Professor René Wasserman Award 2020 - Filip Podjaski
Investigations into Nanostructured Materials for Water Splitting and Direct Solar Energy Harvesting
EPFL thesis n°9424 (2019)
Thesis directors: Prof. B. V. Lotsch and Prof. A. Fontcuberta i Morral
For his outstanding contributions in the area of novel materials and compounds for energy harvesting and storage, including the invention of a solar battery.
Increasing global warming and pollution are among the largest environmental and technological challenges we face nowadays. Although renewable energy installations are growing worldwide, their application is limited by conversion and storage possibilities. My research deals with different aspects of such renewable energy transformations and storage concepts and connects them.
For (solar) production of hydrogen as renewable fuel, not only photoabsorbers, but also efficient catalysts are required. Here, we developed a novel concept enabling operando enhancements of catalytic activities with delafossite oxides, making use of an intrinsically expanded noble metal sublattice that enables a corrosion induced growth of an expanded cap layer by substrate induced strain effects, modifying the surface catalytic conversion processes by stabilizing a metastable phase and outperforming even bulk Pt.
Direct photocatalytic conversion processes with novel organic materials such as covalent organic frameworks (COFs) often lack knowledge about intrinsic optoelectronic properties. We introduced activity origin studies for COFs by photocurrent measurement models enabling operando determination of charge carrier generation rates and band positions, which before relied mostly on theoretical calculations.
Last, we investigated and explained the direct solar energy storage properties of the new 2D carbon nitrides poly(heptazine imide) (PHI). After having shown that PHI can be photocharged, acting as both, photoabsorber and storage medium, we introduced “dark photocatalysis”, where the photocatalytic hydrogen evolution with PHI can be triggered on demand after illumination. We revealed many interesting material features explaining the storage process and have shown that PHI can also act as electrode for direct solar batteries, offering a new, earth abundant materials perspective to bypass fluctuations in renewable energy generation.