Ultra-sustainable Fe78Si9B13 metallic glass as a catalyst for activation of persulfate on methylene blue degradation under UV-Vis light

Recent Advances in and Challenges with Fe-Based Metallic Glasses for Catalytic Efficiency: Environment and Energy Fields

Metallic glass is being gradually recognized for its unique disordered atomic configuration and excellent catalytic activity, so is of great significance in the field of catalysis. Recent reports have demonstrated that Fe-based metallic glass, as a competitive new catalyst, has good catalytic activity for the fields of environment and energy, including high catalytic efficiency and stability. This review introduces the latest developments in metallic glasses with various atomic components and their excellent catalytic properties as catalysts. In this article, the influence of Fe-based metallic glass catalysts on the catalytic activity of dye wastewater treatment and water-splitting is discussed. The catalytic performance in different atomic composition systems and different water environment systems, and the preparation parameters to improve the surface activity of catalysts, are reviewed. This review also describes several prospects in the future development and practical application of Fe-based metallic glass catalysts and provides a new reference for the synthesis of novel catalysts.

Fe/Au galvanic nanocells to generate self-sustained Fenton reactions without additives at neutral pH

The generation of reactive oxygen species (ROS) via the Fenton reaction has received significant attention for widespread applications. This reaction can be triggered by zero-valent metal nanoparticles by converting externally added H2O2 into hydroxyl radicals (˙OH) in acidic media. To avoid the addition of external additives or energy supply, developing self-sustained catalytic systems enabling onsite production of H2O2 at a neutral pH is crucial. Here, we present novel galvanic nanocells (GNCs) based on metallic Fe/Au bilayers on arrays of nanoporous silica nanostructures for the generation of self-sustained Fenton reactions. These GNCs exploit the large electrochemical potential difference between the Fe and Au layers to enable direct H2O2 production and efficient release of Fe2+ in water at neutral pH, thereby triggering the Fenton reaction. Additionally, the GNCs promote Fe2+/Fe3+ circulation and minimize side reactions that passivate the iron surface to enhance their reactivity. The capability to directly trigger the Fenton reaction in water at pH 7 is demonstrated by the fast degradation and mineralization of organic pollutants, by using tiny amounts of catalyst. The self-generated H2O2 and its transformation into ˙OH in a neutral environment provide a promising route not only in environmental remediation but also to produce therapeutic ROS and address the limitations of Fenton catalytic nanostructures.

An efficient CuZr-based metallic glasses electrode material for electrocatalytic degradation of azo dyes

Metallic glasses have received a lot of attention on wastewater treatment due to their unique atomic structure, and the use of metallic glasses as electrodes has produced unexpected electrocatalytic degradation effects for many pollutants through combining with electrochemical technology. However, it still is a formidable challenge to find a metallic glass electrode material with both efficient and clean for the catalytic degradation of pollutants. In this work, the Cu55Zr45 metallic glassy ribbons are used as an electrode to degrade azo dyes and show the excellent degradation effect, which can reach 95.6% within 40 min. In the degradation process, almost no additives are produced and Cu55Zr45 metallic glassy ribbons have excellent effects under different pH conditions. Meanwhile, it exhibits good stability for degradation efficiency during the 8 cycle degradation tests of the amorphous alloy electrode. When the copper nanoparticles are exposed on the surface of the ribbons, the oxidized copper obtained synergistically produce activated radicals is the primary degradation mechanism, where the auxiliary degradation mechanisms include electron transfer and the promotion of active chlorine. This research develops a new type of electrode material for wastewater treatment, and the economy and high efficiency of Cu55Zr45 metallic glass endow it the expandable functional applications.

