Journal of Solid State Electrochemistry最新文献

Supercapacitor (SC) electrodes with excellent capacity and multiplicity performance have been in demand for a long time. In this paper, CeO₂/Co₃O₄ nanorod arrays were firstly synthesized by hydrothermal method and thermal treatments, and then NiCo₂S₄ were successfully wrapped around CeO₂/Co₃O₄ nanorod arrays by electrodeposition. On the one hand, the CeO₂/Co₃O₄ nanorod arrays acted as a core layer to provide a scaffold for the continuous and stable conductivity of the electrochemical reaction, while on the other hand, the NiCo₂S₄ played an important role in increasing the capacity due to their high conductivity. The electrochemical properties of NiCo₂S₄@ CeO₂/Co₃O₄ electrode materials were remarkable improvement due to the synergistic and complementary effect. The area capacitance of the prepared NiCo₂S₄@ CeO₂/Co₃O₄ nanorod arrays was 1576.67 mF cm⁻² with a current density of 1 mA cm⁻². And the intrinsic and transfer resistances of the composites were 0.816 Ω and 0.064 Ω. Meanwhile, the asymmetrical supercapacitors exhibited excellent energy density (0.074 mWh cm⁻²) with the power density of 0.805 mW cm⁻². The capacitive retention rate after 5000 cycles was 93.25%. This study demonstrates that the 3D core–shell structure of NiCo₂S₄@ CeO₂/Co₃O₄ nanorod arrays has a good practical application potential in supercapacitor devices.

Supercapacitors as green energy storage devices are widely utilized in vehicle manufacturing, rail transportation, power systems, and other fields. In this study, petal-like NiO was synthesized via a one-step hydrothermal method, followed by the preparation of NiO@ZIF-67 composite electrode material at room temperature. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM) tests demonstrated that the NiO in NiO@ZIF-67 possesses a porous petal-like structure, with ZIF-67 particles uniformly growing on NiO sheets. The effect of ZIF-67 content on the electrochemical performance of NiO was investigated, and results showed that NiO@ZIF-67/1, prepared with a mass ratio of NiO to Co(NO₃)₂·6 H₂O of 1:1, exhibits the optimal electrochemical performance. The specific capacitance of NiO@ZIF-67/1 electrode material reached 188.44 F·g⁻¹ at 1 A/g. Furthermore, the symmetric supercapacitor assembled with NiO@ZIF-67 exhibited a maximum energy density of 41.76 Wh/kg at 1.4 kW/h, with a capacitance retention rate of 87.2% after 5000 cycles.

Graphical abstract

Porous anodic aluminum oxide (AAO) layers have been obtained by two-step anodization of high-purity Al in two types of acid mixtures, i.e., in H₂C₂O₄–H₃PO₄ and, for the first time, in H₂SO₄–H₃PO₄ systems. The kinetics of oxide formation was examined by monitoring the current vs. time curves while the morphology of the resulting layers was carefully verified by scanning electron microscopy (SEM). A special emphasis was put on establishing correlations between electrolyte composition, the kinetics and effectiveness of oxide growth, and the morphological features of AAO layers (pore and cell diameter, porosity), as well as pore arrangement. It was confirmed that the addition of H₃PO₄ to both H₂C₂O₄ and H₂SO₄ electrolytes results in a significant decrease in oxide growth rate, and worsening of pore arrangement, while the values of pore diameter and interpore distance are much less affected. Moreover, the presence of a small amount of phosphoric acid in the reaction mixture allowed for a noticeable increase in pore ordering if anodization was carried out beyond the self-ordering regime, or performing controlled anodization even at voltages at which the burning phenomenon is typically observed. It is strongly believed that manipulating the electrolyte composition by adding another acid may provide another degree of freedom to control the morphology of the resulting nanostructured alumina layers.

