Nanocrystalline Boron-Doped Diamond as a Corrosion-Resistant Anode for Water Oxidation via Si Photoelectrodes

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Due to its high sensitivity to corrosion, the use of Si in direct photoelectrochemical (PEC) water-splitting systems that convert solar energy into chemical fuels has been greatly limited. Therefore, the development of low-cost materials resistant to corrosion under oxidizing conditions is an important goal toward a suitable protection of otherwise unstable semiconductors used in PEC cells. Here, we report on the development of a protective coating based on thin and electrically conductive nanocrystalline boron-doped diamond (BDD) layers. We found that BDD layers protect the underlying Si photoelectrodes over a wide pH range (1–14) in aqueous electrolyte solutions. A BDD layer maintains an efficient charge carrier transfer from the underlying silicon to the electrolyte solution. Si|BDD photoelectrodes show no sign of performance degradation after a continuous PEC treatment in neutral, acidic, and basic electrolytes. The deposition of a cobalt phosphate (CoPi) oxygen evolution catalyst onto the BDD layer significantly reduces the overpotential for water oxidation, demonstrating the ability of BDD layers to substitute the transparent conductive oxide coatings, such as indium tin oxide (ITO) and fluorine-doped tin oxide (FTO), frequently used as protective layers in Si photoelectrodes. 

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Description

Schematic illustration of a photoelectrode based on a boron doped diamond electrode and buried pn-junction Si solar cell for water oxidation and reduction. The PV component (np-Si) is responsible for incident light absorption and charge separation across the pn-junction, whereas oxygen evolution occurs at the boron doped diamond electrode/electrolyte surface and hydrogen evolves at the externally wired metal cathode.

Contact person: Petr Ashcheulov, +420 266 052 544, ashcheulov [at] fzu [dot] cz

Cooperating institutions:

  • Faculty of Biomedical Engineering, Czech Technical University in Prague, Sítna sq. 3105, Kladno, 272 01, Czech Republic
  • Fill Factory S.r.o., Televizní 2618, 756 61 Rožnov pod Radhoštěm, Czech Republic
  • Laboratory for Molecular Engineering of Optoelectronic Nanomaterials, Ecole Polytechnique Fédérale de Lausanne (EPFL), Station 6, Lausanne, 1015, Switzerland
  • J. Heyrovsky Institute of Physical Chemistry, Czech Academy of Sciences, Dolejskova 3, Prague 8, 182 23, Czech Republic
  • New Technologies-Research Centre, University of West Bohemia, Pilsen, 306 14, Czech Republic
  • Research Centre Řež, Husinec-Řež, 250 68, Czech Republic