Dr. Valdés-Morales, Héctor

This study reports the synthesis of erbium (Er)-doped bismuth ferrite (BiFeO3/BFO) nanoparticles at varying molar concentrations (5, 10, and 15 %) using a sol-gel method. X-ray diffraction (XRD) analysis reveals a structural transformation from rhombohedral to orthorhombic upon Er3+ doping, confirming the successful incorporation of Er3+ ions into the BFO lattice. High-resolution transmission electron microscopy (HRTEM) images show that Er-doping leads to a reduction in particle size and a modification of the surface morphology. The bandgap of the Er-doped BFO samples decreases from 2.34 to 2.15 eV with increasing Er content, attributed to the formation of new Er 4f energy levels within the band structure. The magnetic properties of the samples also improve with increasing Er concentration. Photoluminescence (PL) spectra show reduced PL intensity for the 10 % Er-doped BFO sample, indicating a decrease in recombination rates, while electrochemical impedance spectroscopy (EIS) reveals a reduction in charge transfer resistance. Among the samples, the 10 % Er-doped BFO photocatalyst exhibits the highest photocatalytic efficiency. This enhanced activity is attributed to two key factors: efficient separation and migration of photogenerated charge carriers, and a reduced recombination rate of electron-hole pairs, both driven by the rare-earth doping in BFO. Radical trapping experiments further identify hydroxyl (OH•) radicals as the primary species responsible for photocatalytic degradation. This study provides valuable insights into the tunability of BFO's bandgap energy and photocatalytic properties through Er doping.

Background: The main goal of this work is to demonstrate the improvement of visible light absorption for water pollution applications while simultaneously ensuring efficient disintegration of the industrial crystal violet dye (CV) through photocatalytic degradation. This strategy aims to minimize the impact on the local ecosystem. Methods: This study utilized a simple solvent-free and novel solid-state mixing technique to synthesize α-Bi2O3 with surfactant-containing urea (U) and citric acid (CA) at 600 ◦C. The physicochemical properties were utilized to investigate morphological, structural, textural properties, optical, and photostability, the long lifespan of photogenerated charge carriers of hole-electron pairs, and the visible light energy that caused them to disintegrate. Findings: Significantly, the surfactant based on urea was successful in maturing a nanoflower-like α-Bi2O3 (U) with extremely high stability and a versatile application of photocatalysis crystal violet degradation at 83.9% within 60 min. The α-Bi2O3 (U) shows good long-term stability with a 94.8(%) relative standard deviation after the fifth cycle, and the mechanistic analyses were evaluated by trapping experiments. Furthermore, this work provides a strategy to design low-cost and high-efficiency novel methods for sustainable photocatalysts and further investigates environmental applications.

The catalytic efficiency of the materials can be boosted with the selective designing (nanostructures) including the core@shell which aids in attaining the separation of photoinduced charge carriers. However, to effectively separate the carriers and reduce the rate of recombination, tuning the thickness of the shell wall is a vital one. The one-dimensional (1D) rod-like shell wall-controlled ZnO@CeO2 core@shell structures were successfully prepared via co-precipitation and hydrothermal methods using the hexamethylenetetramine (HMTA) as a reagent. The CeO2 shell wall thickness was fine-tuned between 15 and 70 nm with a variation in the concentration of HMTA reagent. The results revealed that the concentration of HMTA played a significant role in the formation of ZnO@CeO2 core@shell structures and in tuning their thickness. The FE-SEM images evidenced the core-shell structures formation with the specific thickness and uniformity. The HR-TEM images confirmed the homogeneity and regular form of the shell thickness. The unit cell and crystallite size were identified from the XRD analysis. The constructed core-shell structures were further employed in the formula of the prototypes of sunscreen and their photoprotective performance was analyzed in the view to cut the solar light irradiation in a new sunscreen formulation. The developed core-shell ZnO@CeO2 structures showed the excellent optical absorption in both the UV as well as visible regions.

Designing low-cost, effective and greener materials via a non-sophisticated strategy is most important for future research. Here, they made a new dual endeavor using carbon dots (CDs) as an environment protection probe for selective detection of environmental toxins, followed by the solid-state structural reformer to prepare NiMoO4 (NM) via mechanochemical-based solid grinding method. The prepared CDs, NM and NM-CDs combination is examined through various techniques. The prepared CDs selectively detect Cr6+, Ru3+, and Doxycycline independently. Also, in this work, a groundbreaking strategy is found to prepare morphology-tailored NM using CDs through a solid-state grinding method without adding any other toxic solvents or reagents. The CDs-induced NM-CDs (15) look like a 2D nano-sheet with enriched surface area compared to its bare NM. The fabricated electrode provides the highest capacitance value of 1947 F g−1, almost three times grander than the bare 1D rod-like electrode. Then, fabricated asymmetric supercapacitor NM-CDs (15)//AC system delivers a high energy density of 43.9 Wh Kg−1 at a power density of 684 W Kg−1. Overall, a single CDs serve multiple roles in the environment and energy applications with a greener structure tailoring agent and a better booster for re energy storage properties.

