Gallium Phosphide photoanode coated with TiO2 and CoOx for stable photoelectrochemical water oxidation

M. Alqahtani, S. Ben-Jabar, M. Ebaid, S. Sathasivam, P. Jurczak, X. Xia, A. Alromaeh, C. Blackman, Y. Qin, B. Zhang, Boon S. Ooi, H. Liu, I. P. Parkin, J. Wu

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15 Scopus citations


Gallium Phosphide (GaP) has a band gap of 2.26 eV and a valance band edge that is more negative than the water oxidation level. Hence, it may be a promising material for photoelectrochemical water splitting. However, one thing GaP has in common with other III-V semiconductors is that it corrodes in photoelectrochemical reactions. Cobalt oxide (CoOx) is a chemically stable and highly active oxygen evolution reaction co-catalyst. In this study, we protected a GaP photoanode by using a 20 nm TiO2 as a protection layer and a 2 nm cobalt oxide co-catalyst layer, which were both deposited via atomic layer deposition (ALD). A GaP photoanode that was modified by CoOx exhibited much higher photocurrent, potential, and photon-to-current efficiency than a bare GaP photoanode under AM1.5G illumination. A photoanode that was coated with both TiO2 and CoOx layers was stable for over 24 h during constant reaction in 1 M NaOH (pH 13.7) solution under one sun illumination.
Original languageEnglish (US)
Pages (from-to)A364
JournalOptics Express
Issue number8
StatePublished - Mar 18 2019

Bibliographical note

KAUST Repository Item: Exported on 2020-10-01
Acknowledgements: Funding: This work is supported by King Abdulaziz City for Science and Technology (KACST), Riyadh, Saudi Arabia. The Future Compound Semiconductor Manufacturing Hub (CS Hub) funded by EPSRC grant EP/P006973/1. Acknowledgements: M.A. and J.W. conceived the idea and wrote the manuscript. M.A. performed the PEC experiments and analysed the data. S.S. performed XPS and related analysis. S. B. conducted Ultraviolet–visible spectroscopy (UV–Vis) and related analysis. P.J. performed AFM and related analysis. ALD CoOx was grown by B.Z. and Y.Q. X. X. and C. B. performed ALD TiO2. M. E. and B. O. measured the gas evolution. All authors reviewed and commented on the manuscript.


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