Hydrothermal Synthesis Technique Research Articles

Effect of double hydrothermal synthesis technique on the electrochemical properties of Co3O4 microflowers for supercapacitor application

Effect of double hydrothermal synthesis technique on the electrochemical properties of Co3O4 microflowers for supercapacitor application

Optimization of FeMn-MOF doped with silver nanoparticles for high-performance supercapattery devices

Supercapacitors are demanded by energy storage devices for both fast charging and discharging performance as well as extended life cycles. The design and manufacture of higher supercapacitor electrodes help a device to function much better. Ag nanoparticles were produced on Fe-MOF and Mn-MOF using the hydrothermal synthesis technique to synthesize unique composite material called FeMn-MOF/Ag (NPs). These refined composites find use in supercapacitors, hydrogen evolution reactions (HER), and electrochemical sensors. Highly conductive silver nanoparticles were added to FeMn-MOF with high rate capability. Apart from their inherent benefits of metal–organic frameworks, the as-made FeMn-MOF/Ag nanoparticles also improved electrical conductivity. When the scan rate was 3 mV s−1, the FeMn-MOF/Ag (NPs) showed a specific capacity (CV) of 1417 C g−1. Similarly, when the applied current density was 2 A g−1, it displayed a specific capacity (GCD) of 2346 C g−1. The FeMn-MOF/Ag (NPs)//AC asymmetric supercapacitor exhibited an energy density of 13 (Wh/kg) and a power density of 1685 (W/kg). For the hydrogen evolution process, the material exhibited an overpotential of 90.22 mV and a Tafel slope of 58.4 mV dec−1. Furthermore, it exhibited exceptional durability in cycling, maintaining 93.3% of its capacitance after undergoing 12,000 cycles. Therefore, these results offer crucial insights into the progress of different electrode materials. The results suggest that FeMn-MOF/Ag nanoparticles possess advantageous characteristics suitable for utilization as electrodes in supercapattery and HER (hydrogen evolution reaction) applications.

Dahlia ball shape bimetallic phosphide-tungsten phosphide composite for anion-exchange membrane water electrolysis

Revolutionizing Water Splitting: Introducing a Breakthrough Single Heterostructure Catalyst for Highly Efficient Hydrogen and Oxygen Evolution Reactions. In this study, we present an innovative method for water splitting that introduces a remarkable single heterostructure catalyst capable of efficiently catalyzing both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Our research utilizes a highly effective hydrothermal synthesis technique to create a unique nanosphere composed of iron cobalt phosphide and tungsten phosphide (FCPWP). This FCPWP nanosphere exhibits finely tuned electronic structures and incorporates multiple active sites, resulting in significantly reduced overpotentials. When operating at current densities of 50 and 100 mA cm−2, the HER overpotentials are as low as 220 mV and 280 mV, respectively, while the OER overpotentials are only 270 mV and 350 mV. By employing the FCPWP nanosphere in a two-electrode electrolyzer configuration, we achieve exceptional results with minimal power requirements. At an operating current density of 10 mA cm−2, the electrolyzer functions at an impressively low voltage of 1.44 V, and at 1.85 V, it attains a high current density of 425 mA cm−2, showcasing an outstanding cell efficiency of 71.63% in an anion exchange membrane electrolyzer. These experimental findings are further supported by computational study. The FCPWP nanosphere emerges as an extraordinary electrocatalyst with dual-functionality for water splitting, offering great promise in the efficient production of hydrogen through electrochemical means. Our research not only introduces a fresh perspective but also paves the way for significant advancements in renewable energy technologies.

Enhancing the supercapacitive performance of soot material induced with manganese cobaltite (MnCo2O4) for supercapacitor application

