Electrochemical Impedance Analysis Research Articles

Unravelling the effect of soxhlet extracted Pisolithus arhizus fungi in bio-sensitized solar cells in response to diverse polar solvents

The potential application of Pisolithus arhizus fungi as an effective sensitizer in bio-sensitized solar cells (BSSCs) is the first of its kind to investigate the photovoltaic performance of BSSCs in polar protic and aprotic solvents. The soxhlet extraction method was employed to extract dye molecules in organic solvents including chloroform, 2-propanol, acetone, ethanol, methanol and DMSO and named PA1, PA2, PA3, PA4, PA5, PA6 to fabricate BSSCs. TiO2 and Platinum were used as working and counter electrodes. The structural, optical, morphological properties of the extracted dyes and dye anchored TiO2 films were analyzed through FTIR, UV–Vis spectroscopy and FESEM analysis. The optical absorption analysis revealed the presence of pisoquinone pigments in the fungi, from flavonoid family. The current-voltage, electrochemical impedance and cyclic voltammetry analysis showed that the PA4 ethanolic-based BSSC demonstrated the highest power conversion efficiency of 1.31 % compared to other DSSCs, with a Jsc of 3.40 mA cm−2 and Voc of 514 mV and the bandgap energy of 1.8eV. The order of the conversion efficiency for DSSCs with different solvents was ethanol (PA4) > methanol (PA5) > acetone (PA3) > DMSO (PA6) > 2-propanol (PA2) > chloroform (PA1). This finding highlights that selecting optimal, novel sensitizers and extraction solvents is crucial to maximize solar cell efficiency.

“Unveiling marigold assembled micro flowers of tungsten oxide towards solid-state flexible pouch and coin cell supercapacitors”

Marigold analogues micro flowers of tungsten oxide (WO3) have been grown in thin film form through simple and cost-effective solution chemistry approach on stainless steel substrate. Aqueous precursor involving WO4-2 ions agglomerated as self-sacrificing template growing initially into the nano-petal, followed by self-assembly; leading to marigold analogues micro flower surface architecture. This enthralling morphology motivated us not only to fabricate supercapacitive electrode but also to design complete solid-state supercapacitor devices in dual configurations: flexible pouch cell and coin cell. Interestingly, both devices even in symmetric configuration yields remarkable potential window of 1.82 V when sandwiched by gel inclusive of Li+ ions dispersed in non-conducting polyvinyl alcohol matrix. Solid-state flexible pouch cell and coin cell delivered specific capacitances of 103.98 ± 3.59 and 30.09 ± 1.03F/g respectively at a scan rate of 5 mV/s. Assembled electrode, coin-cell and flexible pouch-cells have been well assessed in-depth through specific capacitances using cyclic voltammetry and galvanostatic charge discharge, diffusive and capacitive contributions, mechanical bending tests, electrochemical active surface area, and electrochemical impedance analysis. As practical applicability has been demonstrated for designed flexible pouch cell to run small fan and light emitting diode panel whereas coin cell to run light emitting diode panel.

Improved electro-kinetics of new electrolyte composition for realizing high-performance zinc-bromine redox flow battery

Aqueous Redox Flow Batteries (ARFB) are the most prominent technology for large-scale energy storage applications. The energy density of the ARFBs is mainly determined by the electrolyte components, which highly influence the flow battery performance. In the present work, we acutely investigated the various electrolyte compositions and optimized the best electrolyte for realizing the high performance of Zn-Br2 ARFBs. The electrode kinetics, such as rate constant, exchange current density, conductivity, and diffusion coefficient, were analyzed using electrochemical techniques, cyclic voltammetry, and electrochemical impedance analysis. It was observed that zinc bromide (ZnBr2) + perchloric acid (HClO4) + 1-Ethyl-1-methylmorpholinium bromide (MEM) + N-ethyl-N-methylpyrrolidinium bromide (MEP) and ZnBr2 + zinc chloride (ZnCl2) + MEM + MEP electrolytes showed improved performance, where the redox kinetics of 2Br-/Br2 redox couple is greatly enhanced. The presence of perchloric acid unlocks the capacity of full electro-oxidation of bromide (Br-) to bromine (Br2) as it involves 1e- per Br-, which would be highly beneficial to attain high energy density. Further, Zn-Br2 RFB adopted with optimized electrolyte formulation ZnBr2 + HClO4 + MEM+ MEP shows a better round-trip efficiency and displays a stable long cycling performance over 200 cycles with an energy (EE) and coulombic efficiency (CE) of > 68% and > 92%, respectively.

