Effect of Structural Parameters of TiO2 Nanotube Arrays upon Their Photocatalytic/Photoelectrocatalytic Performance

The effect of structural parameters of TiO2 nanotube arrays (TNAs) upon their photocatalytic/photoelectro-catalytic performance is studied by comparing the morphological characteristics and physicochemical properties with different tube lengths prepared from three kinds of electrolytes. The results show that the UV-Vis absorption edge of TNAs red-shifted with the increment of tube length and the short TNAs possess higher bandgap energy. The variation tendency of electrochemical window of TNAs is DMSO (5.5 V)>Cit (3.2 V)>HF (1.8 V). The long TNAs possess higher photocatalytic (PC) reactivity suggesting the surface roughness factor is the main determinant of PC efficiency, although, there is obvious recombination effects for the long TNAs. Evidenced by the positive correlation between tube length and photoelectrocatalytic (PEC) efficiency for TNAs from the same electrolyte, the enhancement of the tube length could lead to better PEC reactivity, but when the tube length is over a certain value, the PEC degradation rate no longer increases but decreases. The long TNAs with large surface roughness factor prepared from Cit and DMSO electrolytes exhibit comparative or even lower PEC performance compared with the short TNAs prepared from HF electrolyte, indicating that the PEC performance of TNAs was dominated by charge separation and photoelectron transfer properties rather than surface roughness coefficient and the tube length.