Electrode Polarization Research Articles

Method—Multi-Cell Testing with Active Driven Gas Layer Concept: Advantages and Limitations

This study validates a novel method for simultaneous durability testing of multiple symmetrical cells with Ni/ceria fuel electrodes. The investigation demonstrates that gas diffusion losses in the multi-cell test setup utilizing the active driven gas layer concept have a smaller impact on cell performance compared to the single-cell setup. This method proves effective for testing multiple identical cells, offering a time and cost-efficient approach. However, testing symmetrical cells with different fuel electrodes reveals an unexpected pseudo-inductive loop in the impedance spectra, observable only in the multi-cell setup. Analysis of impedance spectra and relaxation times indicates that differences in electrode polarization resistance result in varying gas compositions at the two electrodes of a cell, disrupting symmetry and superimposing an additional Nernst voltage term. To understand this, an electrical equivalent circuit model with the Nernst voltage term was developed to reproduce the observed behavior. Comparison of experimental and simulation results substantiates the model and elucidates the mechanisms. The findings indicate that testing multiple cells with the active driven gas layer concept is applicable only for identical cells and not for those with different electrodes.

Research on Fe doping regulation of vanadium-based phosphate material K3V3-xFex(PO4)4/C for potassium-ion battery cathodes

K3V3(PO4)4(KVP), a novel cathode material for potassium-ion batteries (KIBs), is recognized for its stable crystal structure and robust cycling performance. Despite these attributes, it is hampered by poor electronic conductivity and limited rate capability. In this research, Fe3+ has been substituted for a portion of V3+ to modulate the electronic structure of K3V3-xFex(PO4)4/C, aimed at enhancing its electrochemical performance. Theoretical calculations expectedly show that Fe doping at the V site reduces the band gap energy from 2.674 eV to 1.92 eV, thereby improving electron transfer. Both physical and chemical analyses confirm the successful integration of Fe3+ into the crystal structure and the adjustment of relevant lattice parameters. Additionally, Fe serves as an effective catalyst, enhancing the graphitization of the carbon coating. SEM demonstrates that Fe3+ doping encourages the development of a porous structure, which not only promotes electrolyte penetration but also provides a buffer to the crystal framework during K+ deintercalation. K3V3-xFex(PO4)4/C, when doped with Fe3+, shows superior discharge capacity and long-term cycling stability compared to KVP/C. Specifically, K3V2.8Fe0.2(PO4)4/C, with an Fe3+ doping level of x=0.2, exhibits minimal electrode polarization and outstanding rate performance. After 380 cycles at 400 mA·g−1, it maintains a discharge capacity of 46 mAh·g−1, significantly surpassing KVP/C. These findings offer valuable insights into the commercial synthesis of scalable, high-performance rechargeable KIBs cathode materials.

Balance of heat management and salt-resistance on solar interfacial evaporator actively adjusted by the electric field with periodically changed direction

Interfacial desalination is one of the most promising technologies in solar energy utilization, but it usually needs to balance the heat management and the salt-resistance. Dealing with this, the electric field with periodically changed direction for various reversing times could be used to regulate the interfacial desalination. Hence, the evaporator performances including the evaporation rate, evaporation efficiency, salinity of vapor and surface salt-deposition morphology are investigated in this paper. The experimental results show that the periodical electric field has regulative mechanisms of phase change heat transfer, ion diffusion, and salt crystallization on interfacial desalination. By changing the polarity of the high potential electrode, the salt crystals are rarely observable on the evaporator surface even in the 20 wt% NaCl solution, and the evaporation performance of evaporator would be distinct with different reversing time. Besides, the performance of evaporator could be maximized by the electric field with the reversing time of 20 s, which could increase the evaporation rate up to 36.5 % and the evaporation efficiency from 61.9 % to 90.7 %. The combination of the periodical electric field and the interfacial desalination technology with extremely low consumption could be deemed as a solution for the efficient solar utilization.

Dependence of Protein Immobilization and Photocurrent Generation in PSI-FTO Electrodes on the Electrodeposition Parameters.

