Bugra Turan

Upscaling of integrated photoelectrochemical water-splitting devices to large areas

Photoelectrochemical water splitting promises both sustainable energy generation and energy storage in the form of hydrogen. However, the realization of this vision requires laboratory experiments to be engineered into a large-scale technology. Up to now only few concepts for scalable devices have been proposed or realized. Here we introduce and realize a concept which, by design, is scalable to large areas and is compatible with multiple thin-film photovoltaic technologies. The scalability is achieved by continuous repetition of a base unit created by laser processing. The concept allows for independent optimization of photovoltaic and electrochemical part. We demonstrate a fully integrated, wireless device with stable and bias-free operation for 40 h. Furthermore, the concept is scaled to a device area of 64 cm2 comprising 13 base units exhibiting a solar-to-hydrogen efficiency of 3.9%. The concept and its successful realization may be an important contribution towards the large-scale application of artificial photosynthesis.

A modular device for large area integrated photoelectrochemical water-splitting as a versatile tool to evaluate photoabsorbers and catalysts

We present a stand-alone integrated solar water-splitting module with an active area of 64 cm2 and a long-term stable operation. As a photocathode we employ multijunction thin film silicon solar cells that were optimized to deliver a suitable output voltage for spontaneous water-splitting. Two approaches for the design of a suitable front contact are presented to reduce series resistance losses related to the upscale of the photoelectrodes. The photoelectrode is protected from the electrolyte by a sheet metal which connects the rear contact of the solar cell with the hydrogen evolving catalyst. Thereby, the sheet metal ensures long-term stability while the electrical and thermal coupling of the solar cell and the electrolysis cell is maintained. Due to the modular setup, which allows us to vary and optimize the device components (i.e. the solar cell, catalysts, membrane, and electrolyte) individually, the presented water-splitting device provides a convenient toolbox for the optimization of such systems.