Covalent Surface Modification of Gallium Arsenide Photocathodes for Water Splitting in Highly Acidic Electrolyte

Logan E. Garner, K. Xerxes Steirer, James L. Young, Nicholas C. Anderson, Elisa M. Miller, Jonathan S. Tinkham, Todd G. Deutsch, Alan Sellinger, John A. Turner, Nathan R. Neale

Research output: Contribution to journalArticlepeer-review

29 Scopus Citations


Efficient water splitting using light as the only energy input requires stable semiconductor electrodes with favorable energetics for the water-oxidation and proton-reduction reactions. Strategies to tune electrode potentials using molecular dipoles adsorbed to the semiconductor surface have been pursued for decades but are often based on weak interactions and quickly react to desorb the molecule under conditions relevant to sustained photoelectrolysis. Here, we show that covalent attachment of fluorinated, aromatic molecules to p-GaAs(1 0 0) surfaces can be employed to tune the photocurrent onset potentials of p-GaAs(1 0 0) photocathodes and reduce the external energy required for water splitting. Results indicate that initial photocurrent onset potentials can be shifted by nearly 150 mV in pH −0.5 electrolyte under 1 Sun (1000 W m−2) illumination resulting from the covalently bound surface dipole. Though X-ray photoelectron spectroscopy analysis reveals that the covalent molecular dipole attachment is not robust under extended 50 h photoelectrolysis, the modified surface delays arsenic oxide formation that results in a p-GaAs(1 0 0) photoelectrode operating at a sustained photocurrent density of −20.5 mA cm−2within −0.5 V of the reversible hydrogen electrode.

Original languageAmerican English
Pages (from-to)767-773
Number of pages7
Issue number4
StatePublished - 2017

Bibliographical note

Publisher Copyright:
© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

NREL Publication Number

  • NREL/JA-5900-67024


  • covalent surface attachment
  • gallium arsenide
  • photoelectrochemistry
  • surface dipole
  • water splitting


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