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Proceedings Paper

Photoelectrochemical water splitting: silicon photocathodes for hydrogen evolution
Author(s): Emily L. Warren; Shannon W. Boettcher; James R. McKone; Nathan S. Lewis
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Paper Abstract

The development of low cost, scalable, renewable energy technologies is one of today's most pressing scientific challenges. We report on progress towards the development of a photoelectrochemical water-splitting system that will use sunlight and water as the inputs to produce renewable hydrogen with oxygen as a by-product. This system is based on the design principle of incorporating two separate, photosensitive inorganic semiconductor/liquid junctions to collectively generate the 1.7-1.9 V at open circuit needed to support both the oxidation of H2O (or OH-) and the reduction of H+ (or H2O). Si microwire arrays are a promising photocathode material because the high aspect-ratio electrode architecture allows for the use of low cost, earth-abundant materials without sacrificing energy-conversion efficiency, due to the orthogonalization of light absorption and charge-carrier collection. Additionally, the high surfacearea design of the rod-based semiconductor array inherently lowers the flux of charge carriers over the rod array surface relative to the projected geometric surface of the photoelectrode, thus lowering the photocurrent density at the solid/liquid junction and thereby relaxing the demands on the activity (and cost) of any electrocatalysts. Arrays of Si microwires grown using the Vapor Liquid Solid (VLS) mechanism have been shown to have desirable electronic light absorption properties. We have demonstrated that these arrays can be coated with earth-abundant metallic catalysts and used for photoelectrochemical production of hydrogen. This development is a step towards the demonstration of a complete artificial photosynthetic system, composed of only inexpensive, earth-abundant materials, that is simultaneously efficient, durable, and scalable.

Paper Details

Date Published: 24 August 2010
PDF: 7 pages
Proc. SPIE 7770, Solar Hydrogen and Nanotechnology V, 77701F (24 August 2010); doi: 10.1117/12.860994
Show Author Affiliations
Emily L. Warren, California Institute of Technology (United States)
Shannon W. Boettcher, California Institute of Technology
James R. McKone, California Institute of Technology (United States)
Nathan S. Lewis, California Institute of Technology (United States)

Published in SPIE Proceedings Vol. 7770:
Solar Hydrogen and Nanotechnology V
Hicham Idriss; Heli Wang, Editor(s)

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