Hydrogen is the simplest solar fuel to produce and while noble metals are efficient catalysts for photoelectrochemical hydrogen evolution, earth-abundant alternatives will be needed for large-scale use. We have shown that bioinspired molecular clusters based on transition metal sulfides mimics nature's enzymes for hydrogen evolution when deposited on various supports [1, 2, 3]. When these catalysts are deposited on p-type Si they can harvest the red part of the solar spectrum [3, 4]. Such a system could constitute the cathode part of a tandem dream device where the red part of the spectrum is utilized for solar fuel evolution, while the blue part is reserved for the more difficult oxygen evolution. Recently we have found that this system can be improved considerably using a np-Si system which is protected by a relative thick layer of TiO2 [5]. This improvement in corrosion protection by deposition of TiO2will be discussed [6, 7] in greater detail. Finally we willalso discuss the latest progress in combining this with a large band semiconductor and how this can be coupled with necessary protection layers and appropriate catalysts.B. Hinnemann et al., JACS 127, (2005) 5308.T. F. Jaramillo et al., Science 317, (2007) 100.Y. Hou et al., Nature Materials 10, (2011) 434.A. B. Laursen et al. ,Energy Environ. Sci., 5 (2012) 5577.B. Seger, et al. �Sustainable Hydrogen Production from a Molybdenum Sulfide Catalyst on protected n+p -Silicon Photocathode. � Angew. Chem. Int. Ed., 51 (2012) 9128.B. Seger, et al. � Using TiO2 as a Conductive Protective Layer for Photo-cathodic H2 evolution�, JACS 135 (2013) 1057.B. Seger, et al. �Silicon Protected with Atomic Layer Deposited TiO2 Part B- Conducting Versus Tunneling Through the TiO2.�, Accepted Journal of Materials Chemistry A (2013).

New catalyst and protection layers for the tandem design for solar water splitting

247th National Meeting (2014)

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