Herein, we present the solid-state synthesis, structural, thermoelectric, and magnetoresistance characterization of Cu[Cr2-xMx]Se-4 selenospinels (x = 0.3 and 0.5; M = Sn, Ti). Powder X-ray diffraction patterns were fitted using the Rietveld method and are consistent with a spinel-type structure ( F(-)d3m space group) and corroborated by Raman spectroscopy and single-crystal X-ray diffraction. The microstructures and morphologies of these systems were examined using high-resolution transmission electron microscopy (HRTEM) and scanning electron microscopy (SEM). The transport properties of all compounds exhibit a decreasing electrical conductivity (20-600 K) and an increasing Seebeck coefficient (300-600 K) as a function of temperature, displaying typical metallic behavior associated with electron scattering by thermal vibrations of the crystal lattice (electron-phonon scattering), which is corroborated by DFT calculations. We determined that the Seebeck coefficient increases from approximately +21 mu V K-1 (250 K) to +43 mu V K-1 (550 K) in CuCr1.5Sn0.5Se4. Additionally, the selenospinels exhibit electrical conductivities (sigma) of similar to 1000-2000 S cm(-1) at 250 K, comparable to that of the CuCr1.2Ti0.8S4 thiospinel. The carrier concentrations (Hall measurements) and Seebeck coefficients are positive, indicating p-type behavior with a hole concentration of similar to 10(19) cm(-3) for all samples at room temperature. Changes in slope are observed for both Sn and Ti selenospinels, indicating two distinct conduction regimes. The thermal conductivity (kappa(tot)) is similar to 3.0 W m(-1) K-1 for Cu[Cr1.7Ti0.3]Se-4 and Cu[Cr2-xSnx]Se-4 samples at room temperature. The lattice thermal conductivity (kappa(latt)) exhibits remarkably low values (similar to 1.5 W K-1 m(-1)) for Cu[Cr2-xSnx]Se-4, reaching levels comparable to those of established high-performance thermoelectric materials, and is lower than those reported for CuTi2S4 spinel at 300 K (similar to 2.5 W K-1 m(-1)). The magnetoresistance reaches a maximum of similar to 40% close to the ferromagnetic/paramagnetic phase transition temperature.

Titanium niobates (TNOs) are well known for their stability and variable electronic properties; yet their photocatalytic potential remains relatively underexplored. In this work, Ti2Nb10O29 nanoparticles were synthesized via a solvothermal route and evaluated for photocatalytic Rhodamine B degradation. Thermal treatments enabled the formation of different crystal structures, ranging from amorphous to monoclinic (700 - 900 °C) and orthorhombic (1350 °C) phases. Particle size increased from the nanometric to the micrometric scale upon annealing, and pure Ti2Nb10O29 composition was obtained for annealing temperatures above 800 °C. The estimated bandgap for the crystalline samples was around 3.0 eV. Structural and morphological characterizations reveal a strong dependence of photocatalytic performance on phase composition, crystallinity, and particle size. Photocatalytic assays indicated that monoclinic Ti2Nb10O29 obtained by solvothermal synthesis followed by annealing at 800 °C for 2 h exhibits the highest efficiency, achieving over 95% degradation within 2 h and following pseudo-first-order kinetics. Our results show that the photocatalytic performance of the material is governed by a balance between TNO phase formation, crystallinity, and accessible surface area.

Cow dung was used as fuel in the synthesis of zinc oxide nanoparticles via a one-pot combustion method, emphasizing simplicity and environmental friendliness. The synthesized nanoparticles underwent thorough characterization using XRD, FTIR, XPS, UV, EDX and TEM techniques. To evaluate their photocatalytic effectiveness, Titan yellow (TY) dye was chosen as a model pollutant. The study systematically investigated the photocatalytic efficiency and degradation kinetics of the ZnO nanoparticles. Under sunlight, the nanoparticles exhibited significant removal efficiencies, achieving 69 % degradation of TY. A plausible photocatalytic mechanism for these outcomes was also proposed. Overall, the environmentally friendly synthesis of the target photocatalyst demonstrates promising potential for applications in wastewater treatment and other ecological contexts. ZnO NPs derived from Chenopodium exsuccum shown remarkable antibacterial efficacy against a range of pathogens, including Gram-positive ( Staphylococcus aureus, Micrococcus luteus) and Gram-negative ( Klebsiella pneumoniae, Escherichia coli). Furthermore, the nanoparticles demonstrated noteworthy antioxidant efficacy through the removal of 1,1-Diphenyl-2-picrylhydrazyl (DPPH) free radicals. This demonstrates their potential utility in preventing damage caused by oxidative stress and various diseases related to stress.

