Search Results (426)

Nowadays, nanosized mesoporous oxides are of increasing interest to scientists. They can be used as components of heterogeneous catalysts, for photo- and electrocatalysis, as gas sensors, etc. For instance, the desired properties in catalysts include a nano size and homogeneity of the particles that form the catalyst. The particle sizes of oxides are set at the initial stage of their formation, as precursors of precipitation in the context of wet chemistry. The creation of optimal conditions is possible through the use of homogeneous precipitation, where the precipitant is formed within the solution itself as a result of a hydrolysis reaction. The resolution of this issue involved the utilization of urea in our experimental setup, obtaining the hydrolysis products of ammonia and carbon dioxide. Consequently, precipitation reactions can be utilized to obtain hydroxides, carbonates, or hydroxy carbonates of metals. The precursors were calcined, obtaining nanosized mesoporous oxides, which can have a wide range of applications. Nanosized 0.1–50 nm metal oxides were obtained, including those aluminum, iron, indium, zinc, nickel, and cobalt. Full article

Copper-doped indium zinc sulfides were synthesized by heating and stirring a mixture of zinc chloride, indium chloride tetrahydrate, thioacetamide, and copper chloride at 180 °C for 18 h. Among these, Zn_5.7Cu_0.3In₂S₉ exhibited a hydrogen-producing activity of 1660 μmol/g·h, which was approximately five times higher than that of pristine indium zinc sulfide. Therefore, the catalyst was characterized to investigate the effect of Cu addition. PL results revealed that the incorporation of Cu reduced the fluorescence intensity, indicating suppressed recombination of photogenerated electron–hole pairs. DRS showed that the Cu addition enhanced optical absorption in the visible-light region and narrowed the band gap. These findings suggest that the incorporation of copper into indium zinc sulfide improves its photocatalytic activity. Full article

The increasing consumption of edible oils has resulted in a parallel rise in waste cooking oil (WCO), a harmful waste stream but one that also represents a promising raw material. In this study, oil-based binders were synthesised from WCO using various reagents: Sulfuric(VI) acid, hydrobromic acid, acetic acid, salicylic acid, glycolic acid, zinc acetate, ethanol, hydrogen peroxide, and their selected mixtures. The manufacturing process was optimised, and the composites were evaluated for physicochemical and mechanical properties, including compressive strength, bending strength, and water absorption. The best performance was observed for composites catalysed with a mixture of sulfuric(VI) acid and 20% hydrogen peroxide, cured at 240 °C, yielding compressive and bending strengths of 5.20 MPa and 1.34 MPa, respectively. Under modified curing conditions, a compressive strength of 5.70 MPa and a bending strength of 0.75 MPa were obtained. The composite modified with glycolic acid showed the lowest water absorption (3%). These findings demonstrate how catalyst type and curing parameters influence composite structure, porosity, and mechanical behaviour. The study provides new insights into the process–structure–property relationships in oil-based materials and supports the development of environmentally friendly composites from waste feedstocks. Full article

Zinc–air batteries (ZABs) are crucial for renewable energy conversion and storage due to their cost-effectiveness, excellent safety, and superior cycling stability. However, developing efficient and affordable bifunctional electrocatalysts for the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) at the air cathode remains a significant challenge. Manganese (Mn)-based materials, known for their tunable oxidation states, adaptable crystal structures, and environmental friendliness, are regarded as the most promising candidates. This review systematically summarizes recent advances in Mn-based bifunctional catalysts, concentrating on four primary categories: Mn–N–C electrocatalysts, manganese oxides, manganates, and other Mn-based compounds. By examining the intrinsic merits and limitations of each category, we provide a comprehensive discussion of optimization strategies, which include morphological modulation, structural engineering, carbon hybridization, heterointerface construction, heteroatom doping, and defect engineering, aimed at enhancing catalytic performance. Additionally, we critically address existing challenges and propose future research directions for Mn-based materials in rechargeable ZABs, offering theoretical insights and design principles to advance the development of next-generation energy storage systems. Full article

