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

^{1}

^{2}

^{*}

## Abstract

**:**

## 1. Introduction

_{2}), scientists have assumed that this technology would aid the energy crisis [4]. It is an attractive method for producing hydrogen because it is clean, renewable, and abundant. The technological process of photocatalytic water-splitting requires only water, sunlight, and a catalyst and produces clean and renewable oxygen and hydrogen. The process involves the absorption of light by the photocatalyst, which generates electrons and holes. Therefore, it is considered a prospective technique for solving the pollution problem associated with the energy crisis. However, the efficiency of photocatalytic water-splitting is currently too low for utilization in industries [5,6].

_{3}N

_{4}[11], group-III monochalcogenide [12], WS

_{2}Nanosheet [13], MXene [14], and g-ZnO [15], were reported to have had high surface areas and short carrier diffusion lengths, which could effectively reduce the distance that charge carriers need to migrate and improve their efficiency [16,17,18,19,20].

_{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]. However, the effect of the polarization electric field on this material is not yet fully understood. Designing highly efficient catalysts based on 2D polar monolayer materials for photocatalytic water-splitting is critical in developing sustainable energy solutions.

## 2. Results

^{+}/H

_{2}) and the oxidation potential (H

_{2}O/O

_{2}) are −4.44 eV and −5.67 eV, respectively. Since the ΔΦ is 0.441 eV in 2D polar monolayer SiTe, the energy level of the $\left(001\right)$ surface is not equal to that of the $\left(00\overline{1}\right)$ surface. The direction of the polarization electric field ${E}_{eff}$ is from the $\left(001\right)$ surface to the $\left(00\overline{1}\right)$ surface. Therefore electrons and holes are moved to the $\left(001\right)$ surface and the $\left(00\overline{1}\right)$ surface, respectively. On the $\left(001\right)$ surface, the H

_{2}O is reducesed by the electrons according to the following equation,

_{2}O is oxidized the holes according to the following equation,

^{+}/H

_{2}(−4.44 eV), and the VBM is 0.415 eV lower than the energy level of H

_{2}O/O

_{2}(−5.67 eV). Moreover, under the effect of an electric field ${E}_{eff}$, the electrons and holes could be separated quickly; therefore, oxidation and reduction reactions would be carried out efficiently. The results indicated that the band alignment of 2D polar monolayer SiTe is ideal for photocatalytic water-splitting, which involves the production of hydrogen through the use of sunlight and a photocatalyst.

_{zpe}is the difference in zero-point energy, T is the system temperature (298.15 K, in this work), and ΔS is the entropy difference.

_{g,}obtained by the optical properties is 2.38 eV, similar to the band gap calculated by the band structures using the HSE06 method. This confirms that the solar light, which has energy larger than the band gap, will be absorbed efficiently by the 2D polar monolayer SiTe. This indicates that 2D polar monolayer SiTe has the potential to be an efficient photocatalyst with high solar energy conversion efficiency. The band gap of 2D polar monolayer SiTe, which is approximately 2.41 eV, plays a role in improving solar energy conversion efficiency. As shown in Figure 7, strain engineering can shift the absorption edge to longer wavelengths, increasing the absorption of visible light. This is due to the decrease in the band gap of 2D polar monolayer SiTe with increasing strain. The results suggest that strain engineering is a convenient and useful strategy for tuning the optical absorption properties of 2D polar monolayer SiTe.

## 3. Methods

^{−6}eV and 10

^{−3}eV/Å, respectively. The first integration of the Brillouin zone was performed using the Gamma center method in KPOINTS [70]. Structural optimization and static calculations were performed using 12 × 12 × 1 and 15 × 15 × 1 grids, respectively. The vacuum region in the z direction had a thickness of 20 Å to prevent interactions from the periodic structure. Ab initio molecular dynamics (AIMD) simulations were calculated with the canonical ensemble method [71] to investigate the stability of crystal structure. A 5 × 5 × 1 supercell of 2D polar monolayer SiTe at a temperature of 300 K for a total time of 3000 fs with a time interval of 1 fs was set in the simulations. VASPKIT [72] software was applied to generate electronic data from the raw calculated data.

