Search Results (2,478)

The extensive application of synthetic dyes in various industries and potential accidental uncontrolled discharge into natural water bodies have led to significant environmental challenges and a need for effective treatment. In this study, UiO-66 metal–organic framework/activated carbon (MOF/AC) composites were used to evaluate the photocatalytic degradation of Congo Red dye (CR) in aqueous solution under natural solar irradiation. The degradation efficiency of CR was determined using UV-Vis spectroscopy, while material characterization and additional insight into the reaction mechanism were obtained by XRD, FTIR, and Raman analysis. For a 50 ppm CR solution, within a 2 h reaction time, pure MOF achieved 57.2% and 26.3% degradation under solar irradiation and dark conditions, respectively, while the 75/25 MOF/AC composite reached 74% and 38.3% under the same conditions. These results confirm the synergistic interaction between MOF and AC, where AC acts as an electron sink, preventing charge recombination and enhancing photocatalytic activity. Chemisorption occurred simultaneously with photocatalytic degradation on the MOF surface. Reusability tests showed that pure MOF retained the highest stability over repeated cycles. Overall, the combination of MOF and AC enhances catalytic performance, which represents a sustainable approach for treating dye-contaminated wastewater under natural solar conditions. Full article

The quest for enhanced energy efficiency is inextricably linked to advancements in energy storage and conversion, with porous metallic glasses (MGs) serving as catalysts that hold significant potential in this area. In this study, we report the preparation of uniform porous structures by aging-assisted ultrasonic vibration (AAUV). The results indicate that ultrasonic treatment effectively enhances the energy state while preserving the amorphous structure of Zr₆₂Cu_15.5Ni_12.5Al₁₀ MGs. The results demonstrate that UV treatment effectively elevates the energy state while maintaining the amorphous structure. Electrochemical tests reveal significantly improved chemical activity after UV treatment, with a reduced corrosion potential and over 200-fold increase in electrochemical surface area after dealloying. The dealloyed UV-treated samples develop uniform porous structures with Cu-enriched zones, exhibiting exceptional catalytic performance in alkaline media (oxygen evolution reaction: 350 mV, hydrogen evolution reaction: 163 mV), comparable to commercial catalysts. This work provides new insights into developing high-performance MGs through energy-state engineering. Full article

Microbial fuel cells are a new alternative for sustainable energy generation and wastewater treatment technology. To scale up this technology, cost-effective electrodes are required. The electrochemical reduction of oxygen at the cathode is a key reaction for power generation. Noble metals, especially Pt, are extensively used as cathode catalysts in MFC; however, its application is limited to its high cost and catalyst poisoning. Ferroelectric materials are reported as a good candidate due to their spontaneous polarization. The main objective of this study is to prepare and characterize the cost-effective ferroelectric materials LiTa_0.6 Nb_0.4 O₃ and Li_0.95 Ta_0.57 Nb_0.38 Mg_0.15 O₃ in order to test their catalytic activity in air-cathode MFC. Powders were prepared following the solid-state synthesis and characterized using Scanning Electron Microscopy, energy-dispersive X-ray spectroscopy, and X-ray diffraction. To evaluate the electrochemical performance of the catalysts, electrochemical studies such as EIS, CV, LSV, and CA were conducted. In MFC, the performance of our material has been investigated using COD determination and polarization measurement. The obtained results demonstrate the potential of Li_0.95 Ta_0.57 Nb_0.38 Mg_0.15 O₃ as a low-cost and effective catalyst material in MFCs, showing a high COD removal up to 75%, and power-density output of 764 mW/m². Full article

