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Electrochem, Volume 6, Issue 3 (September 2025) – 9 articles

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16 pages, 4106 KiB  
Article
Stability of TiO2–Polypyrrole Heterojunctions for Photoelectrochemical Water Oxidation
by Jhon Puerres, Pablo Ortiz and María T. Cortés
Electrochem 2025, 6(3), 31; https://doi.org/10.3390/electrochem6030031 - 20 Aug 2025
Abstract
TiO2 composites with polypyrrole have gained attention for various applications; however, some reported results on the suitability of this heterojunction for photoelectrochemical water oxidation do not agree. In this sense, it is relevant to further study this material to clarify the role [...] Read more.
TiO2 composites with polypyrrole have gained attention for various applications; however, some reported results on the suitability of this heterojunction for photoelectrochemical water oxidation do not agree. In this sense, it is relevant to further study this material to clarify the role of polypyrrole in this system. Here, TiO2 nanorods were grown on fluorine-doped tin oxide (FTO) substrates by a hydrothermal route; then, polypyrrole coatings were electrochemically synthetized on TiO2 nanorods using a galvanostatic signal. The heterojunctions were characterized by different spectroscopic, microscopic, and electrochemical techniques. As a result, it was found that the polypyrrole underwent a rapid degradation process and that this process occurred independently of the amount of polymer deposited on the TiO2, the illumination direction (back and front of the photoanode), and the type of light used (UV-Vis and Vis). In addition, from the measurements of the band positions of TiO2 and the HOMO level of polypyrrole, it was shown that the TiO2–polypyrrole heterojunction is not suitable for achieving the transfer of photogenerated holes to the electrolyte. These findings contribute to understanding the properties and interaction of two components of wide interest in materials science. Full article
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18 pages, 1864 KiB  
Article
Ternary Nickel-Iron-Phosphorus (NiFeP) Electrocatalysts for Alkaline Water Splitting
by Raminta Šakickaitė, Zita Sukackienė, Virginija Kepenienė, Aldona Balčiūnaitė, Raminta Stagniūnaitė, Gitana Valeckytė and Loreta Tamašauskaitė-Tamašiūnaitė
Electrochem 2025, 6(3), 30; https://doi.org/10.3390/electrochem6030030 - 15 Aug 2025
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Abstract
In this study, ternary NiFeP coatings were fabricated on a copper substrate using a simple, fast, and cost-effective electroless deposition method. The coatings were named Ni85Fe4P12, Ni80Fe8P12, and Ni75Fe [...] Read more.
In this study, ternary NiFeP coatings were fabricated on a copper substrate using a simple, fast, and cost-effective electroless deposition method. The coatings were named Ni85Fe4P12, Ni80Fe8P12, and Ni75Fe12P12, indicating 4, 8, and 12 at % of Fe, respectively. The surface morphology and composition of the coatings were characterized using scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX). The activity of the prepared coatings was evaluated using the water-splitting reaction to determine the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in a 1 M KOH electrolyte solution. Electrochemical measurements were carried out in a temperature range from 25 °C to 55 °C. The HER and OER current density values increased by up to 2.58 and 2.13 times, respectively, with temperature increase compared to the result at 25 °C. All three coatings demonstrated activity in both reactions. Ni85Fe4P12 exhibited the highest catalytic efficiency in the HER, with the overpotential of 340 mV at 10 mAcm−2 and a Tafel slope of 61 mVdec−1. In the OER, the efficiency of the NiFeP catalysts correlated with their Fe content. The overpotential was 412 mV for Ni80Fe8P12 and 432 mV for Ni75Fe12P12 at 10 mAcm−2 with Tafel slopes of 96 and 91 mVdec−1, respectively. This study underscores the critical influence of Fe content on the catalytic efficiency of NiFeP coatings, with reduced Fe content enhancing HER and increased Fe content benefits OER. Full article
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19 pages, 2474 KiB  
Article
Unraveling the Role of Aluminum in Boosting Lithium-Ionic Conductivity of LLZO
by Md Mozammal Raju, Yi Ding and Qifeng Zhang
Electrochem 2025, 6(3), 29; https://doi.org/10.3390/electrochem6030029 - 4 Aug 2025
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Abstract
The development of high-performance solid electrolytes is critical to advancing solid-state lithium-ion batteries (SSBs), with lithium lanthanum zirconium oxide (LLZO) emerging as a leading candidate due to its chemical stability and wide electrochemical window. In this study, we systematically investigated the effects of [...] Read more.
