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Photoelectrochemical (PEC) water splitting is a promising approach to harvest and store solar energy [1]. Silicon has been widely investigated for PEC photoelectrodes due to its suitable band gap (1.12 eV) matching the solar spectrum [2]. Here we investigate employing nickel both as a catalyst and protecting layer of a p-type silicon photocathode for photoelectrochemical hydrogen evolution in basic electrolytes for the first time. The silicon photocathode was made by depositing 15 nm Ti on a p-type silicon wafer followed by 5 nm Ni. The photocathode afforded an onset potential of ~0.3 V vs. the reversible hydrogen electrode (RHE) in alkaline solution (1 M KOH). The stability of the Ni/Ti/p-Si photocathode showed a 100 mV decay over 12 h in KOH, but the stability was significantly improved when the photocathode was operated in potassium borate buffer solution (pH ≈ 9.5). The electrode surface was found to remain intact after 12 h of continuous operation at a constant current density of 10 mA/cm2 in potassium borate buffer, suggesting that Ni affords good protection of Si based photocathodes in borate buffers.

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Publication history
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Acknowledgements

Publication history

Received: 02 September 2014
Revised: 05 November 2014
Accepted: 09 November 2014
Published: 17 January 2015
Issue date: May 2015

Copyright

© Tsinghua University Press and Springer-Verlag Berlin Heidelberg 2014

Acknowledgements

Acknowledgements

This work was supported by a grant from Stanford GCEP, Precourt Institute of Energy and by the U.S. Department of Energy, Office of Basic Energy Sciences, Division of Materials Sciences and Engineering under Award No. DOE DE-SC0008684 (for the microscopy and spectroscopy characterization part of this work). M. J. K. acknowledges support from an NSF Graduate Fellowship.

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