its lower energy consumption and higher mass transfer efficiency. The zero-gap flow-through reactor with a novel 3D porous Ti/RuO2-TiO2@Pt electrode is a superior alternative for the treatment of industrial wastewater. [ABSTRACT FROM AUTHOR]

Flexible pressure sensors have many potential applications in the monitoring of physiological signals because of their good biocompatibility and wearability. However, their relatively low sensitivity, linearity, and stability have hindered their large-scale commercial application. Herein, a flexible capacitive pressure sensor based on an interdigital electrode structure with two porous microneedle arrays (MNAs) is proposed. The porous substrate that constitutes the MNA is a mixed product of polydimethylsiloxane and NaHCO3. Due to its porous and interdigital structure, the maximum sensitivity (0.07 kPa−1) of a porous MNA-based pressure sensor was found to be seven times higher than that of an imporous MNA pressure sensor, and it was much greater than that of a flat pressure sensor without a porous MNA structure. Finite-element analysis showed that the interdigital MNA structure can greatly increase the strain and improve the sensitivity of the sensor. In addition, the porous MNA-based pressure sensor was found to have good stability over 1500 loading cycles as a result of its bilayer parylene-enhanced conductive electrode structure. Most importantly, it was found that the sensor could accurately monitor the motion of a finger, wrist joint, arm, face, abdomen, eye, and Adam's apple. Furthermore, preliminary semantic recognition was achieved by monitoring the movement of the Adam's apple. Finally, multiple pressure sensors were integrated into a 3 × 3 array to detect a spatial pressure distribution. Compared to the sensors reported in previous works, the interdigital electrode structure presented in this work improves sensitivity and stability by modifying the electrode layer rather than the dielectric layer. ARTICLE HIGHLIGHTS: HIGHLIGHTS • An interdigital electrode structure composed of two porous microneedle arrays greatly increases the sensitivity of the pressure sensor. • The pressure sensor has good stability over 1500 cycles due to the bilayer parylene-enhanced porous microneedle array electrode structure. • The pressure sensor can accurately monitor the movements of body parts and has a certain ability to recognize speech. [ABSTRACT FROM AUTHOR]

In vanadium redox flow batteries, the flow field geometry plays a dramatic role on the distribution of the electrolyte and its design results from the trade-off between high battery performance and low pressure drops. In the literature, it was demonstrated that electrolyte permeation through the porous electrode is mainly regulated by pressure difference between adjacent channels, leading to the presence of under-the-rib fluxes. With the support of a 3D computational fluid dynamic model, this work presents two novel flow field geometries that are designed to tune the direction of the pressure gradients between channels in order to promote the under-the-rib fluxes mechanism. The first geometry is named Two Outlets and exploits the splitting of the electrolyte flow into two adjacent interdigitated layouts with the aim to give to the pressure gradient a more transverse direction with respect to the channels, raising the intensity of under-the-rib fluxes and making their distribution more uniform throughout the electrode area. The second geometry is named Four Inlets and presents four inlets located at the corners of the distributor, with an interdigitated-like layout radially oriented from each inlet to one single central outlet, with the concept of reducing the heterogeneity of the flow velocity within the electrode. Subsequently, flow fields performance is verified experimentally adopting a segmented hardware in symmetric cell configuration with positive electrolyte, which permits the measurement of local current distribution and local electrochemical impedance spectroscopy. Compared to a conventional interdigitated geometry, both the developed configurations permit a significant decrease in the pressure drops without any reduction in battery performance. In the Four Inlets flow field the pressure drop reduction is more evident (up to 50%) due to the lower electrolyte velocities in the feeding channels, while the Two Outlets configuration guarantees a more homogeneous current density distribution. [ABSTRACT FROM AUTHOR]

Redox cycling is a powerful amplification strategy for reversible redox species within miniaturized electrochemical sensors. Herein, we generate three‐dimensional (3D) porous carbon nanofiber electrodes by CO2 laser‐writing on electrospun polyimide (PI) nanofiber mats, referred to as laser‐induced carbon nanofibers (LCNFs). The technique allowed the fabrication of interdigitated electrode (IDE) arrays with finger width and gap distance of ~400 μm and ~40 μm, respectively, offering approximately 3.5 times amplification efficiency (AF) and 95 % collection efficiency (CE). Such dimensions could not be achieved with IDEs fabricated on conventional PI film because the devices were short‐circuited. Stacked electrodes were also constructed as an alternative to the IDE design. Here, nanofiber mats as thin as ~20 μm were fabricated and used as vertical insulation between two LCNF band electrodes. While redox cycling efficiency was similar, the IDE design is more favorable considering the lower complexity and better signal reproducibility. Our strategy thus paves the way for creating flexible 3D porous electrodes with redox cycling ability that can be integrated into microfluidics and lab‐on‐a‐chip systems. In particular, the devices offer inherent flow‐through features in miniaturized analytical devices where separation and sensitive detection could be further realized. [ABSTRACT FROM AUTHOR]

