Search Results (388)

Metallaphotoredox catalysis merges the powerful bond-forming abilities of transition metal catalysis with unique electron or energy transfer pathways accessible in photoexcited states, injecting new vitality into organic synthesis. However, most transition metal catalysts cannot be excited by visible light. Thus, prevalent metallaphotoredox catalytic systems require dual catalysts: a transition metal catalyst and a separate photosensitizer. This leads to inefficient electron transfer between these two low-concentration catalytic species, which often limits overall photocatalytic performance. Single-atom site catalysts (SASCs) offer a promising solution, wherein isolated and quasi-homogeneous transition metal sites are anchored on heterogeneous supports. When semiconductors are employed as the support, the photosensitive unit and transition metal catalytic site can be integrated into one system. This integration switches the electron transfer mode from intermolecular to intramolecular, thereby significantly enhancing photocatalytic efficiency. Furthermore, such heterogeneous catalysts are easier to separate and reuse. This review summarizes recent advances in the application of SASCs for photocatalytic organic synthesis, with a particular focus on elucidating structure–activity relationships of the single-atom sites. Full article

With the dual challenges of global energy scarcity and worsening environmental issues, the efficient and selective conversion of CO₂ into CH₄-an environmentally friendly fuel with high energy density—offers considerable application potential. In this study, a 2D-Cu₂O/carbon nitride (2D-Cu₂O/CN) heterojunction catalyst was successfully prepared. Notably, 2D-Cu₂O/CN shows enhanced light absorption capacity, reduced charge-transfer resistance, and efficient separation of photogenerated electron–hole pairs. It exhibits a CH₄ yield of 14.1 μmol·g⁻¹·h⁻¹, 4-fold higher than that of CN. This study provides a feasible approach for the design of high-efficiency photocatalysts for CO₂ reduction to CH₄. Full article

In this study, a novel Bi₂O₃/BiOBr_0.9I_0.1 (BO0.9−BBI0.1) composite photocatalyst was successfully synthesized via a single-pot solvothermal method for the efficient degradation of 2,4-dichlorophenoxyacetic acid (2,4-D) under visible light. The structure, morphology, and optical properties of the photocatalyst were characterized through X-ray diffraction (XRD), Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), UV–vis diffuse reflectance spectra (DRS), Steady-state photoluminescence (PL), and Electrochemical Impedance Spectroscopy (EIS). The composite exhibits a 3D hierarchical morphology with increased specific surface area and optimized pore structure, enhancing pollutant adsorption and providing more active sites. Under visible light irradiation, BO0.9−BBI0.1 achieved a 92.4% removal rate of 2,4-D within 2 h, with a reaction rate constant 5.3 and 4.6 times higher than that of pure BiOBr and BiOI, respectively. Mechanism studies confirm that photogenerated holes (h⁺) and superoxide radicals (·O₂⁻) are the primary active species, and the Z-scheme charge transfer pathway significantly promotes the separation of electron-hole pairs while maintaining strong redox capacity. The catalyst also demonstrated good stability over multiple cycles. This work provides a feasible dual-modification strategy for designing efficient bismuth-based photocatalysts for pesticide wastewater treatment. Full article

This study investigates the activation mechanism of boron-doped carbon (BMC) catalysts for the degradation of the antibiotic sulfamethoxazole (SMX) via persulfate (PMS) activation. The catalysts were synthesized using a sequential double-melting calcination method, resulting in mesoporous carbon nanosheets characterized by hierarchical macro-mesopores and atomically dispersed dual active sites. Comprehensive characterization was performed using BET, SEM, TEM, FT-IR, XPS, XRD, and Raman techniques. The optimized BMC catalyst demonstrated excellent performance, achieving complete removal of sulfamethoxazole (100%) and a high mineralization rate (~90%) within 45 min. Mechanistic analysis, including electron paramagnetic resonance (EPR), revealed that the degradation predominantly follows a singlet oxygen (1O2)-dominated pathway. The system exhibited broad applicability to various pollutants, along with notable operational stability and robust resistance to common environmental interferents. Persulfate activation was primarily attributed to boron-active sites, while the hierarchical mesoporous structure facilitated both pollutant enrichment and catalytic efficiency. Full article

