AC Electrochemical Impedance Spectroscopy Research Articles

Site Disorder Drives Cyanide Dynamics and Fast Ion Transport in Li6PS5CN.

Halide argyrodite solid-state electrolytes of the general formula Li6PS5 X exhibit complex static and dynamic disorder that plays a crucial role in ion transport processes. Here, we unravel the rich interplay between site disorder and dynamics in the plastic crystal argyrodite Li6PS5CN and the impact on ion diffusion processes through a suite of experimental and computational methodologies, including temperature-dependent synchrotron powder X-ray diffraction, AC electrochemical impedance spectroscopy, 7Li solid-state NMR, and machine learning-assisted molecular dynamics simulations. Sulfide and (pseudo)halide site disorder between the two anion sublattices unilaterally improves long-range lithium diffusion irrespective of the (pseudo)halide identity, which demonstrates the importance of site disorder in dictating bulk ionic conductivity in the argyrodite family. Furthermore, we find that anion site disorder modulates the presence and time scales of cyanide rotational dynamics. Ordered configurations of anions enable fast, quasi-free rotations of cyanides that occur on time scales of 1011 Hz at T = 300 K. In contrast, we find that cyanide dynamics are slow or frozen in Li6PS5CN when site disorder between the cyanide and sulfide sublattices is present at T = 300 K. We rationalize the observed differences in cyanide dynamics in the context of elastic dipole interactions between neighboring cyanide anions and local strain induced by the configurations of site disorder that may impact the energetic landscape for cyanide rotational dynamics. Through this study, we find that anion disorder plays a decisive role in dictating the extent and time scales of both lithium ion and cyanide dynamics in Li6PS5CN.

Electrodeposited zinc cellulose nanocrystals composite coatings: Morphology, structure, corrosion resistance and electrodeposition process

Nanoparticles, particularly ceramic, have been widely investigated as beneficial additives in electrodeposited zinc coatings. However, exploiting cellulose-based nanocrystals derived from plant sources is attractive due to their cost-effectiveness and sustainability. In this work, we assessed the impact of various concentrations of cellulose nanocrystals, ranging from 0 to 8 v/v%, on the characteristics of zinc coatings obtained through electrodeposition. We investigated the morphology and structure of the zinc deposits using scanning electron microscopy (SEM), x-ray diffraction (XRD), and confocal microscopy (CM). Corrosion resistance was evaluated through mass loss measurements and electrochemical tests including DC (potentiodynamic polarization) and AC (electrochemical impedance spectroscopy) measurements. Increasing cellulose nanocrystal concentrations up to 7 v/v% notably enhanced the corrosion resistance in 0.5 M NaCl solution. In comparison to coatings with no cellulose addition, the 7 v/v% cellulose concentration resulted in: i) an increase in polarization resistance from 586 Ω cm2 to 1850 Ω cm2, ii) a decrease in corrosion current density from 3.21 × 10−5 A/cm2 to 0.76 × 10−5 A/cm2, and iii) a reduction of the corrosion rate from 0.15 mm/year to 0.08 mm/year assessed after 24-h immersion. Furthermore, the addition of this optimal concentration of nanocrystals enhanced current efficiency to approximately 95%, without compromising microhardness, which remained around 184 HV0.1. Additionally, the incorporation of cellulose nanocrystals resulted in a more compact coating with reduced roughness (Ra ∼0.69 μm). This work thus showcases the significant and beneficial impact of cellulose nanocrystals in producing enhanced electrodeposited zinc coatings.