This study investigates the immobilization of cyanobacterial photosystem I (PSI) from Synechocystis sp. PCC 6803 onto fluorine-doped tin oxide (FTO) conducting glass plates to create photoelectrodes for biohybrid solar cells. The fabrication of these PSI-FTO photoelectrodes is based on two immobilization processes: rapid electrodeposition driven by an external electric field and slower adsorption during solvent evaporation, both influenced by gravitational sedimentation. Deposition and performance of photoelectrodes was investigated by UV-Vis absorption spectroscopy and photocurrent measurements. We investigated the efficiency of PSI immobilization under varying conditions, including solution pH, applied electric field intensity and duration, and electrode polarization, with the goals to control (1) the direction of migration and (2) the orientation of the PSI particles on the substrate surface. Variation in the pH value of the PSI solution alters the surface charge distribution, affecting the net charge and the electric dipole moment of these proteins. Results showed PSI migration to the positively charged electrode at pH 6, 7, and 8, and to the negatively charged electrode at pH 4.4 and 5, suggesting an isoelectric point of PSI between 5 and 6. At acidic pH, the electrophoretic migration was largely hindered by protein aggregation. Notably, photocurrent generation was consistently cathodic and correlated with PSI layer thickness, and no conclusions can be drawn on the orientation of the immobilized proteins. Overall, these findings suggest mediated electron transfer from FTO to PSI by the used electrolyte containing 10 mM sodium ascorbate and 200 μM dichlorophenolindophenol.

The high-rate cycling stability of the LiFe0.6Mn0.4PO4/C cathode material is enhanced through in-situ Nb-doping

LiFe0.6Mn0.4PO4/C, due to its low cost and safety advantages, is gradually becoming a safe and reliable commercial lithium battery storage material. However, its lower capacity at high rates and poor cycle performance limit its further industrial application. To address this, this work used a one-step solvothermal method to prepare Li(Fe0.6Mn0.4)1‑xNbxPO4 (x = 0, 0.01, 0.02, 0.03) cathode materials to improve electrochemical performance. Characterization of the samples indicates that Nb doping promoted the growth of the material's [001] crystal orientation, thus enhancing the lithium ion diffusion rate, effectively reducing electrode polarization and charge transfer resistance, which helps to explain its excellent rate performance. More importantly, Nb doping increases the M-O bond energy, making the LMFP/C metal-oxygen framework more stable, and enhancing the stability of the crystal structure of lithium ions intercalating and deintercalating during cycling. The electrochemical test results further indicate that the LFMP/CNb0.02 cathode exhibits excellent electrochemical performance. It has remarkable capacities of 156.9 mAh·g‑1 at 0.2 C and 135.9 mAh·g‑1 at 1 C, particularly showing an initial discharge specific capacity of 121.4 mAh·g‑1 at a high rate of 5 C. After 500 cycles, it still maintains a capacity of 114.3 mAh·g‑1, with a capacity retention rate of 94.15 %, significantly outperforming the original LMFP/C (initial discharge specific capacity of 109.8 mAh·g‑1) which only retains 61.47 % of its capacity after 300 cycles.

One-step in situ doping of Sb achieves enhanced performance of [001]-oriented nano-LiFe0.6Mn0.4PO4/C cathode high-rate materials

The LiFe0.6Mn0.4PO4/C composite has become a cost-effective and reliable material for lithium battery storage in commercial applications, due to its significant safety benefits. However, its industrial application is limited by its suboptimal high-rate capacity and unsatisfactory cycling performance. To address this issue, Li(Fe0.6Mn0.4)1-xSbxPO4 (x = 0, 0.01, 0.03, 0.04, 0.05) materials were synthesized using a one-step solvothermal method in this study, aiming to modulate the microstructure and achieve Sb doping, thereby enhancing the electrochemical performance. The electrochemical test results indicate that LFMP/C doped with Sb (designated as LFMP/C-Sb0.04) displays exceptional electrochemical performance, with remarkable capacities of 166.6 mAh·g−1 and 146.8 mAh·g−1 at 0.2C and 1C, respectively. Notably, it achieves a capacity of 126.1 mAh·g−1 at a high rate (5C) and maintains an impressive capacity retention rate of 93.6 % after 300 cycles, outperforming the original LMFP/C (109.5 mAh·g−1), which retains only 61.5 % of its initial capacity. Further characterization of the samples reveals that in situ Sb doping promotes the growth of the [001] crystal orientation, enhancing the lithium-ion diffusion rate and effectively reducing electrode polarization and charge transfer resistance, thereby contributing to its exceptional rate performance. Moreover, Sb doping increases the M − O binding energy, strengthens the metal-oxygen framework, mitigates the Jahn-Teller effect caused by Mn3+ dissolution, and enhances its cycling stability.