Photo-Fenton advanced oxidation processes are promising and sustainable approaches for water treatment, particularly under visible-light irradiation. In this study, Cu-Fe bimetallic catalysts supported on silica and γ-alumina were developed for visible-light-driven photo-Fenton reactions, with emphasis on the influence of metal ratios and support-metal interactions on charge–carrier dynamics and hydroxyl radical formation. Comprehensive characterization (XRD, TEM, UV-Vis DRS, PL, TCSPC, and EPR) revealed stronger metal–support interactions and higher metal dispersion on γ-alumina, while silica-supported catalysts showed CuO aggregation at higher Cu loadings. Catalytic performance was evaluated using coumarin oxidation as both a model reaction and a quantitative probe for ^•OH radical generation. Alumina-supported catalysts exhibited superior activity, and ^•OH production increased with increasing Cu content on both supports. Importantly, iron was found to play a dual role: low Fe loading enhances photo-Fenton activity, whereas higher Fe content promotes charge–carrier recombination, leading to reduced activity under visible-light irradiation. These results highlight how the interplay between Fe/Cu ratio and support material governs charge dynamics and provides clear guidelines for the rational design of efficient heterogeneous photo-Fenton catalysts. Full article

To optimize the electrocatalytic reaction process through the synergistic effects of V and Ni, this study employed a two-step hydrothermal method to successfully construct a V₂O₅ composite structure grown on a Ni(OH)₂ substrate (denoted V₂O₅/Ni(OH)₂-2). Electrochemical evaluation revealed that this catalyst exhibits efficient bifunctional activity in 1.0 M KOH electrolyte. For the hydrogen evolution reaction (HER), it requires a mere 89.6 mV overpotential to achieve a current density of −10 mA cm⁻². The catalyst also demonstrates excellent performance in the oxygen evolution reaction (OER), demanding only 198 mV overpotential to drive a current density of 10 mA cm⁻², while maintaining low overpotential increases even at high current densities. Furthermore, it exhibits outstanding long-term stability during a 12 h continuous test. When assembled as a dual-electrode overall water splitting device, the system requires a voltage of only 2.82 V to drive a high current density of 100 mA cm⁻², showcasing its significant potential for practical applications. Full article

Catalytic transfer hydrogenation (CTH) provides a practical and sustainable approach for reducing unsaturated compounds, serving as an alternative to high-pressure H₂ in laboratory and fine chemical contexts. This broad reaction class includes asymmetric transfer hydrogenation (ATH), a key strategy in enantioselective synthesis due to its operational simplicity, high stereocontrol, and compatibility with sensitive functional groups. A central variable governing CTH efficiency is the role of bases, which may function as essential activators, co-hydrogen donors, or be entirely absent depending on the catalytic system. This review provides a comparison of base-assisted, base-free, and base-as-co-hydrogen-donor CTH methodologies across diverse metal catalysts and substrates. We highlight how bases such as triethylamine, K₂CO₃, and NaOH facilitate catalyst activation, modulate hydride formation, and tune reactivity and selectivity. The dual function of bases in formic-acid-driven systems is examined alongside synergistic effects observed with mixed-base additives. In contrast, base-free CTH platforms demonstrate how tailored ligand frameworks, metal-ligand cooperativity, and engineered surface basicity can eliminate the need for external additives while maintaining high activity. Through mechanistic analysis and cross-system comparison, this review identifies the key structural, electronic, and environmental factors that differentiate base-assisted from base-free pathways. Emerging trends—including greener hydrogen donors, advanced catalyst architectures, and additive-minimized protocols—are discussed to guide future development of sustainable CTH processes. Full article

High-valent metal species (iron, manganese, cobalt, copper, and ruthenium) based advanced oxidation processes (AOPs) have emerged as sustainable technologies for water remediation. These processes offer high selectivity, electron transfer efficiency, and compatibility with circular chemistry principles compared to conventional systems. This comprehensive review discusses recent advances in the synthesis, stabilization, and catalytic applications of high-valent metals in aqueous environments. This study highlights their dual functionality, not only as conventional oxidants but also as mechanistic mediators within redox cycles that underpin next-generation AOPs. In this review, the formation mechanisms of these species in various oxidant systems are critically evaluated, highlighting the significance of ligand design, supramolecular confinement, and single-atom engineering in enhancing their stability. The integration of high-valent metal-based AOPs into photocatalysis, sonocatalysis, and electrochemical regeneration is explored through a newly proposed classification framework, highlighting their potential in the development of energy efficient hybrid systems. In addition, this work addresses the critical yet underexplored area of environmental fate, elucidating the post-oxidation transformation pathways of high-valent species, with particular attention to their implications for metal recovery and nutrient valorization. This review highlights the potential of high-valent metal-based AOPs as a promising approach for zero wastewater treatment within circular economies. Future frontiers, including bioinspired catalyst design, machine learning-guided optimization, and closed loop reactor engineering, will bridge the gap between laboratory research and real-world applications. Full article

In the realm of composite solid propellant research, the enhancement of energy performance without altering the underlying formulation holds paramount significance. This investigation employed an in situ displacement technique to establish a highly reactive interface, successfully synthesizing the [nCu+nCo+nFe]/μAl composite material, which considerably augmented the energy performance of RDX/AP. The decomposition pathways of ammonium perchlorate (AP) and RDX were optimized, resulting in a reduction in their thermal decomposition temperatures by 1.3 °C and 22.4 °C, respectively. Simultaneously, the highly reactive interface promoted efficient oxygen transport, thereby facilitating more rapid and complete reactions of aluminum. Moreover, the distinct dual-catalyst efficacy of the composite significantly enhanced the combustion efficiency of the composite energy micro-unit. Consequently, the [nCu+nCo+nFe]/μAl+RDX/AP composite energetic micro-units exhibited a notable decrease in combustion duration (from 1.58 s to 1.07 s) and elevated combustion flame temperatures (ranging from 1712.8 °C to 2205.6 °C) alongside an expanded combustion area, thus underscoring its potential for advanced propulsion applications. Full article

This study examines the role of public procurement of artificial intelligence (AI) as a catalyst for transformative change in State functions. Building on the concept of transformative law, it argues that law should not merely regulate technological innovation but actively guide and shape it in accordance with democratic values and the rule of law. Within this framework, public procurement emerges as a strategic instrument for (re)structuring the very configuration of public governance and institutions. This analysis highlights key legal issues surrounding the procurement of AI, starting with the premise of its dual function: on the one hand, as a tool for optimising acquisition procedures and, on the other, as the object of acquisition itself. Among the most pressing issues analysed are the definitions of algorithmic legality and accountability, the asymmetry of expertise between public authorities and private suppliers, and the regulatory complexity that characterises the field, especially in light of the recently adopted EU AI Act. Finally, this study conceptualises the public procurement of AI as a form of legal infrastructure, capable of securing systemic and enduring transformations for the State and its institutions. Full article

The expensive nature and limited availability of platinum (Pt) cathodes pose a significant challenge for the widespread adoption of microbial fuel cell (MFC) technology. Although many alternatives have been studied, very few reports provide a systematic head-to-head comparison of different Ni–oxide cathodes under the same operational conditions. This research investigates cost-effective nickel-based metal oxide composites (Ni–TiO₂, Ni–Cr₂O₃, Ni–Al₂O₃) as catalysts for the oxygen reduction reaction (ORR), using Pt as a reference point. The performance of the MFC was thoroughly evaluated in terms of power output, chemical oxygen demand (COD) removal, and Coulombic efficiency (CE). The Pt cathode exhibited the highest performance (275 mW m⁻², 87% COD removal, 35% CE), confirming its catalytic advantages. Among the alternative materials, the Ni–TiO₂ composite yielded the best outcomes (224 mW m⁻², 79% COD removal, 17.7% CE), markedly surpassing the performances of Ni–Cr₂O₃ (162 mW m⁻², 72%, 24% CE) and Ni–Al₂O₃ (134 mW m⁻², 64%, 11.6% CE). Koutecký–Levich analysis clarified the mechanisms at play: Pt facilitated a direct 4-electron ORR process, while the composites operated through a 2-electron mechanism. Notably, the semiconductor properties of Ni–TiO₂ resulted in a higher electron transfer number (n = 2.8) compared to the other composites (n ≈ 2.3), which accounts for its increased efficiency. With its low production cost, Ni–TiO₂ presents an exceptional cost-to-performance ratio. By linking catalytic performance directly to the electronic nature of the oxide supports, this study offers clear design guidelines for selecting non-precious cathodes. The dual evaluation of electrochemical efficiency and cost-to-performance distinguishes this study from prior reports and underscores its practical significance and originality. This study highlights Ni–TiO₂ as a highly sustainable and economically viable catalyst, making it a strong candidate to replace Pt for practical MFC applications that focus on simultaneous power generation and wastewater treatment. Full article

Nitrate contamination of water resources poses significant ecological and public health risks. This study developed a cobalt-immobilized microplastic catalyst (Co–MP) capable of activating peroxymonosulfate (PMS) and facilitating formic-acid-assisted catalytic denitrification of nitrate. Characterization via Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR), Energy-Dispersive X-ray Spectroscopy (EDX), and X-ray diffractometry (XRD) confirmed successful Co deposition, with the surface cobalt content reaching 5.2%. The system’s performance was optimized using Response Surface Methodology (RSM), identifying catalyst dosage and Co(II) concentration as the most significant factors. Under the optimized conditions (pH 5.5, reaction time 120 min, catalyst dosage 1.5 g L⁻¹, and Co(II) concentration 60 mg L⁻¹), the system achieved a nitrate removal efficiency of 90.6%, in excellent agreement with the model prediction (90.93%), along with an 86.7% reduction in total nitrogen, confirming stepwise denitrification to gaseous nitrogen species (N₂). The Co(II)/Co(III) redox cycle, sustained by PMS-assisted regeneration and driven by formic acid as the electron donor, ensured stable performance with minimal cobalt leaching (0.05 mg L⁻¹). This coupled oxidative–reductive system offers a sustainable dual-remediation strategy that simultaneously achieves selective nitrate conversion and valorizes microplastic waste for catalytic environmental applications. Full article

