Amorphous TiO2 coatings stabilize Si, GaAs, and GaP photoanodes for efficient water oxidation

Shu Hu, Matthew R. Shaner, Joseph A. Beardslee, Michael Lichterman, Bruce S. Brunschwig, Nathan S. Lewis

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Abstract

Although semiconductors such as silicon (Si), gallium arsenide (GaAs), and gallium phosphide (GaP) have band gaps that make them efficient photoanodes for solar fuel production, these materials are unstable in aqueous media.We show that TiO2 coatings (4 to 143 nanometers thick) grown by atomic layer deposition prevent corrosion, have electronic defects that promote hole conduction, and are sufficiently transparent to reach the light-limited performance of protected semiconductors. In conjunction with a thin layer or islands of Ni oxide electrocatalysts, Si photoanodes exhibited continuous oxidation of 1.0 molar aqueous KOH to O2 for more than 100 hours at photocurrent densities of >30 milliamperes per square centimeter and ∼100% Faradaic efficiency. TiO2-coated GaAs and GaP photoelectrodes exhibited photovoltages of 0.81 and 0.59 V and light-limiting photocurrent densities of 14.3 and 3.4 milliamperes per square centimeter, respectively, for water oxidation.

Original languageEnglish
Pages (from-to)1005-1009
Number of pages5
JournalScience
Volume344
Issue number6187
DOIs
Publication statusPublished - Jan 1 2014

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Hu, S., Shaner, M. R., Beardslee, J. A., Lichterman, M., Brunschwig, B. S., & Lewis, N. S. (2014). Amorphous TiO2 coatings stabilize Si, GaAs, and GaP photoanodes for efficient water oxidation. Science, 344(6187), 1005-1009. https://doi.org/10.1126/science.1251428