Journal of Electroanalytical Chemistry最新文献

In this paper, an amperometric biosensor model with substrate and product inhibition kinetics is analysed. This model is a steady-state system of reaction-diffusion equations with non-linear terms related to non-Michaelis-Menten kinetics of an enzymatic reaction. We present the approximate analytical expression of the substrate and product concentrations using well-founded methods, namely the Taylors series method (TSM) and the Adomian decomposition method (ADM). These methods proved that they fit for all values of parameters in this model. The steady-state biosensor current, biosensor substrate sensitivity and resistance are also discussed. We also present the numerical solution of the described model using MATLAB programming, and it is noted that there is satisfactory agreement in comparing the analytical solution with numerical results for all possible values of parameters. The effects of the parameters, such as inhibition constants, diffusion parameters, bulk concentration and Michaelis-Menten constant on the sensitivity and the resistance of the biosensor are analysed.

Atomic hydrogen could participate in multiple electrochemical reactions during egress from Palladium (Pd) into aqueous environments. Possible reactions include hydrogen recombination to form H₂, the oxygen reduction reaction (ORR) and “hydrogen ionisation” to form H⁺. Here, bulk measurements and microelectrode-based methods were used to mechanistically investigate such reactions occurring during hydrogen egress from Pd. Significant ORR was detected on hydrogen-charged Pd (Pd-H) surfaces, when using a Platinum (Pt) microelectrode (ME) in the redox competition mode. However, minor hydrogen recombination was also detected while using the Pt ME in the sample generation-tip collection (SG-TC) mode. Hydrogen ionisation is observed to occur when Pd (H) is anodically polarised. These reactions can all be linked to the highly negative equilibrium potential of the atomic H/H⁺ redox couple. Atomic hydrogen being a strong reducing agent thus tends to efficiently reduce various oxidants in solution resulting in different products, under varying conditions.

The effect of magnetohydrodynamic (MHD) convection on the behavior of oxygen bubbles generated by alkaline water electrolysis is investigated in this paper. In order to avoid mutual obstruction of bubbles and get clear images, a special electrolytic cell with a wire anode is designed to conduct the experiments. The current densities in our experiments are between 0.15 and 0.35 A/cm², which are relatively low but common values in ordinary industrial electrolyzers. The results show that external magnetic field can reduce the cell voltage slightly and change the distribution of bubble detachment size. The induced MHD convection is found to be able to accelerate the diffusion of gas components in to the bulk electrolyte, resulting in a low comprehensive current efficiency, and further leading to longer growth cycle and larger separation diameter of oxygen bubbles. In addition, different from the “coalesce-and-bounce” detachment pattern, bubbles generated in magnetic field will undergo a sliding motion on the electrode surface during their growth process, which shows a lower coalescence frequency and a smoother detachment. Our work suggests that the driving effect of magnetic field on oxygen bubbles may be positive only at high current densities.

In the wake of environmental enigmas including global warming and the exhaustion of traditional hydrocarbon sediments, the usage of eco-friendly power generation is of paramount importance today. Alternatives to traditional fossil fuels such as hydrogen are clean, safe, and environmentally friendly. Moreover, hydrogen as a renewable energy source, as the only by product of burning hydrogen is water. Many electrochemical energy conversion methods rely on the oxygen evolution reaction (OER), but creating effectual, economical electrocatalysts for it has proven difficult. The multifunctional electrocatalyst, nickel selenide-anchored cobalt telluride, has been found to be effective in catalyzing oxygen evolution processes in alkaline medium. CoTe and NiSe, generated hydrothermally, exhibit promising electrocatalytic activity. However, their composite NiSe@CoTe, possesses higher OER durability. The presence of NiSe in the CoTe matrix responses a powerful OER responses due to the synergistic effect in alkaline environment. The NiSe@CoTe nanocomposite shows minimal Tafel value (39 mV/dec) and lower overpotential (247 mV) to attain a current density of 10 mA/cm², whereas the pristine CoTe and NiSe needed higher overpotential to attain same current density. Following 16 h of utilizing the same catalyst, OER stability was maintained with 88 % current density retention.

In this paper, a wire beam electrode (WBE) was used to explore the local corrosion processes of X100 pipeline steel in simulated solution containing HCO₃⁻ in static and flow conditions. The results indicated that the WBE's current density mapper was remarkably consistent with the polarization curves. Therefore, WBE is an efficient online corrosion monitoring approach. The WBE discovered undetectable pitting and passivation qualities within the X100 pipeline steel under static conditions. However, the corrosion current density of X100 steel was substantially higher under flow conditions than under static ones. The addition of HCO₃⁻ ions significantly decreased the corrosion resistance of the X100 steel. In the 0.3 mol/L HCO₃⁻ simulated solution, dynamic corrosion was 92 times faster than static. The corrosion of X100 steel was enhanced by the combined effects of fluid movement and HCO₃⁻ ions. Additionally, X100 steel produced significant irregular edge pitting when the critical level of HCO₃⁻ was 0.2 mol/L under dynamic conditions, and an erosion theory was proposed to explain this phenomenon.