Continuous advancements in application technology aimed at higher efficiency and power density place ever-increasing demands on mechanical components and construction elements—and, consequently, on the lubricating greases employed. This is particularly true for rolling bearings, where greases are exposed to high mechanical loads and wide temperature ranges. A current example can be found in the bearings of hybrid vehicle powertrains, which are subjected to extreme thermal and mechanical stress due to engine downsizing, high rotational speeds, and radiant heat from the combustion engine. A collaborative project between the Competence Center for Tribology (KTM) at Mannheim University of Applied Sciences and the OWI Science for Fuels gGmbH (OWI), affiliated with RWTH Aachen University, demonstrated that the loss of lubricating performance—which ultimately leads to bearing failure—is directly linked to changes in the thickener structure. Various degradation processes reduce yield stress and viscosity, thereby eliminating the typical grease characteristics. Mechanical, thermal, oxidative, and catalytic processes all play decisive roles. This paper presents analytical methods that enable these individual influencing factors to be investigated and evaluated independently. These approaches can significantly reduce the need for time-consuming and costly laboratory tests in grease development and qualification. Full article

This study investigates the valorization of two agri-food residues, specifically olive pomace (alperujo, A) and banana peel (B), into efficient N-doped carbon-based catalysts for polluted wastewater treatment. The residues were converted into hydrochar (HA and HB), which were subsequently N-doped using polyethylenimine (PEI) in combination with cross-linkers (glutaraldehyde (GTA) or 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide (EDC)) to optimize their catalytic properties. The enhanced hydrochars were utilized as catalysts for the removal of organic pollutants from water by activation of peroxymonosulfate (PMS). Characterization techniques, including CHNS, FTIR, XPS, SEM and electrochemical analysis, were employed to understand the physicochemical properties of the materials. The catalytic activity was evaluated using Reactive Black 5 (RB5) as a model pollutant, with the N-doped alperujo-derived hydrochar cross-linked with EDC (N-HA-EDC) showing the best performance, achieving 80% removal in 60 min and an adsorption capacity of 97 mg/g. The versatility of this functionalization approach was assessed through tests with three pharmaceuticals, corroborating the adaptability and efficacy of the catalyst and demonstrating its potential for wastewater treatment applications. This study provides insights into the development of sustainable, cost-effective carbocatalysts, aligning with circular economy and zero waste principles. Full article

ZSM-5 zeolites with varying aluminum content were subjected to steam treatments of different severities by adjusting the temperature, duration, and water vapor pressure. The steamed samples were characterized using a range of analytical techniques. A quantitative assessment of the aluminum species—namely, tetrahedrally coordinated framework Al, dislodged framework Al, non-framework pentacoordinated Al, and non-framework hexacoordinated Al—was achieved through a combination of EDX analysis on Cs-exchanged materials and quantitative ²⁷Al MAS NMR spectroscopy, including spectral simulation. Contrary to previous reports, the catalytic activity per framework Al site in unsteamed ZSM-5 increases with aluminum content at low Si/Al ratios, aligning with recently proposed medium effects. Notably, at the point of maximum activity enhancement due to steaming, equivalent amounts (1:1) of framework and dislodged framework Al—both in tetrahedral coordination—are observed. The maximum enhancement factor per framework Al site, for a given material and reaction, remains independent of the specific steaming conditions (temperature, time, and pressure). However, the degree of activity enhancement varies with the type of reaction: it is more pronounced for n-hexane cracking (α-test) than for m-xylene isomerization. This suggests that both catalyst modification and reaction characteristics contribute to the observed steam-induced activity enhancement. A synergistic interaction between Brønsted and Lewis acid sites appears to underpin these effects. One plausible mechanism involves the strengthening of Brønsted acidity in the presence of adjacent Lewis acid sites. This enhancement is expected to be more significant for n-hexane cracking, which demands higher acid strength compared to m-xylene isomerization. In cases of n-hexane cracking, the increased acid strength and the formation of olefins via reactions on Lewis acid sites may act cooperatively. Importantly, the dislodged framework Al species—tetrahedrally coordinated in the hydrated catalyst at ambient temperature and functioning as Lewis acid sites in the dehydrated zeolite under reaction conditions—are directly responsible for the observed enhancement in acid activity. The transformation of framework Al into dislodged framework Al species is reversible, as demonstrated by hydrothermal treatment of the steamed samples at 150–200 °C. Nonetheless, reinsertion of Al into the framework is not fully quantitative: a portion of the dislodged framework Al is irreversibly converted into non-framework penta- and hexacoordinated species during the hydrothermal process. Among these, non-framework pentacoordinate Al species may serve as counterions to balance the lattice charges associated with framework Al. Full article

