Search Results (9)

Metal anodes, such as those based on Ca, Mg, Na and Li, are considered to be one of the keys to the further development of high-energy-density rechargeable batteries. The thickness of these metal anodes directly affects the energy density of the battery. However, the fabrication of thin anodes poses technical challenges which often result in using excessively thick metal anodes in batteries. Here we present, for the first time, a study on the development of a thin Ca battery anode fabricated by electrodeposition. The battery anode with a thickness of approximately 10 µm corresponds to a charge density of 4.0 mAh cm⁻². This study systematically investigates the electrodeposition behavior of Ca using a 1.0 M Ca(BH₄)₂ in THF as the electrolyte. A systematic evaluation of electrodeposition parameters—including substrate pretreatment, current density, hydrodynamics and charge density by area—is conducted. Scanning electron microscopy (SEM) and complementary image analysis provide detailed insights into these parameters. Electrodeposition offers a promising route to achieve a defined battery cell balance with minimal excess of metal at the anode. This will improve overall battery performance and efficiency. The findings contribute to the advancement of fundamental aspects of rechargeable batteries, particularly Ca-based batteries. Full article

CoFe-based catalysts have shown excellent activity for the oxygen evolution reaction (OER), with the oxidation states of the active sites playing a crucial role in determining catalytic performance. However, how to effectively increase the oxidation state of these active sites remains a key challenge. In this work, a facile treatment with NaBH₄ solution was employed to modulate the surface state of CoFeO_xH_y catalysts, inducing an enhanced OER activity. The overpotential at 10 mA cm⁻² for the NaBH₄-treated CoFe catalyst was reduced to 270 mV, indicating improved OER activity. X-ray diffraction (XRD), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS) results reveal that NaBH₄ treatment induced a phase reconstruction of the CoFe oxalate framework, a critical step in enhancing its catalytic properties. The strong reducing ability of NaBH₄ strengthened the Co-Fe interaction, allowing the retention of low-valence Co species while facilitating the formation of high-valence Fe sites. This dual modulation of Co and Fe oxidation states significantly accelerated charge transfer kinetics, ultimately boosting OER performance. These findings highlight the importance of improving the oxidation states of active sites in CoFe-based catalysts, providing insights for developing efficient catalysts for electrochemical water splitting. Full article

The compound p-Nitrophenol (p-NP) is widely recognized as a highly toxic nitro-aromatic substance that urgently requires emission control. Reducing p-NP to p-aminophenol (p-AP) not only decreases its toxicity and mineralization properties in nature but also provides a key raw material for the chemical and pharmaceutical industries. The study used coal fly ash (CFA) as a catalyst carrier for synthesizing the p-NP reduction catalyst. Using CFA as an alternative option not only reduces costs but also achieves the objective of treating waste with waste compared to utilizing commercial solid materials for synthesizing catalysts. By employing hydrochloric acid and sodium hydroxide pretreatment methods, the physicochemical properties of CFA are significantly improved, enhancing the dispersion of palladium (Pd) nanoparticles. The structural features of the prepared samples were characterized using various surface analysis techniques, and both intermittent and continuous modes were experimentally tested for the model catalytic reaction involving the sodium borohydride (NaBH₄)-mediated reduction of p-NP. The results demonstrate that CFA has potential in wastewater treatment. Full article

The interaction between metal particles and the oxide support, the so-called metal–support interaction, plays a critical role in the performance of heterogenous catalysts. Probing the dynamic evolution of these interactions under reactive gas atmospheres is crucial to comprehending the structure–performance relationship and eventually designing new catalysts with enhanced properties. Cobalt supported on TiO₂ (Co/TiO₂) is an industrially relevant catalyst applied in Fischer−Tropsch synthesis. Although it is widely acknowledged that Co/TiO₂ is restructured during the reaction process, little is known about the impact of the specific gas phase environment at the material’s surface. The combination of soft and hard X-ray photoemission spectroscopies are used to investigate in situ Co particles supported on pure and NaBH₄-modified TiO₂ under H₂, O₂, and CO₂:H₂ gas atmospheres. The combination of soft and hard X-ray photoemission methods, which allows for simultaneous probing of the chemical composition of surface and subsurface layers, is one of the study’s unique features. It is shown that under H₂, cobalt particles are encapsulated below a stoichiometric TiO₂ layer. This arrangement is preserved under CO₂ hydrogenation conditions (i.e., CO₂:H₂), but changes rapidly upon exposure to O₂. The pretreatment of the TiO₂ support with NaBH₄ affects the surface mobility and prevents TiO₂ spillover onto Co particles. Full article