Niobium oxides are promising materials for catalytic applications due to their unique structural versatility and surface chemistry. Nb2O5 nanomaterials were synthesized via a solvothermal method at 150 °C using niobium oxalate as a precursor. A comprehensive characterization of the material was performed using electron microscopy, X-ray diffraction, and Raman spectroscopy. The as-prepared nanoparticles primarily crystallized in a mixture of the TT-Nb2O5 phase (TT from the German Tief-Tief, meaning “low-low”) and niobic acid, while subsequent thermal treatment at 900 and 1100 °C induced a phase transformation to T-Nb2O5 and H-Nb2O5, respectively (T from the German Tief, meaning “low”, and H from Hoch, meaning “high”). The as-prepared samples consist of micro-coils composed of interconnected nanometer-scale fibers, whereas the morphology changes into rods when they are treated at 1100 °C. The photocatalytic performance of the nanoparticles was evaluated by comparing the as-prepared and thermally treated samples. The as-prepared nanoparticles exhibited the highest photocatalytic activity under visible illumination, achieving 100% degradation after 180 min. More interestingly, the treatment of the as-prepared material with H2O2 modified the surface species formed on the Nb2O5, altering the photocatalytic behavior under various illumination conditions. This sample showed the highest photocatalytic activity under UV illumination, reaching 100% degradation after 75 min. On the other hand, the calcined samples are practically inactive, attributed to the loss of active catalytic sites during thermal treatment and phase transformation.

ABSTRACTThis study introduces a novel method for the effective doping of hexagonal molybdenum trioxide (h‐MoO3) microstructures with different contents of nickel, significantly enhancing its electrochemical performance in aluminum‐ion batteries (AIBs). Ni doping does not alter the high crystallinity and phase purity of the pristine oxide but modifies its defective structure and electronic properties. Electrochemical tests, including cyclic voltammograms and charge–discharge cycling, showed improvements in capacity and stability for Ni‐doped samples as compared with undoped ones. Moreover, the incorporation of Ni was found to enhance the structural integrity and electrochemical stability of h‐MoO3, preventing the formation of intermediate phases during cycling and reducing resistance at the electrode–electrolyte interface. The existence of an optimal Ni doping of about 1 at% is evidenced. Samples with this Ni content attain a stabilized specific capacity of 230 mAh g−1 over 100 cycles, doubling that reported in previous works for h‐MoO3 composites with carbon nanotubes. Nickel‐doped h‐MoO3 shows exciting potential for advanced AIB applications, paving the way for further energy storage technology advancements.

This work reports the cost-effective synthesis of dual-phase cobalt molybdate (alpha/beta-CoMoO4) nanorods and highlights the unique electrochemical advantages arising from the coexistence of the two polymorphs. Using a facile coprecipitation method followed by calcination and mechanical grinding, nanorods with controlled alpha/beta phase ratios were obtained. Structural (XRD, FTIR) and morphological (SEM/TEM) analyses confirmed the successful engineering of a dual-phase architecture, while magnetic measurements evidenced antiferromagnetic ordering below 11.4 K. When evaluated as anodes for lithium-ion batteries, alpha/beta-CoMoO4 nanorods displayed stable lithiation/delithiation processes, high specific capacity (up to 1246 mAh g- 1), and remarkable rate performance, retaining substantial capacity even at 10 Ag- 1. The improved reversibility and cycling performance (up to 289 cycles) are attributed to the complementary lithium storage mechanisms of the alpha (intercalation + conversion) and beta (conversion) phases, which synergistically enhance kinetics and structural resilience. These findings underline the crucial role of phase engineering in tailoring the electrochemical behavior of CoMoO4, opening new opportunities for low-cost, high-performance anode materials in next-generation energy storage systems.

