Tuning Band Alignment and Optical Properties of 2D van der Waals Heterostructure via Ferroelectric Polarization Switching

TL;DR

This study theoretically demonstrates how ferroelectric polarization switching in 2D heterostructures can modulate band alignment and optical properties, enabling tunable photocatalytic water splitting.

Contribution

It introduces a method to control band alignment and optical absorption in 2D heterostructures via ferroelectric polarization switching, advancing photocatalyst design.

Findings

Polarization switching dramatically changes band alignment.

Different polarization directions favor hydrogen or oxygen evolution.

Enhanced charge separation and optical absorption in visible/infrared.

Abstract

Favourable band alignment and excellent visible light response are vital for photochemical water splitting. In this work, we have theoretically investigated how ferroelectric polarization and its reversibility in direction can be utilized to modulate the band alignment and optical absorption properties. For this objective, 2D van der Waals heterostructures (HTSs) are constructed by interfacing monolayer MoS2 with ferroelectric In2Se3. We find the switch of polarization direction has dramatically changed the band alignment, thus facilitating different type of reactions. In In2Se3/MoS2/In2Se3 heterostructures, one polarization direction supports hydrogen evolution reaction and another polarization direction can favour oxygen evolution reaction. These can be used to create tuneable photocatalyst materials where water reduction reactions can be selectively controlled by polarization switching. The modulation of band alignment is attributed to the shift of reaction potential caused by spontaneous polarization. Additionally, the formed type-II van der Waals HTSs also significantly improve charge separation and enhance the optical absorption in the visible and infrared regions. Our results pave a way in the design of van der Waals HTSs for water splitting using ferroelectric materials.