Graphite electrode (GE) is an alternative, commercially available, and ready-to-use electrode for a wide range of electroanalytical applications. Electrochemical activation of GE is an efficient step in the preparation of high-performance electrochemical (bio-)sensors. In the present study and the continuation of our research project in the lab about the effect of activation of GE surface on the alteration of electrode structure (formation of different functional groups) and subsequent influence on the sensitive determination of various analytes, a simple and low-cost electrochemical sensor based on the graphite electrode extracted from the battery is developed to measure pyrazinamide (PZA), an antibiotic that is mostly used in treating tuberculosis. Two activation strategies including potentiostatic and potentiodynamic were tested and according to the results, utilizing the potentiodynamic strategy represents good performance in the sensitive detection of PZA. Morphological characterization of activated GE was done using scanning electron microscopy (SEM). A comparison of the effective surface area of the activated and bare GE revealed that the activation process increased the effective surface area of the electrode by 1.6 times. The electroanalytical response of PZA at the activated GE surface was studied utilizing cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques. The impact of various parameters on the reduction current response of PZA was investigated and it was found that the developed electrochemical sensor can successfully determine PZA within the concentration ranges of 1.31–29.81 µM under the optimized conditions and the limit of detection (LOD) was calculated to be 0.89 µM as well. Analysis of real samples such as pharmaceutical formulations and human serum demonstrated excellent recoveries, revealing the promising capability of the proposed sensor for PZA determination.

Significant advancements have been made in the development of lithium-oxygen batteries, achieving impressive results. However, their practical application is hindered by issues such as short cycle life, rapid capacity decay, and low energy conversion efficiency. Selecting suitable electrolytes and cathode catalysts can effectively address these challenges and enhance battery performance. This study investigates the use of Fe₂O₃ and FeS₂ as cathode catalysts for lithium-oxygen batteries. The structural characteristics and surface morphologies of the Fe₂O₃ and FeS₂ samples were analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The electrochemical performances of these catalysts were compared, showing that FeS₂ has a higher charge/discharge specific capacity (5740 mAh g⁻¹ at a current density of 100 mA g⁻¹) compared to Fe₂O₃ (2676 Ah g⁻¹ at the same current density). Furthermore, FeS₂ exhibited better cycling stability, maintaining 97 cycles at 100 mA g⁻¹ current density with a 500 mAh g⁻¹ specific capacity limit and demonstrating lower electrochemical impedance. Electrocatalytic oxygen reduction tests also revealed that FeS₂ exhibits higher oxygen reduction reaction (ORR) catalytic activity than Fe₂O₃. These results indicate that FeS₂ outperforms Fe₂O₃ as a cathode catalyst in lithium-oxygen batteries.

The performance of electrically rechargeable zinc-air batteries (ErZAB) depends on the efficiency of bifunctional electrocatalysts. Herein, four different forms of the nickel oxide/nitrogen-doped reduced graphene oxide (NiO/rGO), with various amounts of the Acacia Ataxacantha leaves extract, were synthesized by a hydrothermal method. The effect of the extract loading on the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is reported. The energy dispersive X-ray spectra confirm that the plant extract can act as a dopant for nitrogen and reductant for the graphene oxide, whereas the field emission scanning electron microscopic (FE-SEM) images demonstrate that the NiO nanoparticles were uniformly dispersed onto the surface of the rGO thereby providing greater number of active sites for electrocatalytic activity. The electrochemical characterization reveals that the doping of the N improves the bifunctional electrocatalytic activity of NiO-rGO nanocomposite. Furthermore, the ORR and OER onset potential were found to decrease and increase with an increase in the loading level of the plant extract respectively. It was found that 7.5 mL of the plant extract is the optimum loading level to achieve the highest ORR and OER electrocatalytic activities. Furthermore, battery testing indicated that the bifunctional electrocatalyst showed outstanding charge-discharge cycle performances, with its voltage polarization exhibiting a 0.25% decrease in discharge and a 1.4% increase in charge after 50 charge-discharge cycles.

This study involves the preparation of graphitic carbon nitride (G), carbon quantum dots (C), and yttrium oxide (Y) to synthesize GCY nanocomposites. The synthesis process includes two steps: ultrasonication and hydrothermal treatment. The resulting nanocomposites are then evaluated for their super-capacitive performance using a GCY working electrode. The nanocomposites are analyzed using FTIR, FESEM, and HRTEM to confirm their proper synthesis and are then used as electrode materials for electrochemical energy storage. 0.6 GCY, a composite material, has demonstrated a significant specific capacitance of 378.47 F/g, along with an energy density of 18.17 Wh/kg at a power density of 681.4 W/kg. This makes it a highly promising composite electrode for electrical energy-consuming devices, serving as a reliable energy backup. In addition, the 0.6 GCY had an impressive retention rate of 91.54% after undergoing 5000 cycles. Thus, the GCY electrode, which is easily synthesized, exhibits excellent potential for energy storage in supercapacitor applications. This is attributed to its favorable production process, impressive CV and GCD values, and remarkable capacitive retention.