Nanoscale Oxygenous Heterogeneity in FePC Glass for Highly Efficient and Reusable Catalytic Performance

Metallic glass, with its unique disordered atomic structure and high density of low-coordination sites, is regarded as the most competitive new catalyst for environmental catalysis. However, the efficiency and stability of metallic glass catalysts are often affected by their atomic configuration. Thus, the design and regulation of the nanoscale structure of metallic glasses to improve their catalytic efficiency and stability remains a challenge. Herein, a non-noble component, Fe75 P15 C10 amorphous ribbon, is used as a precursor to fabricate a hierarchical gradient catalyst with nanoscale heterogeneous and oxygenous amorphous structure by simple annealing and acid-immersing. The resulting catalyst offers an ultrahigh catalytic ability of kSA• C0 = 3101 mg m-2  min-1 and excellent reusability of 39 times without efficiency decay in dye wastewater degradation. Theoretical calculations indicate that the excellent catalytic performance of the catalyst can be attributed to its unique heterogeneous nanoglass structure, which induces oxygen atoms. Compared to the FePC structure, the FeP/FePCO structure exhibits strong charge transferability, and the energy barrier of the rate-determining steps of the conversion of S2 O8 2- to SO4 -• is reduced from 2.52 to 0.97 eV. This study reveals that a heterogeneous nanoglass structure is a new strategy for obtaining high catalytic performance.

A New Method for Evaluating the Bond Strength of Plasma-Sprayed NiCrBSi Coatings

The bond strength is a critical consideration for the plasma-sprayed NiCrBSi coatings. However, the conventional methods for testing the bond strength of NiCrBSi coatings always cost time and money. If there is a simple method that could predict the bond strength of the prepared NiCrBSi coatings without destroying the coatings, it would be significantly beneficial for industrial applications. In this work, a new method was proposed based on the total areas of the interfacial pores for the NiCrBSi coatings. The NiCrBSi coating was prepared by plasma spraying technology and the as-sprayed coating was subsequently remelted by plasma arc using the powers of 20 kW, 25 kW, and 30 kW, respectively. The interfacial microstructures, the size distributions and total areas of the interfacial pores, interfacial hardness, and bond strength of all prepared coating samples were investigated. After remelting, the number and the total area of interfacial pores decrease with increasing the remelting power. Correspondingly, the interfacial hardness and bond strength of coatings increase with increasing the remelting power The bond strength of coatings basically has a linear relationship with the total area of interfacial pores. The built relationship may be used to predict the bond strength of NiCrBSi coatings.

Excellent dye degradation performance of FeSiBP amorphous alloys by Fenton-like process

Amorphous alloys are being newly applied in wastewater treatment because of their unique atomic packing structure. They possess excellent degradation efficiency, stability and reusability. In this work, Fe₈₀Si₁₀B₁₀ and Fe₈₃Si₅B₈P₄ amorphous ribbons exhibited advanced catalytic performance for the degradation of Methyl Blue (MB) and Rhodamine B (RhB) dyes, and the color removal reach nearly 100% within 11 min for both the dyes. Compared with the Fe₈₀Si₁₀B₁₀ amorphous ribbon, the Fe₈₃Si₅B₈P₄ ribbon showed higher degradation efficiency due to its lower reaction activation energy, higher electron transfer ability and higher Fe content, and the formation of the galvanic cell between the strong Fe-P bonds and the weak Fe-B bonds. It also exhibited high stability and reusability. The degradation efficiency was improved when the appropriate concentration of H₂O₂ is added. As regards the pH, high degradation efficiency was observed in acidic MB solution, but it decreased as the pH increased up to pH 7. The application of the electro-Fenton-like process is discussed, which can effectively improve the degradation performance in a nearly natural solution. This study presents a high efficiency low-cost catalyst for synthetic dye degradation and expands the functional applications of Fe-based amorphous alloys.

