Project

phoelectrochemical water splitting ; plasma properties; micro-batteries; solid state Li ion conductors ; pulsed laser deposition ; oxynitrides

Lead
Gepulste Laserabscheidung dünner Schichten für die Umwandlung erneuerbarer Energien und Energiespeicherung Dépôt laser pulsé de couches minces pour la conversion d'énergie renouvelable et le stockage d'énergie Deposizione laser pulsata di film sottili per la conversione di energia rinnovabile e l'accumulo di energia Pulsed laser deposition of thin films for renewable energy conversion and energy storage
Lay summary
Zusammenfassung In den Materialwissenschaften und der Technologie sind Dünnfilme allgegenwärtig. Dabei eignet sich besonders die Methode der gepulsten Laserabscheidung (PLD, für „pulsed laser deposition“) für die Herstellung von Oxidmaterialien mit komplexer chemischer Zusammensetzung. In diesem Kontext müssen allerdings zwei Fälle genannt werden, in welchen die Umsetzung von PLD auf ihre Grenzen stösst. Dies ist der Fall, wenn Stickstoff partiell in die Kristallstruktur von Oxidfilmen eingebaut werden soll. So ist die Fabrikation von solchen Oxynitriden, relevante Materialien für die Erzeugung von Wasserstoff durch solare Wasserspaltung, anspruchsvoll. Eine weitere Herausforderung in PLD besteht, wenn die Zusammensetzung der Filme einen hohen Gehalt an leichten Elementen aufweisen soll. Ein Beispiel hier ist der erschwerte Einbau von Lithium, dem drittleichtesten Element, in Dünnfilme. Erwartungshorizont / Erwartete Ergebnisse Unser Interesse besteht darin, die limitierenden Faktoren der Dünnfilmherstellung ausfindig zu machen und zu umgehen, um sowohl Oxynitridfilme, als auch Filme mit einem hohen Lithiumgehalt zu erzeugen. Bei Oxynitridfilmen besteht grosses Interesse, deren grundlegende Materialeigenschaften besser zu verstehen, um die Effizienz dieser Photokatalysatoren zu erhöhen. Lithium-haltige Materialien, besonders als Elektrolyten, gelten als wichtige Ausgangsstoffe für kleinformatige Feststoffbatterien. Gesellschaftsrelevanter, wissenschaftlicher Hintergrund Wasserstoff, welcher mittels Sonnenenergie durch Wasserspaltung erzeugt wird, gilt als emissionsarmer, erneuerbarer Kraftstoff, bei dessen Umwandlung in Energie lediglich Wasser als Produkt anfällt. Miniaturisierte Feststoffbatterien werden entsprechend dem «Ein-Chip-System» als integrierte Schaltkreise entwickelt, welche letztlich auf sichere Art als tragbare, biomedizinische Implantate genutzt werden könnten. Stichwörter Photoelektrochemische Wasserspaltung, Plasmaeigenschaften, Mikrobatterien, Lithium-haltige Feststoffelektrolyte, gepulste Laserabscheidung, Oxynitride 22. April 2022

Direct link to Lay Summary

Last update: 25.04.2022

Number	Title	Start	Funding scheme

Thin film deposition technology is largely applied for the fabrication of devices or device components such as protective coatings, interface engineering, and surface functionalization. Thin films with selected morphological and crystalline properties are also used for fundamental studies in almost all fields of Materials Science. Pulsed laser ablation is a thin film deposition method particularly suited for ceramic materials with complex chemical composition. The proposer of this project is head of the Thin Films & Interfaces group at the Paul Scherrer Institute. The group has a long-standing experience with pulsed laser ablation with special focus on materials for sustainable energy conversion and energy storage. This research proposal is subdivided into 3 subprojects covering all the 3 research lines of the group. A.Fundamental investigation of the pulsed laser ablation process focusing in particular the problem of the compositional transfer between the starting material and the film. The versatility of the technique, and the many deposition parameters that can be varied over large ranges, open many opportunities but also introduce more complexity. The ablated material consists of ionic and neutral species, in various exited states and kinetic energies, showing different expansion profiles and specific interactions with the gaseous environment. These aspects affect the composition of the film, especially for light elements, such as Li. Using plasma imaging and mass spectrometry we can correlate the growth conditions to the composition and expansion profile of the ablated material, and finally to the composition of the film. B.Thin films for all-solid-state all-oxide micro-batteries. Micro-batteries are miniaturized power sources fabricated by thin film deposition technologies for portable/wearable devices, microelectronics, and biomedical implants. Micro-batteries are based on Li-ion conductors and the Li content suffers severe loss during the deposition process, thus lowering the ionic conductivity or compromising the phase stability. In spite of many research efforts, nowadays only one material, LiPOxNy, can effectively be used as electrolyte for these devices. This limits enormously any further development in this field. This subproject is dedicated to the search of materials alternative to LiPOxNy for micro-batteries. C.Operando characterization of the solid/liquid interface during photoelectrochemical water splitting. Many oxynitride materials promise great potential as visible light responsive semiconductors able to use solar energy to provide electron/hole pairs with energies suitable to split water molecules and generate H2and O2 gas. H2 can then be stored and used as a renewable solar fuel. Oxynitride thin films can be used for operando X-ray absorption spectroscopy to monitor the changes of the local geometric and electronic structure of the solid/liquid interface to identify the rate determining mechanism of the overall catalytic process.These three projects are complementary aspects of the primary research effort of the group: find new materials’ solution for renewable and sustainable energy resources. The common denominator is the scientific and technical problem of the compositional transfer. On one hand, the aforementioned Li loss compromises the stability and functionality of the ionic conductors. On the other, the chemical composition of the oxynitride semiconductors affect their optical and conducting properties, hindering the water splitting activity. Under these perspectives, subprojects B) and C) offer a wide playground for subproject A) which in turns is expected to provide solutions to grow better materials for B) and C). The budget requested is mainly intended to be used to support the education of 3 PhD students affiliated to the Department of Chemistry and Applied Bioscience of the ETH Zurich, under the direct supervision of the applicant.