Electrochem, Volume 6, Issue 1 (March 2025) – 9 articles

In a plant microbial fuel cell (P-MFC), the plant provides the fuel in the form of exudates secreted by the roots, which are oxidised by electroactive bacteria. The immature plant is hampered by low energy yields. Several factors may explain this situation, including the low open-circuit voltage of the plant cell. This is a function of the development of the biofilm formed by the electroactive bacteria on the surface of the anode, in relation to the availability of the exudates produced by the roots. In order to exploit the fertilising role of biochars, a plant cell was developed from C. citratus and grown in a medium to which 5% by mass of coconut shell biochar had been added. Its effect was studied as well as the distance between the electrodes. The potential of Cymbopogon citratus was also evaluated. Three samples without biochar, with inter-electrode distances of 2, 5 and 7 cm, respectively, identified as SCS2, SCS5 and SCS7, and three with the addition of 5 % biochar, with the same inter-electrode distance values, identified as S2, S5 and S7, were prepared. Open-circuit voltage (OCV) measurements were taken at 6 a.m., 1 p.m. and 8 p.m. The results showed that all the samples had high open-circuit voltage values at 1 p.m. Samples containing 5% biochar had open-circuit voltages increased by 16 %, 8.94% and 5.78%, respectively, for inter-electrode distances of 2, 5 and 7 cm compared with those containing no biochar. Furthermore, the highest open-circuit voltage values were obtained for all samples with C. citratus at an inter-electrode distance of 5 cm. The maximum power output of the PMFC with C. citratus in this study was 75.8 mW/m², which is much higher than the power output of PMFCs in recent studies. Full article

In this study, we developed lithium–sulfur rechargeable batteries using chemically modified thermoplastic sulfur polymers as cathode active materials, aiming to effectively utilize surplus sulfur resources. The resulting high-sulfur-content resins exhibited self-healing properties, extensibility, and adhesiveness. By leveraging its high solubility in specific organic solvents, we successfully introduced sulfur-based compounds into porous carbon via vacuum impregnation using a solution, rather than conventional thermal impregnation. Charge–discharge measurements of lithium–sulfur (Li-S) secondary batteries assembled with this more uniform composite cathode, compared to those using elemental sulfur, demonstrated an increased discharge capacity in the initial cycles and at higher rates. Full article

The electrocatalytic reduction of nitric oxide and nitrogen dioxide (NOx) remains a significant challenge due to the need for stable, efficient, and cost-effective materials. This study presents a novel support system for NOx reduction in alkaline media, composed of ZrO₂-WO₃-C (ZWC), synthesized via coprecipitation. Platinum nanoparticles (10 wt.%) were loaded onto ZWC and Vulcan carbon support, using similar methods for comparison. Comprehensive physicochemical and electrochemical analyses (N₂ physisorption, XRD, XPS, SEM, TEM, and cyclic and linear voltammetry) revealed that PtZWC outperformed PtC and commercial PtEtek in NOx electrocatalysis. Notably, PtZWC exhibited the highest total electric charge for NOx reduction. At the same time, the hydrogen evolution reaction (HER) was shifted to more negative cathodic potentials, indicating reduced hydrogen coverage and a modified dissociative Tafel mechanism on platinum. Additionally, the combination of WO₃ and ZrO₂ in ZWC enhanced electron transfer and suppressed HER by reducing NO and hydrogen atom adsorption competition. While the incorporation of WO₃ and ZrO₂ lowered the surface area to 96 m²/g, it significantly improved pore properties, facilitating better Pt nanoparticle dispersion (3.06 ± 0.85 nm, as confirmed by SEM and TEM). XRD analysis identified graphite and Pt phases, with monoclinic WO₃ broadening PtZWC peaks (20–25°). At the same time, XPS confirmed oxidation states of Pt, W, and Zr and tungsten-related oxygen vacancies, ensuring chemical stability and enhanced catalytic activity. Full article

Sodium-ion batteries (SIBs) have garnered significant attention as a cost-effective and sustainable alternative to lithium-ion batteries (LIBs) due to the abundance and eco-friendly extraction of sodium. Despite the larger ionic radius and heavier mass of sodium ions, SIBs are ideal for large-scale applications, such as grid energy storage and electric vehicles, where cost and resource availability outweigh the constraints of size and weight. A critical component in SIBs is the electrolyte, which governs specific capacity, energy density, and battery lifespan by enabling ion transport between electrodes. Among various electrolytes, composite polymer electrolytes (CPEs) stand out for their non-leakage and non-flammable nature and tunable physicochemical properties. The incorporation of NASICON (Na Super Ionic CONductor) fillers into polymer matrices has shown transformative potential in enhancing SIB performance. NASICON fillers improve ionic conductivity by forming continuous ion conduction pathways and reduce polymer matrix crystallinity, thereby facilitating higher sodium-ion mobility. Additionally, these fillers enhance the mechanical properties and electrochemical performance of CPEs. Hence, this review focuses on the pivotal roles of NASICON fillers in optimizing the properties of CPEs, including ionic conductivity, structural integrity, and electrochemical stability. The mechanisms underlying sodium-ion transport facilitated by NASICON fillers in CPE will be explored, with emphasis on the influence of filler morphology and composition on electrochemical properties. By scrutinizing the recent findings, this review underscores the potential of NASICON-based composite polymer electrolytes as appropriate material for the development of advanced sodium-ion batteries. Full article

