TiO_2 Nanotubes Formed in Aqueous Media: Relationship between Morphology, Electrochemical Properties and the Photoelectrochemical Performance for Water Oxidation

摘要

The effect of voltage and electrolyte composition on the formation of TiO_2 nanotube films over its morphology, semiconductor properties and photoelectrochemical performance for water oxidation was studied. TiO_2 nanotube films were formed by potentiostatic anodization in 0.1 MH_2SO_4/0.05MHF and 0.1MH_2SO_4/0.05MNH_4F during 1 h at four different voltages. SEM images showed a more significant chemical attack when NH4F was employed, evidenced by larger tube diameters and thinner films. The semiconductor properties were altered by the nature of the counter-ion utilized during film growth, obtaining films with a higher density of donor and less positive flat band potential in NH_4F electrolytes. The films formed in NH4F showed higher photopotentials and photocurrent related to the modification of their morphology and semiconductor properties, attaining a maximum at formation voltage of 15 V.