The development of efficient, highly stable photocatalysts is essential to address the two challenges of environmental remediation and renewable energy. Structurally strong Zeolitic Imidazolate Framework-8 (ZIF-8) has intrinsic drawbacks, including a large bandgap and fast charge-carrier recombination. This paper presents a highly efficient approach to designing the optoelectronic behaviour of ZIF-8 via controlled nickel doping. Ni(x)-ZIF-8 (0, 2.5, 5, 7.5, and 10 mol, x), and bimetallic metal–organic frameworks were prepared via a simple room-temperature process. Through adequate characterization, the incorporation of Ni²⁺ into the ZIF-8 lattice has been demonstrated to be successful, resulting in substantial structural and electronic changes. Framework integrity was confirmed using XRD and FTIR analysis, which revealed increased microstrain and the formation of Ni-N bonds. Most importantly, UV-Vis spectrophotometry and electrochemical studies indicated that the bandgap was systematically narrowed: a pristine ZIF-8 had a high bandgap of 3.65 eV, and a Ni(10)-ZIF-8 had a low bandgap of 3.23 eV, while charge-transfer resistance was reduced significantly. All these synergies led to high photocatalytic performance. The best Ni(2.5)-ZIF-8 catalyst achieved a desirable result, degrading methylene blue to more than 98.5%, which was far superior to that of the pure framework. Moreover, the hydrogen evolution reaction (HER) showed higher electrocatalytic activity, with a significantly lower overpotential and higher current density. This article defines Ni doping as an effective route to convert ZIF-8 into a high-performance, dual-functional photocatalyst. It opens the door to implementing solar-powered environmental remediation and hydrogen generation using ZIF-8. Full article

Hybrid electric vehicles (HEVs) frequently cycle their internal combustion engines (ICE), potentially cooling the three-way catalyst (TWC). This challenges the use of compressed natural gas (CNG), as methane (CH₄) requires high temperatures for TWC oxidation. This study experimentally investigates the performance, engine-out emissions (CO, NO_x, CH₄, NMHC, CO₂), and catalyst temperatures of a Toyota RAV4 hybrid vehicle on gasoline (G), CNG, and dual fuel (MIX) during the WLTC. Engine-out emissions were measured upstream of the TWC. Results showed similar engine work output (~17.8 kWh/100 km), while CNG significantly reduced fuel mass consumption (−18.7%) and CO₂ emissions (−27.5%) compared to gasoline, driven by both its higher LHV and higher average BTE. CO (−32.3%) and NO_x (−34.0%) emissions were lower with CNG, linked to leaner operation and significantly retarded ignition timing for NO_x control. However, CH₄ emissions drastically increased with CNG. This study reveals a synergy between the same retarded ignition timing strategy used to successfully control engine-out NO_x (−34.0%) and created a positive secondary effect, raising pre-TWC temperatures by 4.5%. Higher thermal condition is essential for the aftertreatment of chemically stable methane, highlighting a direct link between the engine’s NO_x control logic and the potential to mitigate methane slip. Full article

Dry reforming of methane (DRM) is a promising method for turning two major greenhouse gases, CO₂ and CH₄, into syngas (H₂ + CO). This syngas has the right H₂/CO ratio for making valuable chemicals and liquid fuels. However, there are significant challenges that make it tough to implement commercially. One big issue is that the process requires a lot of energy because it is highly endothermic, needing temperatures over 700 °C. This high heat can quickly deactivate the catalyst due to carbon build-up (coking) and the thermal sintering of metal nanoparticles. Researchers increasingly recognize mechanochemistry—a non-thermal, solid-state technique employing mechanical force to drive chemical transformations—as a sustainable, solvent-free strategy to address these DRM challenges. This mini-review critically assesses the dual role of mechanochemistry in advancing DRM. First, we examine its established role in creating advanced catalysts at lower temperatures. Here, mechanochemical methods help produce well-dispersed nanoparticles, enhance strong interactions between metal and support, and develop bimetallic alloys that resist coke formation and show great stability. Second, we delve into the exciting possibility of using mechanochemistry to directly engage in the DRM reaction at near-ambient temperatures, which marks a major shift from traditional thermocatalysis. Lastly, we discuss the key challenges ahead, like scalability and understanding the mechanisms involved, while also outlining future directions for research to fully harness mechanochemistry for converting greenhouse gases sustainably. Full article