Synergistic effects of anionic surfactant doping on dielectric and electro-optical properties of nematic liquid crystals by cyano-ionic interactions

Modern research has long focused on controlling and optimizing the dielectric, electro-optical and optical attributes of liquid crystals (LCs) to increase their technological value. Numerous approaches have been investigated for this reason in an effort to overcome various issues such as high response time, high driving voltage requirements, low dielectric anisotropy and limited operating temperature range, etc. The strategy utilizing binary/multicomponent systems is the most investigated and seems to have the most potential out of all the other techniques. In keeping with the same subject, the influence of anionic surfactant on the dielectric, electro-optical, and optical properties of nematic LC (NLC) has been examined. Precisely, dodecane-1-sulfonic acid sodium salt (SDS) which is an anionic surfactant was dispersed in a room temperature NLC E7 at various concentrations. Our findings reveal a significant alteration in the electro-optical behavior resulting from the introduction of an anionic surfactant, extending well beyond the instance of electrode polarization, albeit with a detrimental impact on performance within the low-frequency range as a result of increased ionic contribution. The main findings of this study include a 17.5%% increase in dielectric anisotropy, an appreciable reduction of about 30%% in threshold voltage and rotational viscosity, and approximately 64% reduction in response time in the host NLC due to the addition of anionic salt in it. A significant photoluminescence quenching of about 64%% is observed after dispersion of 3.0% by weight anionic surfactant in E7. These findings offer potential pathways for the development of future technologies in various domains, including photonic devices, biological imaging, light-emitting diodes (LEDs), and luminescent markers.

Effect of ionic liquid on soft epoxy-amine electroactuators

Energy conversion represents a challenge in various fields of applications such as soft robotics or microfluidics technologies, particularly in terms of electromechanical coupling for actuators. The dielectric elastomers are a variety of electroactive polymers (EAP) which require high electric fields to be used as actuators. It is well-known that the presence of ionic impurities can have an influence of their electro-mechanical response under high electric field (i.e. above 1 MV/m). More precisely, it can be responsible for the bending of the sample under constant electric field. Here, we investigate the impact of a small content, i.e. from 0.1 wt% to 10 wt% of an imidazolium Ionic Liquid (IL) on the electromechanical response of a soft epoxy-amine network. The interest of this study therefore lies in its position at the frontier between dielectric polymers and ionic polymers. Dielectric spectroscopy revealed a significant increase of electric conductivity (≈2 orders of magnitude) when adding only 0.1 wt% of IL and up to 4 orders of magnitude with 10 wt% of IL at T = 20 °C for f = 10 Hz. It also evidenced the presence of the electrode polarization for all the samples doped with IL. The bending test carried out at E = 0.1 MV/m revealed no bending for pure epoxy-amine and a slow kinetics of bending for all the samples doped with IL with displacement evolving throughout the experiment (i.e. over 4 h). As evidenced by dielectric spectroscopy and bending tests, it is clear that the presence of a small quantity of ionic moieties (whether doping agent or impurity) can strongly modify the electromechanical behavior of elastomer commonly described as dielectric.