## 4. Conclusions

## Supplementary Materials

## Author Contributions

## Funding

## Institutional Review Board Statement

## Informed Consent Statement

## Data Availability Statement

## Conflicts of Interest

## References

- Esswein, A.J.; Nocera, D.G. Hydrogen production by molecular photocatalysis. Chem. Rev.
**2007**, 107, 4022–4047. [Google Scholar] [CrossRef] [PubMed] - Nishiyama, H.; Yamada, T.; Nakabayashi, M.; Maehara, Y.; Yamaguchi, M.; Kuromiya, Y.; Nagatsuma, Y.; Tokudome, H.; Akiyama, S.; Watanabe, T.; et al. Photocatalytic solar hydrogen production from water on a 100–m(2) scale. Nature
**2021**, 598, 304–307. [Google Scholar] [CrossRef] [PubMed] - Wang, Z.; Li, C.; Domen, K. Recent developments in heterogeneous photocatalysts for solar-driven overall water splitting. Chem. Soc. Rev.
**2019**, 48, 2109–2125. [Google Scholar] [CrossRef] [PubMed] - Fujishima, A.; Honda, K. Electrochemical Photolysis of Water at a Semiconductor Electrode. Nature
**1972**, 238, 37–38. [Google Scholar] [CrossRef] [PubMed] - Li, Y.; Li, Y.; Sa, B.; Ahuja, R. Review of two-dimensional materials for photocatalytic water splitting from a theoretical perspective. Catal. Sci. Technol.
**2017**, 7, 545–559. [Google Scholar] [CrossRef][Green Version] - Ran, J.; Zhang, J.; Yu, J.; Jaroniec, M.; Qiao, S.Z. Earth–abundant cocatalysts for semiconductor-based photocatalytic water splitting. Chem. Soc. Rev.
**2014**, 43, 7787–7812. [Google Scholar] [CrossRef] - Pan, J.; Shao, X.; Xu, X.; Zhong, J.; Hu, J.; Ma, L. Organic Dye Molecules Sensitization-Enhanced Photocatalytic Water-Splitting Activity of MoS
_{2}from First-Principles Calculations. J. Phys. Chem. C**2020**, 124, 6580–6587. [Google Scholar] [CrossRef] - Wang, Y.; Zhang, Y.; Wang, Y.; Zeng, C.; Sun, M.; Yang, D.; Cao, K.; Pan, H.; Wu, Y.; Liu, H.; et al. Constructing van der Waals Heterogeneous Photocatalysts Based on Atomically Thin Carbon Nitride Sheets and Graphdiyne for Highly Efficient Photocatalytic Conversion of CO
_{2}into CO. ACS Appl. Mater. Interfaces**2021**, 13, 40629–40637. [Google Scholar] [CrossRef] - Li, S.; Shi, M.; Yu, J.; Li, S.; Lei, S.; Lin, L.; Wang, J. Two-dimensional blue-phase CX (X = S, Se) monolayers with high carrier mobility and tunable photocatalytic water splitting capability. Chin. Chem. Lett.
**2021**, 32, 1977–1982. [Google Scholar] [CrossRef] - Li, J.; Huang, Z.; Ke, W.; Yu, J.; Ren, K.; Dong, Z. High solar-to-hydrogen efficiency in Arsenene/GaX (X = S, Se) van der Waals heterostructure for photocatalytic water splitting. J. Alloys Compd.
**2021**, 866, 158774. [Google Scholar] [CrossRef] - Wang, X.; Maeda, K.; Thomas, A.; Takanabe, K.; Xin, G.; Carlsson, J.M.; Domen, K.; Antonietti, M. A metal-free polymeric photocatalyst for hydrogen production from water under visible light. Nat. Mater.
**2009**, 8, 76–80. [Google Scholar] [CrossRef] - Zhuang, H.L.; Hennig, R.G. Single-Layer Group-III Monochalcogenide Photocatalysts for Water Splitting. Chem. Mater.
**2013**, 25, 3232–3238. [Google Scholar] [CrossRef] - Sang, Y.; Zhao, Z.; Zhao, M.; Hao, P.; Leng, Y.; Liu, H. From UV to near-infrared, WS
_{2}nanosheet: A novel photocatalyst for full solar light spectrum photodegradation. Adv. Mater.**2015**, 27, 363–369. [Google Scholar] [CrossRef] [PubMed] - Guo, Z.; Zhou, J.; Zhu, L.; Sun, Z. MXene: A promising photocatalyst for water splitting. J. Mater. Chem. A
**2016**, 4, 11446–11452. [Google Scholar] [CrossRef] - Huang, B.; Zhou, T.; Wu, D.; Zhang, Z.; Li, B. Properties of vacancies and N-doping in monolayer g-ZnO: First-principles calculation and molecular orbital theory analysis. Acta Physica Sinica
**2019**, 68, 246301. [Google Scholar] [CrossRef] - Bai, Y.; Luo, G.; Meng, L.; Zhang, Q.; Xu, N.; Zhang, H.; Wu, X.; Kong, F.; Wang, B. Single-layer ZnMN
_{2}(M = Si, Ge, Sn) zinc nitrides as promising photocatalysts. Phys. Chem. Chem. Phys. PCCP**2018**, 20, 14619–14626. [Google Scholar] [CrossRef] - Jian, C.; Ma, X.; Zhang, J.; Yong, X. Strained MoSi
_{2}N_{4}Monolayers with Excellent Solar Energy Absorption and Carrier Transport Properties. J. Phys. Chem. C**2021**, 125, 15185–15193. [Google Scholar] [CrossRef] - Li, X.; Cui, B.; Zhao, W.; Xu, Y.; Zou, D.; Yang, C. Novel 2D B
_{2}S_{3}as a metal-free photocatalyst for water splitting. Nanotechnol.**2021**, 32, 225401. [Google Scholar] [CrossRef] - Liu, H.; Gao, L.; Xue, Y.; Ye, Y.; Tian, Y.; Jiang, L.; He, S.; Ren, W.; Shai, X.; Wei, T.; et al. Two-dimensional semiconducting Ag
_{2}X (X = S, Se) with Janus-induced built-in electric fields and moderate band edges for overall water splitting. Appl. Surf. Sci.**2022**, 597, 153707. [Google Scholar] [CrossRef] - Xie, M.; Li, Y.; Liu, X.; