A two-compartment photoelectrochemical cell for solar hydrogen production

In the near future, we need new, clean fuels and alternative sources of hydrocarbons for chemical synthesis. We are investigating a device to directly convert solar light into chemical energy. For this purpose, many materials have already been proposed recently. However, currently very little research has been devoted to the integration of these materials into a working device that outputs separated streams of hydrogen and oxygen. We have designed a fuel cell-like, two-compartment photoelectrochemical cell to enhance efficiency by optimizing transport of reagents and intermediates and by minimizing electrical losses. At the photoanode side, TiO2 absorbs light and uses that energy to split water into oxygen and protons while generating electrons. The protons are transported through a membrane to the other compartment, while electrons pass via an external circuit. At that side, electrons and protons are combined to hydrogen gas on a platinum catalyst. In such a system, each reaction compartment can be optimized independently. First, rate-limiting factors were determined by monitoring photocurrents under a variety of conditions. Besides the water splitting reaction, proton transport was identified as a critical factor and product accumulation at either side was detrimental for long-term performance. This insight was already used to improve performance with modified materials. Implementation of advanced materials could increase efficiencies of this device to a practical level.Was awarded the prize for best oral presentationstatus: publishe