Zhao Zong-Yan, Dai Wen-Wu
Faculty of Materials Science and Engineering, Kunming University of Science and Technology , Kunming 650093, People's Republic of China.
Inorg Chem. 2015 Nov 16;54(22):10732-7. doi: 10.1021/acs.inorgchem.5b01714. Epub 2015 Oct 29.
As a promising photocatalyst driven by visible light, BiOI suffers from its lower conduction band edge position, which leads to its inability to produce hydrogen from photocatalytic water splitting. However, BiOI has an open layered intergrowth structure, which makes it easily cleavable along (001) plane. Thus, inspired by the progress of graphene-like two-dimensional nanomaterials, researchers believe that single-layer BiOI presents excellent photocatalytic activity for water splitting. To further explore the relationship between intrinsic properties and photocatalytic performance of BiOI ultrathin film, its electronic structure and optical properties as a function of layer thickness are systematically investigated by using first-principle calculations. The calculated results indicate that the quantum confinement effects can cause the following variations: band gap increasing, band edge position upshifting, and built-in electric field strengthening, which are very favorable for enhancement of photocatalytic performance. Importantly, if the layer thickness is less than 3 nm, the conduction band edge position will be higher than the reduction potential of H(+)/H2 and thus appropriate for the overall photocatalytic water-splitting reaction. However, layer thickness also caused disadvantageous reduction of sunlight absorption, which is noticed and avoided in practice.
作为一种有前景的可见光驱动光催化剂，BiOI存在导带边缘位置较低的问题，这导致其无法通过光催化水分解产生氢气。然而，BiOI具有开放的层状共生结构，使其易于沿(001)面解理。因此，受类石墨烯二维纳米材料进展的启发，研究人员认为单层BiOI对水分解具有优异的光催化活性。为了进一步探索BiOI超薄膜的本征性质与光催化性能之间的关系，通过第一性原理计算系统地研究了其作为层厚函数的电子结构和光学性质。计算结果表明，量子限域效应会导致以下变化：带隙增大、带边位置上移和内建电场增强，这些都非常有利于光催化性能的提高。重要的是，如果层厚小于3 nm，导带边缘位置将高于H(+)/H2的还原电位，从而适合整体光催化水分解反应。然而，层厚也会导致太阳光吸收不利地减少，这在实际中需要注意并避免。
