This project, part of the overall strategy of the Wixforth group (UAU), aims towards understanding and realising acoustically assisted (photo) catalysis, employing SAWs on semiconductor hybrid chips. Hence, it combines experience in semiconductors and soft-matter physics over two decades. The application of ultrasonic SAWs in heterogeneous catalysis was pioneered by Inoue et al., who showed that a SAW significantly lowers the activation energy for several catalytic reactions, as the SAW brings an additional degree of freedom to the catalytic processes by supplying additional energy, lattice deformations and large dynamic electric fields and field gradients simultaneously.
Until now, however, it is still unclear whether mechanocatalysis (substrate deformation) or electrocatalysis (large electric fields/gradients) is responsible for the observed impressive effects. Here, we aim to investigate experimentally the influence of SAW on various heterogeneous model catalytic processes, e.g. water splitting. Semiconductor materials with a metal or metal oxide doping proved very efficient as water splitting catalyst. We will compare thin planar films with micro- and nanostructured surfaces (high resolution lith. at UCAM), nanosized particles and mesoporous solids of the same catalyst, e.g. TiO2. We will study the frequency-, wavelength- and amplitude dependence (CNR) of the catalytic rates and efficiencies (high-frequency IDT fabrication at TWENTE). Acoustic resonators and phononic crystals will be employed to optimise the coupling to the catalyst and SAW intensities (UVEG, UAU2).
The energy necessary for water splitting can be delivered, e.g. sonochemically for a gold-containing titanium dioxide catalyst or – as shown before – by light, forming a photocatalytic reaction. As the main goal we aim for a strongly enhanced rate increase by combining ultrasound and photocatalysis for novel hybrid systems consisting of a (semiconducting) catalyst and an ultrasonic sound field. Long-term, we envision deposition of nanosized catalysts on panels with areas comparable to solar panels, as such large-scale coating of e.g. ZnO is already possible. ESR8-UAU1 will acquire broad knowhow in nanofabrication, surface chemistry, semiconductors, microfluidics and soft-matter physics and will be fully integrated in the Graduate Programme of the Cluster of Excellence NIM with access to a wide range of transferable-skill activities, workshops and schools.
MSc or a diploma in physics, materials science, physical chemistry or comparable. A background in experimental catalysis or biophysics and cleanroom processing will be considered a plus.
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