60 Search Results

Plastic imposes a critical threat to the environment, ecosystems and human health, because of low utilization efficiency of plastics. Here, we demonstrate a sustainable highly efficient cascade photocatalysis for upcycle plastics to value-added acetic acid using Fe single atom catalysts (Fe@C3N4 SAC) at ambient conditions. Inspired by Phanerochaete chrysosporium microbial, the defected Fe@C3N4 SAC acts as a as a bifunctional cascade photocatalyst for both Fenton-like and CO2 reduction reactions. During the reaction, hydroxyl radicals (*OH) form and subsequently oxidize plastics into CO2 intermediates. These CO2 intermediates were then photo-reduced to CH3COOH on the same catalyst via cascade photocatalysis. The mechanismmore » was confirmed by in situ multimodal microscopy and spectroscopies, with density functional theory calculations. A state-of-art CH3COOH yield of 63.8 mg h-1 gcat-1 from PVC, 12.7 mg h-1 gcat-1 from PE, 5.4 mg h-1 gcat-1 from PET, and 5.3 mg h-1 gcat-1 from PP were directly obtained under AM1.5G solar irradiation and further validated under real sunlight (~ 0.6 sun), achieving 5.6 mg h-1 gcat-1 from PET, using low-cost Fe@C3N4 SAC in a sealed reactor by enhancing the photon transport and utilization efficiency. The techno-economic analysis shows it is promising to practically mitigate plastic based on broader social welfare assessments.« less

Although heterogeneous photo‐Fenton reactions on nanoparticulate iron oxides effectively degrade organic pollutants, the underlying surface mechanisms remain debated. Here, we demonstrate how these pathways are modulated by specific hematite crystal facets. To investigate the influence of particle surface structure, methylene blue (MB) adsorption and photodegradation kinetics are examined using facet‐engineered hematite nanoparticles with distinct exposed facets. The results reveal that MB photodegradation strongly depends on both pH and facet orientation. When normalized by surface area, (116) facet shows higher photodegradation activity than those with (104) or (001) facets. This enhanced activity is attributed to favorable electronic structure and surface characteristics,more » including a smaller optical bandgap, faster charge transfer, and superior H₂O₂ decomposition. In contrast, the photodegradation capacity follows (104) 〉 (116) 〉 (001), primarily due to the higher density of surface‐active sites on the (104) facet. These sites promote coupled MB adsorption and degradation, enabling removal of a greater overall quantity of MB. Additionally, under high pH conditions, hematite can degrade MB in the dark, with capacities following (001) ≫ (116) 〉 (104). These findings underscore the critical catalytic role of specific hematite surfaces and advance the understanding of facet‐dependent photoinduced redox chemistry at mineral–water interfaces.« less

Hematite’s common (001) and (012) facets are frequently used in model studies of lead (Pb) adsorption behavior, but there is a lack of research on the high-energy facets, e.g. (104), present in nature. Also, few studies have attempted to connect the molecular details of facet-specific Pb adsorption to macroscopic uptake behavior. Here, to address these knowledge gaps, we investigated Pb(II) adsorption behaviors on facet-engineered hematite nanoparticles dominated by (001), (104), and (116). Adsorption experiments revealed significant variations in Pb(II) uptake among the three samples, with (001) demonstrating the highest capacity and (116) showing the best adsorption efficiency when normalized tomore » specific surface area. Adsorption kinetics followed the pseudo-second-order model, indicating the adsorption process is governed mostly by chemisorption. Adsorption isotherms were well fitted by the Langmuir model, indicating uptake proceeds until roughly monolayer adsorption. Detailed characterization revealed Pb(II) was adsorbed as single atoms with complex inner-sphere binding modes that varied across different facets, indicating adsorption is both structurally and energetically facet-dependent. Co-adsorption experiments further demonstrated Cu²⁺, Zn²⁺, and humic acid significantly promoted Pb(II) adsorption. This study advances the understanding of hematite surface reactivity in controlling macroscopic wet adsorption behaviors, providing valuable insights into the environmental fate of Pb(II).« less