Mechanochemical Synthesis of Sodium-Ion Conducting Chloride NaTaCl6

All-solid-state sodium batteries have been attracting attentions owing to their high energy density and safety. Solid electrolytes play a significant role in the electrochemical performances of all-solid-state batteries. Chloride-based solid electrolytes are particularly important for achieving high energy densities because of their high oxidation stability, ionic conductivity, and formability. Fewer sodium-ion conducting chlorides have been developed compared to lithium-ion conducting materials. It is necessary to discover the chlorides as the end-member of sodium-ion conductors. In this study, we report the development of a new NaTaCl6 chloride as an end-member sodium-ion conductor with high ionic conductivity. NaTaCl6 sample was mechanically prepared using a planetary ball mill apparatus. The X-ray diffraction patterns of the obtained sample displayed a broad pattern similar to the reported NaTaCl6 (ICSD#36519), suggesting that the sample contains both amorphous and crystalline phases. The reference intensity ratio method was used to investigate the weight ratios of the amorphous phases in the sample. The ratio was approximately 45 %. Transmission electron microscopy observations suggested that the sample consisted of the amorphous matrix and crystalline with the crystallite size of approximately 20 nm. The electrical conductivities of the pelletized samples were measured using two-terminal AC electrochemical impedance spectroscopy. The sample pellets were prepared by uniaxial pressing at 360 MPa without heat treatment. The pellet sample had the relative density of 85 % (powder density: 3.32 g cm–3, pellet density: 2.83 g cm–3). The sample shows σ 25ºC of 6.2×10–5 S cm–1, and the activation energy of 0.37 eV. To determine the NaTaCl6 onset oxidation voltage (OOV), linear sweep voltammetry measurement was carried out. The OOV of the sample at 60 ºC was 3.8 V vs. Na15Sn4. To demonstrate the high oxidation stability of NaTaCl6 in all-solid-state sodium batteries, it was used in a positive electrode by mixing Na3V2(PO4)3 as the active material and the buffer layer. The cell exhibited an initial reversible capacity of 96 mAh g–1 and stable cycling after 40 cycles with the capacity retention of 99.5 %. A 3.3 V all-solid-state sodium battery without oxide solid electrolytes was successfully operated. In this study, the NaTaCl6 electrolyte was developed with a high ionic conductivity and oxidation stability.Acknowledgement: This work was partly supported by JSPS KAKENHI (Grant Numbers: JP21H04701 and JP19H05816) and MEXT Program: Data Creation and Utilization-Type Material Research and Development Project Grant Number JPMXP1122712807.

Kinetic and transport characteristics of LiNi0.8Co0.1Mn0.1O2 lithium-ion batteries

A balance must be found between energy density, cost and life for energy-typed lithium-ion batteries. Solving this problem requires a deep understanding of the electrode interface reaction mechanism. In this paper, electrochemical AC impedance spectroscopy (EIS) is used to study the impedance spectrum characteristics of lithium-ion batteries comprising LiNi0.8Co0.1Mn0.1O2 (NCM811) and graphite electrodes separately in a symmetrical battery system under different states of charge and temperature. The de Levie - Finite Length Pore (Ls) element is used to differentiate Li+ diffusion resistance Rion inside the porous electrode and charge transfer process resistance Rct in the Faraday reaction. The dependencies of Rion and Rct on temperature and state of charge (SOC) are obtained. Based on the Rion measurements, we calculate MacMullin number (Nm) and then characterize the difficulty of Li ion transportation of NCM811 and graphite electrodes in one cell. The results indicate directions for improving the power design of commercial energy-typed lithium-ion power batteries.

Preparation, transport and Na-storage properties of monoclinic – Na2FeSiO4 for Na-ion batteries

Na2FeSiO4 (NFS) is considered one of the promising cathode materials for rechargeable sodium-ion batteries (SIBs). In this work, the monoclinic phase of NFS is prepared for the first time by a polymer-assisted synthesis technique. The nano-sized NFS particles and pores/voids are characterized by field-emission scanning transmission electron microscopy (FE-SEM) and N2-adsorption/desorption analysis, respectively. The temperature-dependent transport properties of monoclinic (Pn) NFS are also studied by AC electrochemical impedance spectroscopy (EIS). Monoclinic NFS exhibits electrical conductivity of 2.2 (±0.01) × 10−6 S cm−1. The I-V measurement technique further verifies these results. Moreover, the activation energy obtained for this crystallographic phase is found to be 1.57 eV. The initial charge capacity is found to be 225 mAhg−1 at a current rate of 0.1C (13.5 mAg−1) in the voltage range of 1.5–4.2 V, which is closer to the theoretical capacity (∼276 mAhg−1) of NFS. Despite the better-conducting properties along with less activation energy, the monoclinic phase of NFS is not found to be cyclable for long-term cycling. The plausible reason for capacity fading in this phase of the NFS is discussed in detail.

