Fabrication and characterization of novel iodine doped hollow and mesoporous hematite (Fe2O3) particles derived from sol-gel method and their photocatalytic performances

Rare Earth Element Speciation in Coal and Coal Combustion Byproducts: A XANES and EXAFS Study

Transitioning to a low-carbon economy, necessary to mitigate the impacts of anthropogenic climate change, will lead to a significant increase in demand for critical minerals such as rare earth elements (REE). Meeting these raw materials requirements will be challenging, so there is increasing interest in new sources of REE including coal combustion byproducts (CCBs). Extraction of REE from CCBs can be advantageous as it involves reusing a waste product, thereby contributing to the circular economy. While a growing body of literature reports on the abundance of REE in CCBs globally, studies examining the key factors which control their recovery, including speciation and mode of occurrence, are lacking. This study employed synchrotron-based X-ray absorption spectroscopy to probe the speciation and local bonding environment of yttrium in coals and their associated CCBs. Linear Combination Fitting identified silicate and phosphate minerals as the dominant REE-bearing phases. Taken together with the results of extended X-ray absorption fine structure (EXAFS) curve fitting, we find there is minimal transformation in the REE host phase during combustion, indicating it is transferred in bulk from the coals to the CCBs. Accordingly, these findings can be incorporated into the development of an efficient, environmentally conscious recovery process.

Nanotechnologies in ceramic electrochemical cells

Although they are emerging technologies for achieving high-efficiency and green and eco-friendly energy conversion, ceramic electrochemical cells (CECs), i.e. solid oxide electrolysis cells (SOECs) and fuel cells (SOFCs), are still fundamentally limited by their inferior catalytic activities at low temperature, poor thermo-mechanical stability, high material cost, etc. The materials used in electrolytes and electrodes, which are the most important components in CECs, are highly associated with the cell performances. Therefore, rational design of electrolytes and electrodes with excellent catalytic activities and high stabilities at relatively low cost is a meaningful and valuable approach for the development of CECs. Nanotechnology is a powerful tool for improving the material performances in CECs owing to the favourable effects induced by the nanocrystallization of electrolytes and electrodes. Herein, a relatively comprehensive review on the nanotechnologies implemented in CECs is conducted. The working principles of CECs and the corresponding challenges were first presented, followed by the comprehensive insights into the working mechanisms of nanocrystalline materials in CECs. Then, systematic summarization and analyses of the commonly used nano-engineering strategies in the fabrication of CEC materials, including physical and chemical methods, were provided. In addition, the frontiers in the research of advanced electrolyte and electrode materials were discussed with a special emphasis on the modified electrochemical properties derived from nanotechnologies. Finally, the bottlenecks and the promising breakthroughs in nanotechnologies were highlighted in the direction of providing useful references for rational design of nanomaterials for CECs.

The role of tin species in doped iron (III) oxide for photocatalytic degradation of methyl orange dye under UV light

Iron (III) oxide, a stable semiconductor with versatile applications, was synthesized alongside Sn-doped Fe₂O₃ (Sn-Fe₂O₃) using the sol-gel technique. Characterization via X-ray diffraction, field-emission scanning electron microscopy, and UV-visible spectroscopy confirmed the presence of α- and γ-Fe2O3 phases in the synthesized powders. Incorporation of the dopant reduced the initial band gap energy of Fe₂O₃ (2.2 eV) by approximately 0.1 eV. To evaluate photocatalytic performance, Fe₂O₃ and Sn-Fe₂O₃ were tested for decolorization efficiency of a methyl orange solution. Results revealed the 5 wt% Sn-doped catalyst as optimal, achieving complete degradation of methyl orange within 120 min under simulated solar light. The addition of small amounts of Sn effectively reduced the Fe₂O₃ band gap and significantly enhanced photocatalytic performance. Investigation of pH and dye concentration impact on photocatalytic degradation revealed superior activity under acidic conditions compared to alkaline. Furthermore, maintaining a moderate concentration of methyl orange (10 ppm) ensured optimum photocatalytic activity.

