Nanostructured transition metal oxide electrodes for the light-induced water splitting – a combinatorial approach

Helge Stein, Ruhr-Universität Bochum, Bochum, Germany
Chinmay Khare, Ruhr-Universität Bochum, Bochum, Germany
Kirill Sliozberg, Ruhr-Universität Bochum, Bochum, Germany
Robert Meyer, Ruhr-Universität Bochum, Bochum, Germany
Wolfgang Schuhmann, Ruhr-Universität Bochum, Bochum, Germany
Alfred Ludwig, Ruhr-Universität Bochum, Bochum, Germany

Discovery and optimization of metal oxide-based semiconductors that are abundant, stable and non-toxic for photoelectrochemical water splitting is envisaged by using a combinatorial approach. Despite increasing efforts in recent decades, there is still no material that matches the necessary criteria for efficient water photoelectrolysis. Up to now only a fraction of all possible metal oxides has been investigated and only a few of them show promising properties for solar water splitting. The predominantly investigated binary oxides Fe2O3, TiO2 and WO3 do not show sufficient stability, a suitable bandgap, efficient light absorption, high catalytic activity or charge carrier lifetimes. As the number of possible multinary mixtures of yet to be found materials is enormous, new methods of rapid synthesis and high-throughput/high-quality evaluation need to be implemented.

In this contribution, we will demonstrate the suitability of combinatorial reactive magnetron sputtering of metal oxides libraries subsequently analyzed by high throughput EDX, XRD, and photoelectrochemistry in an optical scanning droplet cell. Visualization of the obtained multidimensional datasets will be addressed as composition, structure and function need to be correlated to gain an in-depth knowledge of the synthesized new materials. Ongoing development and optimization of metal oxide thin film materials libraries for solar water splitting in the quaternary materials systems Fe-W-Ti-O and its three ternary sub systems will be covered. An example of the optimization by nanostructuring through sputtering from a glancing angle deposition geometry will be given.

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