Self-Enhancing Photoelectrochemical Properties in van der Waals Ferroelectric CuInP<sub>2</sub>S<sub>6</sub> by Photoassisted Acid Hydrolysis
Shun Wang, Ningbo Fan, Zhou Zhou, Yiqi Hu, Qiang Hui, Qiankun Li, Jinshuo Xue, Ziwen Zhou, Zhijian Feng, Qingyu Yan, Yuyan Weng, Rujun Tang, Fengang Zheng, Ronglei Fan, Bin Xu, Liang Fang, Lü You
Abstract
(CIPS), has recently emerged as a potentially promising material for photoelectrochemical (PEC) water splitting due to its intrinsic ferroelectric polarization for spontaneous photocarrier separation. However, the poor kinetics of the hydrogen evolution reaction (HER) greatly limits its practical applications. Herein, we report self-enhancing photocatalytic behavior of a CIPS photocathode due to chemically driven oxygen incorporation by photoassisted acid oxidation. The optimal oxygen-doped CIPS demonstrates a >1 order of magnitude enhancement in the photocurrent density compared to that of pristine CIPS. Through comprehensive spectroscopic and microscopic investigations combined with theoretical calculations, we disclose that oxygen doping will lower the Fermi level position and decrease the HER barrier, which further accelerates charge separation and improves the HER activity. This work may deliver a universal and facile strategy for improving the PEC performance of other van der Waals metal thiophosphates.