Efficient photocatalytic degradation of Rhodamine B dye using solar light-driven La-Mn co-doped Fe2O3 nanoparticles

This work aims to develop a highly efficient solar light-induced photocatalyst based on La-Mn co-doped Fe₂O₃ nanoparticles. Pure Fe₂O₃ and La-Mn co-doped Fe₂O₃ nanoparticles were fabricated by a simple co-precipitation method. The photocatalysts were analyzed for their morphological, structural, and magnetic characteristics. Scanning electron microscopy analysis demonstrated the formation of semi-spherical nanoparticles along with small aggregations. The size of nanoparticles was measured using a transmission electron microscope and found in the range of 42-49 nm. The crystalline nature and geometry of synthesized nanoparticles were investigated using X-ray diffraction analysis. Due to the incorporation of La-Mn, the saturation magnetization and remanent magnetization of the nanoparticles decreased from 6.17 to 2.89 emu/g and 1.15 to 0.52 emu/g, respectively, while the coercivity was reduced from 756.72 to 756.67 Oe. The surface area of nanoparticles was increased from 77.93 to 87.45 m²/g as a result of La-Mn co-doping. The photocatalytic performance of the Fe₂O₃, La_0.1Mn_0.3Fe_1.6O₃, and La_0.2Mn_0.2Fe_1.6O₃ catalysts was assessed by their capability to degrade Rhodamine B (RhB) under solar light illumination. La_0.2Mn_0.2Fe_1.6O₃ displayed exceptional degradation performance, degrading RhB to 91.78% in 240 min, in comparison to La_0.1Mn_0.3Fe_1.6O₃ (71.09%) and pristine Fe₂O₃ (58.21%) under specified reaction conditions ((RhB) = 50 ppm; (catalyst) = 40 mg/L; pH = 7; T = 25 °C)). RhB degradation was affected by changing pH, catalytic dosage, dye concentration, and temperature. The degradation of RhB was found to be pseudo-1st order kinetics. The exceptional photocatalytic performance of La_0.2Mn_0.2Fe_1.6O₃ catalysts showed that the synthesized nanoparticles could be effectively utilized to remove organic pollutants from industrial wastewater.

Bifunctional PDDA-stabilized β-Fe2O3 nanoclusters for improved photoelectrocatalytic and magnetic field enhanced photocatalytic applications

Bifunctional β-Fe2O3@PDDA nanoclusters applied for the efficient photoelectrocatalytic oxygen evolution reaction and magnetic field enhanced photocatalytic degradation of pollutants.

Fabrication, application, optimization and working mechanism of Fe2O3 and its composites for contaminants elimination from wastewater

Fe₂O₃ and its composites have been extensively investigated and employed for the remediation of contaminated water with the characteristics of low cost, outstanding chemical stability, high efficiency of visible light utilization, excellent magnetic ability and abundant active sites for adsorption and degradation. In this review, the potentials of Fe₂O₃ in water remediation were discussed and summarized in detail. Firstly, various synthesis methods of Fe₂O₃ and its composites were reviewed and compared. Based on the structures and characteristics of the obtained materials, their applications and related mechanisms in pollutants removal were surveyed and discussed. Furthermore, several strategies for optimizing the remediation processes, including dispersion, immobilization, nano/micromotor construction and simultaneous decontamination, were also highlighted and discussed. Finally, recommendations for further work in the development of novel Fe₂O₃-related materials and its practical applications were proposed.

Aerobic Oil-Phase Cyclic Magnetic Adsorption to Synthesize 1D Fe2O3@TiO2 Nanotube Composites for Enhanced Visible-Light Photocatalytic Degradation

In this work, Fe₂O₃@TiO₂ nanostructures with staggered band alignment were newly designed by an aerobic oil-phase cyclic magnetic adsorption method. XRD and TEM analyses were performed to verify the uniform deposition of Fe₂O₃ nanoparticles on the nanotube inner walls of TiO₂. The steady-state degradation experiments exhibited that 1FeTi possessed the most superior performance, which might be ascribable to the satisfying dark adsorption capacity, efficient photocatalytic activity, ease of magnetic separation, and economic efficiency. These results indicated that the deposition of Fe₂O₃ into TiO₂ nanotubes significantly enhanced the activity of Fe₂O₃, which was mainly ascribed to the Fe₂O₃-induced formation of staggered iron oxides@TiO₂ band alignment and thus efficient separation of h⁺ and e^-. Furthermore, the PL intensity and lifetime of the decay curve were considered as key criterions for the activity's evaluation. Finally, the leaching tests and regeneration experiments were also performed, which illustrated the inhibited photodissolution compared with TiO₂/Fe₃O₄ and stable cycling ability, enabling 1FeTi to be a promising magnetic material for photocatalytic water remediation.