Experimental investigation on microstructure, hardness and corrosion resistance of an electromagnetic welded titanium-stainless steel dissimilar materials

The electromagnetic welding (EMW), often known as magnetic pulse welding, is a solid-state welding technology that is used to join two different materials using high-velocity impact. In this study an attempt was made to join the Titanium(Ti)- Stainless Steel(SS 304) materials with the help of multi turn disc coil along with the field shaper. A comparative investigation was conducted on the joint’s microstructure, as well as its mechanical and corrosion properties. Inverted optical microscopy (OM) and x-ray diffraction (XRD) were used to do the microstructural characterization of the joint. The micro-Vickers hardness test was used to analyse the material’s mechanical properties. In addition, electrochemical experiments were run on the Ti-SS 304 EMW junction as well as the component materials to establish how resistant they were to corrosion. Using an electrochemical impedance analyzer, the levels of corrosion that were caused by the structures were measured while they were submerged in a solution of nitric acid at room temperature. The microstructural pictures revealed a wave-like pattern at the material’s interface, which is evidence of strong adhesion between the components. The micro vickers hardness of the joints was within the permitted range, as was the corrosion rate.

In-situ electrochemical impedance analysis of a commercial SOFC stack fueled by real wood gas

The combination of solid oxide fuel cells (SOFCs) and wood gasification has the potential to significantly increase renewable electricity production and decrease emissions. Depending on the quality of the wood gas, degradation processes have a significant impact on the reliability and lifetime of the SOFC. Using electrochemical impedance spectroscopy (EIS) and subsequent distribution of relaxation times (DRT) analysis, the impact on the degradation of coupling wood gasification with a commercial SOFC stack is determined in this study. The thermal behavior of the SOFC stack under various operating conditions, as well as various synthetic wood gas mixtures classified by their hydrogen-to-carbon (H/C) ratio, was assessed. The decrease in the H/C ratio from 8 to 1, observed during syngas and real wood gas operation, leads to a rightward shift in the Nyquist plots, suggesting an increase in the SOFC stack's impedance. Correlations between variations in the H/C ratio and their effects on anodic electrooxidation, ionic conduction, gas transport, and diffusion were identified using DRT analysis to interpret the EIS results. By incorporating an upstream desulfurization system and ensuring an H/C ratio greater than 2, the coupling of biomass gasification with the SOFC stack was stable to degradation issues.

Enhancement capacitance of FTO electrodes via the electrospun ZnO thin film coating for supercapacitor applications; the role of dopants

The present study aimed to investigate the electrochemical performance of nanostructured ZnO thin films (TFs) on the fluorine-doped tin oxide (FTO) substrate. The pure ZnO TFs, Al-doped ZnO TFs, and Cu-doped ZnO TFs were fabricated using electrospinning and post calcination at 400 °C. The electron microscopy studies revealed that electrospun nanofiber masks changed to dense TFs with an average thickness of 250–290 nm constructed by 10–20 nm connected nanoparticles (NPs). The doping of Al and Cu into ZnO TFs increased the hydrophilicity. Cyclic voltammetry (CV), electrochemical impedance (EIS), charge-discharge profiles, and Mott-Schottky (M − S) analysis were performed on the samples to evaluate the capacitance performance of pure and doped ZnO TFs. The semiconductor of TFs was n-type. The results confirm that all films can be used as a supercapacitor. Also, our results suggest that Cu-doped ZnO (CZO) TFs are the best choice for a supercapacitor electrode due to their 1.14 F cm−2 areal capacitance at 1 mA cm−2 applied current.

New insights into the mechanism causing the loss of anti-corrosion property of superhydrophobic titanium surfaces