Hexagonal sodium tungsten bronze (h-Na_xWO_3+x/2·yH₂O) nanorods were obtained by simple acid precipitation in 16 min at 97 °C, evidencing the saving of time and energy. The W-OH₂ modes were observed in Raman and Fourier transform infrared (FTIR) spectra to confirm the presence of structural water. The h-Na_xWO_3+x/2·yH₂O was subjected to heat treatment at 300 °C to analyze the effects of heating on the material. X-ray photoelectron spectroscopy (XPS) and diffuse reflectance ultraviolet-visible absorption spectra (UV-vis) indicated the occurrence of diffusion on the surface-bulk of Na⁺ ions, and the band gap changed from 2.7 eV to 2.4 eV with heating. Electrochromic devices based on h-Na_xWO_3+x/2·yH₂O were constructed. The sample without heat treatment and with structural water loss presented the electrochromic efficiency of 127.5 cm²/C and 561.8 cm²/C, respectively, evidencing the creation of vacancies for the intercalation of lithium ions from heat treatment. Also, density functional theory calculations were performed to study the lithium diffusion process in the interstitial Na-WO₆ channels of sodium tungsten bronze.

Graphical abstract

Superparamagnetic manganese ferrite nanoparticles stabilized with β-cyclodextrin (βCD-MFO) were prepared by co-precipitation at room temperature and hydrothermal methods using temperatures of 120 and 140 °C. Similar samples, without βCD, were prepared for comparison (MFO). Samples called βCD-MFO140 and MFO140, heated at 140 °C during the synthesis, showed the best characteristics. The βCD-MFO140 is formed by nanoparticles of 5 nm and it presents the highest surface area, the highest porosity, and a hydrophilic surface. Alternatively, the MFO140 presented a crystallite size near 25 nm and a hydrophobic surface. Both nanocomposites were applied to modify carbon paste electrodes and evaluated using differential pulse voltammetry for the determination of dopamine. They showed promising responses such as sensitivities of 0.09 and 0.23 µA µmol⁻¹ L and low detection limit of 2.28 and 0.39 µmol L⁻¹ for MFO140 and βCD-MFO140, respectively, in a linear range between 11.97 and 39.68 µmol L⁻¹ for MFO140 and between 3.99 and 15.95 µmol L⁻¹ for βCD-MFO140. Both sensors demonstrated good reproducibility with a relative standard deviation of 12.7%. The CPE βCD-MFO140 exhibits better selectivity for dopamine. According to these results, the βCD-MFO140 electrode demonstrated better electrochemical performance with potential for application in real samples, which can be ascribed to its higher surface area and porosity, as well as its hydroxylated surface that makes this electrode more hydrophilic.

Graphical abstract

The bipolar plate is an important part of the proton exchange membrane fuel cell, which has high requirements for mechanical properties and strength. Composite bipolar plates have the advantages of easy processing and corrosion resistance, but there are problems such as difficulty in balancing between mechanical properties and electrical conductivity. In this study, surface-coating modification of chopped carbon fibers was carried out by catalytic chemical vapor deposition, and multi-walled carbon nanotube-coated carbon fiber composites with better interfacial contact properties and improved specific surface area were prepared and added to polyvinylidene fluoride/expanded graphite to synthesize composite bipolar plates. Due to the selective distribution of carbon nanotubes and the synergistic construction of conductive pathways with carbon fibers, the performance of the composite bipolar plate was improved, with a conductivity of 116.01 S/cm, a flexural strength of 50.37 MPa, and both good hydrophobicity and corrosion resistance and a corrosion current density of 0.804 µA cm⁻². The results show that the prepared composite bipolar plates meet the requirements in fuel cell use, and the use of carbon nanotubes coated with carbon fibers to synergistically construct conductive networks has also proven to be a potential performance enhancer for composite bipolar plates.