Design and perspective of amorphous metal nanoparticles from laser synthesis and processing

Amorphous metal nanoparticles (A-NPs) have aroused great interest in their structural disordering nature and combined downsizing strategies (e.g. nanoscaling), both of which are beneficial for highly strengthened properties compared to their crystalline counterparts. Conventional synthesis strategies easily induce product contamination and/or size limitations, which largely narrow their applications. In recent years, laser ablation in liquid (LAL) and laser fragmentation in liquid (LFL) as "green" and scalable colloid synthesis methodologies have attracted extensive enthusiasm in the production of ultrapure crystalline NPs, while they also show promising potential for the production of A-NPs. Yet, the amorphization in such methods still lacks sufficient rules to follow regarding the formation mechanism and criteria. To that end, this article reviews amorphous metal oxide and carbide NPs from LAL and LFL in terms of NP types, liquid selection, target elements, laser parameters, and possible formation mechanism, all of which play a significant role in the competitive relationship between amorphization and crystallization. Furthermore, we provide the prospect of laser-generated metallic glass nanoparticles (MG-NPs) from MG targets. The current and potential applications of A-NPs are also discussed, categorized by the attractive application fields e.g. in catalysis and magnetism. The present work aims to give possible selection rules and perspective on the design of colloidal A-NPs as well as the synthesis criteria of MG-NPs from laser-based strategies.

Phase Transformation-Induced Improvement in Hardness and High-Temperature Wear Resistance of Plasma-Sprayed and Remelted NiCrBSi/WC Coatings

The remelting method is introduced to improve the properties of the as-sprayed NiCrBSi coatings. In this work, tungsten carbide (WC) was selected as reinforcement and the as-sprayed and remelted NiCrBSi/WC composite coatings were investigated by X-ray diffraction, scanning electron microscopy, hardness test and tribology test. After spraying, WC particles are evenly distributed in the coating. The remelting process induced the decarburizing reaction of WC, resulting in the formation of dispersed W2C. The dispersed W2C particles play an important role in the dispersion strengthening. Meanwhile, the pores and lamellar structures are eliminated in the remelted NiCrBSi/WC composite coating. Due to these two advantages, the hardness and the high-temperature wear resistance of the remelted NiCrBSi/WC composite coating are significantly improved compared with those with an as-sprayed NiCrBSi coating; the as-sprayed NiCrBSi coating, as-sprayed NiCrBSi/WC composite coating and remelted NiCrBSi/WC composite coating have average hardness of 673.82, 785.14, 1061.23 HV, and their friction coefficients are 0.3418, 0.3261, 0.2431, respectively. The wear volume of the remelted NiCrBSi/WC composite coating is only one-third of that of the as-sprayed NiCrBSi coating.

Role of Boron in Enhancing Electron Delocalization to Improve Catalytic Activity of Fe-Based Metallic Glasses for Persulfate-Based Advanced Oxidation

Metallic glasses (MGs) with superior catalytic performance have recently been recognized as attractive candidates for wastewater treatment. However, further improving their performance will require knowledge of how to precisely regulate their electronic structures via compositional control. Here, two Fe-based MGs (Fe₇₈Si₉B₁₃ and Fe₈₀Si₉B₁₁) were prepared to compare how slightly altering boron content affected their electronic structure and catalytic performance. Density functional theory revealed that the Fe₇₈Si₉B₁₃ MG with 2 atom % higher boron exhibits an attractive electron delocalization, a high persulfate adsorption energy, and a superb work function due to precise regulation of the electronic structure, leading to exceptional degradation performance for seven organic pollutants. Furthermore, it can be reused 23 times without significant deterioration of catalytic performance, amorphous structure, and surface morphology. This work provides a new paradigm for the fundamental theory explaining how electronic structure is controlled by composition, creating a solid foundation to explore novel catalysts for water treatment.