Electrochemical membranes (ECMs) and porous electrodes have gained much attention in a broad range of applications including water and wastewater treatment, energy production and storage, and carbon dioxide capture. Lab scale batch experiments (electrochemical stirred cells) are the baseline for developing ECMs and porous electrodes. We observed electrochemical dissolution of metal fasteners (alligator clips), used to hold porous conductive and non‐conductive membranes in batch electrochemical cells, despite being kept outside the electrolyte. The electrolyte migrated through the porous membranes by the action of capillary forces, forming a closed electrochemical circuit with the metal fasteners. This unexpected leaching can lead to misleading results for electrochemical experiments on porous electrodes and ECMs. In this study, we compared (1) porous membranes versus non‐porous electrodes, (2) hydrophilic versus hydrophobic membranes, and (3) conductive versus non‐conductive membranes in their ability to cause capillary wetting‐induced corrosion of metal fasteners. We proposed a simple solution for the problem: separating the metal fasteners from the porous membrane electrode with a non‐porous conductive graphite foil, which keeps the electrochemical circuit open. We have validated this solution and propose it as a standard method for experiments using porous electrodes and electrically conductive membranes. [ABSTRACT FROM AUTHOR]

The process of diffusion of lithium ions into porous carbon electrode materials obtained by hydrothermal carbonization of plant raw materials at different temperatures was the galvanostatic intermittent titration technique. The diffusion coefficient of lithium ions in the electrode material was calculated and its dependence on the intercalation degree x was analyzed. It was found that with the increase in the carbonation temperature of the raw material, which results in the removal of gaseous aliphatic and then aromatic molecules with low molecular weight, processes of cyclization and aromatization of molecules, as well as intensive carbonization of the raw material, the formation of carbon layers and primary graphite nuclei, the coefficient diffusion increases due to ordering the structure of the porous carbon material and reducing its specific surface area and total pore volume. When the maximum value of the intercalation degree is reached, the diffusion coefficient of lithium ions is 3.6·10 – 12 сm²/s (х = 0.28), 7.9·10 – 12 сm²/s (х = 0.44), and 1.9·10 – 10 сm²/s (х = 0.19) for samples obtained at carbonization temperatures of 600, 750, and 1000 °C, respectively. A comparative analysis of the values of the diffusion coefficient, calculated on the basis of the data of galvanostatic intermittent titration technique and electrochemical impedance spectroscopy, was carried out. [ABSTRACT FROM AUTHOR]

The size, geometry and arrangement of pores can significantly affect both the activity of electrocatalysts and the performance of supercapacitors. Electrochemical impedance spectroscopy (EIS) is a powerful, non-invasive diagnostic tool for characterizing porous conductive media. To date, the impedance of porous electrodes characterized by the distribution of pore sizes has been described only on the basis of numerical models. Here, for the first time, the impedance of such systems is provided in the form of analytical solutions valid in high and low frequency range. The model enables traditional equivalent circuit fitting to impedance of electrodes characterized by log–normal distribution of pore sizes. The analytical expressions for the circuit elements give access to the electrode idealized geometry in terms of log-normal distribution. The model was applied for the analysis of the electrochemical impedance of activated carbon electrode in a sulphuric acid solution. The width of pore size distribution, mean pore radius, pore length and the number of pores can be determined from a single impedance spectrum.

Miniaturized energy storage devices, such as electrostatic nanocapacitors and electrochemical micro-supercapacitors (MSCs), are important components in on-chip energy supply systems, facilitating the development of autonomous microelectronic devices with enhanced performance and efficiency. The performance of the on-chip energy storage devices heavily relies on the electrode materials, necessitating continuous advancements in material design and synthesis. This review provides an overview of recent developments in electrode materials for on-chip MSCs and electrostatic (micro-/nano-) capacitors, focusing on enhancing energy density, power density, and device stability. The review begins by discussing the fundamental requirements for electrode materials in MSCs, including high specific surface area, good conductivity, and excellent electrochemical stability. Subsequently, various categories of electrode materials are evaluated in terms of their charge storage mechanisms, electrochemical performance, and compatibility with on-chip fabrication processes. Furthermore, recent strategies to enhance the performance of electrode materials are discussed, including nanostructuring, doping, heteroatom incorporation, hybridization with other capacitive materials, and electrode configurations.