In this paper, we provide new insights into the mechanism causing the loss of anti-corrosion property of superhydrophobic titanium (SHP Ti) during potentiodynamic polarization (PDP) measurements. The water contact angle and sliding angle values of the SHP Ti, produced by a facile two-step process: anodizing and coating, were >160° and 6±2°, respectively. The anodization of Ti resulted in randomly distributed micro-clusters of TiO2-xCly covering the Ti surface homogeneously while the low surface energy organic coatings were inhomogeneous in coverage and specifically distributed over the micro-clusters alone of the anodized titanium surface. The electrochemical impedance (EIS) analysis of the SHP CP-Ti samples has shown more than an order of magnitude improvement in their barrier /polarization resistance (Rp) values at ∼ 100 MΩ.cm2 suggesting the effectiveness of the SHP coatings as a barrier against corrosion in neutral chloride environments. However, the Rp values (∼ 10 M Ω.cm2) of the SHP coatings obtained from the PDP analysis were an order of magnitude lower than the Rp values derived from the EIS. SHP CP-Ti samples showed dual passive range behaviour with an initial narrow passive region due to the porous anodized TiO2-xCly layer while the later stage passivity due to the barrier TiO2 layer, where the outer anodized porous TiO2-xCly layer was less effective against corrosion in neutral chloride media. Detailed analysis showed that in PDP, the sample lost its SHP because of the permeation of electrolyte into the hierarchical surface, due to its sensitivity to polarization, owing to the lower thickness of the organic layers. The mechanism involved in the loss of SHP and the limitation of the PDP technique for the corrosion analysis of SHP / organic coatings on metal surfaces is highlighted.

Silver nanoparticles reinforced on silk fibroin/carboxymethylcellulose composite films for electrical applications

This study proposes the fabrication of silver nanoparticles (AgNPs) on silk fibroin-carboxymethylcellulose (SF-CMC) composite films for advancement in electronic device applications. Bombyx mori silk fibroin is a biopolymer that is used as a bio-template in the fabrication of AgNPs. Various silver nitrate (AgNO3) combinations are added to the prepared SF solution to synthesize AgNPs. To develop stand-alone biopolymer-nanocomposite (SF-CMC/AgNPs) films, SF-AgNPs colloidal solution is blended with CMC solution. Ultra Violet – Visible (UV–Vis), Photoluminescence (PL), Fourier Transform Infra-red Spectroscopy (FT-IR), X-ray diffraction (XRD), Transmission Electron Microscopy (TEM) and Atomic Force Microscopy (AFM) have been employed to the prepared SF-CMC/AgNPs composites toevaluate the physical, chemical, structural, morphological, and topographical information of the composite films. Furthermore, the composites are subjected to LCR Hi-tester and electrochemical workstation CH instrument to analyze the AC, DC conductivity, dielectric characteristics, and electrochemical impedance analysis of SF-CMC/AgNPs composites. The UV–visible spectra reveals the formed nanoparticles in spherical shape with average particle size 35–40 nm. XRD reveals the formed AgNPs in face centred cubic (FCC) structure; TEM reveals the average particle size of 35 nm. AC conductivity of the SF-CMC/AgNPs composite found to be 4.0 × 10−4 to 8.04 × 10−4 S/cm. In spite of the presence of AgNPs, measurements of the dielectric behaviourof pure CMC and SF-CMC materials exhibit good dielectric performance. The obtained results demonstrated that the SF-CMCfilms exhibit significant conductivity following AgNPs incorporation and may therefore be used in biosensor and wearable electronic device applications.

Multi-walled carbon nanotubes with embedded nickel sulphide as an effective electrocatalyst for Bi-functional water splitting

Water-splitting presents a viable solution to expanding energy needs. To maximise water-splitting performance, transition metal sulphides, a very efficient electrocatalyst, have been extensively researched. It is unable to generate hydrogen (H2) and oxygen (O2) because to active sites and weak electrical conductivity. Some carbon-based materials offer superior dispersion capacities and bigger active sites for charge transfer to circumvent these restrictions. This work presents an efficient electrocatalyst combining carbon nanotubes (CNTs) and electrochemically active Nickel sulphides, Ni17S18 (NiS), synthesized by using a wet-chemical approach. The improved electrocatalytic performance of NiS@CNTs can be attributed to higher surface area and higher electrical conductivity of CNTs. Furthermore, linear-sweep voltammetry (LSV) and electrochemical impedance analysis (EIS) were also utilized for the electrochemical investigations. The addition of CNTs to NiS showed a over-potential of 330 mV at 40 mA cm−2, with a Tafel slope of 47 mV dec−1 for OER. Similarly, we have also investigated the HER activity of the as-prepared electrocatalysts at the same current density, having a over-potential of 280 mV with a Tafel slope of 102 mV dec−1.

Electrochemical Detection of Bisphenol A Based on Gold Nanoparticles/Multi-Walled Carbon Nanotubes: Applications on Glassy Carbon and Screen Printed Electrodes.