(Invited) Garnet-Type Electrolytes for All-Solid-State Lithium Metal Batteries

All solid-state Li batteries are foreseen as the future state of battery technology due to their safety, high energy density, and high potential window as compared to the present organic liquid electrolyte batteries. Li-ion conducting garnet-type electrolytes have received considerable research interests due to their compatibility with Li metal anode, good ionic conductivity (10-3 S/cm) and wide electrochemical window (~ 6V vs. Li).1 Garnet-type Li6.5La3-xAxZr1.5-xTax+0.5O12 (A = Ca, Sr, Ba; x = 0.1, 0.5) solid electrolytes were prepared by conventional solid-state synthesis and spark plasma synthesis (SPS).2-4 The formation of the cubic garnet-type structure was confirmed by powder X-ray diffraction (PXRD). Microstructure of the solid electrolytes were analysed by scanning electron microscopy (SEM) and cross-sectional analyses showed that the SPS processed samples are highly dense compared to the same compositions prepared by conventional solid-state route. The AC electrochemical impedance spectroscopy (EIS) was used to measure the impedance of solid electrolytes and found that all samples exhibit bulk conductivity in the order of 10-4 S/cm at room temperature. SPS processed samples showed an excellent Li-ion charge transfer resistance and the highest critical current density compared to the samples prepared by conventional solid-state synthesis. X-ray photoelectron spectroscopy (XPS) analyses were conducted on SPS-processed samples to quantify the impurity layers on garnet surface. Electrochemical performance of a hybrid cell consisting of liquid Li-ion electrolytes and garnet electrolyte will be discussed. References Wang, K. Fu, S. Palakkathodi Kammampata, D. W. McOwen, A. Junio Samson, L. Zhang, G. T. Hitz, A. M. Nolan, E. D. Wachsman, Y. Mo, V. Thangadurai and L. Hu, Chem. Rev., 2020, 120, 4257–4300.Palakkathodi Kammampata, R. H. Basappa, T. Ito, H. Yamada and V. Thangadurai, ACS Appl. Energy Mater., 2019, 2, 1765–1773.Palakkathodi Kammampata, H. Yamada, T. Ito, R. Paul and V. Thangadurai, J. Mater. Chem. A, 2020, 8, 2581–2590.Yamada, T. Ito, S. P. Kammampata and V. Thangadurai, ACS Appl. Mater. Interfaces, 2020, 12, 36119–36127.

Initiated Chemical Vapor Deposited Anion-Conducting Solid-State Polymeric Electrolytes for All Solid-State Batteries: Impacts of Deposition Conditions and Polymer Composition on Performance Metrics

Achieving both high energy and power density, two traditionally opposed battery metrics, requires moving away from the 200+ years-old 2D layered battery configuration to a three-dimensional all solid-state battery (3D SSB) configuration. The enhanced power and energy benefits bestowed by a 3D SSB design have been demonstrated in the Li-ion 3D SSB literature.1 However, due to limitations in thermal and electronic conductivity of Li-Ion active materials, 3D Li-ion SSBs are limited to microscale dimensions. A potential means around this limitation is to switch to conductive metal electrodes such as Zn and Ag, for which 3D architectures have been demonstrated.2 In such a case, the remaining roadblock to a macroscale 3D SSB is the submicron-thick solid-state electrolyte, which requires a non-line-of-sight deposition method for incorporation into the complex 3D base electrode. Initiated chemical vapor deposition (iCVD) is a non–line-of-sight method that is ideal for generating conformal polymer coatings on complex 3D architectures. We focus on polymers amenable to iCVD protocols that can be modified post-deposition to introduce anion conduction pathways that can facilitate Ag and Zn redox. Submicron-thick coatings of poly-dimethylaminomethylstyrene (pDMAMS) that are pinhole-free and electronically insulating on both 2D planar and complex 3D electrode architectures are prepared via iCVD. The pDMAMS coatings are rendered anion-conducting through a vapor-phase methylation process and subsequent ion exchange to yield desirable anion species (e.g., OH–, Br–, or HCO3 –). X-ray photoelectron spectroscopy, ATR-IR spectroscopy, and solid-state magic-angle spinning NMR spectroscopy confirm the structure of the pDMAMS film before and after quaternization, while atomic force microscopy and cyclic voltammetry with redox probes confirm conformality and absence of pinholes in the submicron film. With the use of cyclic voltammetry and AC electrochemical impedance spectroscopy, the electronic and ionic conductivities of the polymer films are measured before and after quaternization. Molecular dynamics simulations of pDMAMS as a function of anion and H2O content in the film are used to generate computational results (e.g., glass-transition temperature Tg, anion conductivity) for comparison to experimental results.1. Long, J.W.; Dunn, B.; Rolison, D.R.; White, H.S. Chem. Rev. 2004, 104, 10, 4463–4492.2. Parker, J.F.; Chervin, C.N.; Nelson, E.S.; Rolison, D.R.; Long, J.W. Energy Environ Sci. 2014, 7, 1117-1124.

