Ionics最新文献

A new strategy has been made to investigate low-cost porous carbon electrode material by using bio-waste raw date seeds activated with potassium hydroxide (KOH) to synthesize porous carbon cobalt oxide composite (PCCo) using facile one-step carbonization and to achieve high specific capacitance. The characterization of PCCo composite was done by powder X-ray diffraction, Fourier transform infrared spectrometer, field emission scanning electron microscopy, high-resolution transmission microscopy, Brunauer–Emmett–Teller (BET), and Raman spectroscopy techniques to confirm the chemical changes, morphology, and structural phase. It is observed that there is a high specific surface area (397 m² g⁻¹) and an abundant mesopores for PCCo composite. This hierarchical morphology structure offers good ion/electron transport channels for better electrochemical characteristics. The maximum specific capacitance was found to be 496 F/g at a scan rate of 10 mV/s, and also from the galvanostatic charge–discharge curve, it was 671 F/g at a current density of 1.5 A/g. The fabricated SSC PCCo-0.4//PCCo-0.4 device provides an energy density of 47.4 Wh kg⁻¹ and a power density of 853.2 W kg⁻¹ with a capacitance retention of 84.4% and a coulombic efficiency of 97% even after 5000 cycles. These results suggest that porous carbon composites are cost-effective, technologically unique, and eco-friendly for environmental supercapacitor applications.

Graphical abstract

Scheme: Schematic depicted of the synthesis of PCCo-0.4 composites by one-step carbonization and activation process from date seed and cobalt oxide (Co₃O₄).

Nowadays, the advancement of eco-friendly, clean, sustainable and renewable new energy has emerged as a research priority for scientists worldwide. Electrolytic water technology is founded on the principle of electrochemical or photoelectric decomposition of water, is deemed as one of the most promising and most feasible approaches to reach industrial production. Traditional OER (oxygen evolution reaction) electrocatalysts like IrO₂ and RuO₂ are beset by high costs and vulnerability to poisoning. Hence, it is essential to develop more economical, more stable and more efficient materials for the application of OER reactions. In this study, a series of AQ-doped (AQ = anthraquinone) MOF-74 materials were fabricated through a one-step solvothermal approach. The surface loading of the conjugated organic small molecule AQ on CoNi-MOF-74 is capable of effectively boosting the inadequate electrical conductivity of the bulk MOF material, thus significantly enhancing the performance of OER. The optimized ratio of material composition of AQ20@MOF-74 displayed significantly enhanced OER activity. with a lower overpotential of 272 mV at 10 mA cm⁻² and a smaller Tafel slope of 78 mV dec⁻¹. The research findings presented in this thesis provide a novel approach for the design and optimization of highly efficient OER electrocatalysts based on MOFs.

This work is concerned with the improvement of dye-sensitized solar cell efficiency by incorporating aurum into palladium which serves as a counter electrode (CE) for the device. The CE has been prepared via the liquid phase deposition (LPD) technique. The effect of the concentration of aurum (III) chloride trihydrate (HAuCl₄.3H₂O) on the properties and the performance of the device has been studied. The sources of palladium and aurum are potassium hexachloropalladate (K₂PdCl₆) and HAuCl₄.3H₂O, respectively. A dominant phase of Au–Pd exists in the sample. The morphological shape of AuPd is a truncated nanohexagon plate. The particle size of AuPd increases with the concentration of HAuCl₄.3H₂O, but its crystallite size decreases until an optimum concentration of 0.5 mM. The device employing AuPd CE with 0.5 mM HAuCl₄.3H₂O yielded the highest efficiency of 6.69%. This is because this device possesses the highest coverage area, highest particle density, biggest particle size, smallest crystallite size, highest IPCE, lowest R_s and R_ct, longest τ, highest J_pc, J_o, and J_lim. In conclusion, AuPd is found as a suitable CE candidate in efficient DSSC.