The disposal of wastewater resulting from petroleum industries presents a major environmental challenge due to the presence of hard-to-degrade organic pollutants, such as oils and hydrocarbons, and high chemical oxygen demand (COD). In this study, an efficient and eco-friendly method was developed to treat such wastewater using a photocatalyst composed of biochar derived from pistachio shells and loaded with zinc oxide (ZnO) nanoparticles. The biochar-ZnO composite was prepared via a co-precipitation-assisted pyrolysis method to evaluate its efficiency in the photocatalytic degradation of petroleum wastewater (PW). The synthesized material was characterized using various techniques, including scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier transform infrared (FTIR) spectroscopy, to determine surface morphology, crystal structure, and functional groups present on the catalyst surface. Photocatalytic degradation experiments were conducted under UV and sunlight for 90 h of irradiation to evaluate the performance of the proposed system in removing oil and reducing COD levels. Key operational parameters, such as pH (2–10), catalyst dosage (0–0.1) g/50 mL, and oil and COD concentrations (50–500) ppm and (125–1252) ppm, were optimized by response surface methodology (RSM) to obtain the maximum oil and COD removal efficiency. The oil and COD were removed from PW (90.20% and 88.80%) at 0.1 g/50 mL of PS/ZnO, a pH of 2, and 50 ppm oil concentration (125 ppm of COD concentration) under UV light. The results show that pollutant removal is slightly better when using sunlight (80.00% oil removal, 78.28% COD removal) than when using four lamps of UV light (77.50% oil removal, 75.52% COD removal) at 0.055 g/50 mL of PS/ZnO, a pH of 6.8, and 100 ppm of oil concentration (290 ppm of COD concentration). The degradation rates of the PS/ZnO supported a pseudo-first-order kinetic model with R² values of 0.9960 and 0.9922 for oil and COD. This work indicates the potential use of agricultural waste, such as pistachio shells, as a sustainable source for producing effective catalysts for industrial wastewater treatment, opening broad prospects in the field of green and nanotechnology-based environmental solutions in the development of eco-friendly and effective wastewater treatment technologies under solar light. Full article

A novel metal–organic framework based on zinc ions, designated as Zn-URJC-12, has been synthesized and applied for the first time in the cycloaddition reaction between carbon dioxide and epoxides. This MOF is constructed from two different organic linkers: 5-aminoisophthalic acid and 4,4′-biphenyldicarboxylic acid. The framework features –NH₂ functional groups coordinated to Zn(II) centers, as confirmed by single-crystal X-ray diffraction analysis. Zn-URJC-12 demonstrates exceptional chemical stability in polar organic solvents, such as methanol, while maintaining thermal stability up to 250 °C. The material exhibits high catalytic efficiency in the cycloaddition of CO₂ with epoxides, achieving yields of 100% and 76% for propylene oxide and allyl glycidyl ether, respectively. Additionally, Zn-URJC-12 maintains its structural integrity and catalytic performance during five successive reaction cycles. These findings underscore Zn-URJC-12 as a promising heterogeneous catalyst for the valorization of CO₂ into cyclic carbonates. Full article

Microplastics have emerged as pervasive contaminants in various ecosystems, raising considerable concerns regarding their impact on environmental health and public safety. The degradation of microplastics is thus recognized as a pressing global challenge. Photocatalytic degradation has emerged as a promising approach due to its potential for efficiency and environmental sustainability. Nevertheless, there remains a need to investigate emerging trends and advancements to understand and fully optimize this technique. Consequently, PRISMA guidelines were employed to define the search parameters, enable the identification of pertinent scholarly articles, and systematically gather bibliographic data from the published literature from 2005 to October 2024. A bibliometric analysis of 204 research articles derived from merged Scopus and Web of Science datasets was conducted to map the field’s research landscape. The analysis showed a robust annual publication growth rate of 17.94%, with leading contributions from China, India, Mexico, and the United Kingdom. Keyword analysis revealed that the commonly applied photocatalysts are titanium dioxide and zinc oxide in the photocatalytic degradation of polyethylene terephthalate, polypropylene, polystyrene, polyvinyl chloride, high-density polyethylene, and low-density polyethylene. Advances in collaboration across Asia and Europe have bolstered the research landscape. However, challenges persist in achieving cost-effective scalability, ensuring the safety of degradation byproducts, and translating laboratory findings into real-world applications. Emerging trends include the development of visible-light-responsive catalysts, advanced nanocomposites, and sustainable photocatalytic technologies. This study underscores the utility of bibliometric tools in identifying knowledge gaps and guiding the development of innovative approaches for microplastic degradation as part of environmental remediation efforts. Full article

Efficient electrocatalysts for the oxygen reduction reaction (ORR) are essential for numerous energy storage and conversion systems, including zinc–air batteries and fuel cells. Cutting-edge Pt/C catalysts remain the most efficient ORR catalysts to date; however, their high cost and inadequate stability impede their use in commercial devices. Recently, transition metal-based electrocatalysts are being pursued as ideal alternatives for cost-effective and efficient materials with a promising future. This review provides an in-depth analysis of the principles, synthesis, and electrocatalytic assessment of noble metal and transition metal-based catalysts derived from diverse gel precursors, including hydrogels, aerogels, xerogels, metal–organic gels, and metal aerogels. Electrocatalysts derived from gel precursors have garnered significant interest due to their superior physicochemical properties, including an exceptionally high surface area, adjustable porosity, adaptability, and scalability. Catalysts obtained from gel precursors offer numerous advantages over conventional catalyst synthesis methods, including the complete utilization of precursors, precise control over surface area and porosity, and uniform distribution of ORR active sites. Among the various types, metal aerogels are distinguished as the superior catalysts, exceeding the Department of Energy’s (DoE) 2025 targets for the mass and specific activities of ORR catalysts. In contrast, hydrogel- and aerogel-derived catalysts excel in terms of ORR activity, specific surface area, and the potential to incorporate high loadings of single-atom catalysts composed of transition metals. Ultimately, we unequivocally categorized the electrocatalysts into high-, moderate-, and low-performance tiers, identifying the most promising catalyst candidate within each gel classification. Concluding insights, future outlooks, and recommendations were provided for the advancement of cost-effective, scalable electrocatalysts derived from gels for fuel cells and zinc–air batteries. Full article