(Digital Presentation) Develop Cell Internal Resistance Measurement Tool As a Lib Cell Characterization Technology

As LiB cell is not a pure ohmic device but a complex electrochemical device with capacitive and inductive behaviors, its characteristic and performance will vary depending on the input signals, frequencies, and usage conditions. And as LiB cell is a non-linear system, its internal resistance (IR) depends significantly on variables, like aging (state of Health: SOH), state of charge (SOC), temperature, applying current rate and period. The IR is an intrinsic property of a cell representing its characteristic, performance, and health status at the measuring point. Therefore, its precise measurement is essential for its usage for cell characterization, quality control (QC), and grading-selection criteria for designing cell, module, pack, host system, and thermal management, health monitoring-prediction criteria. However, IR measurement is inherently complex and requires sophisticated procedures (1,2). Direct wave DC pulse and AC electrochemical impedance spectroscopy (EIS) are the prevalent techniques used for cell IR characterization (1,2). Most cell QC processes use the AC-impedance tool at 1.0 kHz with voltage, and IEC-62660 adopt a DC pulse, Hybrid Pulse Power Characterization (HPPC) method, and new proposals, like a multisine signals method and a pulse-multisine, have been proposed (1,2). However, the AC-impedance tool (1.0 kHz) cannot represent the dynamic behaviors of the cell and system compared to the DC pulse (3). In addition, some DC pulse test requires pre-testing conditions and a long test period; furthermore, there is no harmonized test technologies among the battery standards and some best practices of the LiB cell testing and characterization. To adopt a test method and condition as a QC tool for cell characterization that should be simple and not be time-consuming on pre-measurement condition and testing procedure to perform (3).This research aims to propose simple IR measurement tools in which test results are comparable with each other’s and do not require a long period of pre-test conditioning time and a time-consuming test period. We evaluated four test methods of the cell IR measurement at four temperature conditions (0 ~ 5 ℃, RT (20 ~ 25 ℃), 35 ℃, and 45 ℃). In addition, we selected five types of cell groups (two 18650 cells, two pouch-type cells, and one prismatic cell) to evaluate the IR. The four IR measurement test methods are classified with DC pulse tools (simplified DC pulse method and HPPC) and AC pulse signal tools (Full range EIS and AC-pulse Impedance at 1.0 kHz). Test results studied the relationship between cells’ IR response behaviors by each type of pulse and the electrochemical mechanism of the cells. After comparing those test results, the best IR characterization tool and procedure will be proposed as a standard LiB cell characterization technology.We found the simplified DC pulse method is simple and not time-consuming on both pre-test condition and testing procedure to perform and provide reasonable dynamic behaviors of the cell system compared to other methods. Figure 1 shows the trends of cell IR changes according to the experimental variables, applied current rate and frequency from the simplified DC pulse method. The blue color dot zone shown the optimum applied current rate and frequency and the red color dot zone shown the optimum frequency (3).Reference:1) Thomas R. B. Grandjean, Jakobus Groenewald, Andrew McGordon, Widanalage D. Widanage and James Marco, Batteries 2018, 4, 49; doi:10.3390/batteries4040049.2) Mohammad A. Hoque, Petteri Nurmi, Arjun Kumar, Samu Varjonen, Junehwa Song, Michael G. Pecht, Sasu Tarkoma Journal of Power Sources 513 (2021) 2305193)3) Jaesik Chung, Kwang Jung, and Giovanni Flores, 2020 NASA Aerospace Battery Workshop November 17 ~ 19 2020 Figure 1

NiO-Ba0.95Ca0.05Ce0.9Y0.1O3-δ as a Modified Anode Material Fabricated by the Tape Casting Method.