Vanadium-doped hexagonal molybdenum trioxide (h-MoO3) has been systematically investigated as a cathode material for aluminium-ion batteries (AIBs). The evolution of the structural, morphological, compositional, optical, and electrochemical properties of h-MoO3 doped with different vanadium concentrations were analysed by X-ray diffraction (XRD), micro-Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), high resolution transmission microscopy (HRTEM), SEM and TEM-energy-dispersive X-ray microanalysis (EDS), X-ray photoelectron spectroscopy (XPS), UV-Vis optical absorption and electrochemical techniques. Moderate vanadium doping maintains the hexagonal structure of the oxide host and does not adversely affect the crystallinity of the samples, while inducing morphological changes and local lattice distortions. Optical measurements revealed a significant reduction in the band gap by increasing the dopant concentration, suggesting enhanced electronic conductivity. Electrochemical studies demonstrated that vanadium incorporation improves charge transfer kinetics and cycling stability, with an optimal doping level corresponding to a V/Mo atomic ratio of 0.16, yielding a high specific capacity of similar to 240 mA h g(-)(1) at 100 mA g(-)(1) over 100 cycles. However, an excessive vanadium content led to secondary phase formation, structural degradation, non-homogeneous dopant spatial distribution, and decreased electrochemical performance. Ex-situ SEM-EDS and Raman analysis confirmed the excellent structural stability of vanadium-doped h-MoO3 upon cycling, with uniform chloroaluminate species intercalation. These findings establish vanadium doping as an effective strategy to enhance h-MoO3 for AIB applications, providing a balance between enhanced conductivity, electrochemical stability, and structural integrity.

A novel material, Fe3O4@D-Tryptophan, was synthesized by functionalizing Fe₃O₄ nanoparticles with D-tryptophan. The Fe3O4 nanoparticles were prepared via co-precipitation of FeCl3·6H2O and FeCl2·4H2O under alkaline conditions. The resulting material was characterized using X-ray diffraction (XRD), infrared spectroscopy (IR), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), and magnetization measurements. XRD analysis confirmed the spinel structure and high purity of Fe3O4@D-Tryptophan, while FT-IR spectra revealed the characteristic vibrations of the functional groups introduced by D-tryptophan. Magnetization studies demonstrated that the magnetic properties of the ferrite remained largely unchanged after functionalization. FE-SEM coupled with energy dispersive X-ray spectroscopy (EDS) verified the elemental composition. TEM images showed well-defined spherical crystallites with an average size of 12 nm. Furthermore, the adsorption performance of Fe3O4@D-Tryptophan was evaluated using titan yellow (TY) dye. The material exhibited a high adsorption efficiency of 99.73

This study presents groundbreaking results in the field of rechargeable aluminium-ion batteries, achieving stable capacities exceeding 300 mAh g-1 for more than 300 cycles. The key to this achievement lies in the utilization of tailor-made carbon materials and a urea-AlCl3-based electrolyte. The article investigates the optimal physicochemical properties of the active material necessary for effective electrodes for these aluminium-ion batteries. This investigation employs a wide range of materials characterization techniques (XRD, SEM-EDX, N2 adsorption-desorption isotherms, Hg porosimetry, XPS, FTIR, Raman and TEM-EDX) and electrochemical performance analyses to delve into the subject. These findings represent a significant improvement in the capacity of aluminium-ion batteries, bringing us closer to their implementation and commercialization. This achievement is attributed to the utilization of readily available, cost-effective, and non-corrosive materials. The ability to customize carbon xerogels and the use of the urea-AlCl3 electrolyte offer promising avenues for the practical implementation of these advanced battery technologies, leading to further enhancements in their performance and widespread adoption in various applications. This study reveals ground-breaking advancements in rechargeable aluminium-ion batteries, achieving remarkable stability with capacities surpassing 300 mAh g-1 over 300 cycles. Using tailor-made carbon materials and a urea-AlCl3 electrolyte, the research investigates optimal physicochemical properties, employing various characterization techniques. These findings promise significant progress in commercializing aluminium-ion batteries, driven by cost-effective and customizable materials. image

