Transparent conductive oxide as a protective layer in the development of an effective
photoanode for solar water splitting applications.
Jennifer Halpin
1,2
, Jan Kegel
1,2
, Ian Povey
1
, Martyn Pemble
1,2
1
Tyndall National Institute, University College Cork, Ireland
2
Department of Chemistry, University College Cork, Cork, Ireland
The inherent stability, visible light transparency and hole transport properties of titanium
dioxide (TiO
2
) has been utilized to overcome the critical problem of photocorrosion in
photoanode materials for water splitting applications.
The splitting of water using visible light illumination is considered the “Holy Grail” of
renewable energy research. The ability to generate hydrogen fuel without consuming fossil
fuels or producing carbon dioxide would have a significant impact on energy production
worldwide.
Cadmium sulfide (CdS) possesses almost the ideal band gap energy for visible light water
splitting (ca. 2.4eV). However its practical application as a photoanode is severely limited by
photocorrosion. Here, we propose that a thin layer of a more stable material such as titanium
dioxide could provide the necessary protection. As a transparent conductive oxide TiO
2
is
ideally suited as a protective layer as it allows visible light to reach the cadmium sulfide
underneath while also facilitating charge carrier transport to the solid electrode / aqueous
electrolyte interface.
A thin (ca. 2-5nm) layer of titanium dioxide is applied by atomic layer deposition (ALD)
using TMDA and water as the precursors, a nitrogen carrier gas and a substrate temperature
of 180°C. ALD allows for the conformal growth and accurate thickness control that is
required for the protective layer. We demonstrate that this is particularly important when
depositing onto CdS since the surface roughness of the CdS layer can result in pin-hole
formation. This poster will present an analysis of a titanium dioxide protected cadmium
sulfide photoanode by means of electrochemical measurements, photoluminescence (PL),
scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray
diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and UV-visible spectroscopy.
This work forms part of the research currently underway at Tyndall funded by the Science
Foundation Ireland (Republic of Ireland), National Science Foundation (US) and Department
for Employment and Learning (Northern Ireland) US: Ireland project RENEW- Research into
Emerging Nanostructured Electrodes for the Splitting of Water, Grant Number 13/US/I2543
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