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Bipolar electrospray for the synthesis of defined hetero-aggregates: Process design and in situ diagnostics

Subject Area Mechanical Process Engineering
Technical Thermodynamics
Term since 2021
Project identifier Deutsche Forschungsgemeinschaft (DFG) - Project number 462396181
 
Nanoparticle aggregates of two different materials in contact with each other, so-called heteroaggregates (HAs), offer the prospect of a variety of new or improved applications, e.g., in the fields of catalysis, sensing and environmental remediation. In order to fully exploit this potential, tailor-made manufacturing processes and adapted characterization methods are required to assess particle properties, particularly their morphology and the type and strength of the heterocontact, and to link these to their application characteristics. The overall goal of the project is the synthesis of HAs with defined contact areas, their characterization and their photocatalytic application. The synthesis is carried out using a combination of a bipolar electrospray (BPES) and a subsequent in-flight temperature treatment, by which a wide variety of material combinations and particle morphologies with different contact areas can be realized. While in the first funding period the synthesis route and in situ characterization methods have been successfully developed, the second phase will focus on the aimed synthesis of HAs for selected photocatalytic applications, namely the decomposition of dyes and per- and polyfluoroalkyl substances (PFAS) and the production of hydrogen. This overall aim requires further development of the ES functionality, characterization methods and assessment of the performance of the synthesized particle systems. To that end, the BPES must be adapted for each material system, addressing operational regions of spray stability and high bipolar collisions efficiency. Optical in-situ measurement techniques are used to control the process, including wide-angle light scattering (WALS), fluorescence quenching and PIV to determine droplet and aggregate sizes and to obtain information about the collision process and evaporation kinetics, and UV-Vis absorption spectroscopy (AS) to determine the bandgap energy. Additional techniques, such as aerosol photoemission spectroscopy, TEM, XPS and ICP-MS are used to further interpret the hetero-aggregate properties. Optical diagnostic methods are further developed, including a scattering correction for UV-Vis AS and the adaptation of WALS evaluation for complex structures consisting of spherical and flake-like particles. Dedicated reactors are developed and various analytical techniques are used to assess the performances of the synthesized HA systems, which are linked to HA properties. Collaborations with various working groups of the PP have been agreed upon, which - among other aspects - serve the better understanding of the process through modelling approaches and advanced evaluation of data from in and ex situ methods.
DFG Programme Priority Programmes
 
 

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