Fe-Based Metallic Glasses and Dyes in Fenton-Like Processes: Understanding Their Intrinsic Correlation

Fe-based metallic glasses have been demonstrated as effective heterogeneous catalysts in Fenton-like processes for dye degradation. Yet, currently corresponding studies have limitations due to the limited study object (dyes) and the correlation between metallic glasses and dye pollutants in Fenton-like processes is still not comprehensively studied. Accordingly, this work intensively investigated the thermal catalytic behavior correlations between two Fe-based metallic glasses (Fe78Si9B13 and Fe73.5Si13.5B9Cu1Nb3) and eight different dyes. Results indicated a lower activation energy in the more active metallic glass and a dependence of the activation energy of Fe-based metallic glasses in dye solutions. In addition, a high H2O2 concentration led to a declined catalytic efficiency but a photo-enhanced Fenton-like process overcame this limitation at high concentration of H2O2 due to the decrease of pH and enhancement of irradiation. Furthermore, the average mineralization rates of Fe78Si9B13 and Fe73.5Si13.5B9Cu1Nb3 have been measured to be 42.7% and 12.6%, respectively, and the correlation between decolorization and mineralization revealed that a faster decolorization in a Fenton-like process contributed to a higher mineralization rate. This work provides an intrinsic viewpoint of the correlation between Fe-based metallic glasses and dyes in Fenton-like processes and holds the promise to further promote the industrial value of metallic glasses.

Fast Activating Persulfate by Crystallization of Fe-Based Metallic Glasses with External Energy

Very recently, crystallization of metallic glasses (MGs) has presented promising properties in the catalytic field. This work has investigated enhanced catalytic performance of crystallized Fe78Si9B13 ribbons for fast activating persulfate (PS) with assistance of UV-vis light and heat. The ribbons were obtained by annealing at 750°C (Fe-A750) and cibacron brilliant yellow 3G-P (BY 3G-P) dye was used as pollutant. The results indicated that UV-vis light had limited capability to enhance PS activation efficiency by crystallized ribbons while the reaction rate using heat at 65°C was 7.5 times higher than at 25°C, suggesting an advanced performance with heat assistance of Fe-A750 ribbons. Activation energy ∆E for Fe-A750 was measured as 44.5 kJ mol-1. In addition, 5 times reusability could be achieved for Fe-A750 ribbons under 45°C without catalytic decay. The surface morphologies of glassy ribbons, as-annealed Fe-A750 ribbons, HCl-treated Fe-A750 ribbons and after-reused Fe-A750 ribbons have also been systematically studied. This work provides a novel clue to promote applicability of novel crystallized ribbons from MGs.

Pt nanoparticles decorated heterostructured g-C3N4/Bi2MoO6 microplates with highly enhanced photocatalytic activities under visible light

Exploring an efficient and photostable heterostructured photocatalyst is a pivotal scientific topic for worldwide energy and environmental concerns. Herein, we reported that Pt decorated g-C₃N₄/Bi₂MoO₆ heterostructured composites with enhanced photocatalytic performance under visible light were simply synthesized by one-step hydrothermal method for methylene blue (MB) dye degradation. Results revealed that the synthetic Pt decorated g-C₃N₄/Bi₂MoO₆ composites with Bi₂MoO₆ contents of 20 wt.% (Pt@CN/20%BMO) presented the highest photocatalytic activity, exhibiting 7 and 18 times higher reactivity than the pure g-C₃N₄ and Bi₂MoO₆, respectively. Structural analyses showed that Bi₂MoO₆ microplates were anchored on the wrinkled flower-like g-C₃N₄ matrix with Pt decoration, leading to a large expansion of specific surface area from 10.79 m²/g for pure Bi₂MoO₆ to 46.09 m²/g for Pt@CN/20%BMO. In addition, the Pt@CN/20%BMO composites exhibited an improved absorption ability in the visible light region, presenting a promoted photocatalytic MB degradation. Quenching experiments were also conducted to provide solid evidences for the production of hydroxyl radicals (^•OH), electrons (e⁻), holes (h⁺) and superoxide radicals (^•O²⁻) during dye degradation. The findings in this critical work provide insights into the synthesis of heterostructured photocatalysts with the optimization of band gaps, light response and photocatalytic performance in wastewater remediation.

