Kaleb Julius Strahringer

Investigation of Photocatalytic Water Splitting with Time-Resolved Photoelectron-Photoion Coincidence Spectroscopy

Using sunlight to split water into oxygen and hydrogen offers a sustainable route to producing hydrogen as a source of energy from abundant resources. While directly breaking the H–O bond requires 6.66 eV [1], excitation of a chromophore that mediates the reaction can significantly reduce the necessary photon energy.

We aim to investigate electron-driven proton-transfer (EDPT) reactions in chromophore-water complexes proposed for photocatalytic water splitting [2]. Such hydrogen-transfer reactions from water to the chromophore occuring upon optical excitation can be seen as the initial step of a water splitting reaction.

To elucidate the energetics and dynamics of such reactions we use spectroscopic techniques ranging from high-resolution nanosecond-laser fluorescence spectroscopy combined with cluster isolation techniques to time-resolved photoelectron–photoion coincidence spectroscopy with monochromatic XUV radiation. The latter technique uses two femtosecond Laser pulses: a pump pulse to excite the chromophore and trigger the reaction and a time-delayed XUV probe pulse to ionize it. By measuring the kinetic energy and angular distribution of photoelectrons ejected by the probe pulse in dependence of the time-delay, we gain insights into the temporal development of the electronic structure of the system. Detecting the photoions in coincidence to the electrons allows us to distinguish signals from different possible reaction products.

[1] Esteves-López et al., Phys. Chem. Chem. Phys. 18 (2016) 25637
[2] Liu et al., Chem. Phys. 464 (2016) 78

Supervisors: Frank Stienkemeier & Sebastian Hartweg