Processing waste carbonaceous materials into useful products presents a sustainable alternative to its recovery. An effective and environmentally benign way of reusing such waste is to convert them into electrodes capable of supporting energy conversion reactions. This study introduces a cost-effective synthesis of a composite electrode for supercapacitor application using a waste carbonaceous soot obtained from Tema Steels Limited, a local steel manufacturing company in Ghana, having it subjected through thermal treatment at 500 °C and synergizing with annealed MnCo2O4 to augment the soot’s supercapacitive capabilities. The fabricated composite electrode comprises treated (thermally activated) soot combined with annealed MnCo2O4 material in 1:1 mass ratio, using a facile hydrothermal synthesis technique. Halogen like chlorine negatively affect the supercapacitive performance of soot, the as-received soot was subjected to a 500°C, 2-hour thermal treatment to optimize its performance, effectively reducing chlorine content from 4.1 to 2.1 at. weight percent and notably augmenting its specific surface area (SSA). SSA increased from 183.3 m2g−1 to 253.3 m2g−1, a 27.6 % increment after thermal treatment. The electrode’s supercapacitive performance was utilized using a 3 M KOH electrolyte solution employed in a three-electrode system. Attaining a current density of 3Ag−1, the composite electrode achieved a specific capacitance of 2818 Fg−1. The fabricated composite electrode demonstrated a stable charge/discharge capability by retaining around 87 % of its capacity after 10,000 cycles, establishing its practicality for applications in electrochemical storage.

Synthesis of multifunctional rGO/g-C3N4/FeTiO3 ternary nanocomposites for photocatalyst, antibacterial, and ecotoxicity assessment of zebrafish embryo model

The wastewater from the dye and pharmaceutical industries antibiotics has caused serious environmental and health problems for humans and other species. For the development of superior photocatalysts, effective separation of photogenerated electron-hole pairs is essential in addition to optimizing solar absorption throughout a wide wavelength range. In order to produce bare, rGO/g-C3N4, rGO/FeTiO3, and rGO/g-C3N4/FeTiO3 (GCNFeT NCs) nanocomposites, this study describes the fabrication of perovskite-type titanate (FeTiO3) and its incorporation onto graphitic carbon nitride (g-C3N4) and reduced graphene oxide (rGO) using a hydrothermal synthesis technique. The generated nanocomposites structural, morphological, and optical properties were evaluated. After being exposed to solar light for 90 min, the resultant GCNFeT NCs efficiently broke down 80 % of Tetracycline (TC) and 90 % of Malachite Green (MG) dye. The photocatalytic efficacy is significantly improved by these results when compared to the pure and binary composites. Substantial catalytic efficiency to GCNFeT NCs was shown by the degradation rate constant (k) for MG and TC elimination by GCNFeT NCs, which was almost 20 times greater than that of pure and binary composites. Additionally, the antibacterial activity of GCNFeT nanocomposites was studied, and the results showed that it was significantly more efficient against Gram-negative bacteria than Gram-positive bacteria, including Escherichia coli and Staphylococcus aureus. Furthermore, the freshwater zebrafish embryo development proved effective in assessing the non-toxicity of GCNFeT NCs. Our research findings indicate that high doses, GCNFeT NCs induce less toxicity in zebrafish embryo (6.25–100 µg/L). These results demonstrated the enhanced mechanism of GCNFeT NCs, indicating their great potential for use in antibacterial and water remediation applications.

Photovoltaic performance of TiO2 and ZnO nanostructures in anthocyanin dye-sensitized solar cells

Abstract This research paper reports the fabrication and evaluation of titanium dioxide (TiO2)- and zinc oxide (ZnO)-based dye-sensitized solar cells with anthocyanin dye extracted from pomegranate. TiO2 and ZnO were synthesized using the hydrothermal synthesis and chemical bath deposition techniques, respectively. The scanning electron microscopy analysis showed that TiO2 had nanopillars made up of nano rods with dimensions of 111.866, 90.521, and 81.908 nm, while ZnO had hexagonal patterned nanorods with lengths of 283.294 nm and diameters of 91.782 nm. The absorption spectra of the pomegranate dye were analysed and the strongest absorption peak was found to be at 520 nm, which corresponds to the existing anthocyanin pigment. The band gap of pomegranate dye was noted down to be 2.45 eV. The performance of the dye-sensitized solar cells was evaluated using one sun illumination (100 mW/cm2) where the dye-sensitized solar cell with TiO2 nanopillars achieved an improved efficiency of 0.46% whereas the dye-sensitized solar cell with ZnO nanorods showed a considerably reduced efficiency of 0.42%.