Chitosan/Microcrystalline Cellulose Overlaid rGO/Fe3O4 Films: Broadband Dielectric Spectroscopy Investigations

Hybrid and straightforward inorganic/organic composites that can be used simultaneously for energy storage are reported. Films from chitosan (Cs) with microcrystalline cellulose (MCC) implanted with reduced graphene oxide (rGO) and/or magnetic Fe3O4 nanoparticles were fabricated. The reinforcement of the Cs/MCC films with rGO and /or Fe3O4 was studied through Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis, and scanning electron microscopy with energy dispersive electron spectroscopy. In addition, their magnetic, conductivity, dielectric constant, and dielectric loss behaviors were studied. The magnetic investigations of the two films loaded with Fe3O4 have supper paramagnetic behavior. The saturation magnetization was decreased with the presence of rGO. At lower frequencies, the contribution of charge transport and interfacial polarization causes a sudden and nearly linear increase in permittivity with decreasing frequency. Unfortunately, no indication of electrode polarization was found, which reduces the ability of the prepared composition to store electrical energy. The electric modulus representation was employed to determine the relaxation time of the interfacial polarization quantitatively and numerically. No indication of electrode polarization was found.

Features of Increasing the Wear Resistance of 90CrSi Tool Steel Surface under Various Electrophysical Parameters of Plasma Electrolytic Treatment

The paper investigates the feasibility of plasma electrolytic treatment (PET) of 90CrSi tool steel to enhance hardness and wear resistance. The influence of electrophysical parameters of PET (polarity of the active electrode, chemical-thermal treatment, and polishing modes) on the composition, structure, morphology, and tribological properties of the surface was studied. Tribological tests were carried out under dry friction conditions according to the shaft-bushing scheme with fixation of the friction coefficient and temperature in the friction contact zone, measurements of surface microgeometry parameters, morphological analysis of friction tracks, and weight wear. The formation of a surface hardened to 1110–1120 HV due to the formation of quenched martensite is shown. Features of nitrogen diffusion during anodic PET and cathodic PET were revealed, and diffusion coefficients were calculated. The wear resistance of the surface of 90CrSi steel increased by 5–9 times after anodic PET followed by polishing, by 16 times after cathodic PET, and up to 32 times after subsequent polishing. It is shown that in all cases, the violation of frictional bonds occurs through the plastic displacement of the material, and the wear mechanism is fatigue wear during dry friction and plastic contact.

Enhanced electrochemical performance of 3D-printed electrodes via blue-laser irradiation and (electro)chemical treatment

Extrusion-based 3D printing technologies, especially fused filament fabrication (FFF) using conductive filaments, have significantly advanced in electroanalytical applications by enabling the fabrication of electrochemical sensors. Nonetheless, 3D-printed electrodes produced from commercially available conductive filaments (e.g., polylactic acid containing carbon black - CB/PLA) often contain a low amount of conductive material (∼20 % wt. carbon black), requiring surface activation protocols to enhance their electrochemical performance. In this study, we investigated the combination of blue-laser (BL) irradiation and (electro)chemical treatment (EC) to improve the performance of 3D-printed electrodes. For this purpose, 3D-printed CB/PLA electrodes were subject to blue laser activation (laser power = 280 mW and scan rate = 30 mm s-1) followed by an electrochemical procedure in 0.5 mol L-1 NaOH solution (application of +1.4 V and – 1.0 V both for 200 s). After the combined treatment, a considerable improvement in the voltammetric profile response (Ipa/Ipc = 1.00 and ΔEp = 136 mV) was achieved using 1 mmol L-1 [Fe(CN)6]3-/4- (equimolar concentration) as the redox probe when compared to polished electrodes (Ipa/Ipc = 0.85 and ΔEp = 690 mV). Scanning electron microscopy, infrared spectroscopy data and X-ray photoelectron spectroscopy showed that the combined treatment promotes the remotion of insulating PLA material, exposing more conductive sites and functional groups. Moreover, electrochemical impedance spectroscopy results showed low resistance to charge transfer and capacitance double-layer measurements revealed an increase in the electroactive area after surface activation. As proof of concept, emerging contaminants such as hydroxychloroquine (HCQ) and paracetamol (PRT) were determined in tap water and pharmaceutical samples using treated 3D-printed CB/PLA electrodes and square-wave voltammetry. Linear ranges of 0.20 - 12.30 µmol L-1 and 1.0–30.0 µmol L-1 with limit of detection values of 0.01 and 0.2 µmol L-1 were obtained for HCQ and PRT, respectively. Appropriate recovery values (90 - 111 %) for the analysis of spiked samples were achieved.

Reduced Surface Area for the Oxygen Reduction Reaction in Porous Electrode via Electrical Conductivity Relaxation.