Zinc oxide (ZnO) photocatalysts are recognized for their ease of synthesis, cost-effectiveness, efficiency, scalability, and environmental compatibility, making them highly suitable for addressing wastewater contamination. In this study, various compositions of kaolinite were used for the hydrothermal deposition of ZnO, including 0.5%, 0.75%, 1%, and 1.25%. The main purpose of this study was to evaluate the effect of kaolinite toward the enhanced performance of ZnO through modification of particle size, morphology and surface functional groups. Several analytical techniques were employed to obtain structural and optical results, including scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and UV–visible spectroscopy, revealing significant changes in particle shape, particle size, surface functional groups, and optical band gap when kaolinite was added. The ZnO/kaolinite composite (sample 4) with 1.25% kaolinite content demonstrated outstanding photocatalytic performance for the degradation of methylene blue in natural sunlight. For sample 4, 15 mg of the dye in a 3.4 × 10⁻⁵ M dye solution exhibited a degradation efficiency of 99%. In contrast, when using 15 mg of catalyst dose and 1.5 × 10⁻⁵ M dye solution, the degradation efficiency was observed to be almost 100%, thus indicating that catalyst dose and dye concentration affect degradation efficiency. The reusability test revealed that sample 4 retained degradation efficiency of 98% after five cycles without showing any morphological changes. By decorating ZnO with kaolinite mineral clay, this study provides exciting findings and insights into the development of low-cost photocatalysts, which could be used to produce solar-powered hydrogen and treat wastewater. Full article

In this work, the effect of the palladium precursor on the Oxygen Reduction Reaction (ORR) performance of lignin-based electrospun carbon fibers was studied. The fibers were spun from a lignin-ethanol solution free of any binder, where different Pd salts were added at two concentration levels. The system implemented to perform the spinning was a coaxial setup in which the internal flow contains the precursor dispersion with the metallic precursor, and ethanol was used as external flow to help fiber formation and prevent drying before generating the Taylor cone. The obtained cloths were thermostabilized in air at 200 °C and carbonized in nitrogen at 900 °C. The resulting carbon fibers were characterized by physicochemical and electrochemical techniques. The palladium precursor significantly affects nanoparticle distribution and size, fiber diameter, pore distribution, surface area and electrochemical behavior. The fibers prepared with palladium acetylacetonate at high Pd loading and carbonized at 900 °C under a CO₂ atmosphere showed high mechanical stability and the best ORR activity, showing near total selectivity towards the 4-electron path. These features are comparable to those of the commercial Pt/C catalyst but much lower metal loading (10.6 wt.% vs. 20 wt.%). The most promising fibers have been evaluated as cathodes in a zinc–air battery, delivering astonishing stability results that surpassed the performance of commercial Pt/C materials in both charging and discharging processes. Full article

Recent advances in zinc complexes for stereoselective ring-opening polymerization (ROP) and copolymerization (ROCOP) highlight their pivotal role in synthesizing biodegradable aliphatic polyesters and polycarbonates. These materials address the urgent demand for sustainable alternatives to petroleum-based plastics, with stereochemical control directly impacting polymer crystallinity, thermal stability, and degradability. Zinc catalysts, leveraging low toxicity and versatile coordination chemistry, enable precise stereoregulation, whose performance is modulated by ligand steric/electronic effects, coordination geometry, and reaction conditions. This review summarizes the recent developments in zinc complexes for stereoselective ROP and ROCOP, focusing on ligand design strategies to enhance catalytic performance. Full article