The development of new chemically resistant anodes for protonic ceramic fuel cells (PCFCs) is urgently required to avoid the costly deep hydrogen purification method. Ba0.95Ca0.05Ce0.9Y0.1O3−δ (5CBCY), which is more chemically resistant than BaCaCe0.9Y0.1O3−δ, was here tested as a component of a composite NiO–5CBCY anode material. A preparation slurry comprising 5CBCY, NiO, graphite, and an organic medium was tape cast, sintered and subjected to thermal treatment in 10 vol.% H2 in Ar at 700 °C. Differential thermal analysis, thermogravimetry, quadrupole mass spectrometry, X-ray diffraction analysis, scanning electron microscopy, the AC four-probe method and electrochemical impedance spectroscopy were used for the investigation. The electrical conductivity of the Ni–5CBCY in H2–Ar at 700 °C was 1.1 S/cm. In the same gas atmosphere but with an additional 5 vol.% CO2, it was slightly lower, at 0.8 S/cm. The Ni–5CBCY cermet exhibited repeatable electrical conductivity values during Ni-to-NiO oxidation cycles and NiO-to-Ni reduction in the 5CBCY matrix, making it sufficient for preliminary testing in PCFCs.

Influence of Ti Substitution on Electrochemical Performance and Evolution of LiMn1.5−x Ni0.5TixO4 (x = 0.05, 0.1, 0.3) as a High Voltage Cathode Material with a Very Long Cycle Life

The high voltage spinel material LiMn1.5Ni0.5O4 (LMNO) has the potential to increase the energy density of lithium batteries. However, its battery performance suffers from poor long-term cycling and high-temperature stability. In order to overcome these limitations, we have studied the effect of partial substitution of Mn with Ti and LiMn1.5−x Ni0.5TixO4 (x = 0.05, 0.1, 0.3), LMNTO, materials have been synthesized in a newly modified sol-gel method and then characterized by TEM, SEM (EDX), AC Electrochemical Impedance Spectroscopy and Soft X-ray Spectromicroscopy. We have demonstrated that the long-term cycling limitation with these types of materials can be resolved and herein 2000 cycles at a high C-rate have been demonstrated in half cells. We have attributed this behavior to a possible charge compensation mechanism as evidenced by a Soft X-ray Spectromicroscopy study of delithiated LMNTO materials. This work takes high energy density batteries based on high voltage spinel material one step further towards commercialization, and it is believed that further improvement can be achieved using new electrolyte formulations.

TEMPO mediated electrochemical oxidation of 4-pyridinemethanol using Pd and Pt Co-deposited polyaniline modified carbon fiber paper

Co-deposition of palladium and platinum (Pd–Pt) nanoparticles on the conducting polymeric film of Polyaniline (PAn) modified carbon fiber paper (CFP) electrode was carried out by using eletrochemical method. The modified electrode has been used for the oxidation of 4-pyridinemethanol. The electrochemical properties of fabricated multi-layered films on carbon fiber paper (Pd-Pt/PAn/CFP) were studied by electrochemical AC impedance spectroscopy and cyclic voltammetry (CV). Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) characterization technics were environmentally benign and sustainable are used to analyze the structural properties of modified multi-layered electrode. The relative sizes and distribution of the nanoparticles on the electrode surface were analyzed using Scanning electron microscopy (SEM) and optical profilometry characterization techniques. Electrochemical studies by CV showed that the Pd–Pt/PAn/CFP electrode had better electrochemical activity similar to PAn/CFP and Bare CFP electrode towards extensive electrochemical oxidation of 4-pyridinemethanol in presence of TEMPO (2,2,6,6-Tetramethylpiperidinyl-1-oxyl) in aqueous acidic medium.