The development of high-performance solid electrolytes is critical to advancing solid-state lithium-ion batteries (SSBs), with lithium lanthanum zirconium oxide (LLZO) emerging as a leading candidate due to its chemical stability and wide electrochemical window. In this study, we systematically investigated the effects of cation dopants, including aluminum (Al3+), tantalum (Ta5+), gallium (Ga3+), and rubidium (Rb+), on the structural, electronic, and ionic transport properties of LLZO using density functional theory (DFT) and ab initio molecular dynamics (AIMD) simulations. It appeared that, among all simulated results, Al-LLZO exhibits the highest ionic conductivity of 1.439 × 10−2 S/cm with reduced activation energy of 0.138 eV, driven by enhanced lithium vacancy concentrations and preserved cubic-phase stability. Ta-LLZO follows, with a conductivity of 7.12 × 10−3 S/cm, while Ga-LLZO and Rb-LLZO provide moderate conductivity of 3.73 × 10−3 S/cm and 3.32 × 10−3 S/cm, respectively. Charge density analysis reveals that Al and Ta dopants facilitate smoother lithium-ion migration by minimizing electrostatic barriers. Furthermore, Al-LLZO demonstrates low electronic conductivity (1.72 × 10−8 S/cm) and favorable binding energy, mitigating dendrite formation risks. Comparative evaluations of radial distribution functions (RDFs) and XRD patterns confirm the structural integrity of doped systems. Overall, Al emerges as the most effective and economically viable dopant, optimizing LLZO for scalable, durable, and high-conductivity solid-state batteries. Full article
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14 pages, 3666 KiB  
Review
Electrochemical (Bio) Sensors Based on Metal–Organic Framework Composites
by Ping Li, Ziyu Cui, Mengshuang Wang, Junxian Yang, Mingli Hu, Qiqing Cheng and Shi Wang
Electrochem 2025, 6(3), 28; https://doi.org/10.3390/electrochem6030028 - 4 Aug 2025
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Abstract
Metal–organic frameworks (MOFs) have characteristics such as a large specific surface area, distinct functional sites, and an adjustable pore size. However, the inherent low conductivity of MOFs significantly affects the charge transfer efficiency when they are used for electrocatalytic sensing. Combining MOFs with [...] Read more.
Metal–organic frameworks (MOFs) have characteristics such as a large specific surface area, distinct functional sites, and an adjustable pore size. However, the inherent low conductivity of MOFs significantly affects the charge transfer efficiency when they are used for electrocatalytic sensing. Combining MOFs with conductive materials can compensate for these deficiencies. For MOF/metal nanoparticle composites (e.g., composites with gold, silver, platinum, and bimetallic nanoparticles), the high electrical conductivity and catalytic activity of metal nanoparticles are utilized, and MOFs can inhibit the agglomeration of nanoparticles. MOF/carbon-based material composites integrate the high electrical conductivity and large specific surface area of carbon-based materials. MOF/conductive polymer composites offer good flexibility and tunability. MOF/multiple conductive material composites exhibit synergistic effects. Although MOF composites provide an ideal platform for electrocatalytic reactions, current research still suffers from several issues, including a lack of comparative studies, insufficient research on structure–property correlations, limited practical applications, and high synthesis costs. In the future, it is necessary to explore new synthetic pathways and seek; inexpensive alternative raw materials. Full article
(This article belongs to the Special Issue Feature Papers in Electrochemistry)
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18 pages, 3493 KiB  
Article
Red-Billed Blue Magpie Optimizer for Modeling and Estimating the State of Charge of Lithium-Ion Battery
by Ahmed Fathy and Ahmed M. Agwa
Electrochem 2025, 6(3), 27; https://doi.org/10.3390/electrochem6030027 - 31 Jul 2025
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Abstract
The energy generated from renewable sources has an intermittent nature since solar irradiation and wind speed vary continuously. Hence, their energy should be stored to be utilized throughout their shortage. There are various forms of energy storage systems while the most widespread technique [...] Read more.
