Simultaneous Enhancement of Charge Separation and Hole Transportation in a TiO2–SrTiO3 Core–Shell Nanowire Photoelectrochemical System

Abstract

Efficient charge separation and transportation are key factors that determine the photoelectrochemical (PEC) water-splitting efficiency. Here, a simultaneous enhancement of charge separation and hole transportation on the basis of ferroelectric polarization in TiO₂–SrTiO₃ core–shell nanowires (NWs) is reported. The SrTiO₃ shell with controllable thicknesses generates a considerable spontaneous polarization, which effectively tunes the electrical band bending of TiO₂. Combined with its intrinsically high charge mobility, the ferroelectric SrTiO₃ thin shell significantly improves the charge-separation efficiency (η_separation) with minimized influence on the hole-migration property of TiO₂ photoelectrodes, leading to a drastically increased photocurrent density ( J_ph). Specifically, the 10 nm-thick SrTiO₃ shell yields the highest J_ph and η_separation of 1.43 mA cm⁻² and 87.7% at 1.23 V versus reversible hydrogen electrode, respectively, corresponding to 83% and 79% improvements compared with those of pristine TiO₂ NWs. The PEC performance can be further manipulated by thermal treatment, and the control of SrTiO₃ film thicknesses and electric poling directions. This work suggests a material with combined ferroelectric and semiconducting features could be a promising solution for advancing PEC systems by concurrently promoting the charge-separation and hole-transportation properties.