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

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 (eta(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 eta(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.