Casein phosphopeptide/antimicrobial peptide co-modified SrTiO3 nanotubes for prevention of bacterial infections and repair of bone defects

Endowing titanium surfaces with multifunctional properties can reduce implant-related infections and enhance osseointegration. In this study, titanium dioxide nanotubes with strontium doping (STN) were first created on the titanium surface using anodic oxidation and hydrothermal synthesis techniques. Next, casein phosphopeptide (CCP) and an antimicrobial peptide (HHC36) were loaded into the STN with the aid of vacuum physical adsorption (STN-CP-H), giving the titanium surface a dual function of "antimicrobial-osteogenic". The surface of STN-CP-H has a suitable roughness and good hydrophilicity, which is conducive to osteoblasts. STN-CP-H had a 99 % antibacterial rate against S. aureus and E. coli and effectively prevented the growth of bacterial biofilm. Meanwhile, the antibacterial mechanism of STN-CP-H was initially explored with the help of transcriptome sequencing technology. STN-CP-H could greatly increase osteoblast adhesion, proliferation, and expression of osteogenic markers (alkaline phosphatase, runt-related transcription) when CCP and Sr worked together synergistically. In vivo, the STN-CP-H coating could effectively promote new osteogenesis around titanium implant bone and had no toxic effects on heart, liver, spleen, lung and kidney tissues. A potential anti-infection bone healing material, STN-CP-H bifunctional coating developed in this work efficiently inhibited bacterial infection of titanium implants and encouraged early osseointegration.

MoS2 Modified Aluminum Electrode for Detection of Calcium Oxalate through Electrochemical Oxidation

The disposal of electronic waste (E-waste), encompassing discarded items such as computers, televisions, fridges, cellphones, and associated cabling, presents a significant challenge to both societal welfare and environmental health. Addressing e-waste management is critical to achieving several of the Sustainable Development Goals (SDGs). This study introduces a novel approach to repurposing aluminum from discarded electrical cables for the creation of high-efficiency electrodes that can detect oxalic acid in human urine samples. The process involves stripping 2mm thick cables to yield 7cm long aluminum rods. These rods are then coated with MoS2 nanoparticles via a hydrothermal synthesis technique. X-ray diffraction (XRD) analysis confirms the presence of MoS2 in the 1T phase, while Fourier-transform infrared spectroscopy (FTIR) and Raman spectroscopy provide insights into the vibrational modes and chemical composition. Field emission scanning electron microscopy (FESEM) imaging depicts the MoS2 as having a flower-like nanostructure composed of interwoven nanosheets. The resulting nanocomposite sensor demonstrates an enhanced electrical current response, along with notable selectivity and stability, likely due to the combined effects of the MoS2 materials. The sensor’s amperometric signal is directly correlated with the oxalate ion concentration within a range of 10 to 300 μM and exhibits a detection threshold as low as 2 μM. This sensor technique was evaluated alongside a standard colorimetric assay for measuring oxalic acid levels in urine specimens. Findings indicated a strong correlation (R=0.954) between oxalic acid concentrations assessed using the biosensor and those obtained through the colorimetric approach.Keywords: E-waste, Aluminum Electrodes, MoS2 Nanoparticles, Oxalic Acid Detection, and Electrochemical Sensing, Figure 1

The synthesis and characterization of novel boron-containing B/Al-ZSM-12 zeolite

In this study, new type of boron-substituted Al-ZSM-12 was developed using hydrothermal synthesis technique and methyltriethylammonium chloride as a template; physical and chemical characteristics of B/Al-ZSM-12 were studied in detail. The presence of tetrahedral boron in the isomorphically substituted zeolite was confirmed by FTIR, Raman, DRS UV–Vis, DRIFTS, 29Si and 11B NMR, and ICP–MS methods. Due to the incorporation of boron into Al-ZSM-12 zeolite, the resulting crystallites of B/Al-ZSM-12 have a shorter b-axis length compared to unsubstituted Al-ZSM-12. Moreover, boron atoms do not affect the change in the structure of Al-ZSM-12 zeolite, while being embedded in the framework, affect acidic properties, increasing total acidity and a providing high concentration of Brønsted acid sites compared to Al-ZSM-12. Meanwhile, the surface area increases from 320 m2 g−1 for Al-ZSM-12 to 350 m2 g−1 for B/Al-ZSM-12.