An analytical method with no need for laborious sample preparation before determining the total Sn in canned tomatoes by hydride generation (HG) coupled to inductively coupled plasma optical emission spectrometry (ICP OES) was developed. The ultrasound-assisted extraction with various reagents (acidic media: HCl, HNO₃, CH₃COOH or aqua regia and alkaline: TMAH) that could replace the traditional wet sample digestion in the presence of a concentrated HNO₃-H₂O₂ mixture was tested and compared. Tin hydride was generated directly from the prepared sample solution in the reaction with 1% NaBH₄ or via prior acidification with a 1 mol L⁻¹ HCl. The effect of the sample pretreatment before HG-ICP OES measurements on the Sn signal was also examined. The best results were obtained with aqua regia as the extraction medium, followed by a simple two-fold dilution of the sample extract combined with the addition of L-cysteine. The developed method was characterized by a detection limit of Sn at 0.74 ng g⁻¹, a precision of better than 6%, and a trueness, verified by the analyte spike-and-recovery test, of 98.4–104%. Its usefulness was demonstrated by the determination of Sn in seven canned tomatoes. Full article

This article aimed to compare the degradation efficiencies of different reactants applicable for the oxidative or reductive degradation of a chlorinated anionic azo dye, Mordant Blue 9 (MB9). In this article, the broadly applied Fenton oxidation process was optimized for the oxidative treatment of MB9, and the obtained results were compared with other innovative chemical reduction methods. In the reductive degradation of MB9, we compared the efficiencies of different reductive agents such as Fe⁰ (ZVI), Al⁰, the Raney Al-Ni alloy, NaBH₄, NaBH₄/Na₂S₂O₅, and other combinations of these reductants. The reductive methods aimed to reduce the azo bond together with the bound chlorine in the structure of MB9. The dechlorination of MB9 produces non-chlorinated aminophenols, which are more easily biodegradable in wastewater treatment plants (WWTPs) compared to their corresponding chlorinated aromatic compounds. The efficiencies of both the oxidative and reductive degradation processes were monitored by visible spectroscopy and determined based on the chemical oxygen demand (COD). The hydrodechlorination of MB9 to non-chlorinated products was expressed using the measurement of adsorbable organically bound halogens (AOXs) and controlled by LC–MS analyses. Optimally, 28 mol of H₂SO₄, 120 mol of H₂O₂, and 4 mol of FeSO₄ should be applied per one mol of dissolved MB9 dye for a practically complete oxidative degradation after 20 h of action. On the other hand, the application of the Al-Ni alloy/NaOH (100 mol of Al in the Al-Ni alloy + 100 mol of NaOH per one mol of MB9) proceeded smoothly and seven-times faster than the Fenton reaction, consumed similar quantities of reagents, and produced dechlorinated aminophenols. The cost of the Al-Ni alloy/NaOH-based method could be decreased significantly by applying a pretreatment with Al⁰/NaOH and a subsequent hydrodechlorination using smaller Al-Ni alloy doses. The homogeneous reduction accompanied by HDC using in situ produced Na₂S₂O₄ (by the action of NaBH₄/Na₂S₂O₅) was an effective, rapid, and simple treatment method. This reductive system consumed quantities of reagents that are almost twice as low (66 mol of NaBH₄ + 66 mol of Na₂S₂O₅ + 18 mol of H₂SO₄ per one mol of MB9) in comparison with the other oxidative/reductive systems and allowed the effective and fast degradation of MB9 accompanied by the effective removal of AOX. A comparison of the oxidative and reductive methods for chlorinated acid azo dye MB9 degradation showed that an innovative combination of reduction methods offers a smooth, simple, and efficient degradation and hydrodehalogenation of chlorinated textile MB9 dye. Full article