Using a mixed solution of (NH₄)₂TiF₆ and H₃BO₃, this study performed liquid phase deposition (LPD) to deposit TiO₂ on graphite felt (GF) for application in the negative electrode of a vanadium redox flow battery (VRFB). The results revealed that LPD-TiO₂ uniformly coated GF, effectively transforming the original hydrophobic nature of GF into a superhydrophilic nature. After annealing at 500 ℃ in an atmospheric environment, the oxygen vacancies in the TiO₂ thin film were optimized, considerably enhancing its mass transfer efficiency and electrochemical activity. The VRFB comprising the LPD-TiO₂/GF negative electrode achieved a coulombic efficiency, voltage efficiency, and energy efficiency of 96.2%, 71.8%, and 69.3%, respectively, at 125 mA/cm², which were significantly superior to the corresponding efficiencies of 95.7%, 60.3%, and 57.7%, respectively, achieved by the VRFB with the acid cleaned GF. These findings demonstrate that the proposed technology has great potential for application in VRFBs.

The bismuth terephthalate metal–organic framework (Bi(TPA).MOF) was synthesized as a methanolysis catalyst using a solvothermal method, by reacting terephthalic acid (TPA) with bismuth nitrate pentahydrate (Bi(NO₃)₃·5H₂O) in dimethylformamide (DMF) at 383.15 K. The structure, morphology, and composition of the resulting MOF were characterized using advanced surface analytical techniques, including X-ray diffraction (XRD), Fourier-transform infrared (FTIR) spectroscopy, Raman spectroscopy, and scanning electron microscopy coupled with energy-dispersive X-ray (SEM–EDX), which confirmed successful formation of the Bi(TPA).MOF structure. The catalytic performance of Bi(TPA).MOF was then assessed in the sodium borohydride (NaBH₄) methanolysis reaction, demonstrating remarkable activity. The optimization of key reaction parameters, such as catalyst loading, NaBH₄ concentration, methanol volume, and reaction temperature, was conducted. Notably, Bi(TPA).MOF exhibited an outstanding hydrogen generation rate (HGR) of 321,996 mL/min·g_catalyst, with an activation energy of 39.9 kJ/mol, calculated via the Arrhenius equation. These results significantly surpass those previously reported in the literature, positioning Bi(TPA).MOF as a promising and efficient catalyst for enhancing hydrogen production through NaBH₄ methanolysis.

In this work, a high-performance binder-free electrode for supercapacitor applications is fabricated using self-doped TiO₂ nanotube arrays (TNAs) adorned with copper cobaltite (CuCo₂O₄). A two-step electrochemical anodization technique was used to produce highly ordered TNAs with a large surface area and electrochemical properties. To improve electrical conductivity, oxygen vacancies, and Ti³⁺ states were added to the pristine TNAs during the self-doping process. Instead of requiring polymer binders, these nanotube arrays act as a strong scaffold. Following that, an easy electrochemical deposition procedure was used to uniformly deposit CuCo₂O₄ nanoparticles onto the self-doped TNAs. Due to its large surface area, superior electron transport capabilities, and numerous redox-active sites, the resulting self-doped TNA/CuCo₂O₄ composite greatly improves electrochemical performance. A significant capacitive behavior was observed when the electrodes were examined in Na₂SO₄ electrolyte. Measurements using cyclic voltammetry (CV) and galvanostatic charge–discharge (GCD) revealed a long cycle stability, good rate capability, and high areal capacitance. The self-doped TNA electrode achieves the greatest areal capacitance of 29.19 mF/cm² at a current density of 0.1 mA/cm², along with good rate capability and long-term cycle stability, with capacitance retention of 97.36% after 5000 cycles. A remarkable areal capacitance of 669.59mF/cm² was achieved for the self-doped TNAs/CuCo₂O₄ electrode at a scan rate of 5 mV/s. The synergistic impact of self-doped TiO₂ and CuCo₂O₄ in increasing electron transfer and ion diffusion was further confirmed by electrochemical impedance spectroscopy (EIS), which also indicated a low charge-transfer resistance (R_ct) of 4.641 Ω. Combining the benefits of pseudocapacitive characteristics of CuCo₂O₄ with the improved conductivity of self-doped TNA, the self-doped TNA/CuCo₂O₄ composite electrode presents a potential option for energy storage devices. This binder-free, self-doped TNA electrode decorated with CuCo₂O₄ shows great promise for application in the next generation of supercapacitors, providing enhanced cycling durability, power density, and energy density.