Synthesis of hexagonal mesoporous silica from coal fly ash and their evaluation as adsorbent for gallium recovery

Adsorption of gallium (Ga) utilizing solid waste synthetic materials can achieve both high-value solid waste use and solve the supply–demand paradox of Ga. To efficiently recover Ga in solution, this article describes a hydrothermal synthesis technique of mesoporous materials from the acid leaching residue of coal fly ash (CFA). According to the findings, the mesoporous silica synthesized by hydrothermal reaction with CTAB: nSiO32-=1:0.085 around 120℃ during 24 h exhibits a maximum specific surface area (771.25 m2/g) along with hexagonal mesoporous structure. Pseudo-second-order kinetic model that has an excellent correlation coefficient (R2 > 0.99) can explain this adsorption system. Since Freundlich model fits this adsorption action better, the process is multi-molecular layer adsorption. The thermodynamic fitting results show that the adsorption of Ga by mesoporous silica is an endothermic and spontaneous chaotic reaction. The adsorption mechanism could be depicted using ion exchange and coupling. The adsorption efficiency of Ga is still higher than 80 % after the material has been regenerated by multiple resolution. In conclusion, mesoporous silica prepared by CFA acid leaching residue has the potential to adsorb Ga.

Constructing Direct Z-Scheme Y2TmSbO7/GdYBiNbO7 Heterojunction Photocatalyst with Enhanced Photocatalytic Degradation of Acetochlor under Visible Light Irradiation.

This study presents a pioneering synthesis of a direct Z-scheme Y2TmSbO7/GdYBiNbO7 heterojunction photocatalyst (YGHP) using an ultrasound-assisted hydrothermal synthesis technique. Additionally, novel photocatalytic nanomaterials, namely Y2TmSbO7 and GdYBiNbO7, were fabricated via the hydrothermal fabrication technique. A comprehensive range of characterization techniques, including X-ray diffractometry, Fourier-transform infrared spectroscopy, Raman spectroscopy, UV-visible spectrophotometry, X-ray photoelectron spectroscopy, transmission electron microscopy, X-ray energy-dispersive spectroscopy, fluorescence spectroscopy, photocurrent testing, electrochemical impedance spectroscopy, ultraviolet photoelectron spectroscopy, and electron paramagnetic resonance, was employed to thoroughly investigate the morphological features, composition, chemical, optical, and photoelectric properties of the fabricated samples. The photocatalytic performance of YGHP was assessed in the degradation of the pesticide acetochlor (AC) and the mineralization of total organic carbon (TOC) under visible light exposure, demonstrating eximious removal efficiencies. Specifically, AC and TOC exhibited removal rates of 99.75% and 97.90%, respectively. Comparative analysis revealed that YGHP showcased significantly higher removal efficiencies for AC compared to the Y2TmSbO7, GdYBiNbO7, or N-doped TiO2 photocatalyst, with removal rates being 1.12 times, 1.21 times, or 3.07 times higher, respectively. Similarly, YGHP demonstrated substantially higher removal efficiencies for TOC than the aforementioned photocatalysts, with removal rates 1.15 times, 1.28 times, or 3.51 times higher, respectively. These improvements could be attributed to the Z-scheme charge transfer configuration, which preserved the preferable redox capacities of Y2TmSbO7 and GdYBiNbO7. Furthermore, the stability and durability of YGHP were confirmed, affirming its potential for practical applications. Trapping experiments and electron spin resonance analyses identified active species generated by YGHP, namely •OH, •O2-, and h+, allowing for comprehensive analysis of the degradation mechanisms and pathways of AC. Overall, this investigation advances the development of efficient Z-scheme heterostructural materials and provides valuable insights into formulating sustainable remediation strategies for combatting AC contamination.

Electrochemical and impedance analysis of nickel oxide nanoflakes-based electrodes for efficient chromo supercapacitors

In response to the dynamic advancement of our growing world, there is a tenacious need for sophisticated technologies and continuous refinement of existing knowledge through rigorous scientific endeavors, all with a focus on achieving sustainable development goals for a cleaner and more prosperous future. In this context, this study involves a novel approach to the synthesis of highly porous and stable nickel oxide (NiO) nanoflakes assembled with stacked nanosheet thin films through hydrothermal methods. These films are in-detail examined for their redox-active chromo-supercapacitive properties. The hydrothermal synthesis technique yields thin films with exceptional adhesion to the electrode surface, remarkable chemical stability, and suitable porous structure. These characteristics are strategically employed to facilitate rapid ion intercalation and deintercalation processes, thereby enhancing electrochemical activity. Notably, films deposited for 6-hour reaction times deliver a higher areal capacitance of 140 mF/cm² (and capacity of 70 mC/cm2) at 0.5 mA/cm², which is higher than other electrodes and earlier reports. In-situ, optical investigations further underscore the high coloration efficiency of 44.14 cm²/C, coupled with large optical modulation of 56.5 % and enduring the electrochemical and electrochromic stability. Further research and optimization of NiO-based materials hold significant potential for the development of efficient, smart, and sustainable energy storage solutions in the evolving field of electrochromic supercapacitors to meet the demands of next-generation electronic systems.

