Bifunctional doping effect on the TiO2 nanowires for photoelectrochemical water splitting

Rutile TiO2 nanorods (TONRs) with a length of 3.7 μm were synthesized using a simple hydrothermal method. In order to control the morphology of the film and doping effect, Si was then added to the reaction solution. Si-doped TONRs (Si-TONRs) film shows distinct morphological properties such as thinner diameter, shorter length, and large surface area coverage of nanorods (NRs) compared to those of the pristine TONRs film. Furthermore, a Mott–Schottky analysis confirmed that a small amount of increased carrier concentration was induced by the Si doping while the flat-band potential (EFB) is maintained as constant. The linear sweep voltammograms displayed an outstanding photocurrent density of Si-TONR film with 2.75 mA/cm2 at 0 V vs. Ag/AgCl, compared with 0.88 mA/cm2 of the TONR film. Also, Si-TONR film revealed a solar-to-hydrogen (STH) conversion efficiency exceeding 2%, which is a 3-fold increased efficiency compared to that of TONR film and is ascribed to the favorable charge transportation through the novel nanoarchitecture which minimizes the charge recombination due to the increased electron concentration.