Facile Solvothermal Synthesis of Hollow BiOBr Submicrospheres with Enhanced Visible-Light-Responsive Photocatalytic Performance

In this work, hierarchical hollow BiOBr submicrospheres (HBSMs) were successfully prepared via a facile yet efficient solvothermal strategy. Remarkable effects of solvents upon the crystallinities, morphologies, and microstructures of the BiOBr products were systematically investigated, which revealed that the glycerol/isopropanol volumetric ratio played a significant role in the formation of hollow architecture. Accordingly, the underlying formation mechanism of the hollow submicrospheres was tentatively put forward here. Furthermore, the photocatalytic activities of the resulting HBSMs were evaluated in detail with photocatalytic degradation of the organic methyl orange under visible light irradiation. Encouragingly, the as-obtained HBSMs with striking recyclability demonstrated excellent visible-light-responsive photocatalytic performance, which benefits from their large surface area, effective visible light absorption, and unique hollow feature, highlighting their promising commercial application in waste water treatment.

Synthesis and application of V2O5-CeO2 nanocomposite catalyst for enhanced degradation of methylene blue under visible light illumination

Methylene blue dye is among the toxic, mutagenic, and carcinogenic pollutants. Hence, its treatment via photocatalytic degradation is an important remediation method for the sake of a healthy environment. Herein, the V₂O₅-CeO₂ nanocomposite catalysts were synthesized via a simple precipitation-thermal decomposition approach and used for the photodegradation of methylene blue in the presence of H₂O₂ as an effective electron scavenger under visible light illumination. The nanocomposite catalysts were systematically characterized to investigate the effects of V₂O₅ with the aids of X-ray, morphology, light absorption, catalytic activity, and charge transfer properties of the nanocomposite catalysts. The VC-2 nanocomposite prepared with NH₄VO₃:CeO₂ molar ratios at 0.15:1 was found to be the best efficient catalyst where ≥98% of methylene blue was degraded within 25 min irradiation time. From the kinetics analysis, its rate constant was found to be higher than those of the pure V₂O₅ and CeO₂ catalysts by a factor of 12.0 and 13.5, respectively. The plausibly mechanistic elucidation of charge transfer and utilization of reactive species are conspicuous allegations of the combined effects of the nanocomposite catalyst, H₂O₂ sacrificial agent, and visible light for the photodegradation of the dye.

Recent progress in magnetic nanoparticles: synthesis, properties, and applications

The rapid development of advanced nanotechnology has continuously changed many aspects of society. One important nanostructured material, magnetic nanoparticles (NPs), has applications in many areas including clean energy, biology and engineering because of their special magnetic properties. The synthesis of magnetic nanomaterials with desired sizes and morphology has attracted great attention. Nanomaterials with different properties can be combined to construct multifunctional nanoplatforms through systematic surface engineering. The surface modification of magnetic NPs presents the opportunity for them to be used in many practical applications. Functionalized magnetic NPs have been successfully applied in catalysis, as thermoelectric materials, for drug delivery, as imaging agents in nuclear magnetic resonance and in biosensors. In this review, synthetic methods for magnetic NPs and some of their important properties are described. Then the latest progress of the application of magnetic NPs in energy and biology has been summarized and discussed. Finally, we discuss some issues that still need to be solved and the prospects for magnetic NPs.

Facile Synthesis and Enhanced Visible-Light Photocatalytic Activity of Novel p-Ag3PO4/n-BiFeO3 Heterojunction Composites for Dye Degradation

In this work, Ag₃PO₄ microparticles were decorated onto the surface of BiFeO₃ microcuboids through a precipitation method to obtain p-Ag₃PO₄/n-BiFeO₃ heterojunction composites. The composites were employed for the degradation of acid orange 7 (AO7) under visible-light irradiation. It is found that the composites exhibit much higher photocatalytic efficiency than bare BiFeO₃. Meanwhile, the intrinsical visible-light-driven photocatalytic activity of Ag₃PO₄/BiFeO₃ composites was further confirmed by the degradation of phenol. In addition, the photo-Fenton-like catalysis property of the composite was also evaluated. The photocurrent analysis indicates that the combination of BiFeO₃ with Ag₃PO₄ leads to the inhibition of recombination of photoinduced electrons and holes. The obvious enhancement in the photocatalytic activity of the composite is mainly ascribed to the efficient photogenerated charge separation and interfacial charge migration caused by the formation of Ag₃PO₄/BiFeO₃ p-n heterojunctions.

A ZnO/ZnFe2O4 uniform core–shell heterojunction with a tubular structure modified by NiOOH for efficient photoelectrochemical water splitting

It is known that heterojunction photoelectrodes can improve light absorption and accelerate the separation of photogenerated carriers in the field of photoelectrochemical (PEC) water splitting.