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EN11.04.05 : Water Splitting by Defects

5:00 PM–7:00 PM Apr 3, 2018

PCC North, 300 Level, Exhibit Hall C-E

Description
Samar Fawzy1 Mostafa Omar1 Nageh Allam1

1, American University in Cairo, New Cairo, , Egypt

Using TiO2 nanostructures in photoelectrochemical water-splitting have attracted intensive research as one of the most promising methods for Hydrogen production. Unfortunately, the challenge to overcome the large band gas is still persisting. Alloying, annealing in a reducing atmosphere, and multipodal nanotubes have proven to be effective pathways owing to structure modification, band gap tuning, graded refractive index, and easier charge transport. Herein, we make use of alloyed single and multipodal Ti-Nb-Zr-O nanotubes (MPNTs) annealed under different atmospheres: Air, O2, and H2 to enhance TiO2 behavior. SEM was used to confirm the formation of MPNTs. Structural analysis using XRD, Raman Spectroscopy, and XPS confirmed the formation of a single mixed oxide Ti-Nb-Zr-O in a strained-anatase crystal structure in both Air and Oxygen atmosphere, while on the other hand, ZrTiO4 appeared in the Hydrogen annealed samples. XPS analysis showed the formation of valence band tail states causing a band-gap reduction in the hydrogen annealed samples, which in turn reflected on the absorption spectra, which showed a similar tail, reaching NIR/Vis. region. Mott-Schottky analysis showed 4 orders of magnitude increase in the carrier density when compared to other annealing atmospheres. These synergistic effects resulted in almost 25-fold enhancement in the photocurrent compared to Oxygen and Air annealing. Multinary metal oxides would act as a promising candidate for engineering the required material properties for efficient PEC because of the vast number of possible material combinations.

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