Magnetometry, neutron diffraction experiments, and high-resolution transmission electron microscopy (HRTEM) were performed to study the magnetic behavior of CuCr2-xSnxS2Se2 (0.2 <= x <= 1.0) solid solutions and experimentally determine the appropriate magnetic structure for these systems. For all samples, the main phase with normal spinel-type structure (Fd (3) over barm) was refined. For low Sn concentration a minority monoclinic phase appears also corroborated with HRTEM analyses. Together with the results from magnetization experiments, neutron diffraction measurements allowed to establish that for samples with x <= 0.4 there is a ferromagnetic long-range order at high temperatures labeled with the 3d irrep m Gamma(+)(4) of Fd (3) over barm.1 ', while for x > 0.4 no magnetic signal is observed, indicating that the ferromagnetic behavior is suppressed and replaced with a spin-glass-like state.

A new series of [Fe3−xLnx]O4 nanoparticles, with Ln = Gd; Dy; Lu and x = 0.05; 0.1; 0.15, was synthesized using the coprecipitation method. Analyses by X-ray diffraction (XRD), Rietveld refinement, and high-resolution transmission electron microscopy (HRTEM) indicate that all phases crystallized in space group Fd3¯m, characteristic of spinels. The XRD patterns, HRTEM, scanning electron microscopy analysis (SEM-EDS), and Raman spectra showed single phases. Transmission electron microscopy (TEM), Rietveld analysis, and Scherrer’s calculations confirm that these materials are nanoparticles with sizes in the range of ~6 nm to ~13 nm. Magnetic measurements reveal that the saturation magnetization (Ms) of the as-prepared ferrites increases with lanthanide chemical substitution (x), while the coercivity (Hc) has low values. The Raman analysis confirms that the compounds are ferrites and the Ms behavior can be explained by the relationship between the areas of the signals. The magnetic measurements indicate superparamagnetic behavior. The blocking temperatures (TB) were estimated from ZFC-FC measurements, and the use of the Néel equation enabled the magnetic anisotropy to be estimated.

Titanium niobium oxides (TNO) are chemically recovered from a mineral composed of cassiterite, columbotantalite, rutile and wollastonite. The process involves a series of steps, including pyrometallurgical processes, leaching, and liquid-liquid extraction. It takes advantage of the naturally occurring Ti in the extracted mineral, avoiding the separation of Ti and Nb to directly obtain the valuable Ti-Nb-O compounds. Two compositions can be obtained (Ti2Nb10O29 2 Nb 10 O 29 or TiNb2O7, 2 O 7 , named TNO-cal and TNO-black, respectively) depending on the thermal treatment after the chemical separation from the original mineral. These compounds have been characterized to describe their composition, morphology and crystallographic properties. The recovered material, without any further purification or functionalization, has been studied as anodes in Lithium-ion batteries (LIBs). Different electrochemical behavior has been observed for voltage ranges of 1-3 V and 0.01-3 V, being the second range which gives best results. In the 1-3V range, TNO-black exhibits a reversible capacity of up to 101.4 mA h g-1 at 1C and maintains 97 % capacity retention after 200 cycles, this is mainly due to Li + insertion/de-insertion processes. Additionally, when expanding the voltage range down to 0.01V, TNO-black displays a specific capacity of approximately 139.1 mA h g- 1 after 200 cycles at 1C, whereas TNO-cal reaches a specific capacity of 169 mA h g- 1 . Extended cycling experiments at a 1C rate for both electrodes reveal that after 200 cycles samples deliver efficiencies relative to the maximum discharge capacity values of 83.4 % (TNO-cal) and 64.4 % (TNOblack), with mean coulombic efficiencies of 97.5 %. These results demonstrate that the recovered materials can effectively function as anodes for LIBs, offering promising application potential, despite the presence of residual silica from the mining process.