Oxygen reduction reaction (ORR) performance of porous electrode is critical for solid oxide fuel cells (SOFCs). However, the effects of gas diffusion on the ORR in porous media need further investigation, although some issues, such as nonthermal surface oxygen exchange, have been attributed to gas diffusion. Herein, La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) with various porosity, pore radii and gas permeability were investigated via the electrical conductivity relaxation method and analysed using the distributed of characteristic time (DCT) model. The ORR is revealed with three characteristic times, which are gas diffusion, oxygen exchange via the surface corresponding to small pores, and oxygen exchange to large pores. Gas diffusion delays the oxygen surface exchange reaction, resulting in very low chemical oxygen surface exchange coefficient compared with that obtained with dense sample under the assumption that all the surfaces are active for the ORR. Reduced surface area is thus defined to quantitatively represent the gas diffusion effects. The reduced surface area increases with increasing gas permeability, demonstrating the importance of electrode engineering for fast gas transport. Moreover, reduced surface area is suggested for replacing the specific surface area to calculate the electrode polarization resistance using the ALS model.

Crystallographically textured zinc nucleation and planar electrodeposition for zinc metal batteries via magnetoelectric and magnetization effects

The premature failure of zinc metal anodes is critically associated with the uncontrollable nucleation and random orientation of hexagonal Zn electrodeposits. Herein, we realize to control the crystallographical texture of zinc crystal nuclei and enable planar electrodeposition by simply applying a magnetic field. We unveil the novel mechanism of magnetoelectric and magnetization effects on the different deposition behavior under magnetic fields. The magnetohydrodynamic effect can flatten the uneven electrode surface during electrodeposition by deflecting the motion of Zn2+ ions. Especially, influences of the Hall effect on electrode polarization and magnetization effect on crystallographical Zn nucleation are first uncovered and validated. We demonstrate the proper use of these magnetic field-related effects is propitious to dense, homogeneous, and highly reversible deposition/dissolution of Zn metal anodes. The cycle lives of Zn anodes are extended 2–4 times at different currents and cycling capacities. Moreover, exceptional reversibility of 99.85 % is achieved. Full cells with a low N/P ratio of 5.4 and ultrahigh cathode mass loading of 19.98 mg cm−2 can release stable capacity up to 3.2 mAh cm−2. Our study provides new paradigms for magnetic field regulation of Zn metal battery electrochemistry, as well as for other external field applications in adjusting battery performance.

Enhancing Heavy Metal Detection through Electrochemical Polishing of Carbon Electrodes.

Our research addresses the pressing need for environmental sensors capable of large-scale, on-site detection of a wide array of heavy metals with highly accurate sensor metrics. We present a novel approach using electrochemically polished (ECP) carbon screen-printed electrodes (cSPEs) for high-sensitivity detection of cadmium and lead. By applying a range of techniques, including scanning electron microscopy, energy-dispersive spectroscopy, Raman spectroscopy, electrochemical impedance spectroscopy, and cyclic voltammetry, we investigated the impact of the electrochemical potential scan range, scan rate, and the number of cycles on electrode response and its ability to detect cadmium and lead. Our findings reveal a 41 ± 1.2% increase in voltammogram currents and a 51 ± 1.6% decrease in potential separations (n = 3), indicating a significantly improved active electrode area and kinetics. The impedance model elucidates the microstructural and electrochemical property changes in the ECP-treated electrodes, showing an 88 ± 2% (n = 3) decrease in the charge transfer resistance, leading to enhanced electrode electrical conductivity. A bismuth-reduced graphene oxide nanocomposite-modified, ECP-treated electrode demonstrated a higher cadmium and lead sensitivity of up to 5 ± 0.1 μAppb-1cm-2 and 2.7 ± 0.1 μAppb-1cm-2 (n = 3), respectively, resulting in sub-ppb limits of detection in spiked deionized water samples. Our study underscores the potential of optimally ECP-activated electrodes as a foundation for designing ultrasensitive heavy metal sensors for a wide range of real-world heavy metal-contaminated waters.

