Pushing Oxide Catalysis: Atomic-Scale View at Photocharges

What truly happens to light-generated charge inside a catalyst? When sunlight hits certain materials, it excites their electrons and creates charged particle pairs that could help produce clean fuels such as hydrogen or carbon-neutral chemicals. Yet these charge pairs often recombine or get trapped before they reach the surface, where useful chemical reactions take place. This loss of efficiency limits today`s solar-fuel technologies, and the reason lies in processes that occur on extremely small length and time scales. The POP project (Pushing Oxide Catalysis: Atomic-Scale View at Photocharges) aims to uncover these hidden processes by observing how photo-excited charge behaves at the atomic scale. In many metal oxides, light can create special localized states called polarons that distort their surroundings and become trapped. Naturally occurring defects together with intentionally added dopants, can either support or hinder the movement of such charge carriers. Understanding this delicate balance is crucial for improving photo-catalytic efficiency, yet a comprehensive picture has remained out of reach because these processes are too fast and too small to observe with conventional methods. Within the framework of the Research Groups programme funded by the Austrian Science Fund (FWF), POP brings together three complementary approaches to overcome this challenge. Franceschis team at TU Wien will grow highly precise oxide samples with carefully controlled impurities and defect levels, aiming to create reliable model systems for studying photo-excited charge. Pateras group at the University of Innsbruck will develop advanced microscopy techniques capable of imaging the motion of charge in real time, with the goal of directly visualizing how defects and dopants affect charge dynamics. Reticcioli will implement new machine-learning-based computer models to simulate excited-state dynamics, seeking to establish a theoretical framework that captures the interplay between photo-generated free carriers and polaron formation. By combining these efforts, POP will reveal how photo-excited charges form, travel, recombine, or become trapped in catalytic materials such as hematite, bismuth vanadate, and cobalt oxide. Importantly, it will also show how defects and dopants influence these processes at the atomic level. These insights aim to support future efforts toward developing more efficient photo-catalysts and could gradually contribute to long-term progress in sustainable fuel production.