We report a non-enzymatic electrochemical sensing platform for creatinine based on a nickel-nanoparticle/carbon-quantum-dot (NiNP–CQD) hybrid interface. In this system, the analytical signal originates from the direct electrocatalytic oxidation of creatinine mediated by the Ni(II)/Ni(III) redox couple (Ni(OH)₂/NiOOH), which forms during electrochemical activation of nickel in alkaline media. These redox centers act as catalytic sites that oxidize creatinine without requiring enzymes or biomolecular labels. The CQDs provide a conductive sp²-rich network with abundant oxygenated groups that promote homogeneous nucleation and dispersion of NiNPs, enhancing both surface area and electron-transfer efficiency. Electrochemical characterization of the modified electrodes was performed using the ferricyanide/ferrocyanide redox couple as the electron-transfer probe. Structural and microscopic characterization confirms uniform NiNP deposition on the CQD layer, while electrochemical studies demonstrates that the composite outperforms CQDs or NiNPs alone in current density, linearity, and resistance to active-site saturation. The resulting sensor exhibits a wide linear range (10–1000 µM), high area-normalized sensitivity (1.41 µA µM⁻¹ cm⁻²), and a low detection limit of 5 µM. Selectivity tests reveal minimal interference from common physiological species. By explicitly leveraging a catalyst-driven, enzyme-free oxidation pathway, this NiNP–CQD architecture provides a robust, stable, and scalable platform for clinically relevant creatinine detection. Full article

High-entropy alloy (HEA) thin films have attracted considerable attention owing to their multi-element synergistic effects, high stability, tunable electronic structure, and low-cost potential. In this study, an FeCoNiMoCu HEA thin-film electrode was successfully fabricated via coating and vacuum sintering techniques, using equiatomic Fe, Co, Ni, Mo, and Cu powders as precursors. The crystal structure, surface morphology, elemental composition/distribution, and chemical states of the FeCoNiMoCu HEA thin-film electrode were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS), respectively. The hydrogen evolution reaction (HER) performance of the electrode was evaluated in four different electrolyte systems. Additionally, the influence of electrolyte temperature on HER activity was investigated, with the corresponding activation energy (E_a) calculated for each tested system. Results demonstrate that the FeCoNiMoCu HEA thin-film electrode exhibits outstanding HER performance across multiple electrolyte systems. Compared with conventional HER catalysts, this FeCoNiMoCu thin-film electrode achieves a balance between high catalytic activity and broad electrolyte compatibility, filling the research gap in HEA thin-film catalysts with superior performance in various complex electrolyte environments and providing a new reference for the development of low-cost, high-stability HER catalysts for practical applications. Full article

This work demonstrates for the first time a cost-effective modification of stainless-steel electrodes with an Fe³⁺ precursor via the deep-and-dry method (DDM) at processing temperatures between 20 °C and 80 °C, enabling their simultaneous applicability for both OER and HER in zero-gap electrolyzers. The approach offers a durable and economical alternative to conventional nickel-based electrodes. Morphological and compositional analyses by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) demonstrated a pronounced temperature-dependent evolution of surface features. At 20 °C, the coatings exhibited high porosity and incomplete coverage, whereas treatment at 60 °C yielded a compact, uniform, and continuous layer with suppressed Fe/Ni exposure and enhanced oxygen incorporation. Electrochemical characterization in 25% KOH by cyclic voltammetry and polarization measurements confirmed reversible redox behavior and comparable electrochemically active surface areas across all samples, with the 60 °C electrodes achieving the highest catalytic activity. In electrolysis cell tests (zero gap), the optimized electrodes delivered low cell voltages, current densities up to 1.35 A cm⁻², and power outputs approaching 3.5 W cm⁻². These results establish processing temperature as a decisive factor for tailoring the morphology, composition, and performance of DDM-fabricated electrodes, underscoring the promise of 60 °C-treated electrodes for efficient hydrogen production. Full article