Bisphenol A (BPA) has been classified as an endocrine-disrupting substance that may cause adverse effects on human health and the environment. The development of simple and sensitive electrochemical biosensors is crucial for the rapid and effective quantitative determination of BPA. This work presents a study on electrochemical sensors utilizing gold nanoparticle-modified multi-walled carbon nanotubes (CNT/AuNPs). Glassy carbon electrodes (GCEs) and screen-printed electrodes (SPEs) were conveniently modified and used for BPA detection. AuNPs were electrodeposited onto the CNT-modified electrodes using the galvanostatic method. The electrodes were properly modified and characterized by using Raman spectroscopy, cyclic voltammetry (CV), and electrochemical impedance analysis (EIS). The electrochemical response of the sensors was studied using differential pulse voltammetry (DPV) and constant potential amperometry (CPA) for modified GCE and SPE electrodes, respectively, and the main analytical parameters were studied and optimized. Problems encountered with the use of GCEs, such as sensor degradation and high limit of detection (LOD), were overcome by using modified SPEs and a flow injection device for the measurements. Under this approach, an LOD as low as 5 nM (S/N = 3) was achieved and presented a linear range up to 20 μM. Finally, our investigation addressed interference, reproducibility, and reusability aspects, successfully identifying BPA in both spiked and authentic samples, including commercial and tap waters. These findings underscore the practical applicability of our method for accurate BPA detection in real-world scenarios. Notably, the integration of SPEs and a flow injection device facilitated simplified automation, offering an exceptionally efficient and reliable solution for precise BPA detection in water analysis laboratories.

Enhancement in photocatalytic and electrochemical performance of hydrothermally synthesized β-Bi2O3 via Ni incorporation

β-Bi2O3 and Ni-incorporated β-Bi2O3 nanoparticles with different Ni incorporating amounts (0, 2, and 4 at. wt. %) were successfully synthesized through a viable hydrothermal process. As-synthesized nanoparticles were analyzed by complementary analytical tools such as X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), high resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), energy dispersive X-ray spectroscopy (EDS), UV–visible spectroscopy (UV–Vis), and photoluminescence spectroscopy (PL) for structural, microstructural, compositional, and spectral properties. The photocatalytic performance of synthesized nanoparticles was assessed by subjecting them to visible light irradiation and monitoring the decomposition of rhodamine-B dye. The findings demonstrated that the inclusion of Ni(4%) in β-Bi2O3 nanoparticles significantly enhanced its photocatalytic activity compared to pristine β-Bi2O3 which is desirable for environmental remediation. This improvement may be caused by increased generation of electron-hole (e−-h+) pairs, reduced recombination rate of these pairs, enhanced absorption of visible light, and a decreased band gap energy. To evaluate the specific capacitance characteristics of synthesized electrode materials, cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance analyses were conducted. The super capacitance activities of prepared electrode materials were observed in the order of Bi2O3 < Ni(2%)-Bi2O3 < Ni(4%)-Bi2O3. Notably, Ni(4%)-Bi2O3 nanocomposite exhibited higher supercapacitance, which can be attributed to the effective role of appropriate nickel incorporation in Bi2O3. These results suggested that the incorporation of Ni(4%) into β-Bi2O3 to form a nanocomposite showed greater capability as an effective electrode material for advanced energy storage devices, especially supercapacitors.

Carbon based cobalt titanate perovskite nanocomposite: Synthesis, characterization, and excellent visible light driven photocatalytic performance

Titanium-based perovskite oxides are the promising photocatalysts for an efficient degradation of organic pollutants. However, charge carriers recombination and wide band gap energy are still the main challenges in their visible-light-driven photocatalytic applications of Titanate perovskites, ATiO3. The immobilization of Titanium-based perovskites on a carbonaceous substrate such as nitrogen-rich carbon nitride, can be considered as an excellent option for enhancing photocatalytic performance. Here, the CoTiO3/C3N5 nanocomposite was synthesized by simple reflux method and used for photocatalytic degradation of three organic pollutants including methylene blue (MB), tetracycline hydrochloride (TC), and bisphenol A (BPA). The results indicated that the photocatalytic activity of the CoTiO3 perovskite was considerably improved by introducing C3N5 nanosheets and fabricating CoTP/C3N5 nanocomposite. The crystalline structure of CoTiO3/C3N5 (CoTP/C3N5) nanocomposites was confirmed successfully by XRD analysis. The specific surface area of the synthesized CoTP/C3N5 nanocomposite was 8.15 m2/g calculated by N2 adsorption–desorption technology. In the 60th minute of the photocatalytic process, the degradation efficiency of MB, TC, and BPA by CoTP/C3N5 were obtained as 98.70, 60.33, and 92.90 %, respectively, which were higher than pristine CoTiO3 nanorods and C3N5 nanosheets. Electrochemical impedance analysis shows that the CoTP/C3N5 nanocomposite has good electrochemical performance. The improvement photocatalytic activity CoTP/C3N5 can be attributed to the suppressing the recombination of photogenerated electrons and holes and good electrochemical performance with high electron transfer capability. The results achieved from UV–Visible Diffused Reflectance Spectroscopy (DRS), mott-schottky measurements and the photocatalytic degradation experiments in the presence of scavengers confirmed the significantly accelerating the Z-scheme charge transfer mechanism where photoexcited carriers can migrate between CoTiO3 perovskite and C3N5 nanosheets.

