TiO₂nanotube (T_NT) surface treatment revisited: Implications of ZnO, TiCl₄, and H₂O₂treatment on the photoelectrochemical properties of T_NT and T_NT–CdSe

Abstract

The surface treatment of an anodized TiO(2) nanotube (T_NT) is very desirable for enhancing its photoelectrochemical properties and often is a prerequisite to deposition of any overlying layer for photoactivity efficiency improvement. This study provides a comparative analysis of the effects of such surface treatments and the mechanistic insights behind the observed improvements in the performance of the treated T_NTs. T_NT surface treatment using three approaches, viz., TiCl(4), Zn(NH(3))(4)(2+), and H(2)O(2) is examined. TiCl(4) and Zn(NH(3))(4)(2+) treatment results in the formation of discontinuous islands of the respective oxides with 5-10 nm and 15-20 nm diameter particles. TiCl(4) treatment demonstrates an increase of 7.4% in photovoltage and is the most effective of the three approaches. Zn(NH(3))(4)(2+) treatment also results in an ~2% increase in photovoltage. However, a surface treatment of T_NT using H(2)O(2) results only in a favourable shift in flatband potential (80 mV). The T_NTs are rendered ineffective as H(2)O(2) treatment causes the destabilization of the T_NT at the base. Finally, the activity of an overlying chalcogenide layer is improved with the TiCl(4) and Zn(NH(3))(4)(2+) treatment (and not with H(2)O(2)) as evident from the photoelectrochemical responses: (J(T_NT-TiO(2)-CdSe) > J(T_NT-ZnO-CdSe) > J(T_NT-CdSe) > J(T_NT-H(2)O(2)-CdSe)).

Self-Ordered Titanium Dioxide Nanotube Arrays: Anodic Synthesis and Their Photo/Electro-Catalytic Applications

“…Hossain and co-workers [222] investigated T-NTA-CdSe nanocomposite based material by decorating the nanotubes with bubble like CdSe nanoclusters by chemical bath deposition technique. Other methods to simultaneously synthesize and attach CdSe onto T-NTA include the common successive ionic layer absorption and reaction (SILAR) method [223] as well a solvothermal deposition [224]. Coupling CdS with CdSe in tandem on T-NTA has also been investigated [225] and showed the CdS/CdSe couple had the highest performance over CdS or CdSe alone on T-NTA.…”

Surface Passivation of TiO2 Nanowires Using a Facile Precursor-Treatment Approach for Photoelectrochemical Water Oxidation

“…Recent studies have demonstrated the photovoltage decay experiment as a useful method to determine the presence of surface trap states for photoanode materials 40,41. (b) Chronoamperometric I-t curve for TiO 2 -TBU collected at 1.23 V vs. RHE under white light illumination.…”

TiO2 Nanotube/Chalcogenide-Based Photoelectrochemical Cell: Nanotube Diameter Dependence Study

“…Unlike mesoporous TiO 2 supports, ordered nanostructures, such as high aspect ratio selforganized TiO 2 nanotube layers [8][9][10] or epitaxially grown TiO 2 nanorods 11,12 , offer the advantage of directed charge transport and controlled phase separation between donor and acceptor parts of the solar cell and thus they seem very promising for nanoscale solar hybrid technologies 9 . Recently, non-silicon solar cells based on TiO 2 nanotube layers sensitized by organic dyes 8 , perovskites 13 and chalcogenides [14][15][16][17] have been presented. The latter class of materials is comparably more stable under UV light and ambient conditions, which make these materials promising for future generation of solar cell devices.…”