Abstract
Nanotubes (NTs) of Ta3N5 were synthesized by nitridation of Ta2O5 NTs. The samples were studied by scanning electron microscopy, UV-VIS spectrophotometry, x-ray diffraction and photoelectrochemical (PEC) measurements carried out in aqueous solutions of Na2SO4 and Fe(CN)6 3-/4-. The results show the presence of trapping states on illuminated pristine Ta3N5 NTs in Na2SO4 (aq). These trapping states act as recombination center for photogenerated holes, affecting the photocatalytic performance of Ta3N5 NTs. On the other hand, by using Fe(CN)6 3-/4- (aq) the photogenerated holes were scavenged efficiently without giving rise to the trapping states at Ta3N5 NTs/solution interface. The results obtained by cyclic voltammetry, linear sweep voltammetry and electrochemical impedance spectroscopy have shown that the presence of these trapping states is a limiting step for water oxidation using pristine Ta3N5 NTs.
Highlights
Aiming to produce hydrogen from efficient solar-driven water splitting systems, many research groups have devoted their efforts to the study and development of photocatalysts [1,2, 3]
The results obtained by cyclic voltammetry, linear sweep voltammetry and electrochemical impedance spectroscopy have shown that the presence of these trapping states is a limiting step for water oxidation using pristine Ta3N5 NTs
In a previous study on Ta2O5 NTs prepared by anodization, we have found that anodization temperature controls the adherence of the NTs on the substrate
Summary
Aiming to produce hydrogen from efficient solar-driven water splitting systems, many research groups have devoted their efforts to the study and development of photocatalysts [1,2, 3]. Once the visible spectrum accounts nearly half of the total energy from the sun that reaches the surface of the earth, the development of stable materials presenting absorption within the visible range is a key factor towards efficient water splitting systems. Within this context, Ta3N5 has emerged as a promising candidate, presenting adequate bandgap of ca. Improved PEC activity from pristine Ta3N5 can be obtained by using a hole scavenging solution of Fe(CN)6 3-/4- [8]. The use of hole scavenging electrolytes such as Na2SO3, Fe(CN)6 3/4-, have resulted to improve PEC performance of other semiconductors [2,9]
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