Two dimensional (2D) semiconducting light absorbers, have recently considered as promising components to improve the efficiency in the photocatalytic hydrogen production via water splitting. In this work, by employing density functional theory computations, we introduced novel SiX₂ (X = P, As) nanosheets in tetragonal (penta-) and orthorhombic (rec-) phases, as promising light absorber semiconductors for overall water splitting. The predicted nanomembranes exhibit good mechanical, dynamical and thermal stabilities. They also show small cleavage energies in the range of 0.31 J/m² to 0.39 J/m², comparable to that of the graphene and thus suggesting the feasibility of their experimental exfoliation. Notably, predicted monolayers are semiconductors with indirect band gaps of 2.65 eV for penta-SiP₂, 2.35 eV for penta-SiAs₂, 1.89 eV for rec-SiAs₂, and a direct band gap of 2.21 eV for rec-SiP₂. These nanomaterials however show relatively large interlayer quantum confinement effects, resulting in smaller band gap values for bilayer lattices. We observed a huge difference between the electron and hole mobilities for penta-SiP₂ and rec-SiAs₂ monolayers and highly directional dependent electron and hole mobilities in rec-SiP₂, yielding an effective separation of photogenerated charge carriers. Remarkably, these novel nanomembranes show strong absorption in the visible region of light as well as suitable band edge positions for photocatalytic water splitting reaction, specifically under neutral conditions.

二维（2D）半导体光吸收剂最近被认为是有望通过分水提高光催化制氢效率的有希望的组件。在这项工作中，通过采用密度泛函理论计算，我们引入了新颖的SiX ₂（X = P，As）纳米片处于四方（五相）和正交晶（rec-）相，作为有希望将其用于总水分解的光吸收剂半导体。预测的纳米膜表现出良好的机械，动力学和热稳定性。它们还显示出在0.31 J / m ²至0.39 J / m ²范围内的小分裂能与石墨烯相当，因此暗示了其实验性剥离的可行性。值得注意的是，预测的单层是具有五价SiP ₂的2.65 eV，五价SiAs _2的2.35 eV，rec-SiAs _2的1.89 eV和rec-SiP ₂的2.21 eV的直接带隙的间接带隙的半导体。然而，这些纳米材料显示出相对较大的层间量子限制效应，从而导致双层晶格的带隙值较小。我们观察到的电子和空穴迁移率之间的巨大差异为五的SiP ₂和REC-SIAS _2个在REC-SiP的单层和高度定向依赖性电子和空穴迁移率₂，可以有效分离光生载流子。值得注意的是，这些新型纳米膜在可见光区域表现出较强的吸收能力，并且在光催化水分解反应中具有合适的能带边缘位置，特别是在中性条件下。