Study on high voltage (5 V) spinel lithium manganese oxide LiNi0.5Mn1.5O4 by doping niobium

AbstractThe effect of niobium ions with high‐valence doping on high‐voltage LiNi0.5Mn1.5O4 (LNMO) materials was investigated. LiNi0.5Mn1.5−xNbxO4 was prepared by doping high‐valent niobium ions into LiNi0.5Mn1.5O4 material using the organic assisted combustion method. The experimental samples were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X‐ray diffraction (XRD), X‐ray photoelectron spectroscopy (XPS), electrochemical impedance (EI), and cyclic voltammetry (CV) analysis. The experimental results show that ‐doping with high‐valence niobium ions changes the orientation of the crystal plane growth of spinel particles, and the morphology of these particles changes from the octahedral shape before doping to the spherical shape after doping. With the increase in doping amount, the crystal structure changes gradually, resulting in the Li0.96Nb1.01O3 impurity phase. The doping of high valence‐niobium ions increases the content of Mn3+ in the material, resulting in the appearance of a 4 V discharge platform and the formation of a 4.7 and 4 V discharge platforms. The doping of Nb can improve the cycling stability of LiNi0.5Mn1.5O4 material, but the specific capacity of the material is reduced.

Microcavity well-plate for automated parallel bioelectronic analysis of 3D cell cultures

Three-dimensional (3D) in vitro cell culture models serve as valuable tools for accurately replicating cellular microenvironments found in vivo. While cell culture technologies are rapidly advancing, the availability of non-invasive, real-time, and label-free analysis methods for 3D cultures remains limited. To meet the demand for higher-throughput drug screening, there is a demanding need for analytical methods that can operate in parallel. Microelectrode systems in combination with microcavity arrays (MCAs), offer the capability of spatially resolved electrochemical impedance analysis and field potential monitoring of 3D cultures. However, the fabrication and handling of small-scale MCAs have been labour-intensive, limiting their broader application. To overcome this challenge, we have established a process for creating MCAs in a standard 96-well plate format using high-precision selective laser etching. In addition, to automate and ensure the accurate placement of 3D cultures on the MCA, we have designed and characterized a plug-in tool using SLA-3D-printing. To characterize our new 96-well plate MCA-based platform, we conducted parallel analyses of human melanoma 3D cultures and monitored the effect of cisplatin in real-time by impedance spectroscopy. In the following we demonstrate the capabilities of the MCA approach by analysing contraction rates of human pluripotent stem cell-derived cardiomyocyte aggregates in response to cardioactive compounds. In summary, our MCA system significantly expands the possibilities for label-free analysis of 3D cell and tissue cultures, offering an order of magnitude higher parallelization capacity than previous devices. This advancement greatly enhances its applicability in real-world settings, such as drug development or clinical diagnostics.

Sputtered vanadium carbon nitride (VCN) thin films: a potential electrode for supercapacitors