The CuO anode prepared by the traditional slurry coating method still suffers from limited lithium-ion transport kinetics due to the long diffusion lengths and tortuous transport paths resulting from the addition of conductive agents and binders. In this study, we have prepared the integrated CuO@Cu electrode with the porous CuO nanosheets in situ vertically grown on Cu current collector using a chemical etching method. The integrated electrode design improves the electrical conductivity of the electrode, and the porous nanosheets increase the contact area of the electrolyte and buffer the volume variation of CuO during cycling. Moreover, the vertically grown CuO nanosheets can shorten the lithium ion diffusion path and reduce the tortuosity of lithium ion transport pathways, thus realizing fast lithium ion storage kinetics. While the slurry coating CuO powder electrode shows a capacity of 13.3 mAh g−1 at 20 A g−1, our integrated CuO@Cu electrode still delivers a capacity of 181.6 mAh g−1 at 20 A g−1. This study demonstrates that rational structural design can significantly improve Li-ion storage kinetics. [ABSTRACT FROM AUTHOR]

In this study, we developed a pioneering non-enzymatic electrochemical sensor utilizing a flexible porous graphene electrode modified with ZnO nanoparticles (ZnO/fPGE sensor) to assess hypoxanthine (HXA) content in pork at post-mortem time. The ZnO/fPGE sensor was synthesized via hydrothermal method and direct laser writing with a CO2 laser on a polyimide film at ambient conditions. Its characterization was analyzed by Raman, Fourier-transform infrared spectroscopy, field-emission scanning microscopy, energy-dispersive x-ray spectroscopy, and cyclic voltammetric techniques. Linear response, the limit of detection, and sensitivity to the HXA were enhanced with the values of the range from 1.5 to 150, 0.14 µM, and 6.6 µA μM−1 cm−2, respectively. Effective resistance to common physiological interferences (such as uric acid, ascorbic acid, dopamine, glucose, and xanthine) was indicated, and additionally, the determination of HXA concentration in real samples with good selectivity is attributed to the synergistic effects between ZnO nanoparticles and fPGE. Therefore, the ZnO/fPGE has provided a favorable electrical environment for developing high-performance electrochemical biosensors to determine hypoxanthine in pork meat. [ABSTRACT FROM AUTHOR]

The poor electrochemical activity and low wettability of graphite felt (GF) electrodes significantly limit the energy efficiency and power of vanadium redox flow batteries (VRFBs). To solve these problems, we developed an N-doped porous carbon-coated electrode by the carbonization of zeolitic imidazolate framework-8- (ZIF-8-) coated GF. By controlling the carbonization temperature, the effects of temperature on the structural morphology, pore structure, and amount and type of functional groups of the electrode were confirmed. In addition, the effect of the change in the pore structure and the amount and type of functional groups on the electrocatalytic activity for the vanadium redox reaction was demonstrated. The synthesized N-doped porous carbon-coated electrode, which showed the best electrochemical activity, had a sufficient amount of nitrogen functional groups with a high ratio of graphitic N and the highest surface area and pore volume among all the samples, providing abundant active sites for the VO2+/VO2+ redox reaction. The VRFB fabricated using prepared electrode exhibited energy and voltage efficiencies of 70.44% and 73.44%, respectively, at 200 mA cm-2, which were 11.77% and 11.08% higher than those of the bare GF electrode. Furthermore, the modified battery operated effectively at a high current density of 350 mA cm-2. The energy efficiency exhibited excellent stability over 500 charge/discharge cycles at 250 mA cm-2. Hence, this study presents a promising method for the development of high-performance VRFB electrodes. [ABSTRACT FROM AUTHOR]

