Increasing solar hydrogen production of TiO2 nanorods-based photoanodes by surface treatments.
Teresa Andreu a, Damián Monllor-Satoca a, Cristian Fàbrega a, Joan Ramon Morante a b
a Catalonia Institute for Energy Research, Jardins de les Dones de Negre, 1, 2nd floor, sant adria del valles, barcelona, 8930, Spain
b University of Barcelona (UB). Dept. Electronics, Martí i Franquès, 1. 08028 Barcelona. Spain, Spain
Poster, Cristian Fàbrega, 036
Publication date: 31st March 2013

Titania nanorods photoanodes still constitute one of the best candidates for hydrogen production by direct photoelectrocatalysis in spite of its intrinsic drawbacks such as a limited solar spectra light absorption caused by its wide band gap .Unlike other materials with much more suitable band gaps (e.g. WO3and Fe2O3), TiO2has appropriate alignment of energy levelsavoiding the need of an extra bias, obtaining a favorable energy balance and reduced cost of the produced hydrogen.

These features, together with their potential capacity to be integrated as active electrode in an advanced tandem cell, claim for the improvement and optimization of the hydrogen photogeneration in order to increase the photoelectrode efficiency.

In this contribution, different strategies for the improvement of titania nanorods photoanodes´ performance are presented, paying special attention to their surface states and its their influence on their final performance.

These strategies are generally based on heating treatments in different reductive atmospheres that lead to the formation of surface states as well as modifications on the electrical properties (charge carrier concentration and diffusion lengths ...) of rutile nanorods. Using IPCE measurements observed that the material modification affected differently depending on the excitation wavelength. Finally, by means of XPS, Mott-Schottky and EIS measurements, a model is proposed to explain such behavior.

The strategies followed in this work have been proved to be effective in increasing the photoanodes’ overall efficiency. An increasing of 300% in relation with the non-treated samples can be reached by these methods, so as conversion efficiencies up 60-70% in UV part of the spectra and some improvement in the visible part below the theoretical band gap.



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