The preparation of efficient thin film-based electrode materials is a vital prerequisite for practical energy storage devices. Herein, we have prepared unique vanadium carbon nitride (VCN) thin films on FTO substrates by pulsed DC magnetron sputtering technique for competent supercapacitor electrodes. XRD analysis confirmed the crystalline nature of VCN thin films. SEM and AFM revealed a smooth morphology with an average grain size of 30 nm. Raman spectra showed two broad peaks around 1346 and 1589 cm−1, belonging to the D-band and G-band of VCN. The surface electronic states of VCN were investigated by XPS analysis, which confirmed the formation of pure VCN films without any impurities. The electrochemical performance of the thin film electrode was evaluated using cyclic voltammetry (CV), Galvanostatic charge–discharge (GCD), and Electrochemical impedance analysis (EIS). The electrochemical results showed the VCN thin films exhibited super capacitive behaviours. The maximum specific capacitance (Cs) value of 78.2 F g−1 was obtained from GCD studies. A variation in charge transfer resistance is detected from the EIS study, which arises due to the partial oxidation of the active nitride component. The VCN electrode showed good cycling stability, retaining 87% of its capacitance at a current density of 5 A g−1 even after 2000 cycles. The sputtered VCN films have been demonstrated as potential thin film electrodes for electrochemical supercapacitors for practical energy storage devices.

Suppressing Anodic Degradation of Lithium-Ion Batteries by Sinusoidal Waveform Charging Method

The effects of Constant current-Constant voltage charging and combined sinusoidal waveform charging methods on the internal structure of LiFePO4 battery have been discussed in detail in this study. Experimental results clearly indicated that after 600 cycles, the battery that utilized the charging method had retained about 94% of state of health. In the electrochemical impedance analysis and cyclic voltammetry tests, the portion of the SEI film impedance was increased about 0.08 mΩ. In the micro structured view, no significant SEI film formation was observed on the surface of the negative electrode that used the battery in the present charging method. Finally, in the analysis of the SEI film composition, it was found that the Li2CO3 and Li2O content in the Li element was only about 15.97% and 4.42% in the battery employing this charging method, and the battery component contents in the CC-CV charging method were 27.2% and 6.69% respectively.

Structural, Optical, Morphological and Electrical Properties of Cu doped Calcium Stannate Nanoparticles for Electrochemical Performance

In this work, co precipitation method was adopted to synthesis Cu (0.01M, 0.02M, and 0.03M) doped CaSnO3 nanoparticles and the structural, optical, morphological and electrochemical characterization were studied using XRD, FTIR, UV–Visible, Photoluminescence, SEM and Cyclic voltammetry with Electrochemical impedance analysis. It is noticed from XRD patterns that the peaks shift towards higher angles attributed to the substitution of Cu2+ ions for Ca2+ ions, and confirms the orthorhombic structure of Cu2+ doped CaSnO3. The average crystallite size is found between 40 – 49 nm for Cu doping. FTIR analysis boosts the confirmation of Cu doping in to the CaSnO3 nanoparticles by the presence of vibrational peaks at 698 cm-1, 622 cm-1, and 581 cm-1 due to Cu-O stretching and the peak 483 cm-1 due to Sn-O stretching vibration. The calculated band gap values are 4.7 eV, 4.8 eV, and 4.9 eV for Cu doping. The PL emission study showed light emission towards the visible region. SEM analysis proved well-formed cubed particles about &lt; 2µm. Specific capacitance values are highest for 0.02 M Cu doped CaSnO3 at about 1694F/g, compared to 572 F/g, 922 F/g, and 1626 F/g for pure, 0.01 M, and 0.03 M Cu doped CaSnO3 particles, respectively, at a scan rate of 10 mV/s. Overall, these findings indicate that 0.02 M and 0.03 M Cu doped CaSnO3 are promising candidates for energy storage applications.

