Photoelectrocatalytic water oxidation at Mo:BiVO4 / transition metals modified electrodes

Olga Krysiak, Ruhr-Universität , Bochum, Germany
João Junqueira, Ruhr-Universität , Bochum, Germany
Tim Bobrowski, Ruhr-Universität, Bochum, Germany
Wolfgang Schuhmann, Ruhr-Universität, Bochum, Germany

The semiconducting oxides resistant to photo-corrosion in aqueous solutions which are able to efficiently absorb visible light are up to now the best materials for solar light-driven photo-electrochemical water splitting devices. Each of the well-known single-metal-oxide semicon-ductors, such as TiO2, WO3, Fe2O3, ZnO has disadvantages and does not display the required performance for application in solar to chemical energy conversion. Combining of single oxide semiconductors into binary and ternary systems or the use of catalysts and co-catalysts may enable us to overcome their present limitations and obtain materials with improved pro¬perties. Due to the fact that the oxygen evolution reaction is the rate-determining step in solar-driven water splitting the most promising way to enhance the properties of such devises is seen in the deposition of oxygen evolution catalysts on the surface of photoanodes. We examined the activity of the oxygen evolution reaction catalysts composed of Ni, Fe and Cr. A catalyst material is deposited on the surface of a molybdenum doped bismuth vanadate photoanode by spray-coating. The choice of the deposition method gives possibilities to attain composition and thickness gradients of the catalyst. The structure of prepared materials was examined by surface analysis techniques e.g. XPS, SEM, EDX, etc. The photoelectrocatalytic activity of the materials was examined by means of an optical scanning droplet cell (OSDC). The wetted area of the sample surface is defined by the tip diameter and forms the working electrode in the electrochemical three-electrode setup which enables localized characterization of the studied sample. Photoelectrochemical characterization includes open circuit potential determination, steady-state photocurrent and incident photon-to-current conversion efficiency measurements. The obtained results are used to define the photoactivity and band structure: flat band potential and bandgap of the investigated material.

The authors are grateful to the financial support of the DFG within the framework of the SPP1613 (SCHU929/12-1 and 12-2). O. A. K. acknowledges financial support from the MAESTRO Grant UMO-2013/10/A/ST5/00245, awarded by NCN Poland.

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