The energy generated from renewable sources has an intermittent nature since solar irradiation and wind speed vary continuously. Hence, their energy should be stored to be utilized throughout their shortage. There are various forms of energy storage systems while the most widespread technique is the battery storage system since its cost is low compared to other techniques. Therefore, batteries are employed in several applications like power systems, electric vehicles, and smart grids. Due to the merits of the lithium-ion (Li-ion) battery, it is preferred over other kinds of batteries. However, the accuracy of the Li-ion battery model is essential for estimating the state of charge (SOC). Additionally, it is essential for consistent simulation and operation throughout various loading and charging conditions. Consequently, the determination of real battery model parameters is vital. An innovative application of the red-billed blue magpie optimizer (RBMO) for determining the model parameters and the SOC of the Li-ion battery is presented in this article. The Shepherd model parameters are determined using the suggested optimization algorithm. The RBMO-based modeling approach offers excellent execution in determining the parameters of the battery model. The suggested approach is compared to other programmed algorithms, namely dandelion optimizer, spider wasp optimizer, barnacles mating optimizer, and interior search algorithm. Moreover, the suggested RBMO is statistically evaluated using Kruskal–Wallis, ANOVA tables, Friedman rank, and Wilcoxon rank tests. Additionally, the Li-ion battery model estimated via the RBMO is validated under variable loading conditions. The fetched results revealed that the suggested approach achieved the least errors between the measured and estimated voltages compared to other approaches in two studied cases with values of 1.4951 × 10−4 and 2.66176 × 10−4. Full article
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16 pages, 1936 KiB  
Article
Electrocoagulation of Spent Coolant by Dissimilar Fe-Al Combination
by Shu Pei Ng, Weiyi Wu, Min Qian, Yuelong Preston Zhu, Xinying Deng, Shuyun Chng, Yi Jin Tan, Yi Qing Kek, Shi Jun Zachary Yong, Li Wei Low and Wenjin Yan
Electrochem 2025, 6(3), 26; https://doi.org/10.3390/electrochem6030026 - 11 Jul 2025
Viewed by 338
Abstract
Electrocoagulation is rapidly gaining prominence in wastewater treatment due to its capabilities and less reliance on additional chemicals. While a lot of research efforts have been focused on the influence of the anode material, power supply, and reactor design, the contribution of the [...] Read more.
Electrocoagulation is rapidly gaining prominence in wastewater treatment due to its capabilities and less reliance on additional chemicals. While a lot of research efforts have been focused on the influence of the anode material, power supply, and reactor design, the contribution of the cathode to contaminant removal has been less explored. In this study, we investigated the performance of stainless steel (SS-304) and aluminium (Al-6061) electrodes in both similar and dissimilar configurations for a 120 min electrocoagulation treatment of spent machinery coolant. The anode–cathode configurations, including SS-SS, Al-Al, SS-Al and Al-SS, have been investigated. Additionally, we examined the effects of the initial pH and agitation methods on the process performance. Our findings indicated that the type of cathode could significantly affect the floc formation and contaminant removal. Notably, the combination of an Al anode and SS cathode (Al(A)-SS(C)) demonstrated a synergistic improvement in the Chemical Oxygen Demand (COD), with a removal of 84.3% within a short treatment time (<20 min). The final COD removal of 91.4% was achieved with a turbidity level close to 12 Nephelometric Turbidity Units (NTU). The Al anode readily released the Al ions and formed light flocs at the early stage of electrocoagulation, while the SS cathode generated heavy Fe hydroxides that mitigated the flotation effect. These results demonstrated the cathode’s significant contribution in electrocoagulation, leading to potential savings in the treatment time required. Full article
(This article belongs to the Special Issue Feature Papers in Electrochemistry)
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18 pages, 2455 KiB  
Article
Chemical Stability of PFSA Membranes in Heavy-Duty Fuel Cells: Fluoride Emission Rate Model
by Luke R. Johnson, Xiaohua Wang, Calita Quesada, Xiaojing Wang, Rangachary Mukundan and Rajesh Ahluwalia
Electrochem 2025, 6(3), 25; https://doi.org/10.3390/electrochem6030025 - 4 Jul 2025
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Abstract
Laboratory data from in-cell tests at and near open circuit potentials (OCV) and ex-situ H2O2 vapor exposure tests are used to develop a fluoride emission rate (FER) model for a state-of-the-art 12-µm thin, low equivalent weight, long-chain perfluorosulfonic acid (PFSA) [...] Read more.