This study presents a cost-effective method for producing high-performance cathodes for aluminum-air batteries. Commercial fuel cell cathodes are modified through electrodeposition of nickel and manganese species. The optimal conditions for electrodeposition are determined using a combination of structural (Raman, SEM, TEM) and electrochemical (LSV, EI, discharge curves) characterization techniques. The structural analysis confirms successful incorporation of nickel and manganese species onto the cathode surface. Electrochemical tests demonstrate enhanced electrochemical activity compared to unmodified cathodes. By combining the favorable properties of electrodeposited manganese species with nickel species, a high-performance cathode is obtained. The developed cathode exhibits capacities of 50 mA h cm−2 in aluminum-air batteries across a wide range of current densities. The electrodeposition method proves effective in improving electrochemical performance. A key advantage of this method is its simplicity and cost-effectiveness. The use of commercially available materials and well-established electrodeposition techniques allows for easy scalability and commercialization. This makes it a viable option for large-scale production of high-performance cathodes for the next-generation energy storage devices.

New RbNiFe(PO4)2 phosphate, both in single and powder forms, was synthesized by flux method and solid state reaction. It is characterized by crystal-X-ray diffraction, HRTEM, IR and Raman spectroscopy and UV-diffuse reflectance. Its crystal structure adopts the monoclinic P21/c space group with the cell parameters: a= 5.134 (4) & ANGS;, b= 14.547(2) & ANGS;, c= 9.230(2) & ANGS;; & beta;=103.76(3) degrees and Z= 4. The RbNiFe(PO4)2 framework has a threedimensional structure, consisting of chains of edge-sharing NiO6, isolated FeO5 and PO4 tetrahedra sharing vertices and edge to form large tunnels along the [100] direction, where Rb + cations are placed. The IR and Raman data are in good agreement with the number of PO4 groups determined in crystal structure. Diffuse reflectance spectroscopy leads to a gap energy of 3.15 eV. It also proved the presence of isolated Fe3+ ions from low energy due to the inter-electronic transition from oxygen to Ni (II) and the non-existence of d-d transition related to iron. The colorimetric properties of the compound result mainly from d-d visible transitions related to the Ni2+ cation in octahedral coordination. The magnetic study revealed that below the temperature of TN =21K an antiferromagnetic character appears with a Curie-Weiss constant of Ө =-97 K.

The growing demand of energy needs the search for alternative energy sources different to fossil fuels. The use of biomass as energy source is one of the most studied, because there are high value products that can be produced from biomass. One of these products is gamma-valerolactone, that can be obtained from furfural, which is a biomass derived product. To transform furfural into gamma-valerolactone is necessary a bifunctional catalyst and a hydrogen source. In this work, gamma-valerolactone was obtained from furfural using 2-propanol as solvent and as hydrogen donor on Zr supported on sepiolite catalysts. It was demonstrated that sepiolite, which is a cheap material, can be used to develop efficient catalysts to produce high yields to gamma-valerolactone from furfural in one-pot. The cat-alysts that presented the highest yield to gamma-valerolactone were the ones with intermediate Zr-content (9-17 wt% ZrO2). The highest TOFs have been obtained by those catalysts with Zr-loading up to 9 wt% ZrO2, in which the ZrO2 nanoparticles are well dispersed on the support and no formation of large clusters of ZrO2 has been observed. Lewis and Bronsted acid sites are essential in the catalysts to produce the reactions to transform furfural into gamma-valerolactone in one-pot, although in the present work, low concentration of Bronsted acid sites were observed in the catalysts. A possible positive role of basic sites to promote some intermediate steps has been also proposed. The catalytic results obtained are in the order of catalysts with Zr supported on zeolitic supports.

