Impact of surface patterning on oxygen vacancy formation and subsequent photoelectrochemical performance of TiO2 nanostructures

This research demonstrates unique approach for fabricating patterned titanium (Ti) substrates through micro-milling and using them to grow dual-topographic TiO<inf>2</inf> Micro-Nanofibers by anodization. X-ray diffraction and Raman spectroscopy studies revealed that the TiO<inf>2</inf> lattice on micro-milled substrate exhibited evident lattice expansion compared to TiO<inf>2</inf> grown on the un-patterned Ti substrate. Photoemission studies reveal the oxygen vacancies, and Ti³⁺ states as key factors contributing to this expansion. The resulting Micro-Nanofibrous structures have higher surface area, oxygen vacancies, and enhanced light-harvesting capabilities, which are responsible for higher photocurrent and durability than TiO<inf>2</inf> nanofibers grown on un-patterned Ti substrate. Under 1 sun illumination at 1.23 V<inf>RHE</inf> in 1 M KOH, these structures produced approximately 28 % higher photocurrent than their un-patterned counterparts. The micro-milling technique provides a cost-effective, rapid prototyping solution for generating stable nanostructures with microscale features offering advantages over traditional 3D printing and laser ablation techniques. This method shows great potential for photoelectrochemical water splitting.