Prickly Janus magnetic and photonic microrobots for exosome assays

Microrobots have been widely reported as a powerful tool for biosensing. Attempts in this field tend to improve their functions by using different fabrication technologies. In this paper, a novel prickly Janus magnetic and photonic microrobot is presented for efficient exosome assays by integrating induced self-assembly and hydrothermal synthesis techniques. The induced self-assembly results in Janus magnetic and photonic microrobots with magnetic controllability and striking structure colors, making them ideal for efficient multiplex assays. The hydrothermal synthesis helps the formation of prickly surface, endowing the microrobot with large surface for capturing targets. It was demonstrated that these prickly Janus magnetic and photonic microrobots can carry out multiplex exosome assays with high sensitivity benefiting from their stable structure colors, magnetic autonomous motion, and capacity of enriching.

Efficiency assessment of hydrothermally synthesized Mn2+/3+ modified LaCoO3 nanoparticles for advanced wastewater remediation

Abstract The use of light and a particular material known as a photocatalyst to degrade hazardous dyes in wastewater is an exciting new development in the field of photocatalytic dye degradation. In this study we investigated the characteristic properties and photocatalytic dye degradation of manganese doped lanthanum cobalt (LaCoO3 (LCO)) nanoparticles (NPs). The NPs were synthesised using hydrothermal synthesis techniques and analysed its properties by utilising diverse technologies such as XRD, FeSEM with EDAX, Raman Spectroscopy, Photoluminescence spectroscopy and UV-DRS. From XRD analysis we found that the Mn doped LCO NPs have single phase rhombohedral crystal structures with R 3 ‾ $\overline{3}$ c space group and doping cause expansion of lattice. Surface morphology of the synthesised NPs was found to be altered from spherical to spine/rod like microstructure when Mn is incorporated to LCO lattice. PL spectroscopies show broad photoemission at 360–490 nm after absorbing 310 nm light. From the UV–Vis spectroscopy the optical bandgap of the materials around 4.5 eV, indicating they can absorb visible light effectively. LCO can absorb both UV and visible light, expanding its potential for outdoor applications under natural sunlight. Doping LCO with other elements can modify its bandgap and improve its activity towards specific dyes. LCO exhibits good chemical and thermal stability, making it reusable for multiple cycles. While LCO shows promise as a visible light photocatalyst for dye degradation, its efficiency can vary significantly depending on the specific conditions. We tested Congo Red (CR) dye with prepared photocatalyst to study how well they breakdown in visible light. Studies have reported degradation rates for different dyes ranging from 50 to 90 % within an hour under optimized conditions. The LCMO nanoparticles exhibited noteworthy photocatalytic activity, as evidenced by a degradation efficiency of 77 % within a 30 min timeframe. Our findings indicate that LCMO nanoparticles possess significant potential for environmental clean-up.

Enhancing Bone Implants: Magnesium-Doped Hydroxyapatite for Stronger, Bioactive, and Biocompatible Applications.

Hydroxyapatite (HAp) with the chemical formula Ca10(PO4)6(OH)2 is an inorganic material that exhibits morphology and composition similar to those of human bone tissues, making it highly desirable for bone regeneration applications. As one of the most biocompatible materials currently in use, HAp has undergone numerous attempts to enhance its mechanical strength. This research focuses on investigating the influence of magnesium (Mg) incorporation on the structural and mechanical properties of synthesized magnesium-doped hydroxyapatite (MgHAp) samples. Apart from its biocompatibility, Mg possesses a density and elasticity comparable to those of human bone. Therefore, incorporating Mg into HAp can be pivotal for improving bone formation. Previous studies have not extensively explored the structural changes induced by Mg substitution in HAp, which motivated us to revisit this issue. Hydrothermal synthesis technique was used to synthesize MgHAp samples with varying molar concentrations (x = 0, 0.5, 1.0, and 1.5). Theoretical simulation of HAp and MgHAp for obtaining 3D structures has been done, and theoretical X-ray diffraction (XRD) data have been compared with the experimental XRD data. Rietveld analysis revealed the alteration and deviation of lattice parameters with an increase in the Mg content, which ultimately affect the structure as well the mechanical properties of prepared samples. The findings revealed an increase in compressive stress and fracture toughness as the Mg concentration in the composition increased. Furthermore, using a finite-element analysis technique and modeling of the mechanical testing data, the von Mises stress distribution and Young's modulus values were calculated, demonstrating the similarity of the prepared samples to human cortical bone. Biocompatibility assessments using NIH-3T3 fibroblast cells confirmed the biocompatible and bioactive nature of the synthesized samples. MgHAp exhibits great potential for biomedical applications in the dental, orthopedic, and tissue engineering research fields.