Underground mining environments present elevated occupational health risks, primarily due to substantial exposure to diesel exhaust emissions within confined and poorly ventilated spaces. This study assesses the real-world performance of two advanced retrofit emission control systems—Proventia NOxBuster and Purifilter—installed on underground mining trucks operating in a Spanish mine. Emissions of carbon monoxide (CO), nitric oxide (NO), and nitrogen dioxide (NO₂) were quantified using a Testo 350 multigas analyser, while ultrafine particle (UFP) concentrations were measured with an Engine Exhaust Particle Sizer (EEPS-3090) equipped with a thermodiluter. Controlled tests under both idling and acceleration conditions revealed substantial reductions in pollutant emissions: CO decreased by 60–98%, NO by 51–92%, and NO₂ by 20–87%, depending on the system and operational phase. UFP concentrations during idling dropped by approximately 90%, from 542,000 particles/cm³ in untreated trucks to below 50,000 particles/cm³ in retrofitted vehicles. Under acceleration, the Proventia NOxBuster achieved reductions exceeding 95%. Conversely, Purifilter-equipped trucks exhibited a counterintuitive increase in UFPs within the 5.6–40 nm range, potentially due to ammonia slip events during selective catalytic reduction (SCR). Despite these discrepancies, both systems demonstrated considerable mitigation potential, albeit highly dependent on exhaust temperature (optimal: 200–450 °C), urea dosing precision, and maintenance protocols. This work underscores the necessity of in situ performance verification, regulatory vigilance, and targeted intervention strategies to protect underground workers effectively. Further investigation is warranted into the long-term health benefits, system durability, and nanoparticle emission dynamics under variable load conditions. Full article

This study presents a sustainable and efficient strategy for removing contaminants of emerging concern (CECs) from wastewater using non-metal-doped pyrochar catalysts synthesized via a green, one-step pyrolytic process from pinewood sawdust, urea, and boric acid. The resulting N- and B-doped pyrochars were evaluated for their ability to activate peroxydisulfate (PDS) and degrade a mixture of 25 CECs (15 pesticides and 10 pharmaceuticals). B-doped pyrochar exhibited superior bifunctional performance, combining high adsorption capacity with efficient catalytic PDS activation. Structural characterization confirmed the incorporation of boron into the carbon matrix, generating electron-deficient Lewis acid sites and enhancing the affinity toward PDS and CECs. Quenching and adsorption–degradation analyses revealed a synergistic combination of radical and non-radical pathways, supported by π–π interactions, hydrogen bonding, and Lewis acid–base interactions. Reusability tests confirmed long-term stability and high degradation efficiency over four cycles. These findings demonstrate the potential of B-doped pyrochar as a cost-effective, stable, and environmentally friendly catalyst for practical wastewater treatment. Full article

Dry reforming of methane (DRM) is a method whereby two greenhouse gases (methane and carbon dioxide) are synthesized into a high-value gas. Suitable catalysts with optimal compositions are still in development, as problems concerning coking and metal sintering remain unresolved. Since the late 20th century, catalysts prepared via solution combustion synthesis (SCS) have been applied for catalytic reactions, as these materials (catalyst or supports) demonstrate high catalytic performance; for example, SCS catalysts have been tested in DRM. This review describes the history of solution combustion synthesis, compares it with traditional methods of preparing catalysts for DRM, and charts recent developments in SCS catalytic systems based on Ni and Co. SCS catalysts are prepared by burning nitrates (oxidizing agents) and fuels (reducing agents) at mild pre-ignition temperatures. In this review, the effects of fuel type and mixed-fuel systems on the catalyst composition, as well as its activity in DRM, are described. These catalysts have shown high metal dispersion, good coke resistance, and stable catalytic performance in long-term tests. This review demonstrates the main reasons for catalyst deactivation, such as coke deposition on the catalyst surface, and suggests ways to reduce them. Full article