Micrometer-sized polycrystalline anatase particles are widely used in materials and life sciences, serving as essential components in photocatalytic materials. The ability to tailor their composition, shape, morphology, and functionality holds significant importance. In this study, we identified and examined the non-destructive route of Copper(II) implantation at the surface of polycrystalline TiO2. The [Cu(en)(Im)2]2+ complex ion demonstrated a remarkable affinity to concentrate and bind with the semiconductor’s surface, such as anatase, forming a surface-bound adduct: ≡TiO2 + [Cu(en)(Im)2]2+ → ≡TiO2//[Cu(en)(Im)2]2+. The misalignment of Fermi levels in TiO2//[Cu(en)(Im)2]2+ triggered electron transfer, leading to the reduction of the metal center, releasing Copper(I) in the process. Although less efficient, the released Copper(I) encountered a highly favorable environment, resulting in the formation of the surface complex TiO2:CuIIsc. The implanted Cu(I) was converted back into Cu(II) due to re-oxidation by dissolved oxygen. The penetration of the metal ion into the surface level of the polycrystalline TiO2 lattice was influenced by surface residual forces, making surface grafting of the Cu(II) ion inevitable due to surface chemistry. FTIR, UV–vis, Raman, XRD, EPR, and surface morphological (SEM, EDAX, and HRTEM) analyses identified the typical surface grafting of the Cu(II) cluster complex on the anatase surface matrix. Moreover, the XRD results also showed the formation of an impure phase. The TiO2 polycrystalline materials, modified by the incorporation of copper complexes, demonstrated an enhanced visible-light photocatalytic capability in the degradation of Rhodamine B dye in aqueous solutions. This modification significantly improved the efficiency of the photocatalytic process, expanding the applicability of TiO2 to visible light wavelengths. These studies open up the possibility of using copper complexes grafted on metal oxide surfaces for visible-light active photocatalytic applications. Moreover, this investigation not only showcases the improved visible-light photocatalytic behavior of copper-modified TiO2 polycrystalline materials, but also underscores the broader implications of this improvement in the advancement of sustainable and efficient water treatment technologies.

The study investigates the influence of praseodymium (Pr) doping on bismuth ferrite (BiFeO3/BFO) nanofibers and their structural, morphological, magnetic, optical, and photocatalytic properties. A series of bismuth ferrite nanofibers with varying concentration of Pr (Bi1-xPrxFeO3, x = 0.00, 0.05, 0.10, and 0.15 mol%) were successfully synthesized using an electrospinning technique. XRD patterns revealed that structural transformation occurred from rhombohedral to orthorhombic upon effective doping of Pr3+ into BFO nanofibers. The X-ray photoelectron spectroscopy analysis confirmed that Bi, Fe, and O maintained their native oxidation states of +3 and -2, respectively in the bare and doped systems. Furthermore, the optical band gap value was significantly reduced from 2.35 to 2.22 eV as well as the recombination rates of charge carriers in the doped systems, especially in BP0.15O system. The photocatalytic performance of the prepared samples was studied by measuring the decomposition of rhodamine B (RhB) under sunlight irradiation. Outcomes showed that the doped-BFO nanofibers exhibited enhanced photocatalytic performance compared to pure BFO, with the BP0.15O system showing the 98 % degradation in 60 min. This enhancement could be attributed to the presence of Pr-energy levels, which facilitating enhanced separation, and charge transfer to the surface for the effective redox reactions.

In this study, perovskite-structured lanthanum cobalt oxide(LaCoO3/LCO) systems with particle and flake morphologies were developed using sol−gel and hydrothermal methods, respectively, in order to investigate their morphological structure-dependent properties for potential supercapacitor applications. The structural analysis confirms that both methods yield LaCoO3with improved crystalline properties. The energy storage performance of the developed materials is studied in a three-electrode configuration using a 1 MKOH electrolyte. The results indicated superior electrochemical performance for the LCO nanoflakes, exhibiting specific capacitances of ∼215 F g−1 at a scan rate of 5 mV s−1 and ∼136 F g−1 at a current density of 1 A g−1. In comparison, the LCO nanoparticles showed ∼119 F g−1 at a scan rate of 5 mV s−1 and ∼99F g−1 at a current density of 1 A g−1. This difference can be largely attributed to their respective morphologies, porous structures, and surface defects. Further, the nanoflakes demonstrated an exceptional capacitance retention of ∼97% even after 5000 charge−discharge cycles. The findings of this study suggest that the properties of perovskite LaCoO3 can be tuned by adjusting its morphology through various synthesis methods, making LaCoO3 a viable and robust system for energy storage applications.