Sensing, detoxification and bactericidal applications of nitrogen-doped carbon dots

Here, a one-pot hydrothermal synthesis technique was used to create nitrogen-doped carbon dots (N-CDs). Their structural and optical properties were assessed using XPS, XRD, Raman, UV–Vis, and fluorescence spectrophotometer. The N-CDs demonstrated encouraging emission quenching towards p-NP (p-Nitrophenol) and developed a sensing approach between 0.25 and 125 μM concentrations, from which a linear equation with a 20 nM detection limit was generated. In comparison to river and circulating water samples, the practicality demonstrated positive recovery rates together with impressive accuracy and precision. Additionally, the multi-functionality of N-CDs was investigated further in the catalytic reduction of methyl orange (MO) dye. With a good regression coefficient(0.9904) (R2) and rate constant (Kcat) (0.0208 min−1), N-CDs were able to reduce the azo groups in 8 min completely. Additionally, the bactericidal efficiency of N-CDs against gram-positive (Staphylococcus aureus, Listeria monocytogenes) and gram-negative (Escherichia coli, Salmonella enterica) bacteria was encouraging. The well-diffusion method demonstrated a good zone of inhibition, and the microdilution method demonstrated a promising minimum bactericidal concentration (MBC) of 470–940 μg/mL and minimum inhibitory concentration (MIC) of 240–470 μg/mL. The suggested fluorescent material may prove useful in the future for creating a fluorescence sensor, catalysts to combat water pollution, and antibacterial sprays to combat dangerous microorganisms.

CuAs2O4: Design, Hydrothermal Synthesis, Crystal Structure, Photocatalytic Dye Degradation, Hydrogen Evolution Reaction, Knoevenagel Condensation Reaction, and Thermal Studies.

CuAs2O4 has been explored as a heterogeneous catalyst in the fields of photocatalysis, electrocatalysis, and solvent-free organic transformation reactions. The homogeneity has been successfully attained for the first time by designing a pH-assisted hydrothermal synthesis technique. Single-crystal X-ray diffraction studies reveal that no phase transition has been observed by lowering the temperature up to 103 K with no existence of satellite reflections. The crystal structure exhibits tetragonal symmetry with space group P42/mbc and consists of [CuO6] octahedra and [AsO3E] tetrahedra (E represents the stereochemically active lone pair). Structural investigation shows a cylindrical void inside the structure, which could lead to interesting physical and chemical properties. The photocatalytic dye degradation efficiency with methylene blue (MB) showed ∼100% degradation, though the degradation efficiency increased by 2-fold with the addition of 6% H2O2. The reusability of the catalyst up to the 10th cycle with ∼35% MB dye degradation has been established. It can exhibit HER activity with a low overpotential of 165 mV with respect to RHE to attain the current density of j = 10 mA cm-2. SEM and TEM revealed rod-shaped particles, which supported the large number of catalytic active sites. The structural consistency of the catalyst after photodegradation and HER studies is confirmed by the PXRD pattern. XPS confirms the oxidation state of Cu and As in the compound. The catalytic activity toward the Knoevenagel condensation reaction at moderate temperature under solvent-free condition is also studied. TG-DTA shows an endothermic minimum (Tmin) at 436 °C due to the mass loss of As2O3.