Effect of Ni Addition on Catalytic Performance of Fe87Si5B2P3Nb2Cu1 Amorphous Alloys for Degrading Methylene Blue Dyes

Fe-based amorphous alloys have shown great potential in degrading azo dyes and other organic pollutants. It has been widely investigated as a kind of environmentally friendly material for wastewater remediation. In this paper, we studied the effect of Ni addition on the catalytic performance of Fe87Si5B2P3Nb2Cu1 amorphous alloy for degradation of methylene blue dyes and analyzed the reaction mechanism. (Fe87Si5B2P3Nb2Cu1)86Ni14 amorphous powder with desirable performance was produced by specific ball milling durations. Characterization of the Fe87Si5B2P3Nb2Cu1 and (Fe87Si5B2P3Nb2Cu1)86Ni14 amorphous alloys prepared by ball milling was performed by XRD and SEM. Fe87Si5B2P3Nb2Cu1 and (Fe87Si5B2P3Nb2Cu1)86Ni14 amorphous alloys were used as catalysts to catalyze the degradation of methylene blue dyes, which were detected by UV-VIS near-infrared spectrophotometer. By a series of comparative experiments, it was found that a catalyst dosage of 0.2 g and a reaction temperature of 80 °C were conditions that produced the best catalytic effect. The degradation rate of (Fe87Si5B2P3Nb2Cu1)86Ni14 amorphous alloy to methylene blue dyes prepared by ball milling increased from 67.76% to 99.99% compared with the Fe87Si5B2P3Nb2Cu1 amorphous alloy under the same conditions.

Heat-Activated Persulfate by Fe-Based Metallic Glass: A Comparative Study of Two Dyes

In this work, the heat-activated persulfate (PS) in the presence of Fe78Si9B13 metallic glasses (MGs) shows an extremely difference in degradation of azo dye and triarylmethane dye, where Fe78Si9B13 MGs exhibits a superior activation ability for PS with assistance of heat leading to the fast removal of two dyes. The structural features of Fe78Si9B13 MGs are firstly characterized by X-ray diffraction (XRD) and differential scanning calorimetry (DSC), following analysis of surface topography by scanning electron microscope (SEM). The results show that with the addition of Fe78Si9B13 MGs, the recalcitrant azo dye is completely removed within 5 min while only 6% of removal rate can be achieved without adding MGs, indicating that the refractory azo dye can be easily degraded by sulfate radical (SO4•–) from heat/MGs/PS. On the other hand, no big variation occurs between PS and MGs/PS under heat activation in degrading triarylmethane dye. Sole PS activated by heat results in a fast removal rate, indicating that triarylmethane dye can be easily degraded by PS itself compared to azo dye. The findings in this work present an in-depth understanding of heat/MGs/PS system in dyes degradation.

Evaluation of MnO2-templated iron oxide-coated diatomites for their catalytic performance in heterogeneous photo Fenton-like system

Herein, iron oxide-coated diatomites were prepared through hydrothermal synthesis and sacrificial template redox etching reaction. The microstructure characterization results revealed that the Fe₂O₃ nanorods were uniformly distributed on the surface of diatomite. The effects of diverse synthetic parameters on morphology of as-synthesized Fe₂O₃@diatomite were investigated. When the reaction time was prolonged from 12h to 24h, the morphology of FeOOH would change from nanorods into nanoflowers. Two different crystal phases of Fe₂O₃@diatomite were obtained from the FeOOH@diatomite samples calcined under different atmospheres. The catalytic activity of α-Fe₂O₃@diatomite was evaluated by the heterogeneous photo Fenton-like system through degradation of methylene blue (MB, 10 - 40mgL^-1) in the presence of hydrogen peroxide (H₂O₂, 9mM - 120mM) under UV light irradiation. It was found that α-Fe₂O₃@diatomite composites showed very excellent degradation efficiency, which was about 99% within 120min under UV irradiation. This catalyst extended the range of pH values of homogeneous Fenton reaction, in which the MB removal rate was maintained over 80.8%. Moreover, the α-Fe₂O₃@diatomite catalyst still showed sound reusability after 5 rounds of degradation of MB dye. In principles, a possible photo-catalytic mechanism was proposed to testify metal oxides composites for heterogeneous photo Fenton-like reaction.