Browsing by Author "Bloh, Jonathan Z."

Now showing 1 - 7 of 7
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    Anodic peroxide production for advanced oxidation processes with different metal oxide electrodes in carbonate electrolytes
    (London : Royal Society of Chemistry, 2024-07-19) Schanz, Tobias; Bloh, Jonathan Z.
    As an alternative to the anthraquinone process that can be used directly on site without storage and transport, electrochemical peroxide synthesis is a promising technology to produce reagents for water remediation via Advanced Oxidation Processes (AOP). The focus of research here is on anodic peroxide production, since cathodic synthesis is already at a high degree of maturity. Different materials and electrolytes have been reported for the anode reactions so far. It has also been shown that some electrolytes such as carbonate-based ones lead to the formation of secondary peroxides such as percarbonates which are well-suited as oxidants for AOP. Herein, these materials and electrolytes are evaluated under different conditions with particular focus on the actual oxidation power of the formed product mixtures.
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    Combined anodic and cathodic peroxide production in an undivided carbonate/bicarbonate electrolyte with 144% combined current efficiency
    (Lausanne : Frontiers Media, 2024-05-17) Schanz, Tobias; Stöckl, Markus; Burek, Bastien O.; Holtmann, Dirk; Bloh, Jonathan Z.
    In recent years, the electrochemical synthesis of peroxides has attracted renewed interest as a potential environmentally friendly production compared to the established anthraquinone process. In addition, it is possible to produce the peroxides directly on site, eliminating the need for expensive and hazardous transportation and storage. Cathodic production of hydrogen peroxide from oxygen is already quite well developed. Anodic production from water, on the other hand, is still facing significant challenges, despite its historic pioneering role. In this manuscript we show that anodic and cathodic synthesis of peroxides can even be combined to achieve greater than 100% current efficiency (CE) due to the combined effect of both half-reactions. So far, similar devices have always employed different electrolytes for each, which necessitated the use of a membrane and posed contamination risk. However, herein we show that both half-reactions can also employ the same electrolyte. This enables even an undivided cell, omitting the need for the expensive membranes. Despite its simplicity, this setup yielded an outstanding performance with a combined CE of 144%.
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    Fate and Reactivity of Peroxides Formed over BiVO4 Anodes in Bicarbonate Electrolytes
    (Washington, DC : American Chemical Society, 2023-02-16) Schanz, Tobias; Burek, Bastien O.; Bloh, Jonathan Z.
    [no abstract available]
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    The Importance of Precise Reaction Condition Control for the Comparison of Photocatalyst Materials on the Example of Hydrogen Peroxide Formation over Polymeric Carbon Nitrides
    (Weinheim : Wiley-VCH, 2023-08-02) Wegstein, Deborah; Zaim, Abdelkarim; Burek, Bastien O.; Bloh, Jonathan Z.
    In our study, we aimed to show how different reaction parameters can affect production rates using photocatalytic hydrogen peroxide formation by different polymeric carbon nitrides (PCN). For this purpose, selected materials were first compared under the same reaction conditions and compared with TiO2 (P25). We also show that different light intensities can have a different influence on seemingly similar materials. Since hydrogen peroxide production in the presence of an electron donor proceeds mainly by reduction of oxygen, we also show an influence of the oxygen flow on the formation rates. Thus, with high oxygen fluxes and high intensities of irradiated light, we were able to achieve an H2O2 concentration of 125 mM after about 25 h. Finally, the two best PCN materials were selected to measure light intensity dependence at different wavelengths up to visible light. It was found that they behaved differently at the different wavelengths and thus it could be shown that an exact specification of the reaction parameters is indispensable for comparisons in the literature.
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    One-Step Spark Plasma Erosion Processing of Carbon-Coated Sn-Si Nanoparticles for Lithium-Ion Battery Anodes
    (Basel : MDPI, 2024-09-10) White, Emma Marie Hamilton; Rueschhoff, Lisa M.; Kobayashi, Takeshi; Bloh, Jonathan Z.; Martin, Steve W.; Anderson, Iver E.