Cadmium and zinc oxide compounds of chemical formula Zn_xCd_1-xO, where x = 0–1 with various weight ratios, were synthesized by hydrothermal technique. These compounds are used as novel anode materials in lithium batteries. The crystal structure was investigated by X-ray diffraction (XRD). The crystal structure of ZnO is hexagonal like wurtzite, while the crystal structure of CdO is cubic. The morphology of samples was investigated by field emission scanning electron microscope (FESEM). The morphology of pure CdO is like bacillary, whereas ZnO has spheroid morphology. The Zn_0.4Cd_0.6O sample reveals a coral reef-like structure. X-ray photoelectron spectroscopy (XPS) explained binding energy, chemical composition, and elemental states of ZnO, CdO, and the mixed oxides. The prepared compounds were applied as anode active materials in the collected CR2032 coin cell versus the Li metal. The cyclic voltammetry (CV) studies revealed three cathodic peaks at 1.10, 0.5, and 0.15 V vs. Li⁺, respectively, with ZnO, Zn_0.8Cd_0.2O, and Zn_0.4Cd_0.6O cells. These peaks are for solid electrolyte interface (SEI) formation and lithiation (discharging) processes. On the other hand, there are three main apparent anodic peaks at 0.01, 0.20, and 1.10 V, respectively for delithiation (charging) reactions. Galvanostatic measurements were carried out. Zn_0.4Cd_0.6O cell exhibited the maximum specific capacity of 1213 mAhg⁻¹ for the first discharge process and delivered a capacity of 800 mAhg⁻¹ for cycle life up to 100 cycles. Also, the electrochemical impedance spectroscopy (EIS) measurements demonstrated a reasonable value of charge transfer resistance (R_ct ~ 80.2 Ω) for the Zn_0.4Cd_0.6O cell, which is close to that of pure ZnO (68 Ω). Therefore, Zn_xCd_1-xO materials are good candidates for use as anode electrodes in lithium batteries.

A series of hexagonal perovskite derivative compounds Ba₃W_1+xV_1−xO_8.5+x/2 (x =  − 0.2, − 0.1, 0, 0.1, 0.2) with varying oxygen content was synthesized by high-temperature solid-state reaction route and characterized using X-ray diffraction, SEM–EDX, Raman spectroscopy, XPS, and dielectric spectroscopy. All samples were isostructural, having features of both palmierite and 9R hexagonal perovskite. The unit cell volume showed a continuously decreasing trend with increasing oxygen content. The XPS studies showed no deviation of oxidation states of W⁶⁺ and V⁵⁺ and hence confirmed that the oxygen stoichiometry is solely controlled by the W to V ratio in the samples. The presence of both octahedral MO₆ and tetrahedral MO₄ units in all samples was inferred from temperature-dependent Raman spectroscopic studies. The translational and rotational motion of MO₄ tetrahedra are appreciably affected by temperature. The dc conductivity was obtained directly from the complex ac conductivity derived from temperature-dependent dielectric measurements. It was found that the dc conductivity increases when the composition deviates from x = 0.0, i.e., W:V = 1:1. An estimate of the ion mobility and mobile ion concentration was obtained using the Almond-West formalism. The conductivity was found to be significantly higher in W-rich compounds (x > 0), and the ion mobility was also correspondingly higher. It could be inferred that the compositional dependence of unit cell parameters, particularly a- or b-axis, and the oxygen stoichiometry, play crucial roles in governing the ionic conductivity of these hexagonal perovskite derivatives.

In this present communication, we have synthesized the Bi₂S₃-xC dots (x = 0, 0.03, 0.06, 0.13, 0.27, 0.67 and 1.0) nanocomposite samples by using low temperature hydrothermal method. The XRD measurements confirmed the phase purity and nanocomposite nature of the synthesized samples. FESEM and TEM measurements confirmed that, Bi₂S₃ samples have rod shape of morphology and their sizes (diameter) are between 15-30 nm in pristine Bi₂S₃ and Bi₂S₃-xC dots samples allografted with amorphous C dots. The photocatalytic properties of the Bi₂S₃-xC dots nanocomposite samples against the ciprofloxacin (CIP) antibiotic were studied in detail. The maximum photocatalytic activity was shown by x = 0.67 sample (maximum 88% CIP degradation, in 80 min) due to effective electrons transfer and reduction of charge recombination rate in the p–n junction, formed between the nanocomposite.