Exploring the Potential of α-MnO<sub>2</sub>/ Carbon Nanotubes for Improved Oxygen Reduction Reaction Performance at the Cathode of Alkaline Fuel Cells

In the field of fuel cell technology, the development of cost-effective catalysts is crucial for the commercialization of Alkaline Membrane Fuel Cells (AMFCs). Platinum (Pt) has traditionally been employed as the catalyst in AMFCs, but its high cost poses a major barrier to widespread adoption. In this study, a new catalyst material was developed by incorporating Manganese Dioxide (α-MnO2) into Carbon Nanotubes (CNTs) using hydrothermal synthesis techniques. The synthesized catalyst was characterized using Scanning Electron Microscopy (SEM) and X-ray diffraction (XRD), and its electrocatalytic activity was evaluated through Linear Sweep Voltammetry (LSV) and CV through Rotating Disc Electrode (RDE) experiments. The results showed that the α-MnO2-CNT composite displayed strong durability in the alkaline environment and high electrocatalytic activity for oxygen reduction reaction (ORR). The LSV measurements revealed a current density of -4.1 mA/cm2 and an overpotential of -0.3V relative to Standard Calomel Electrode (SCE) in a 0.1M KOH electrolyte. Additionally, the α-MnO2-CNT composite displayed high methanol tolerance and long-term stability compared to commercial Pt/C catalysts. This study demonstrates that the use of α-MnO2-CNT as a cost-effective alternative to Pt has the potential to facilitate the commercialization of AMFC technology.

Insight into the Growth Mechanism of Low-Temperature Synthesis of High-Purity Lithium Slag-Based Zeolite A.

The utilization of lithium slag (LS), a solid waste generated during the production of lithium carbonate, poses challenges due to its high sulfur content. This study presents a novel approach to enhancing the value of LS by employing alkali fusion and hydrothermal synthesis techniques to produce zeolite A at low temperatures. The synthesis of high-purity and crystalline lithium-slag-based zeolite A (LSZ) at 60 °C is reported for the first time in this research. The phase, morphology, particle size, and structure of LSZ were characterized by XRD, SEM, TEM, N2 adsorption, and UV Raman spectroscopy, respectively. High-purity and crystalline zeolite A was successfully obtained under hydrothermal conditions of 60 °C, an NaOH concentration of 2.0 mol/L, and a hydrothermal time of 8 h. The samples synthesized at 60 °C exhibited better controllability and almost no byproduct of sodalite occurred compared to zeolite A synthesized at room temperature or conventional temperature (approximately 90 °C). Additionally, the growth mechanism of LSZ was elucidated, challenging the traditional understanding of utilization of lithium and enabling the synthesis of various zeolites at lower temperatures.

Synthesis and characterisation of pure zeolite A from fly ash for removal of lead and cadmium

ABSTRACT The primary objective of the present study is synthesis a highly crystalline zeolite A of pure phase using fly ash obtained from a thermal power station located in South India. The mineral composition of fly ash promotes the synthesis of zeolites, which are subsequently used in the treatment of wastewater. The composition of fly ash namely SiO2, Al2O3, and Na2O are enhanced to 88.01% through pre-treatment of original fly ash using HCl of 20% wt. and solid/liquid ratio of 20 during zeolite synthesis. The pre-treated fly ash was effectively converted to zeolite A by adjusting varying synthesis parameters including silica/alumina (Si/Al) ratio (0.8–1.2), hydrothermal synthesis time (3–12 h), and sodium hydroxide to fly ash (NaOH/FA) ratio (0.64–1.2). The fusion-assisted hydrothermal synthesis technique was employed to successfully transform fly ash into a pure phase zeolite A with a crystallinity of 95.01% by optimising the synthesis parameters. X-ray diffraction (XRD), X-ray fluorescence (XRF), scanning electron microscopy (SEM), Burner-Emmett -Teller (BET), and Fourier transform infrared spectroscopy (FTIR) methods were used for characterisation of synthetic zeolite samples. The findings unveiled a single-phase zeolite A with an excellent cation exchange capacity (CEC) of 218.66 meq/g and a high BET surface area of 108.59 m2/g. The efficacy of zeolite A towards heavy metal removal was investigated using Pb+2 and Cd+2 ions through batch experiments. The adsorption of Pb+2 and Cd+2 obeyed pseudo-second-order kinetics and the Langmuir model was found to provide a better description of adsorption isotherm. Synthetic zeolite A exhibited remarkable removal capacities of 277.78 mg/g and 87.729 mg/g for lead and cadmium, respectively. The experimental findings of the present study showcased the conversion of fly ash into a potent zeolite material with significant potential for the remediation of heavy metal-contaminated wastewater.