Advanced characterisation of nanostructured materials for photocatalytic water splitting

Advanced characterisation of nanostructured materials for photocatalytic water splitting

The sunlight is capable of answering the global energy need. Semiconducting materials have been developed to convert solar radiation into fuels for energy storage and mobile applications. Electronic band alignment, carrier transport, and reaction kinetics at interfaces make the system optimization a joint adventure for physicists, materials scientists, and chemists. In our group, we apply structural and electrochemical characterization to study nanostructured materials and their stability.

During the two funding periods (2011-2019) of SPP 1613, “fuels produced regeneratively through light-driven water splitting”, we have teamed up with collaborators including the Bein group, the Fattakhova-Rohlfing group, the Fischer group and the Pentcheva group to study a wide range of photocatalytic structures, from thin films, nanoparticles to elaborated nanostructures of Fe2O3, TiO2, Cu2O, BiVO4, and complex ternary oxides.

A twin boundary in a nanocrystalline Fe2O3 photoanode.

We apply state-of-the-art electron microscopy and spectroscopy to study the surfaces for electrochemical reactions as well as the interfaces for carrier transport. Big data analysis approaches are developed to resolve subtle changes in chemical compositions and bonding characteristics at sub-nanometer resolution. Specifically we use electron energy loss spectroscopy in an aberration corrected scanning transmission electron microscope to understand these changes. We have validated concepts such as nanostructures, localized doping, and strain engineering to improve the catalytic activity.

Stability of photocatalysts is as important as their activity. Oxidation and reduction of oxides can happen at respective anodic and cathodic potentials, especially under sunlight that populates minority carriers. Together with the Mayrhofer group and the Fischer group, we study the corrosion of photocatalysts under various photoelectrochemical conditions. We are developing new methodologies to tackle these questions with the aim to understand the underlying degradation mechanism.

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