Preparation and electrochemical properties of silicon copper alloy for high performance anode

To improve the electrochemical performance of silicon-based anode materials, herein, silicon-copper (Si-Cu) incompatible alloy anode material were prepared via facile chemical reduction and ball milling methods. Subsequently, nitrogen-doped carbon-coated Si-Cu alloy (Si-Cu/N-C) composites were prepared via in-situ polymerization with aniline in the high-temperature calcinations process. X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) were performed to analyze the physical characterization of these materials. Besides, the electrochemical performance of the catalysis was studied by constant current charging and discharging, cyclic voltammetry and electrochemical AC impedance spectroscopy (EIS). Electrochemical tests demonstrate that Si-Cu anode performs a high electrocatalytic activity when the ratio of Si to Cu is 1.5∶1 and the ball milling time is 7 h. The anode exhibits an initial discharge capacity of 1 018.6 mAh/g and a capacity of 499.2 mAh/g after 100 cycles. After the coating modification, TEM result shows that this composite anode material possesses a core-shell structure. When the coating mass of N-doped carbon is 0.45, the Si-Cu/N-C electrode exhibits an initial discharge capacity of 1 147.7 mAh/g and maintains a specific capacity of 857.9 mAh/g after 100 cycles. Furthermore, the capacity retention rate of Si-Cu/N-C anode increases by 10.8% as compared with that of Si-Cu. The improved electrochemical performance after modification is attributed to the unique core-shell structure of Si-Cu/N-C. On the one hand, the N-doped carbon coating layer not only improves the conductivity, but also reduces the contact resistance between the electrolyte and electrode. On the other hand, the nitrogen doping of Si-Cu/N-C composite can increase the active site of lithium storage on the surface, reduce lithium storage potential and form a stable solid electrolyte interface (SEI) film during the cycling process.

Novel MgHf4P6O24 as a Solid Electrolyte in Mg-Sensors

In this research paper, the results of the ac-electrochemical impedance spectroscopy (EIS) of MgHf4P6O24 solid electrolyte employing a two-probe technique between 182-764oC, and from 100 mHz to 32 MHz have been reported for the first time. The results indicate that MgHf4P6O24 is an excellent Mg2+-cation conducting solid electrolyte. The ionic conductivity of MgHf4P6O24 was found to be 4.52 x 10-4 Scm-1 at 747oC and the material exhibited no signature of phase change unlike the MgZr4P6O24 solid electrolyte during the sintering and impedance measurements suggesting that both materials and operational stability has been successfully maintained at 1000 ≤ T/oC ≤ 1300. In addition to this, the design, fabrication and testing of solid-state electrochemical Mg-sensors incorporating MgHf4P6O24 as a solid electrolyte has been successfully demonstrated in molten Al-Mg dilute alloys for the first time in this study. The high-temperature Mg-sensors were designed using the novel Mg2+-cation conducting solid electrolyte by incorporating a biphasic powder mixture of MgCr2O4 + Cr2O3 + O2 as a solid-state reference electrode, which has shown promising trend after successfully sensing the Mg dissolved in molten Al at 700±5oC.

Theoretical Prediction and Experimental Study of Benzimidazole Derivate as a Novel Corrosion Inhibitor for Carbon Steel in 1.0 M HCl

The inhibiting effect of benzimidazole derivate (DBI) on corrosion of carbon steel (CS) at temperature range of 303–333 K was investigated in hydrochloric acid by DC potential dynamic polarization and AC electrochemical impedance spectroscopy. It was found that this compound behaved as a mixed-type inhibitor with predominantly cathodic effect. The EIS results indicate that the inhibition efficiency increases with increasing the inhibitor concentration and the maximum inhibition (%) was obtained in the presence of 10−3 M of DBI. The adsorption of DBI on the carbon steel surface is described by the Langmuir adsorption isotherm and had a physical and chemical mechanism. The results found experimentally were corroborated by DFT-quantum chemical calculations and molecular dynamics simulations (MDS) methods.