Overcoming polarization and dissolution of manganese-based electrodes to enhance stability in electrochemical lithium extraction

The Mn dissolution issue in manganese-based materials (LMO) represents one of the most challenging barriers to further commercial development of electrochemical lithium extraction, which is an efficient and clean way of extracting Li from liquid resources. Here, by leveraging the advantages of composite materials, a novel combination of reduced graphene oxide (rGO) and sulfonated ionic polymers (Nafion) is introduced to relieve the issues of electrode polarization and manganese dissolution, critical factors limiting the durability of LMO electrodes. By modifying with rGO to enhance electronic conductivity and surface characteristics, and capturing dissolved Mn2+ through Nafion, the modified electrode showed significant improvement in cycling stability and lithium adsorption capacity. Experimental results confirm that this synergistic approach effectively mitigates polarization effects and controls disproportionation reactions, thereby enhancing the stability of the lithium extraction process, revealing a notable increase in electrode capacity retention from 79.04 % to 94.64 % after 30 cycles. Additionally, through DFT calculations and XPS analysis, the effectiveness of the manganese capture strategy is validated. This work presents an effective new strategy to extend the lifespan of manganese-based electrodes and enhance their adsorption performance.

Electrode reactions on the aluminum electrode in 1-butyl-3-methylimidazolium chloride chloroaluminate ionic liquid: A comprehensive study

Mechanisms of Al electrochemical deposition/dissolution in acidic AlCl3–1-butyl-3-methylimidazolium chloride (BMImCl) ionic liquids are studied. Stationary polarization curves (SPCs) are obtained in the anodic range of potentials. The anodic SPCs are characteristic of electrode processes, which are complicated by passivation phenomena. The peaks intensity of AlCl4−, Al2Cl7− ions were obtained by in-situ Raman spectroscopy during the aluminum electrode polarization and correlated with the behavior of the SPCs. Based on the results obtained, a mechanism of electrochemical oxidation of aluminum in AlCl3–BMImCl IL is proposed. According to the mechanism in question, the anodic process is complicated by the presence of a following chemical reaction involving AlCl3. Chronopotentiometric studies were carried out to determine diffusion coefficients of Al2Cl7− anion, which are unaffected by the change in the molar ratio of AlCl3 to BMImCl (N). The activation energy (Ea) for the Al2Cl7− diffusion coefficient is independent of N and equals 14.5 ± 0.4 kJ mol−1. Exchange current density (i0) at the Al | AlCl3–BMImCl interface was determined using impedance spectroscopy for the compositions with 1.1 ≤ N ≤ 2.0 at temperatures from 303 to 386 K. The i0 increases from 0.54 ± 0.13 to 2.73 ± 0.22 mA cm−2 with the concentration of the electrochemically active Al2Cl7− anion in the concentration range indicated above at 303 K. The data on i0 is used to calculate the transfer coefficient of cathodic reaction (α = 0.18 ± 0.02), the electrochemical reaction rate constant (ks= (1.1 ± 0.3)∙10−6 cm s−1 (at T = 303 K)) and the Ea for the ks (Eaks = 36.5 ± 0.9 kJ mol−1), which do not depend on the IL composition.

Investigating the impact of strontium doping on neodymium manganite Nanoperovskites: Analysis of structural, optical, and dielectric properties

Nd1-xSrxMnO3 (x = 0, 0.3, 0.5, 0.7) nanoperovskites were fabricated through combustion process, a low-cost technique in contrast to the vacuum methodologies for growth. The singular phase orthorhombic Pbnm crystallized for x = 0 to 0.5; nevertheless, both orthorhombic and monoclinic phases were discerned at x = 0.7. Employing X-ray photoelectron spectroscopy (XPS) spectra, the surface chemistry has been conducted, encompassing the intricate parameters associated with the oxygen reduction reaction (ORR).The BDS analysis at ambient temperature, encompassing the frequency span from 1 Hz to 1000 KHz, elucidates various facets of dielectric properties. Elevated dielectric constants at the low-frequency spectrum are explained by the Maxwell–Wagner effect. With an escalation in doping concentration, there is a concurrent rise in the dielectric constant. The escalation in AC conductivity within the high-frequency domain conforms to Johnscher's universal power law, whereas the ramifications of electrode polarization are delineated through a log-log representation.