Self-Supporting Microporous Layer for Polymer Electrolyte Fuel Cells

Introduction Improving power density is desired in research and development of polymer electrolyte fuel cells (PEFC) [1-5]. A reduction of gas diffusion resistance by down-thinning the gas diffusion layer (GDL) less than 50 μm is desirable [2]. Whilst both the electrocatalyst layers and electrolyte membrane are around 10 μm, the GDL is still relatively thick at about 150 μm [1]. The previous study investigated the possibility and technical issues in using high-strength and thin, porous metallic GDLs [3]. Based on such previous studies, this study aims to develop a self-supporting thin MPL/GDL with improved power density by creating conductive paths and reducing contact resistance with microporous layer (MPL) deposited on various GDLs. Experimental In this study, MPL was screen-printed on various mesh GDLs as substrates. Cells were fabricated by using these materials, and current-voltage characteristics and microstructural observations were performed. Stainless steel (SUS316 977mesh, 28 μm thick), titanium (200mesh, 152 μm thick), and carbon fiber (45 μm thick) were used as mesh GDL materials. The MPLs were composed of carbon black, carbon nanotubes, polytetrafluoroethylene (PTFE), and solvent (a mixture of polyethylene glycol 600 and pure water), which were mixed, screen printed, and heat treated at 300°C for 30 min to fabricate the MPL/GDL. Conventional materials such as Pt/C (TEC10E50E, Tanaka Kikinzoku, Japan) were used for preparing membrane-electrode-assemblies (MEAs). In the electrochemical characterization of this study, current-voltage characteristics were evaluated using an electrochemical impedance analyzer (SAS SP-240, Bio-Logic Science Instruments, France), and various overvoltages were separated. Results and discussion Figure 1 shows the current-voltage characteristics of cells using various MPL/GDLs. The thickness of MPL/GDLs fabricated was ranging from 62 to 180 μm. For comparison, the characteristics of a cell using a standard material, commercially available MPL/GDL (22BB, SGL Carbon, Germany), are also shown. The results indicate that the use of any kind of these MPLs improves cell performance. The electrochemical performance with metallic GDLs was considerably improved by applying MPLs. In particular, GDLs with metallic meshes made of SUS316 show a significant improvement in current-voltage characteristics by depositing MPLs. The activation overvoltage and ohmic overvoltage were comparable to those of 22BB, the commercial GDL/MPL. This is because the contact resistance between the GDL and the catalyst layer is reduced by the carbon component in the MPL, and the electrical conductivity is improved. The concentration overvoltage was also suppressed by depositing the MPL. The cell performance with MPL3/SUS316 977mesh was comparable to that of 22BB. In the future, we aim to further reduce the concentration overvoltage by optimizing e.g., the content of hydrophilic components in MPLs. Acknowledgment This paper is based on results obtained from a project, JPNP20003, commissioned by the New Energy and Industrial Technology Development Organization (NEDO). References Takahashi, T. Ikeda, K. Murata, O. Hotaka, S. Hasegawa, Y. Tachikawa, M. Nishihara, J. Matsuda, T. Kitahara,M. Lyth, A. Hayashi, and K. Sasaki, J. Electrochem. Soc., 169, 044523, (2022).New Energy and Industrial Technology Development Organization (NEDO), Roadmap of Fuel Cells for Heavy-Duty Vehicles, 48, (2022), (in Japanese), https://www.nedo.go.jp/content/100944011.pdf Yamamoto, M. Yasutake, Z. Noda, S. M. Lyth, J. Matsuda, M. Nishihara, A. Hayashi, and K. Sasaki, ECS Trans., 109 (9),265 (2022).Larminie and A. Dicks, Fuel Cell Systems Explained, 2nd ed., John Wiley & Sons, England, 2003.Kitahara, T. Konomi, H. Nakajima, and J. Shiraishi, Kikai B, 76 (761), 101, (2010). Figure 1

Development and Testing of Innovative Carbon Nanotubes/ Copper Composite Foils, Towards Lighter and Mechanically Improved Anode Current Collector for Lithium-Ion Batteries