Three-Dimensionally Micro-Architected Protonic Ceramic Fuel Cells

The solid oxide fuel cells (SOFCs) have been considered as important alternative energy technology, due to a variety of advantages, such as their high energy conversion efficiency, free noxious emissions, and direct use of a wide range of hydrocarbon fuels. Especially, the reverse operation of SOFCs, which is called solid oxide electrolysis cell (SOEC), is currently one of the most promising technologies for fuel production. However, their high-temperature operation (typically >700°C) leads to the rapid degradation of electrodes and necessitates a high balance of plant costs. To make SOFCs more economically feasible and viable, further reduction of operating temperature is inevitable. To this end, the utilization of proton-conducting oxides, which exhibit relatively high ionic conductivity with the low activation energy (<0.5eV), enables protonic ceramic fuel cells (PCFCs) to operate at an intermediate temperature regime (IT, 400–600°C), where the aforementioned benefits of SOFCs can also be accomplished. Moreover, PCFCs prevents the dilution of the fuel during the operation and provides higher resistance of carbon cocking on hydrocarbon fuels.Although the PCFCs have distinct advantages against traditional oxygen conducting SOFCs, the lower-than-predicted performance of PCFCs and scalability issues caused the considerable skepticism of the successful applicability of PCFCs. Most importantly, unlike traditional SOFCs, the development of mixed oxide ion and electron conductors (MIECs) for oxygen reduction reaction (ORR) at the cathode of PCFCs has shown marginal success due to the absence of protonic conduction and still needs to be improved. At the cathode, the ORR is limited to triple phase boundary (TPB), where the electrolyte, gas, and cathode mutually contact, and its geometrical enhancement at the interface area between cathode and electrolyte layers is crucial to improve the performance of PCFCs. Therefore, electrode-electrolyte interface architecting via micro-patterning is one of the most attractive approaches, since it significantly expands the catalytic active sites of TPB near the interface, where ORR preferentially occur. Moreover, this architecting approach also facilitates the use of currently viable state-of-art cathode materials of SOFCs; Lanthanum Strontium Cobalt Ferrite (LSCF), Barium Strontium Cobalt Ferrite (BSCF). Therefore, patterns with a high aspect ratio, which maximize the interface area, are required for significant enhancement of electrochemical performance.Here, for the first time, we describe a three-dimensionally micro-architecting process for anode-supported PCFCs, demonstrating dramatic performance enhancement from the expanded interface area between cathode and electrolyte. The various patterns with high ratios were exactly transferred from the original PUA (polyurethane acrylate) molds to the thin and dense protonic conducting electrolyte layer. The patterns maintained the same aspect ratios during the sintering process and finally increased the interface area of more than 30%. The morphology of the patterned surface was characterized by scanning electron microscope (SEM) and atomic force microscopy (AFM). The AC electrochemical impedance spectroscopy was utilized to examine the electrochemical performances of patterned cells. Our unique patterning method opens the new pathway for further performance enhancement of PCFCs. Figure 1

Electrochemical characterization of the artificial metalloenzyme papain-[(η6-arene)Ru(1,10-phenanthroline)Cl

Electrochemical properties were studied for [(η6-arene)Ru(1,10-phenanthroline)Cl]Cl (arene = C6H5(CH2)2NHCOCH2Cl) organometallic complex 1, protein Papain PAP and its conjugate with organometallic complex 1-PAP. The latter can serve as an artificial metalloenzyme with catalytic activity in transfer hydrogenation. This work demonstrates that AC voltammetry and electrochemical impedance spectroscopy can be used as fast tools to screen the catalytic ability of 1-PAP electrochemically by studies of the catalytic hydrogen evolution reaction (HER). Proteins are known to catalyze this process, but we have shown that additional HER signal associated with the catalytic activity of 1 is observed for its conjugate with Papain 1-PAP.

Synthesis of Silver Nanoparticles Using Chitosan as Stabilizer Agent: Application towards Electrocatalytical Reduction of p‐Nitrophenol

AbstractIn this paper, a simple chemical method is reported for the synthesis of silver nanoparticles using β‐1,4 poly D‐glucosamine as stabilizer agent and their application towards electrocatalytical determination of p‐nitrophenol (p‐NP). The formation of β‐1,4 poly D‐glucosamine capped silver nanoparticles was confirmed using UV‐Vis spectroscopy, Scanning Electronic Microscopy (SEM), and Fourier Transform Infrared (FTIR) spectroscopy. The electrocatalytic activity of the β‐1,4 poly D‐glucosamine capped silver nanoparticles modified graphite carbon electrode (β 1,4 p‐DGA‐AgNPs/GrCE) towards p‐NP was studied using cyclic voltammetry (CV), AC electrochemical impedance spectroscopy (EIS), and amperometric (i–t) studies. Typically, the obtained results were compared with those for unmodified graphite carbon. The results clearly reveal that the end prepared sensor has high electrocatalytic activity for p‐NP reduction. From the DPV results, (β 1,4 p‐DGA‐AgNPs/GrCE) was concluded as viable sensor for the electrochemical determination of p‐NP in a linear range from 1.0×10−6 to 1.0×10−4 mol L−1. The minimum calculated concentration that can be detected by the proposed electrode is 6.0×10−7 mol L−1 in terms of the detection limit ((3×σ)/P).

