Synthese von Metall Nanopartikeln an der Grenzfläche zwischen Flüssigkeit und Flüssigkeit für eine zweiphasige katalytische Synthese von Wasserstoffperoxid an der Grenzfläche von Tropfenreaktoren
Physikalische Chemie von Molekülen, Flüssigkeiten und Grenzflächen, Biophysikalische Chemie
Zusammenfassung der Projektergebnisse
This project established an innovative microelectrochemical platform that combines a micropipette and microelectrode (MP–ME) for operando investigation of catalytic activity and product selectivity at polarized liquid–liquid (L|L) interfaces. The setup enables simultaneous electrochemical polarization of the interface, stabilized at the MP orifice, and independent control of the ME (used as a product sensor) via a bipotentiostat in a scanning electrochemical microscopy (SECM) configuration. Crucially, the ME’s precise positioning allows spatially resolved detection of reaction products and charge-transfer activity—an essential advantage for mechanistic studies under dynamic conditions. This design parallels conventional solidstate systems and marks a significant advancement in catalyst discovery and real-time analysis at L|L interfaces—still underexplored compared to solid-state electrochemistry. The MP–ME methodology represents a breakthrough, rendering L|L interfaces as experimentally versatile as solid-state platforms. It allows direct, real-time measurement of net ionic currents without needing electronic conduction through a solid support, thus overcoming a key limitation of traditional electrochemical setups. A central innovation is the decoupling of electron, ion, and mass transfer processes, enabling their independent quantification and control. This capability was applied to modulate the oxygen reduction reaction (ORR) mechanism— via heterogeneous or homogeneous pathways—toward selective hydrogen peroxide (H₂O₂) production, a green and industrially valuable chemical. Fine-tuning ORR through ion transfer (IT) is especially promising, as L|L systems suppress H₂O₂ over-reduction and eliminate downstream separation steps. The system also differentiated catalytic activity and H₂O₂ selectivity among various nickel selenide-based ORR catalysts, supporting its potential for operando comparative evaluation on par with solid|liquid systems. The methodology extended to photocatalyst-modified L|L interfaces using BiVO₄ nanostructures, revealing how ion dynamics govern photoinduced electron transfer into the organic phase, modulating concurrent water photooxidation and oxygen evolution. P1 These findings point to new avenues for tailoring electrolyte compositions and ionic additives to enhance electrochemical and photocatalytic activity. Another key application is the in situ synthesis of gold nanoparticles (AuNPs) at polarized L|L interfaces, used as model ORR catalysts. By tuning IT kinetics, nanoparticle size distribution could be precisely controlled, offering a sustainable, support-free nanofabrication method. Unlike solid supports, this avoids surface degradation, corrosion, and poor reproducibility. A distinctive feature is its reusability: a single MP, prefilled with precursor, enables multiple deposition cycles. The AuNP-bearing interface is easily regenerated by gently wiping the orifice, allowing consistent NP synthesis. This ion-driven method—powered solely by the Galvani potential—provides electrochemical control over nanomaterial formation and enables real-time evaluation of catalytic performance. In summary, the MP–ME strategy offers a powerful, spatially resolved, operando platform for probing catalytic reactions at soft interfaces. Its ability to independently control electron and ion transfer processes is invaluable for fundamental studies in electrocatalysis, photocatalysis, and green chemical synthesis. It also paves the way for device integration, including membrane-less fuel cells that couple selective H₂O₂ production with energy generation. By leveraging the advantages of soft interfaces—ion permselectivity, low crossover, and tunability—this approach provides a compelling route toward next-generation sustainable energy technologies.
Projektbezogene Publikationen (Auswahl)
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(photo)Characterization of Polarized Liquid|Liquid Interfaces; 32nd Topical Meeting of the International Society of Electrochemistry, Stockholm, Sweden, 19-22 June 2022
S. Rastgar & G. Wittstock
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Single Drops Printed in Liquid as Electrochemical Reactors; 15th International Fischer Symposium, Kloster Seeon, Germany, 12–16 Jun 2022
S. Rastgar, S. Pleis, Y. Zhang & G. Wittstock
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A biphasic catalytic synthesis of hydrogen peroxide, Lecture in “Nanophotonics and Surface Chemistry group seminar” Invited by Prof. Dr. Katharina Al- Shamery at institute of Chemistry at Carl von Ossietzky University Oldenburg, 08 Jun 2023
Shokoufeh Rastgar
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Electrosynthesis of Gold Nanoparticles at Liquid/Liquid Interfaces: A Biphasic Catalytic Synthesis of Hydrogen Peroxide, 74th annual meeting of the International Society of Electrochemistry, Lyon, France, 3-8 September 2023
S. Rastgar
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Local Electrochemistry at Liquid-liquid interfaces, an online talk invited by Prof. Dr. Kristina Tschulik Chair of Electrochemistry and Electrochemical Energy Storage Ruhr- Universität Bochum, September 2023
Shokoufeh Rastgar
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A Biphasic Catalytic Synthesis of Hydrogen Peroxide at Catalytic based Liquid|Liquid Interfaces, ESEAC2024, Ulm, Germany, 23-26 July 2024
S. Rastgar
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Coupled Electron‐ and Ion‐Transfer Processes at a Liquid/Liquid Interface Decorated with Photoactive Nanomaterials. Angewandte Chemie International Edition, 63(39).
Rastgar, Shokoufeh & Wittstock, Gunther
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Ion Transfer at Catalytic-Based Liquid-Liquid Interfaces: A Biphasic Catalytic Synthesis of Hydrogen Peroxide, GDCh 2024, Braunschweig, Germany, 16-19 September 2024
S. Rastgar