Up to now, copper is an essential material for lithium-ion battery industry as preferential candidate for anode current collectors due to its high conductivity, low price, and electrochemical stability in the working potential range of the anodic electroactive material. However, such component, accounting for 8.1% of the battery total weight, does not participate in any energy storage processes. [1] Thus, the trend is in this industry is to decrease the weight as well as the thickness of the collector foil to optimize the gravimetric energy of the whole lithium-ion battery system. It is therefore of interest to explore the development of lighter current collectors with equal/improved mechanical and electrical properties.Nanocarbon materials such as Multi-Wall Carbon Nanotubes (MWCNTs) and Single-Wall Carbon Nanotubes (SWCNTs) display a combination of performances, namely high electrical conductivity, low density and high mechanical stability, of a high interests to be combined with copper as innovative lightweight current collectors. Such nanocarbon/copper composite represents a valid alternative to foster the rapid change the battery technology is undergoing.In 2013, Subramaniam et al. [2] reported the fabrication of a Copper /Carbon nanotubes (Cu-CNTs) composites with a similar specific conductivity than that of copper and an ampacity increased by two orders of magnitude. Moreover, Arai et al. have shown, by Electrochemical impedance analysis, that MWCNTs additive in a copper matrix can serve as preferential electron conduction pathway inside a Lithium-ion battery anode. [3]Recently, a new promising and scalable way to fabricate nanocarbon/copper composite has been demonstrated by our team. The process involved the coating of MWCNTs by a dispersing agent, namely the Polydopamine biopolymer, their spraying, and finally the electrochemical plating of metallic copper inside the porosity of the MWCNTs network.[4]Following similar approach, the present work exhibits the fabrication of a free standing MWCNTs/ Copper composite current collector foil of a thickness of 9 µm, a value reaching the industrial standards required by the Lithium-ion battery market players for the next generation cells.[5] Scanning Electron Microscopy and Transmission Microscopy have been used to investigate the interaction between the copper matrix and the carbonaceous reinforcement additive. Figure 1. displays a cross section of nanocarbon/copper composite obtain via Focused Ion Beam slicing, where homogeneous mixing of copper and carbon phases down to nanoscale is highlighted. Such experiments contribute to the understanding of the copper nucleation mode on modified MWCNTs which remains insufficiently controlled to this day.Nanoindentation technique and electromechanical tensile testing bench were combined to study the mechanical properties of such material to be used under mechanical stress as battery collector. In contrary to conventional indentation technique where the mechanical properties of micro-size area are probed, indentation at nanoscale allow the probing of the local mechanical heterogeneity of a composite material. Using such technique, the fabricated self-standing nanocarbon/copper composite was shown to display average hardness and Young modulus close to those of pure carbon (3.5 GPa and 152 GPa respectively).Electrochemical performances of the composite as anode battery collector are under test into pouch and coin-cells battery architecture. The adhesion strength between the electrode slurry and the nanocomposite substrate material is expected to be reinforced by the addition of a nanocarbon. A focus was made on the impact of the use of this new collector material on the cycling stability of typical Lithium-ion battery commercial mixture. Preliminary results indicate that the Cu/MWCNT composite is a promising current collector material to withstand the expansion/contraction imposed by the working cycles of a rechargeable Lithium-ion battery.[1] Zhu, P. Gastol, D. Marshall, J. Sommerville, R. Goodship, V. Kendrick, E. J Power Sources, 485, 229321 (2021)[2] Subramaniam, C. Yamada, T. Kobashi, K. Sekiguchi, A. Futaba, Yumura, D. N. Hata, K. Nat Commun,4, 2202 (2013).[3] Shimizu, M. Ohnuki, T. Ogasawara, T. Banno, Arai, S., RSC Advances, 9(38), 21939-21945 (2019)[4] Duhain, A. Guillot, J. Lamblin, G. Lenoble, D., RSC Advances,11(63), 40159-40172 (2020)[5] Copper Foil Market, Straits Research, 9.5.2.3.(2022)Figure 1. Scanning Electron Microscopy imaging of the cross section of MWCNTs/Copper composite with a thickness lower than 3 µm – 7kV acceleration, 45° tilt.. Figure 1

Grooved Electrodes for High Power Density Fuel Cells

Proton exchange membrane fuel cells (PEMFCs) are a promising alternative to internal combustion engines, owing to their intrinsic power density, decoupled energy storage and generation, and relatively short refueling time. However, challenges related to cost, performance, and durability continue to prevent wide adoption of PEMFCs.1 Development of alternative electrode structures, which can enable smaller and less expensive PEMFCs with higher power and lower precious metal content, provides a promising path to overcome these challenges.2 Here, we report grooved electrodes, where the transport pathways of H+ and O2 were partitioned. Specifically, H+ are transported through electrode ridges with optimized ionomer content, and O2 is transported through the grooves that separate the electrode ridges. The grooved electrodes made with commercial electrode materials enhanced the performance up to 50%, and the enhancement becomes greater after accelerated durability tests. We verify via electrochemical impedance analyses, limiting current measurements, and multiphysics modeling that the enhancement is due to improved H+ and O2 transport. The work also demonstrates that the electrodes can be further improved by optimizing the electrode geometry, proven via machine learning investigations. These results inform next generation electrode designs for enhanced PEMFC performance and durability. Acknowledgement: This work was supported by the Hydrogen and Fuel Cell Technologies Office (HFTO), Office of Energy Efficiency and Renewable Energy, US Department of Energy (DOE) through the Million Mile Fuel Cell Truck (M2FCT) consortia, technology managers G. Kleen and D. Papageorgopoulos. Financial support for this work from the Laboratory Directed Research and Development (LDRD) program at Los Alamos National Laboratory (LANL) is gratefully acknowledged (Projects 2020200DR and 20210915PRD2). ChungHyuk Lee acknowledges the support of the Natural Sciences and Engineering Research Council of Canada (NSERC).