PHOTO-INDUCED ELECTRON DYNAMICS AT THE TRANSITION-METAL OXIDE–WATER INTERFACE FROM TIME-RESOLVED LIQUID-JET PHOTOEMISSION

Photocatalytic water splitting using transition metal oxides (TMOs) has the potential to play a key role in the sustainable large-scale production of hydrogen.

Due to their activity, cost-effectiveness, and stability TMOs are viewed as attractive materials to catalyze water splitting by harnessing solar energy.

A major challenge is effectively preventing the recombination of electrons and holes in the TMOs produced upon (solar) light absorption.

While these charge recombination processes occur on the pico-to-nanosecond timescale, the whole water splitting process is almost 12 orders of magnitude slower!

This huge difference urgently demands a better understanding of the underlying mechanisms and charge-driven chemical reactions involving electron transfer (reduction reaction) or hole transfer (oxidation reaction) that take place at the TMO semiconductor–liquid interface.

In my WATER-X project I will investigate these sub-10-picoseconds processes at the interface of TMO nanoparticles in bulk water by using time-resolved femtosecond laser photoelectron spectroscopy by applying liquid microjet setup.

The objective is to measure the early-time molecular intermediates and their associated electronic-structures, their lifetimes, energetics, photoelectron angular distributions, and decay mechanisms of the short-lived molecular intermediates.

With this knowledge we can determine the exact mechanisms of light-induced water dissociation and will pave the way to manipulating light-induced interactions to the solid-aqueous interface for improving the efficiency of light-to-energy conversion.

These novel experiments will be performed for four nanoparticle photocatalysts, hematite, titanium dioxide, cerium oxide, and nickel-iron-oxyhydroxide with manifold electronic-structure properties (bandgap, charge carrier dynamics, and energetics), which make them attractive for future applications.