Electrochemical Impedance Spectroscopy as a Practical Tool for Monitoring the Carbonation Process on Reinforced Concrete Structures

Carbonation results in a decrease in the pH of the cementation matrix when CO2(g) from the environment diffused into the concrete structure that can cause the loss of passivity condition on the reinforcing steel surface and leads to early failure of concrete by corrosion attack. There are several monitoring techniques to evaluate the process of lowering the pH in the concrete, named carbonation depth progress. In this research, an electrochemical AC impedance spectroscopy (EIS) technique has been used as an effective laboratory tool for monitoring the evolution of the carbonation progress. A comparison with the traditional phenolphthalein colorimetric technique was also discussed here. Particularly, monitoring is achieved by measuring the change in electrical resistance (Rpo) and capacitance (Cpo) of the concrete bulk, which is obtained from the semicircle at high-frequency region of a typical EIS diagram. According to the EIS results, carbonation progress was observed by a significant increase in the diameter of the semicircle, thus demonstrating the increase in resistivity of ions transmission due to blockade of pores by precipitation of CaCO3 compounds. Furthermore, it was possible to predict the specific time at which the carbonation front reaches the steel-rebar interface at low frequency region and possibly starting a considerable corrosion attack. Finally, the results suggested that EIS technique could be considered a practical tool for evaluating the carbonation progress of reinforced concrete structures without causing structural damage, in addition to the sensitivity of this technique with sufficient accuracy to predict the activation of the reinforcing steel.

Cinnamomum zeylanicum Extract as Green Corrosion Inhibitor for Carbon Steel in Hydrochloric Acid Solutions

The extract of cinnamomum have been evaluated as green inhibitor for the corrosion of Carbon steel in 1M HCl solution was investigated using weight loss, potentiodynamic polarization, ac electrochemical impedance spectroscopy (EIS) , electrochemical frequency modulation (FEM) and energy dispersion spectroscopy (EDS) and scanning electron microscopy (SEM) methods of monitoring corrosion . The inhibitive property of the extract is attributed to the presence of cinnamic aldehyde as major constituent in the extract. measurements showed that this extract act as mixed-type inhibitor. The inhibition efficiency was found to increase with inhibitor concentration. Results obtained by various techniques are close to each other and maximum efficiency of 81.1 % is acknowledged at the inhibitor concentration of 600 ppm. Langmuir isotherm model is found most suitable to explain adsorption behavior of inhibitor for C-steel surface. Molecular adsorption of inhibitor over C- steel surface is found responsible for corrosion inhibition of C-steel in acid.

Electrochemical inhibition bacterial sensor array for detection of water pollutants: artificial neural network (ANN) approach

This work reports on further development of an inhibition electrochemical sensor array based on immobilized bacteria for the preliminary detection of a wide range of organic and inorganic pollutants, such as heavy metal salts (HgCl2, PbCl2, CdCl2), pesticides (atrazine, simazine, DDVP), and petrochemicals (hexane, octane, pentane, toluene, pyrene, and ethanol) in water. A series of DC and AC electrochemical measurements, e.g., cyclic voltammograms and impedance spectroscopy, were carried out on screen-printed gold electrodes with three types of bacteria, namely Escherichia coli, Shewanella oneidensis, and Methylococcus capsulatus, immobilized via poly l-lysine. The results obtained showed a possibility of pattern recognition of the above pollutants by their inhibition effect on the three bacteria used. The analysis of a large amount of experimental data was carried out using an artificial neural network (ANN) programme for more accurate identification of pollutants as well as the estimation of their concentration. The results are encouraging for the development of a simple and cost-effective biosensing technology for preliminary in-field analysis (screening) of water samples for the presence of environmental pollutants.Graphical abstract