Preparation of reduced graphene oxide (RGO) from abundant and inexpensive low-grade coal is regarded as one of the most promising methods for utilizing this resource in a high-value and environmentally sustainable manner. As the main precursor for the fabrication of RGO, graphene oxide (GO) can be extracted from low-grade coal such as lignite, but its size is just in the range of tens to hundreds of nanometers, which limits its practical application. Herein, we demonstrate that large-size RGO sheets can be prepared in large quantities by the pretreatment of lignite using the high temperature–high pressure (HTHP) method. The RGO electrode after the reduction reaction by 50 mM NaBH₄ at 105 °C features porosity and high conductivity, which can facilitate high electrochemical reaction efficiency. Thus, we also demonstrate the use of lignite-derived RGO for supercapacitor electrode materials with high performance. The lignite-derived RGO supercapacitor can deliver outstanding volumetric capacitance (30.6 F cm⁻³), high energy density (4.2 mW h cm⁻³), excellent flexibility (79.5% retention of the initial capacitance at 180° bending), and a long lifespan (112.3% retention of the initial capacitance after 20,000 cycles). It is believed that the proposed large-size RGO based on reasonable optimization of inferior lignite will offer a new prospect for next-generation energy storage applications. Full article

Solid-state composites based on sodium borohydride (NaBH₄) were studied for applications as hydrogen generation materials. Hydrates of cobalt and nickel chlorides subjected to a thermal treatment were added to the composites as catalyst precursors. Using thermal analysis and FTIR spectroscopy, it was shown that the amount of water removed increases with the increasing temperature. Herewith, the water molecules that remained in the samples were strongly bound to the metal and isolated from each other. According to the ultraviolet–visible (UV-vis) spectroscopy data, with the increasing temperature of the thermal pretreatment there took place a substitution of a portion of water molecules by chloride ions in the nearest environment of the metal. It appeared that it was the resulting weakening of the electrostatic field on metal that was mainly responsible for the formation of a more finely dispersed catalytic phase of amorphous cobalt boride in the reaction medium under the action of sodium borohydride. The smaller particles of the active components led to a faster rate of gas generation when water was added to the solid-state NaBH₄ composites. This trend remained for both the cobalt and the nickel catalytic systems even when the activity was calculated per gram of the metal. Thus, for the preparation of solid-state NaBH₄ composites, hydrates of cobalt and nickel chlorides with a low content of water should be used. Full article

In this study, the authors rationally designed a high-performance catalytic filter for continuous flow catalysis. The catalytic filter consisted of ligand-free nanoscale gold (nano-Au) catalysts and nitrogen-doped graphene (N-rGO). The Au catalyst was fabricated in situ onto a pre-formed N-rGO support by the NaBH₄ reduction of the Au precursor, and the size of the nano-Au was fine-tuned. A hydrothermal pretreatment of graphene oxide enriched nitrogen-containing species on the surface of two-dimensional graphene supports and enhanced the affinity of Au precursors onto the support via electrocatalytic attraction. The nano-Au catalysts acted as high-performance catalysts, and the N-rGO acted as ideal filter materials to anchor the catalysts. The catalytic activity of the as-designed catalytic filter was evaluated using 4-nitrophenol (4-NP) hydrogenation as a model catalytic reaction. The catalytic filters demonstrated superior catalytic activity and excellent stability, where a complete 4-nitrophenol conversion was readily achieved via a single pass through the catalytic filter. The as-fabricated catalytic filter outperformed the conventional batch reactors due to evidently improved mass transport. Some key operational parameters impacting the catalytic performance were identified and optimized. A similar catalytic performance was also observed for three 4-nitrophenol spiked real water samples (e.g., surface water, tap water, and industrial dyeing wastewater). The excellent catalytic activity of the nano-Au catalysts combined with the two-dimensional and mechanically stable graphene allowed for the rational design of various continuous flow catalytic membranes for potential industrial applications. Full article