Herein, we report the synthesis, structural and microstructural characterization, and thermoelectric properties of AgSnm[Sb0.8Bi0.2]Te2+m and Br-doped telluride systems. These compounds were prepared by solid-state reaction at high temperature. Powder X-ray diffraction data reveal that these samples exhibit crystal structures related to the NaCl-type lattice. The microstructures and morphologies are investigated by scanning electron microscopy, energy-dispersive X-ray spectroscopy (EDS), and high-resolution transmission electron microscopy (HRTEM). Positive values of the Seebeck coefficient (S) indicate that the transport properties are dominated by holes. The S of undoped AgSnm[Sb0.8Bi0.2]Te2+m ranges from +40 to 57 μV·K−1. Br-doped samples with m = 2 show S values of +74 μV·K−1 at RT, and the Seebeck coefficient increases almost linearly with increasing temperature. The total thermal conductivity (κtot) monotonically increases with increasing temperature (10–300 K). The κtot values of undoped AgSnm[Sb0.8Bi0.2]Te2+m are ~1.8 W m−1 K−1 (m = 4) and ~1.0 W m−1 K−1 (m = 2) at 300 K. The electrical conductivity (σ) decreases almost linearly with increasing temperature, indicating metal-like behavior. The ZT value increases as a function of temperature. A maximum ZT value of ~0.07 is achieved at room temperature for the Br-doped phase with m = 4.

Bionanotechnology is a promising field for the preparation of nano-sized substances in an environmentally safe manner. This study presents the facile preparation of zinc oxide nanoparticles (ZnO-NPs) from prickly pear peels extract by a green chemistry method. Rietveld structural refinement of the X-ray diffraction (XRD) pattern approved the creation of the hexagonal wurtzite structure of ZnO-NPs. The prepared nanoparticles were also identified by X-ray photoelectron spectroscopy (XPS) analysis to check up the chemical states and purity. The peak of optical absorption of the nanoparticle has been observed at 370 nm. The band gap energy of ZnO-NPs is 3.2 eV. The morphology of the nanoparticles is spherical with a particle size of around 10–30 nm and the interplanar lattice spacing is 0.29 nm. ZnO-NPs were found to be a potential candidate for the photodegradation of Methylene Blue (MB, one of the organic dyes) leading to 85

A set of multiphase manganese‐oxide composite materials (Mn2O3@Mn3O4 and Mn3O4@Mn5O8), and a birnessite‐type KxMnO2 oxide are prepared and evaluated as cathodes for Zn‐ion batteries. The species formed when the electrodes are subjected to 2 V in aqueous solutions of MnSO4 and ZnSO4 are analyzed, suggesting an interphase activation leading to enhancement of electrochemical response. For the first time, it is shown that a Zn4(SO4)(OH)6.xH2O phase coats the composite‐type electrodes in the charging stage, contributing to extending the lifetime of the batteries. KxMnO2 electrode with layered birnessite structure shows long cycling life at low current densities (122 mAh g−1 at 30 mA g−1 after 50 cycles) and good efficiencies (ca. 99%) in the 0.1 Mn2+ electrolyte. In contrast, in the 0.5 m Mn2+ electrolyte, high values of specific capacity are delivered by the cell at higher rates, that is, 150 mAh g−1 at 600 mA g−1. In Mn5O8@Mn3O4 the good performance is due to the synergistic effect of the two compounds forming the composite. Thus, after more than 100 cycles this composite displays specific capacity values of 175 mAh g−1 at 2150 mA g−1 in the 0.1 m Mn2+/1 m Zn2+ electrolyte.

Electrochemical activity of different MnO2 phases as electrodes of aluminium-ion batteries (AIBs) is studied. For this purpose, different simple synthesis routes have been carried out to obtain different structures and morphologies: rod-like with tunnelled structure (α-MnO2) and hexagonal micro-pellets with lamellar structure (δ-MnO2). α-MnO2 showed an outstanding capacity (Q) of 120 mA h g−1 at current densities of 100 mA g−1, which remained stable after 100 cycles with efficiencies over 90%. δ-MnO2 showed a good Q of 80 mA h g−1 at current densities of 50 mA g−1 after 50 cycles with efficiencies over 95%. Moreover, cyclic voltammetry (CV) measurements at different rates allowed for a better understanding of the electrochemical behaviour and revealed the contribution relation of diffusive and capacitive-controlled mechanisms in the corresponding AIB system. Besides, cyclic voltammetry (CV) measurements at different rates allowed a kinetic study of the diffusive and capacitive-controlled mechanisms. Conclusions were obtained regarding the dimensionality of α-MnO2 (1D) and δ-MnO2 (2D) and their electrochemical behaviour in AIBs−1