Formation of pure and Au nanoparticles dispersed tio2 nanotube arrays by anodisation as a photoanode in photoelectrochemical cell application
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Date
2016-06
Authors
Loo Foong Ling
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Abstract
Photoelectrochemical (PEC) cell utilising TiO2 nanotubes (TNT) formed by anodization was produced to assess solar-to-hydrogen conversion efficiency. In order to produce the nanotubes, Ti foil was anodised in fluoride containing ethylene glycol (EG) electrolyte and 3 ml of LiOH at 60 V for 60 minutes. The source of fluoride was NH4F and its effect was studied by varying the amount loaded to the EG electrolyte. It was found that as the amount of NH4F used increases, the length and the aspect ratio of the nanotubes produced were increased. The diameter however did not show any obvious changes. The as-anodized TNT arrays formed were amorphous. Annealing was done at 450 °C to transform the amorphous phase to anatase phase. The photocurrent of the PEC cell was found to be dependent on the TNTs formed in different loadings of NH4F with longer length TNTs gave higher photocurrent. The highest photocurrent was 1.61 mA/cm2 formed for 0.5 wt% NH4F in 97 vol% EG and 3 vol% of LiOH sample. The corresponding efficiency was 1.18 %. The lowest photocurrent recorded was for the TNT arrays produced by 0.7 wt% of NH4F and it was thought that the reason for the reduction of photocurrent was due to the destroyed surface morphology of the nanotube array. At high NH4F content, the surface collapsed due to severe thinning of the surface tube wall. TNTs were then decorated with gold nanoparticles (AuNPs) as to assess on the suitability of the dispersion of AuNPs on photocurrent in a PEC. However, it was found that the PEC cell performance did not improve much with the addition of AuNPs on TNTs. The recorded photocurrent was 0.97 mA/cm2.