Sodium–ion batteries are emerging as strong competition to lithium–ion batteries in certain market sections. While these cells do not use critical raw materials, they still feature a liquid electrolyte with all its inherent safety issues, like high flammability and toxicity. Alternative concepts like oxide-ceramic-based all-solid-state batteries feature the highest possible safety while still maintaining competitive electrochemical performance. However, production technologies are still in their infancy, especially for Na all-solid-state batteries, and need to be urgently developed to enable solid-state-battery technology using only abundant raw materials. In this study, the additive-free production of freestanding, undoped NaSICON separators via tape-casting is demonstrated, having an extremely high total Na-ion conductivity of up to 2.44 mS·cm⁻¹ at room temperature. Nevertheless, a strong influence of sample thickness on phase purity as well as electrochemical performance is uncovered. Additionally, the effect of self-coating of NaSICON during high-temperature treatment was evaluated as a function of thickness. While advantageous for increasing the stability against Na-metal anodes, detrimental consequences are identified when separator thickness is reduced to industrially relevant values and mitigation measures are postulated. Full article

The electrochemical properties of the hydrophobic room-temperature ionic liquid 1-propyl-2,3-dimethylimidazolium bis(trifluoromethylsulfonyl)imide (PMMIm(TFSI)) were investigated, for the first time, using an electrochemical double-layer capacitor-mimicking cell containing two identical-sized micro–mesoporous molybdenum carbide-derived carbon electrodes (MMP-C(Mo₂C)), by applying cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) techniques. Surprisingly, despite the substitution of the slightly acidic hydrogen atom with a methyl group at the carbon atom located between two nitrogen atoms in the imidazolium cation, the EIS and CV measurements demonstrated that PMMIm(TFSI) began to decompose electrochemically at the same cell potential (ΔE) as 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIm(BF₄)), specifically at ΔE = 2.75 V. However, the CV and EIS data indicated that PMMIm(TFSI) decomposed with a significantly lower intensity than EMIm(BF₄). Therefore, we believe that the use of PMMIm(TFSI) as the electrolyte will enable the construction of safer supercapacitors that can tolerate short periods of over-polarization up to ΔE = 4.0 V. However, when the ΔE ≤ 3.2 V was applied, EMIm(BF₄) offered higher maximum power compared to PMMIm(TFSI). We found that the calculated maximum gravimetric power precisely describes the maximum ΔE applicable for a supercapacitor candidate. Full article

Due to their diverse properties and functionalities, cost-effective transition metal-based nanomaterials have been rigorously studied for electrochemical applications. Ultrathin nanosheets have been identified as the most effective electrodes for catalyzing water-splitting reactions in both acidic and alkaline environments. Here, we reported ZnWO₄, a member of the tungstate family, as an effective electrocatalyst for promoting the electrochemical hydrogen evolution reaction. The Zn⁺²-stabilized tungstate showed a remarkable cathodic reaction during the water-splitting reaction with low overpotential (136 mV at 10 mA cm⁻²) and small HER kinetics (Tafel Slope = 75.3 mV dec⁻¹) and long-term cyclic durability. The high-valence tungsten stabilized with divalent Zn⁺² promotes electron transfer during the reaction, making it an advanced electrocatalyst for green hydrogen production. Full article

There is a high demand for nickel hydroxide as an engineering material used in the positive electrode of nickel metal hydride (Ni-MH) rechargeable batteries. These batteries are extensively used in various small instruments, disposable batteries, and electric vehicles. The structure of nickel hydroxide significantly influences the discharge capacity and energy density, key properties of Ni-MH batteries, and this structure is primarily determined by the synthesis method used. In this study, nickel hydroxide was synthesized using an electrochemical precipitation method, with current density acting as a parameter to control the desired phase of the product, whether α-nickel hydroxide, β-nickel hydroxide, or a combination of both. At a current density of 50 A/m², the synthesized nickel hydroxide demonstrated a smaller particle size and a superior discharge electrochemical property in comparison to that generated at 500 A/m². The effect of agitation in catholyte was also investigated to examine the change in discharge property of the precipitated material. The product synthesized at 500 A/m² from an agitated catholyte exhibited a tap density of 1.24 g/cc and an improved discharge capacity of 254 mAh per gram of Ni(OH)₂. Full article

This research investigates the corrosion behavior of copper (Cu) through a comprehensive analysis of both plain and nanoporous Cu thin films. A combination of weight-loss methods for quantitative analysis, along with polarization testing and scanning electron microscopy, is employed for both quantitative and qualitative assessments of Cu corrosion dynamics. The corrosion mechanisms in chloride and nitrate solutions are compared, with an additional discussion on the influence of atmospheric oxygen (O₂). The results demonstrate that chloride ions and the presence of O₂ create the most severe corrosion conditions, while the concentration of salts has a relatively minor effect on the corrosion behavior. Notably, the comparative study reveals that nanoporous Cu exhibits a greater corrosion tendency, as indicated by more negative corrosion potentials. However, its corrosion rates are lower than those of plain Cu, as determined by corrosion current density measurements. Full article