Polarization Electric Field in 2D Polar Monolayer Silicon Monochalcogenides SiX (X = S, Se) as Potential Photocatalysts for Water Splitting

Abstract

The polarization electric field generated by the dipole moment can swiftly separate photogenerated carriers. Herein, the first‐principles calculations to study the structural, electronic, polarization electric field, optical, and photocatalytic properties of 2D polar monolayer silicon monochalcogenide SiX (X = S, Se) are studied. The polarization electric field induced by a noncentrosymmetric structure is a direction from the X (X = S, Se) atomic surface to the Si atomic surface. The polar monolayer SiS (SiSe) is an indirect semiconductor with a bandgap of 2.997 eV (2.903 eV). The absorption coefficients of the polar monolayer SiX (X = S, Se) reach the order of 105 cm−1, and the absorption onset can be extended to the visible light region. The band alignment of the 2D polar monolayer SiX (X = S, Se) is suitable for photocatalytic water splitting. The obtained results show that the 2D polar monolayer SiX (X = S, Se) with a polarization electric field is a potential catalyst for photocatalytic water splitting.

Strain-induced ferroelectric polarization reversal without undergoing geometric inversion in blue SiSe monolayer

“…The lattice constant of buckled SiSe is 3.52 Å. 26 Under biaxial strain, the total energy of the monolayer increases, no matter if the strain is compressive or tensile, see Fig. 2 ( Δ ≠ 0 biaxial).…”

“…The blue phase of the SiSe monolayer has been found to be a new type of group IV–VI semiconductor. 24–26 The configuration is non-centrosymmetric and presents an out-of-plane polarization. Due to the large buckling, the polarization reversal is difficult to achieve through the electric field.…”

Enhanced Photocatalytic Activity of Two-Dimensional Polar Monolayer SiTe for Water-Splitting via Strain Engineering

“…For a potential photocatalyst to be effective, the energy level of VBM and CBM must be suitable. As we can see clearly from Figure 5 a, the band alignment of 2D polar monolayer SiTe was calculated by the method reported in the previous literature [ 22 , 31 ]. Firstly, the VBM was calculated by, …”

“…In the recent literature, much research has suggested that 2D polar photocatalysts, which possess a polarization electric field, may be more effective at quickly separating photogenerated carriers [ 21 , 22 , 23 , 24 ]. There has been growing interest in 2D polar materials, such as group IV materials (GeS [ 25 , 26 , 27 ], GeSe [ 28 ], SiS [ 29 , 30 ], SiSe [ 31 ]), III 2 -VI 3 group monolayer In 2 Se 3 [ 32 , 33 , 34 , 35 ], monolayer Al 2 OS [ 36 ], and monolayer AgBiP 2 Se 6 , [ 37 ] as well as Janus monolayer materials (MoSSe [ 38 , 39 , 40 ], PtSSe [ 41 , 42 ], PtSO [ 43 ], and WSeTe [ 44 ]) for use as photocatalysts, thanks to the electric field that can aid in the separation of excited electron-hole pairs [ 45 , 46 , 47 , 48 , 49 ]. Two-dimensional polar monolayer SiM (M=S, Se and Te) possess high carrier mobility; therefore, they have been reported as potentially promising candidates for photocatalytic water-splitting [ 30 , 31 , 50 ], especially 2D polar monolayer SiTe, as it has a suitable band gap and absorbs visible light efficiently [ 50 ].…”