Hydrogen energy possesses immense potential in developing a green renewable energy system. However, a significant problem still exists in improving the photocatalytic H2 production activity of metal-free graphitic carbon nitride (g-C3N4) based photocatalysts. Here is a novel Cu3P/CdS/g-C3N4 ternary nanocomposite for increasing photocatalytic H2 evolution activity. In this study, systematic characterizations have been carried out using techniques like X-ray diffraction (XRD), scanning electron microscopy (SEM), high resolution transmission electron microscopy (HR-TEM), Raman spectra, UV–Vis diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy (XPS), surface area analysis (BET), electrochemical impedance (EIS), and transient photocurrent response measurements. Surprisingly, the improved 3CP/Cd-6.25CN photocatalyst displays a high H2 evolution rate of 125721 μmol h− 1 g− 1. The value obtained exceeds pristine g-C3N4 and Cu3P/CdS by 339.8 and 7.6 times, respectively. This could be the maximum rate of hydrogen generation for a g–C3N4–based ternary nanocomposite ever seen when exposed to whole solar spectrum and visible light (λ > 420 nm). This research provides fresh perspectives on the rational manufacture of metal-free g-C3N4 based photocatalysts that will increase the conversion of solar energy. By reusing the used 3CP/Cd/g-C3N4 photocatalyst in five consecutive runs, the stability of the catalyst was investigated, and their individual activity in the H2 production activity was assessed. To comprehend the reaction mechanisms and emphasise the value of synergy between the three components, several comparison systems are built.

There is an enormous demand for energy storage applications with a high specific capacity, superior energy and power density, and long-life cycles because of the increase in portable electronic appliances. The use of ternary metal oxide electrode materials for energy storage applications in supercapacitors based on multi-redox sites has gained more attention from researchers due to their outstanding specific capacitance and numerous redox sites. Copper cobalt ferrites (CuCoFe2O4) nanoparticles (NPs) have been synthesised by the simple microwave combustion method and employed as a positive electrode material for energy storage in supercapacitors (SCs). To study the physical and electrochemical properties of the prepared nanoparticles by XRD, FTIR, SEM-EDX, HR-TEM, and electrochemical analysis have been carried out. X-ray diffraction planes indicating the cubic spinel structure with a space group of Fd-3m and the crystalline phase purity of the synthesised CuCoFe2O4 NPs were also characterized by Rietveld refinement. HR-TEM analysis of the existing agglomeration of particles and SAED pattern shows the excellent crystalline nature of the materials. The CuCoFe2O4 electrode obtained an outstanding specific capacitance of 237.5 F g−1 at 0.5 A g−1 current density in a 3 M KOH electrolyte in a standard three-electrode system. Further fabricated of a solid-state asymmetric supercapacitor (ASC) device by using CuCoFe2O4 NPs and activated carbon (AC) as the positive and negative electrodes, respectively. This ASC device offers a superior energy density value of 16 Wh kg−1 and a power density of 8048 W kg−1. In addition, the ASCs device exhibits cycle stability of 82 % after 10,000 GCD charge and discharge cycles at a current density of 40 A g−1, displaying its high cycling stability.

For renewable energy, it is crucial to create effective photocatalysts with enhanced photo charge separation and transfer to produce photocatalytic hydrogen (H2) efficiently utilizing light energy. Due to their distinct qualities and features, carbonaceous materials have so far been shown to be high-performance co-catalysts to substitute some conventionally costly metal materials in photocatalytic water splitting. Here, a novel ternary nanocomposite, simple hydrothermal process ball milling assisted and wet impregnation approach, a promising ternary nanocomposite is created as an efficient solar light driven photocatalyst. Utilizing a variety of analytical techniques, 3 % Cu3P/ZnS/g-C3N4 nanocomposites as catalysts were characterized in order to check the hydrogen production and investigate their structural properties. The hydrogen production capability of the catalyst is studied by irradiating Na2SO3 + Na2S solutes using a halogen bulb (250 W). The results demonstrated that in terms of photocatalytic activity towards H2 production, 3 % Cu3P/ZnS/g-C3N4 catalyst performed better than 3 % Cu3P/ZnS, Cu3P, ZnS, and g-C3N4. A composite containing 7.5 wt% g-C3N4 demonstrated exceptional durability during photocatalytic hydrogen production, resulting in a 23,086 mol h− 1 g− 1 rate. Higher stability in electron-hole pairs created a higher absorption level of solar light could be responsible for this remarkable performance.