Bacterially produced poly[(R)-3-hydroxybutyrate] (P3HB) was subjected to an alcoholysis reaction to produce low-molecular-weight (M_n ≈ 10,000 g mol⁻¹) hydroxy-terminated P3HB (LMPHB). Using diethyl zinc as a catalyst, LMPHB was reacted with the cyclic monomers ε-caprolactone and l-lactide in separate ring-opening polymerization (ROP) reactions to produce PHB-b-PCL (PHBCL) and PHB-b-PLA (PHBLA) AB-type crystalline–crystalline diblock copolymers with varying PCL and PLA block lengths. ¹H NMR and GPC were used to confirm the structure of the polymers. DSC was used to measure the thermal properties as well as assessing crystallization. A single-shifting T_g for PHBLA showed the two blocks to be miscible in the melt. The TGA results indicate enhanced thermal stability over the homopolymer P3HB. A study of the crystallization was undertaken by combining WAXD, a second DSC heating regime, and POM. POM showed that the crystallization in PHBCL to be dependent on the crystallization temperature more so than PHBLA, whose composition appeared to be the more definitive factor determining the spherulitic morphology. The results informed the crystallization temperatures used in the production of the melt-crystallized thin films that were imaged using AFM. AFM images showed unique surface morphologies dependent on the diblock copolymer composition, block length, and crystallization temperature. Finally, the enzymatic degradation studies showed these unique surface morphologies to influence how these block copolymers were degraded by enzymes. Full article

This study systematically investigates the effect of surface aluminizing treatment on the microstructure of Fe-20Cr-5B-3Al alloy and its corrosion behavior in liquid zinc. Aluminizing treatment was performed using the powder pack method with NH₄Cl (5 wt.%) as a catalyst. Aluminide layers were prepared on the surface of the Fe-20Cr-5B-3Al alloy, and the microstructure of the aluminide layer was observed and analyzed. The corrosion performance of the alloy in liquid zinc was compared before and after aluminizing treatment in a 128 h corrosion test. The results show that after aluminizing treatment, the α-Fe phase on the alloy surface transforms into the Fe₂Al₅ phase, while the original Fe₂B phase breaks into finer structures that disperse over the Fe₂Al₅ phase. The Cr₂B phase is not affected and maintains its structural integrity. After 128 h of exposure to liquid zinc, although the alloy exhibited good corrosion resistance in liquid zinc, the α-Fe phase was still preferentially corroded, with zinc liquid infiltrating along the α-Fe phase toward the interior. In contrast, after aluminizing treatment, the transformation of α-Fe into Fe₂Al₅, which has excellent corrosion resistance, significantly reduces the corrosion rate and enhances the alloy’s resistance to liquid zinc corrosion. Full article

Nanocomposite hydroxypropyl-beta-cyclodextrin functionalized reduced graphene oxide sheets (HpβCD@rGOs) with zinc oxide flaky structures (ZnOFs) were synthesized. The ZnOFs/HpβCD@rGOs were first characterized to examine their physicochemical characteristics. The ZnOFs exhibited a highly crystalline structure intertwined with HpβCD@rGO sheets. The electrocatalyst experienced excellent electrochemical oxidation current responses toward melatonin (MTN). The interaction between the catalyst and MTN improves electrochemical activity through a synergistic action, which can be measured by a glassy carbon electrode (GCE) modified with ZnOFs/HpβCD@rGOs. This modified electrode with the increased reactive sites and a large electrochemically active surface area allows the rapid oxidation reaction of MTN. The oxidation of MTN was detected and measured with a linearity range around 0.014–0.149 and 1.149–643.341 (µM), with a low detection limit (LOD) of around 0.0105 µM or 10.5 nM. The sensitivity was around 6.19 μA μM⁻¹ cm⁻². The constructed electrode demonstrated a notable level of selectivity to MTN when the interfering (biological) chemicals with a similar structure to MTN were introduced. The real samples were tested in order to examine whether the ZnOFs/HpβCD@rGOs/GCE can be developed for the biomedical monitoring of compounds. The results suggest that ZnOFs/HpβCD@rGOs/GCE can detect MTN in in vitro human samples. Furthermore, the cost-effectiveness, enhanced electrochemical capabilities, and easy fabrication of the electrode make the ZnOFs/HpβCD@rGOs composite a feasible solution for the future industrial development of monitoring tools as sensors. Full article

In the natural environment, mechanical energy is widely available as a sustainable and green energy source. In this paper, we successfully convert mechanical energy on ZnO and ZnO/Eu₂O₃ tribocatalysts via a friction route. Electrons were transferred across the contact interface when the catalyst particles and the polytetrafluoroethylene (PTFE)-sealed magnetic bar rubbed against each other under magnetic stirring. At the same time, holes were left on the catalyst while the PTFE absorbed the electrons. Similar to photocatalysis, organic pollutants can be effectively oxidized by the holes in the valence band of sol-gel catalysts due to their strong oxidative ability. The tribocatalytic tests demonstrated that ZnO and ZnO/Eu₂O₃ could eliminate organic analgesics (paracetamol) under magnetic stirring in the dark. By controlling the quantity of rare earth elements (1, 2, and 3 mol%), stirring speed, and the number of magnetic rods, we could further enhance the tribocatalytic performance. In addition to developing a green tribocatalysis approach for the oxidative purification of organic pollutants, this work offers a potential route for converting environmental mechanical energy into chemical energy, which could be used in sustainable energy and environmental remediation. Full article