EFFECT OF SNO2 POROUS STRUCTURE ON ITS OPTICAL AND PHOTOELECTROCHEMICAL PROPERTIES IN WATER AND WATER-METHANOL SOLUTIONS

Tin(IV) oxide is a wide-gap semiconductor material that is widely used in photooxidation reactions of organic compounds. However, the relationship between energetic and photoelectrocatalytic properties in the oxidation of small organic molecules has not yet been sufficiently explored. In this work, a series of tin oxides were synthesized using hydrothermal, sol-gel, and template methods. Polystyrene spheres with a size of 250 nm, as well as cetyltrimethylammonium bromide, were used as templates. X-Ray diffraction, low-temperature nitrogen adsorption, X-ray photoelectron spectroscopy, Raman spectroscopy and diffuse reflectance spectroscopy methods were used to study the structure, surface composition, optical and energy characteristics. Using photoelectrochemical methods, the potentials of the conduction band and valence band were determined, and photocurrents in aqueous and aqueous-methanol solutions were studied depending on electrode polarization. It is shown that the preparation method (sol-gel or hydrothermal) does not affect the position of energy bands, while the use of a template during synthesis leads to an increase in the average pore diameter in the samples and an increase in photocurrent values in the presence of methanol. It has been established that for template-synthesized samples, the magnitude of photocurrents in a water-methanol mixture increases with an increase in the valence-band potential. The sample prepared by the hydrothermal method using a template showed the highest photocurrent values both in the background electrolyte (17.3 μA/cm2) and in the presence of methanol (26 μA/cm2), compared to the sample prepared without using a template in the electrolyte with the addition of methanol (7.6 μA/cm2) and without it (7.8 μA/cm2).

Quantifying Individual Electrode Polarization and Unraveling Theinteractive Phenomenon in Solid Oxide Fuel Cells

In electrochemically active systems, such as fuel cells, electrolyzers, and batteries, researchers often modify the material chemistry or operating variables at one of the electrodes (e.g., the cathode) to investigate its properties. This approach assumes that changes in measured polarization and cell performance result solely from the modifications made to the selected electrode, while the conditions at the other electrode (e.g., the anode) remain constant. However, the potential interactions between the polarizations of these two electrodes have remained unclear. In our study, we utilize a voltage probe capable of precisely determining electrode polarization. Our findings reveal three key insights:1. The quantification of electrode polarization becomes feasible through the implementation of a voltage probe. 2. The fuel electrode plays a pivotal role in the performance of state-of-the-art solid oxide cells, with its influence being comparable to that of the oxygen electrode. 3. A reciprocal interaction exists between the two electrodes within a solid oxide cell. Consequently, when there are changes in the chemistry or operational conditions at one electrode, the polarization of the other electrode changes simultaneously

Swift and precise detection of unlabeled pathogens using a nanogap electrode impedimetric sensor facilitated by electrokinetics

For the protection of human health and environment, there is a growing demand for high-performance, user-friendly biosensors for the prompt detection of pathogenic bacteria in samples containing various substances. We present a nanogap electrode-based purely electrical impedimetric sensor that utilizes the dielectrophoresis (DEP) mechanism. Our nanogap sensor can directly and sensitively detect pathogens present at concentrations as low as 1–10 cells/assay in buffers and drinking milk without the need for separation, purification, or specific ligand binding. This is achieved by minimizing the electrical double-layer effect and electrode polarization in nanogap impedance sensors, reducing signal loss. In addition, even at low DEP voltages, nanogap sensors can quickly establish strong DEP forces between the nanogap electrodes to control the spatial concentration of pathogens around the electrodes. This activates and stabilizes inter-electrode signal transmission along the nanogap-aligned pathogens, increasing sensitivity and reducing errors during repeated measurements. The DEP-enabled nanogap impedance sensor developed in this study is valuable for a variety of pathogen detection and monitoring systems including point-of-care testing (POCT) as it can detect pathogens in diverse samples containing multiple substances quickly and with high sensitivity, is compatible with complex solutions such as food and beverages, and provides highly reproducible results without the need for separate binding and separation processes.