N/Si co-doped oriented single crystalline rutile TiO2 nanorods for photoelectrochemical water splitting

Abstract

Chemical modification of the aligned single crystalline TiO₂ nanorods provides possibilities to improve their photoelectrochemical (PEC) activity under visible light. This work reports on the N/Si co-doped single crystal rutile TiO₂ nanorods fabricated by a flexible one-step hydrothermal procedure for PEC water splitting, exhibiting a photocurrent of 1.77 mA cm⁻² at 1.23 V vs. RHE and a noticeable visible-light response under standard testing conditions (xenon lamp with an AM 1.5 G filter, 100 mW cm⁻²). The excellent PEC activity can be attributed to the synergetic effect of N and Si co-dopants, which enhances the incident photon to current conversion efficiency both in ultraviolet and visible regions, and improves the charge transfer at the photoanode/electrolyte interface. A solar-powered water splitting device has been designed by combining an efficient perovskite solar cell with the N/Si co-doped TiO₂ NRs-based PEC system, achieving an overall solar-to-hydrogen efficiency of 1.1%. This has been the highest value reported for TiO₂-based PEC systems so far.