Enhanced solar photoelectrochemical conversion efficiency of the hydrothermally-deposited TiO ₂ nanorod arrays: Effects of the light trapping and optimum charge transfer

The vertically aligned TiO ₂ nanorod arrays (NRA) with manipulated aspect ratio were hydrothermally synthesized by changing the amount of the titanium (Ti) precursor in the initial growth solution. FE-SEM images show the optimum morphology, density and aspect ratio of the well-aligned TB-1.2 NRs on the surface of the FTO substrate. The UV-vis-absorption measurements revealed that a sample prepared at TB-1.2 can provide an increased light trapping effect. PEC analyses demonstrated that the TiO ₂ nanorods deposited at TB-1.2 of Titanium butoxide show a relatively high PEC conversion efficiency (3.5 times) compared with the TB-0.8 prepared TiO ₂ at a 1.0 V versus RHE. The higher PEC performance is believed to be the result of an enhancement of the optimum aspect ratio, light trapping, an efficient charge separation, and the high carrier transport in the vertically aligned TiO ₂ NRs. Further, the PEC based organic dye degradation experiments showed 77% and 94% removal of Orange II and methylene blue respectively. Additionally, 109 μmol h ⁻¹ cm ⁻² hydrogen generations were attributed using optimized vertically aligned TiO ₂ NRA's. Thus, the appropriate morphology manipulated the TiO ₂ NRAs are useful for solar conversion applications.