Two different zinc phthalocyanines bearing different numbers of 2-naphthoic acid anchoring groups at the peripheral positions were synthesized and characterized with UV–Vis, proton nuclear magnetic resonance (¹H NMR), fouirer transform infrared (FT-IR), and matrix-assisted laser desorption/ionization mass (MALDI-TOF MS) spectroscopy. Then their electrochemical, and spectroelectrochemical performances were investigated to predict their suitability of them as photosensitizers in dye-sensitized solar cells (DSSC). In the voltammetric analysis results, [2,9,16-Tri-(4-carboxyethylphenoxy)-23-(4-[6-carboxy-2-naphtoxy]) substituted zinc(II) phthalocyanine (ZnPc(3)) and [2,9,16,23-tetra-(4-(6-carboxy-2-naphthoxy) substituted zinc(II) phthalocyanine (ZnPc(4)) illustrate similar electron transfer processes. The substituent environments of the complexes slightly influenced the position and reversibility of the redox couples. Redox processes of ZnPc(3) bearing unsymmetrical carboxyethylphenoxy and 2-naphthoic acid anchoring groups slightly shift towards the positive potentials concerning ZnPc(4) bearing symmetrical 2-naphthoic acid substituents. Peak positions of both complexes reflecting the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) positions indicate the suitability of the complexes for the efficient charge carrier transferring from these photosensitizers to the semiconductor and redox mediator in the DSSC. Pc-based spectroelectrochemical responses of the complexes supported the HOMO and LUMO positions for both neutral and electrogenerated ZnPc species. DSSC responses indicated that ZnPc(3), which has the asymmetric carboxyethylphenoxy and 2-naphthoic acid substituents, gave higher DSSC efficiency with short-circuit photocurrent density (J_SC) (9.54 mA cm⁻²), open circuit potential (V_OC) (697 mV), fill factor (FF) (51%), incident monochromatic photon-to-current conversion efficiency (IPCE) (51%), and power conversion efficiency (ƞ) (3.4%) parameters concerning ZnPc(4) bearing symmetric 2-naphthoic acid anchoring groups.

To control the operating conditions of battery energy storage systems (BESS), the cells are combined into assemblies and modules located mostly in a closed space limited by the battery case. There are air gaps between the cells of the battery assembly. Energy dissipation in cells leads to an intense heat removal in the closed region of the air gap. As a result, the temperature of the battery assembly increases with possible further uncontrolled thermal runaway and subsequent battery ignition. Despite the increasing number of fires and explosions of battery ESSs every year, there is still no theory providing the ability to predict the conditions of fire and explosion safety of energy-intensive energy storage systems based on storage batteries. Particularly, there are no reliable data on the temperature fields of the cells of battery assemblies during intensive charge/discharge processes.

The aim of the work was to analyze the thermal conditions of operation of a storage battery consisting of two typical prismatic cells, taking into account heat transfer in the air gap between the cells. Electrothermal modeling was performed for a fairly typical battery by solving a non-stationary heat conduction equation in a two-dimensional formulation by the finite difference method. The most realistic ranges of variation in the values of influencing factors were considered. In addition, the paper presents assessment of the thermal conditions of operation of a single cell and a comparative analysis of the obtained representative temperatures with the representative temperatures of a battery assembly of two battery cells. It has been established that the temperature of the case of cells of the battery assembly is 3–7 °C (depending on current loads) higher than the temperature of the case of a single cell at equal conditions. The obtained results show the need to take into account the heat transfer between the cells of the battery assembly when analyzing the temperatures of such assemblies.

In this study, a simplified mathematical model was proposed for predicting the performance of an anion exchange membrane-based direct urea/O₂ fuel cell (AEM-DUFC-O) with a serpentine flow channel. Because the effects of under-rib mass transfer and gaseous bubble formation were considered, this model exhibited good agreement with both lab-experimental and literature data, with high R² values of 0.941–0.995 and NRMSE of 0.078–0.019, suggesting that it can reasonably be applied for further analysis and optimization of AEM-DUFC-O. The simulation results indicated that the under-rib mass transfer has a beneficial effect on the fuel cell efficiency, while the formation of gaseous bubbles is detrimental. In addition, the flow-field structure (i.e., rib width and channel dimensions) and operational parameters (i.e., urea and KOH concentrations, temperature, and feeding flow rate) also exhibited crucial impacts and need to be further optimized to maximize the power density output and energy recovery efficiency of AEM-DUFC-O.

The development of cost-effective non-precious metal bifunctional catalysts has become a promising path to meet the commercialization needs of rechargeable zinc-air batteries. Herein, an effective bifunctional catalyst, hierarchical sheet-interconnected fan-shaped N/S-containing Co-based metal organic frameworks (HSFS-N/S-Co-MOFs), has been constructed using 1,2-bis(4-pyridyl)ethane and thiophene-2,5-dicarboxylic acid as dual ligands through a solvothermal approach. Additionally, several cations and anions may affect the microstructures, surface compositions, surface areas, oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) activities of the constructed N/S-MOFs. As a result, the hierarchical sheet-interconnected fan-shaped structure and N/S dual introduction make HSFS-N/S-Co-MOFs exhibit favorable ORR and OER performance in alkaline medium. The current research provides an option to rationally construct other MOFs-based electrocatalysts.