Department of Electronic Information Materials, School of Materials Science and Engineering, Shanghai University, Shanghai, 200444, China.
Materials Science and Engineering, University of Wisconsin-Madison, Madison, WI, 53706, USA.
Adv Mater. 2017 Jul;29(28). doi: 10.1002/adma.201701432. Epub 2017 May 30.
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 TiO -SrTiO core-shell nanowires (NWs) is reported. The SrTiO shell with controllable thicknesses generates a considerable spontaneous polarization, which effectively tunes the electrical band bending of TiO . Combined with its intrinsically high charge mobility, the ferroelectric SrTiO thin shell significantly improves the charge-separation efficiency (η ) with minimized influence on the hole-migration property of TiO photoelectrodes, leading to a drastically increased photocurrent density ( J ). Specifically, the 10 nm-thick SrTiO shell yields the highest J and η of 1.43 mA cm and 87.7% at 1.23 V versus reversible hydrogen electrode, respectively, corresponding to 83% and 79% improvements compared with those of pristine TiO NWs. The PEC performance can be further manipulated by thermal treatment, and the control of SrTiO 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.
高效的电荷分离和输运是决定光电化学（PEC）水分解效率的关键因素。在此，我们报道了在 TiO -SrTiO 核壳纳米线（NWs）的铁电极化基础上同时增强电荷分离和空穴传输的方法。具有可控厚度的 SrTiO 壳层会产生可观的自发极化，这有效地调整了 TiO 的能带弯曲。结合其固有的高电荷迁移率，铁电 SrTiO 薄膜显著提高了电荷分离效率（η），而对 TiO 光电极中空穴迁移率的影响最小，从而导致光电流密度（J）大幅增加。具体来说，10nm 厚的 SrTiO 壳层在 1.23 V 相对于可逆氢电极时，产生了最高的 J 和 η 值，分别为 1.43 mA cm 和 87.7%，与原始 TiO NWs 相比，分别提高了 83%和 79%。PEC 性能可以通过热处理以及控制 SrTiO 薄膜厚度和电极化方向进一步调控。这项工作表明，具有铁电和半导体特性的材料可能是通过同时促进电荷分离和空穴输运来推进 PEC 系统的有前途的解决方案。
