Novel Photoelectrodes and Noble Metal Free Catalysts for Light Driven Water Electrolysis

The generation of fuels from sunlight and water is considered as a task of paramount importance for a sustainable energy supply in the future. Decomposition of water by a photoelectrochemical process is a possibility to harvest solar energy in form of hydrogen in a large scale. For this purpose, a membra­ne can be used which immersed in an aqueous electrolyte and illuminated by sunlight is able to split water into hydrogen and oxygen. Such a device is frequently addressed as artificial leaf. From an eco­nomic and environmental point of view this device should consist of cheap, abundant and non-toxic elements featuring a Solar-to-Hydro­gen (STH) efficiency > 10% and generating hydrogen at a price of ~3 €/kg H₂.

In our lab two approaches have been pursued in the last time to realize artificial leaf type structures:

• triple junction thin film a-Si/µc-Si solar cells in superstrate geometry with integrated catalysts [1],

• tandem junction solar cells combined with novel semiconducting ternary metal oxide anodes [2].

  As photoanode materials Fe₂WO₆ and BiVO₄ are under investigation and have been improved with re­spect to their photovoltage and their photocurrent densities using sol-gel and spray pyrolysis as prepa­ration technique. To lower the costs of the device platinum was replaced by carbon supported MoS₂ nanoparticles as hydrogen evolving catalyst. Deposited as a blend with PEDOT:PSS on the backside of the solar cell an SHE of 3.7% was yielded. RuO₂ was replaced by manganese and cobalt oxide thin films, respectively.

  References:

  [1]      Diana Stellmach, Peter Bogdanoff, Onno Gabriel, Bernd Stannowski, Rutger Schlatmann,

            Roel van de Krol, Sebastian Fiechter; FORMATEX 2013, 880-886.

  [2]      Fatwa F. Abdi, Lihao Han, Arno H.M. Smets, Miro Zeman, Bernard Dam, Roel van de Krol,          NATURE COMM. 2013, 4:2195, DOI: 10.1038/ncomms3195.