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.

良好的能带对准和出色的可见光响应对于光化学水分解至关重要。在这项工作中，我们从理论上研究了如何利用铁电极化及其方向可逆性来调节能带排列和光吸收特性。为此，通过将单层MoS ₂与铁电In ₂ Se ₃连接来构造2D范德华异质结构（HTS）。我们发现极化方向的转换极大地改变了能带排列，从而促进了不同类型的反应。In In ₂ Se ₃ / MoS ₂ / In ₂ Se ₃异质结构，一个极化方向支持氢放出反应，另一个极化方向可以促进氧放出反应。这些可以用于产生可调节的光催化剂材料，其中可以通过极化转换选择性地控制减水反应。能带取向的调节归因于自发极化引起的反应电位的移动。此外，形成的II型范德华HTS还可以显着改善电荷分离并增强可见光和红外光区域的光吸收。我们的结果为使用铁电材料进行水分解的范德华HTS设计铺平了道路。