Herein, we examine the impact of Ga⁺ ion kinetic energy and the target material type on the extent of ion implantation and structural damage in atomic force microscopy probes made of Al₂O₃ and ZnO manufactured by focused ion beam (FIB) using scanning transmission electron microscopy and energy-dispersive X-ray mapping. Penetration of Ga into the Al₂O₃ lattice induced structural distortions and amorphization. For ZnO probes, Ga is uniformly dispersed across the surface, resulting in the formation of distinct clusters. Atom probe tomography further validates the Ga distributions in Al₂O₃ and ZnO nanoprobes. Complementary Monte Carlo simulations with the transport of ionsmore » in the matter program indicated that the introduction of Ga⁺ prompts the generation of cation and anion vacancies, an occurrence more pronounced in Al₂O₃ compared to ZnO. In conclusion, this study not only enriches the knowledge of ion-matter interactions, but also serves as a practical guide for the fabrication of nanoscale functionalized AFM probes.« less

The continuous development of novel catalytic approaches is crucial for advancing efficient CO₂ hydrogenation processes. Drawing inspiration from single-atom catalysis and 2D materials, we designed a new 2D single-atom catalyst with excellent thermal stability by thermally treating Cu-adsorbed γ-AlOOH nanosheets, which yielded a Cu/γ-Al₂O₃ catalyst with high activity in the hydrogenation of CO₂-yielding methanol (CH₃OH), dimethyl ether (DME), and CO as products. The active Cu sites are monodispersed and highly stable due to their cationic oxidation state and their substitution for pentacoordinated aluminum (Al^P) sites on particle surfaces. This study demonstrates an efficient approach for achieving a high CO₂ hydrogenationmore » rate (30.45 mol mol⁻¹ h⁻¹) using a catalyst system that lacks metallic Cu centers, traditionally considered essential for H₂ dissociation, and employs what was previously thought to be an inert metal oxide (γ-Al₂O₃) for CO and CH₃OH production. Ongoing mechanistic studies aim to elucidate the synergy between cationic Cu single atoms and γ-Al₂O₃, a Lewis acid support, in facilitating hydrogen (H₂) activation and methanol formation.« less

Although recycling secondary aluminum can lead to energy consumption reduction compared to primary aluminum manufacturing, products produced by traditional melt-based recycling processes are inherently limited in terms of alloy composition and microstructure, and thus final properties. To overcome the constraints associated with melting, we have developed a solid-phase recycling and simultaneous alloying method. This innovative process enables the alloying of 6063 aluminum scrap with copper, zinc, and magnesium to form a nanocluster-strengthened high-performance aluminum alloy with a composition and properties akin to 7075 aluminum alloy. The unique nanostructure with a high density of Guinier-Preston zones and uniformly precipitated nanoscale η‘/Mg(CuZn)₂more » strengthening phases enhances both yield and ultimate tensile strength by >200%. By delivering high-performance products from scrap that are not just recycled but upcycled, this scalable manufacturing approach provides a model for metal reuse, with the option for on-demand upcycling of a variety of metallic materials from scrap sources.« less

Here, in this work, we examine how radiation impacts the dissolution behavior of boehmite by subjecting dry nanoparticles of different sizes to ⁶⁰Co γ radiation and subsequently analyzing their dissolution behavior in caustic solutions as a function of temperature. The measured kinetics show that irradiation with an amount 228.24 Mrad significantly slows the dissolution rate, particularly for smaller sizes at lower temperatures. Specifically, the temperature-dependent dissolution rates of irradiated 20 nm boehmite versus pristine material in 3 M NaOH solutions were several times lower (e.g., rate constant of 0.026 vs 0.075 h^–1 at 60 °C), with an apparent activation energymore » 40 kJ mol^–1 higher. Although various imaging techniques and X-ray diffraction measurements consistently revealed no obvious differences between pristine and irradiated samples, after irradiation significant binding energy shifts were detected in the X-ray photoelectron Spectroscopy peaks of Al 2p and O 1s, and a change in their relative intensities indicated a lower O/Al ratio. This suggests that γ-irradiation may stabilize boehmite particle surfaces by driving their chemistry and structure toward more stable aluminum oxide forms. This finding may help explain slower dissolution rates of boehmite in nuclear waste and may be useful for the development of more robust predictive models and effective strategies for waste processing.« less