    High density portable energy storage is desirable owing to the energy requirements of portable electronics and electric vehicles. The Li-ion battery’s high energy density could be even further improved through the utilization of alternative materials (instead of carbon) for the anode, such as Sn or Si. Nonetheless, the large volume expansion upon lithiation, up to ~300% for Li22Si5, causes pulverization and rapid capacity degradation during cycling. Sn also forms a Li22Sn5 compound with the equivalent stoichiometric Li capacity but with enhanced ductility. Nano-sized Si and Sn have demonstrated distinctive nanoscale properties, facilitating the retention of higher capacities, particularly when coated with carbon, which improves mechanical stability. To date, the methods of synthesizing coated Si, Sn, or Si-Sn alloyed nanoparticles are complicated, costly, and not readily scalable to meet the demands of cost-effective manufacturing. Spark plasma erosion in a hydrocarbon dielectric has been explored as a one-step process to produce Sn-Si alloy nanoparticles coated with a thin carbon film, offering a scalable and cost-effective processing route. The resulting Sn-Si particles exhibited a bi-modal size distribution at ~5 nm and ~500 nm and were carbon-coated, as intended, from the hydrocarbon dielectric breakdown. The spark-eroded nanoparticles were thoroughly characterized using TEM/EDS, XPS, AES, SSNMR, and TGA, and their improved electrochemical performance was assessed through half-cell experiments.
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    Photocatalytic Synthesis of Hydrogen Peroxide from Molecular Oxygen and Water
    ([Cham] : Springer International Publishing, 2023-05-09) Garcia‑Munoz, Patricia; Valenzuela, Laura; Wegstein, Deborah; Schanz, Tobias; Lopez, Girlie Eunice; Ruppert, Agnieszka M.; Remita, Hynd; Bloh, Jonathan Z.; Keller, Nicolas
    Hydrogen peroxide is a powerful and green oxidant that allows for the oxidation of a wide span of organic and inorganic substrates in liquid media under mild reaction conditions, and forms only molecular water and oxygen as end products. Hydrogen peroxide is therefore used in a wide range of applications, for which the well-documented and established anthraquinone autoxidation process is by far the dominating production method at the industrial scale. As this method is highly energy consuming and environmentally costly, the search for more sustainable synthesis methods is of high interest. To this end, the article reviews the basis and the recent development of the photocatalytic synthesis of hydrogen peroxide. Different oxygen reduction and water oxidation mechanisms are discussed, as well as several kinetic models, and the influence of the main key reaction parameters is itemized. A large range of photocatalytic materials is reviewed, with emphasis on titania-based photocatalysts and on high-prospect graphitic carbon nitride-based systems that take advantage of advanced bulk and surface synthetic approaches. Strategies for enhancing the performances of solar-driven photocatalysts are reported, and the search for new, alternative, photocatalytic materials is detailed. Finally, the promise of in situ photocatalytic synthesis of hydrogen peroxide for water treatment and organic synthesis is described, as well as its coupling with enzymes and the direct in situ synthesis of other technical peroxides.
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    Robust Light Driven Enzymatic Oxyfunctionalization via Immobilization of Unspecific Peroxygenase
    (Weinheim : Wiley-VCH, 2023-06-25) De Santis, Piera; Wegstein, Deborah; Burek, Bastien O.; Patzsch, Jacqueline; Alcalde, Miguel; Kroutil, Wolfgang; Bloh, Jonathan Z.; Kara, Selin
    Unspecific peroxygenases have attracted interest in synthetic chemistry, especially for the oxidative activation of C−H bonds, as they only require hydrogen peroxide (H2O2) instead of a cofactor. Due to their instability in even small amounts of H2O2, different strategies like enzyme immobilization or in situ H2O2 production have been developed to improve the stability of these enzymes. While most strategies have been studied separately, a combination of photocatalysis with immobilized enzymes was only recently reported. To show the advantages and limiting factors of immobilized enzyme in a photobiocatalytic reaction, a comparison is made between free and immobilized enzymes. Adjustment of critical parameters such as (i) enzyme and substrate concentration, (ii) illumination wavelength and (iii) light intensity results in significantly increased enzyme stabilities of the immobilized variant. Moreover, under optimized conditions a turnover number of 334,500 was reached.