Highlights: The novel hybrid structured nanofiber electrode, incorporating crushed nanofibers into the nanofiber network, is designed to effectively resolve the issue of insufficient interfacial bonding of porous nanofiber electrodes on solid electrolyte interfaces. The hybrid nanofibers are covered with in situ exsolved metal nanocatalysts to enhance CO2 reduction reaction rate. Electrochemical and microstructure 3D reconstruction analyses confirmed the hybrid structure's efficiency in improving the contact area at the porous-solid interface, leading to an increase in reaction sites. The unique characteristics of nanofibers in rational electrode design enable effective utilization and maximizing material properties for achieving highly efficient and sustainable CO2 reduction reactions (CO2RRs) in solid oxide electrolysis cells (SOECs). However, practical application of nanofiber-based electrodes faces challenges in establishing sufficient interfacial contact and adhesion with the dense electrolyte. To tackle this challenge, a novel hybrid nanofiber electrode, La0.6Sr0.4Co0.15Fe0.8Pd0.05O3−δ (H-LSCFP), is developed by strategically incorporating low aspect ratio crushed LSCFP nanofibers into the excess porous interspace of a high aspect ratio LSCFP nanofiber framework synthesized via electrospinning technique. After consecutive treatment in 100% H2 and CO2 at 700 °C, LSCFP nanofibers form a perovskite phase with in situ exsolved Co metal nanocatalysts and a high concentration of oxygen species on the surface, enhancing CO2 adsorption. The SOEC with the H-LSCFP electrode yielded an outstanding current density of 2.2 A cm−2 in CO2 at 800 °C and 1.5 V, setting a new benchmark among reported nanofiber-based electrodes. Digital twinning of the H-LSCFP reveals improved contact adhesion and increased reaction sites for CO2RR. The present work demonstrates a highly catalytically active and robust nanofiber-based fuel electrode with a hybrid structure, paving the way for further advancements and nanofiber applications in CO2-SOECs. [ABSTRACT FROM AUTHOR]

The development of high-performance flexible pressure sensors with porous hierarchical microstructures is limited by the complex and time-consuming preparation processes of porous hierarchical microstructures. In this study, a simple modified heat curing process was first proposed to achieve one-step preparation of porous hemispherical microstructures on a polydimethylsiloxane (PDMS) substrate. In this process, a laser-prepared template was used to form surface microstructures on PDMS film. Meanwhile, the thermal decomposition of glucose monohydrate additive during heat curing of PDMS led to the formation of porous structures within PDMS film. Further, based on the obtained PDMS/CNTs electrodes with porous hemisphere array and ionic polymer dielectric layers, high-performance ionic piezocapacitive sensors were realized. Under the synergistic effect of the low-stiffness porous hemisphere microstructure and the electric double layer of the ionic polymer film, the sensor based on an ionic polymer film with a 1:0.75 ratio of P(VDF-HFP):[EMIM][TFSI] not only achieves a sensitivity of up to 106.27 kPa−1 below 3 kPa, but also has a wide measurement range of over 400 kPa, which has obvious advantages in existing flexible piezocapacitive sensors. The rapid response time of 110 s and the good stability of 2300 cycles of the sensor further elucidate its practicality. The application of the sensor in pulse monitoring, speech recognition, and detection of multiple dynamic loads verifies its excellent sensing performance. In short, the proposed heat curing process can simultaneously form porous structures and surface microstructures on PDMS films, greatly simplifying the preparation process of porous hierarchical microstructures and providing a simple and feasible way to obtain high-performance flexible pressure sensors. [ABSTRACT FROM AUTHOR]

La 0.75 Sr 0.25 Cr 0.5 Mn 0.5 O 3-δ (LSCM) mixed conducting has been studied as nanostructured air and fuel electrode, for intermediate temperature symmetric Solid Oxide Fuel cell (S–SOFC). The possible mechanisms involved in the oxygen reduction and hydrogen oxidation reactions of these LSCM nanostructures porous electrodes deposited on La 0.8 Sr 0.2 Ga 0.8 Mg 0.2 O 3-δ (LSGM) electrolyte, were analyzed by electrochemical impedance spectroscopy (EIS) at 700 °C varying the oxygen partial pressure (pO 2) and the hydrogen partial pressure (pH 2). This analysis was complemented by the study of the electrical conductivity by the four-probe DC technique in the range between 300 and 800 °C in flowing dry atmospheres of air or H 2. Results suggested that the O 2 reduction reaction mechanism involves the O 2 - dissociative adsorption and O- ion migration near the surface region, while the H 2 -oxidation reaction limiting-step is controlled by a slow charge transfer process, and H 2 - dissociative adsorption on the ultimate O-layer. [Display omitted] [ABSTRACT FROM AUTHOR]