Typical 2-Cys peroxiredoxins (2-Cys Prxs, AhpC/Prx1 subfamily) are ubiquitous thiol peroxidases that efficiently reduce H₂O₂ and other hydroperoxides via a reactive peroxidatic Cys (C_P). Under elevated hydroperoxide levels, C_P can be hyperoxidized to sulfinic (C_P-SO₂H) or sulfonic (C_P-SO₃H) acids, leading to enzyme inactivation. Notably, eukaryotic 2-Cys Prxs are orders of magnitude more sensitive to hyperoxidation (sensitive Prxs) by H₂O₂ than their bacterial counterparts (robust Prxs). Sensitivity to hyperoxidation also correlates with the catalytic triad composition: enzymes containing threonine (Thr-Prx) are more prone to hyperoxidation by H₂O₂ than those with serine (Ser-Prx). While hyperoxidation is reversed in eukaryotes by an enzyme (sulfiredoxin), it is generally considered irreversible in bacteria. Here, we compared the hyperoxidation susceptibility of three typical 2-Cys Prxs: human Prx2 (Thr-Prx, sensitive), P. aeruginosa (Thr-Prx, robust) and S. epidermidis (Ser-Prx, robust) to lipid hydroperoxides derived from linoleic acid, containing one or two peroxide moieties per molecule. Employing structural analysis, molecular simulations and kinetic assays, we found that lipid peroxides proved to be potent hyperoxidizing agents for all 2-Cys Prx tested, inactivating the enzymes up to 10,000 times faster than H₂O₂. These results may have implications for understanding bacterial oxidative stress responses and antimicrobial resistance. Full article

The aim of this work was high-temperature synthesis of PtPdCoNiCu/C nanoparticles with high-entropy alloy (HEA) structure as catalysts for oxygen reduction reaction. The materials were synthesized using a highly dispersed PtPd/C support, which was impregnated with Cu, Ni, and Co precursors followed by their precipitation with an alkali. Subsequently, the material was subjected to thermal treatment in a tube furnace at 600 °C for 1 h in a stream of argon containing 5% hydrogen. In combination with HRTEM, element mapping and line scan, XRD, and XPS data, these results confirm the successful synthesis of five-component PtPdCoNiCu high-entropy alloy nanoparticles on the surface of the carbon support. The obtained materials are characterized by a high electrochemical surface area of up to 63 m²/g(PGM), as determined by hydrogen adsorption/desorption and CO-stripping, and a high specific oxygen reduction reaction (ORR) activity of approximately 269 A/g(PGM) at 0.9 V vs. RHE. The synthesized material demonstrated outstanding stability, as confirmed by an accelerated stress test of 10,000 cycles. After the test, the electrochemical surface area decreased by only 12%, while the catalytic activity for ORR even increased. The proposed synthetic strategy opens a new pathway for obtaining promising highly stable five-component HEA nanoparticles of various compositions for application in catalysts. Full article

The synthesis of VO_x/MgO catalysts by solution combustion synthesis was investigated using varying molar ratios of glycine to oxidant. The effect of varying the fuel amount on morphology, phase composition, surface area, crystallite size, elemental distribution, and coordination environment around V was investigated. The results showed that the morphology, surface area, and crystallite size are all dependent on the flame temperature during the combustion process, which is dependent on the amount of fuel added. Results also suggested that adding glycine in excess lowers the combustion temperature. The catalysts were tested for the ODH of n-octane. The catalyst with superior catalytic properties was the stoichiometric sample, in which equal molar ratios of the fuel and oxidizer were added. The better catalytic performance was related to the contribution of the VO_x species from the magnesium vanadate phase. This is the only sample in which vanadates were detected. Catalysts synthesized under fuel-lean and fuel-rich conditions were characterized by large crystallites and the absence of detectable magnesium vanadates, using XRD. Full article