Laboratory data from in-cell tests at and near open circuit potentials (OCV) and ex-situ H2O2 vapor exposure tests are used to develop a fluoride emission rate (FER) model for a state-of-the-art 12-µm thin, low equivalent weight, long-chain perfluorosulfonic acid (PFSA) ionomer membrane that is mechanically reinforced with expanded PTFE and chemically stabilized with 2 mol% cerium as an anti-oxidant. The anode FER at OCV linearly correlates with O2 crossover from the cathode and the high yield of H2O2 at anode potentials, as observed in rotating ring disk electrode (RRDE) studies. The cathode FER may be linked to the energetic formation of reactive hydroxyl radicals (·OH) from the decomposition of H2O2 produced as an intermediate in the two-electron ORR pathway at high cathode potentials. Both anode and cathode FERs are significantly enhanced at low relative humidity and high temperatures. The modeled FER is strongly influenced by the gradients in water activity and cerium concentration that develops in operating fuel cells. Membrane stability maps are constructed to illustrate the relationship between the cell voltage, temperature, and relative humidity for FER thresholds that define H2 crossover failure by chemical degradation over a specified lifetime. Full article
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20 pages, 3241 KiB  
Article
Amperometric Alcohol Vapour Detection and Mass Transport Diffusion Modelling in a Platinum-Based Sensor
by Luke Saunders, Ronan Baron and Benjamin R. Horrocks
Electrochem 2025, 6(3), 24; https://doi.org/10.3390/electrochem6030024 - 3 Jul 2025
Viewed by 483
Abstract
An important class of analytes are volatile organic carbons (VOCs), particularly aliphatic primary alcohols. Here, we report the straightforward modification of a commercially available carbon monoxide sensor to detect a range of aliphatic primary alcohols at room temperature. The mass transport mechanisms governing [...] Read more.
An important class of analytes are volatile organic carbons (VOCs), particularly aliphatic primary alcohols. Here, we report the straightforward modification of a commercially available carbon monoxide sensor to detect a range of aliphatic primary alcohols at room temperature. The mass transport mechanisms governing the performance of the sensor were investigated using diffusion in multiple layers of the sensor to model the response to an abrupt change in analyte concentration. The sensor was shown to have a large capacitance because of the nanoparticulate nature of the platinum working electrode. It was also shown that the modified sensor had performance characteristics that were mainly determined by the condensation of the analyte during diffusion through the membrane pores. The sensor was capable of a quantitative amperometric response (sensitivity of approximately 2.2 µA/ppm), with a limit of detection (LoD) of 17 ppm methanol, 2 ppm ethanol, 3 ppm heptan-1-ol, and displayed selectivity towards different VOC functional groups (the sensor gives an amperometric response to primary alcohols within 10 s, but not to esters or carboxylic acids). Full article
(This article belongs to the Special Issue Feature Papers in Electrochemistry)
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21 pages, 3361 KiB  
Article
Alternative Supports for Electrocatalysis of the Oxygen Evolution Reaction in Alkaline Media
by Gwénaëlle Kéranguéven, Ivan Filimonenkov, Thierry Dintzer and Matthieu Picher
Electrochem 2025, 6(3), 23; https://doi.org/10.3390/electrochem6030023 - 25 Jun 2025
Viewed by 510
Abstract
The anodic stability of tungsten carbide (WC) and iron oxide with a spinel structure (Fe3O4) were compared against similar data for nanostructured, boron-doped diamond (BDD), and the benchmark Vulcan XC72 carbon, in view of their eventual application as alternative [...] Read more.
The anodic stability of tungsten carbide (WC) and iron oxide with a spinel structure (Fe3O4) were compared against similar data for nanostructured, boron-doped diamond (BDD), and the benchmark Vulcan XC72 carbon, in view of their eventual application as alternative supports for the anion exchange membrane electrolyzer anode. To this end, metal oxide composites were prepared by the in situ autocombustion (ISAC) method, and the anodic behavior of materials (composites as well as supports alone) was investigated in 1 M NaOH electrolyte by the rotating ring–disc electrode method, which enables the separation oxygen evolution reaction and materials’ degradation currents. Among all supports, BDD has proven to be the most stable, while Vulcan XC72 is the least stable under the anodic polarization, with Fe3O4 and WC demonstrating intermediate behavior. The Co3O4-BDD, -Fe3O4, -WC, and -Vulcan composites prepared by the ISAC method were then tested as catalysts of the oxygen evolution reaction. The Co3O4-BDD and Co3O4-Fe3O4 composites appear to be competitive electrocatalysts for the OER in alkaline medium, showing activity comparable to the literature and higher support stability towards oxidation, either in cyclic voltammetry or chronoamperometry stability tests. On the contrary, WC- and Vulcan-based composites are prone to degradation. Full article
(This article belongs to the Topic Electrocatalytic Advances for Sustainable Energy)
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