Incorporation of pollutants, e.g., heavy metals, or critical elements, e.g., lithium, as impurities in mineral phases can significantly affect their mobility or sequestration in the environment. Even when present at low concentrations, impurities can alter the solubility and reactivity of the host mineral. Here, in this study, we investigate the incorporation of trace amounts of iron (Fe³⁺) and chromium (Cr³⁺) during the crystal growth of the aluminum (Al³⁺) hydroxide, gibbsite, a major component of bauxite ores, an important soil mineral, and a dominant mineral phase in stored radioactive wastes. Using a comprehensive suite of analytical techniques, we show that bothmore » Cr³⁺ and Fe³⁺ can be incorporated into the gibbsite lattice during coprecipitation by replacing Al³⁺ in octahedral sites. These small amounts are consistent with limited to no structural isomorphism shared between Al³⁺ and Cr³⁺/Fe³⁺ hydroxide precipitates, nor room temperature miscibility of their isostructural M₂O₃ oxide forms, in contrast with oxyhydroxide forms where Al³⁺ and Fe³⁺ share similar structural topologies. Despite the limited uptake of Cr³⁺/Fe³⁺, we show that these impurities have significant implications for gibbsite dissolution behavior. The limited uptake of Cr³⁺/Fe³⁺ (e.g. 0.43% Cr³⁺ and 0.4% Fe³⁺), we show that these impurities have significant implications for gibbsite dissolution behavior and subsequent reactivity in complex environments.« less

In subleading powers of soft-collinear effective theory (SCET), the Lagrangian contains couplings between soft quarks and hard-collinear quarks. Matrix elements of the hard-collinear parts of these couplings are radiative jet functions. In the position-space formulation of SCET, the Lagrangians are constructed from operators that appear to be gauge invariant. Nevertheless, we find violations of gauge invariance arise in the hard-collinear sector because gauge transformations can shift the momentum of a hard-collinear quark field from the hard-collinear sector to the soft sector, where the hard-collinear fields, by definition, have no support. The violations of gauge invariance are manifested in perturbation theorymore » in the hard-collinear sector through the absence of certain Feynman diagrams that would be present in full QCD. A consequence of the absence of these diagrams is that the radiative jet functions that follow directly from the position-space Lagrangians are not gauge invariant, and we demonstrate this through explicit calculations in lower-order perturbation theory. We obtain gauge-invariant Lagrangians by adding to existing position-space Lagrangians terms that are proportional to the soft-quark equation of motion. These gauge-invariant Lagrangians are valid for nonzero, as well as zero, quark masses. We also remark briefly on the gauge invariance of certain Lagrangians that have been constructed in the label-momentum formulation of SCET. Published by the American Physical Society 2024« less

Abstract Investigating the structural evolution and phase transformation of iron oxides is crucial for gaining a deeper understanding of geological changes on diverse planets and preparing oxide materials suitable for industrial applications. In this study, in‐situ heating techniques are employed in conjunction with transmission electron microscopy (TEM) observations and ex‐situ characterization to thoroughly analyze the thermal solid‐phase transformation of akaganéite 1D nanostructures with varying diameters. These findings offer compelling evidence for a size‐dependent morphology evolution in akaganéite 1D nanostructures, which can be attributed to the transformation from akaganéite to maghemite (γ‐Fe ₂ O ₃ ) and subsequent crystal growth. Specifically,more » it is observed that akaganéite nanorods with a diameter of ∼50 nm transformed into hollow polycrystalline maghemite nanorods, which demonstrated remarkable stability without arresting crystal growth under continuous heating. In contrast, smaller akaganéite nanoneedles or nanowires with a diameter ranging from 20 to 8 nm displayed a propensity for forming single‐crystal nanoneedles or nanowires through phase transformation and densification. By manipulating the size of the precursors, a straightforward method is developed for the synthesis of single‐crystal and polycrystalline maghemite nanowires through solid‐phase transformation. These significant findings provide new insights into the size‐dependent structural evolution and phase transformation of iron oxides at the nanoscale.« less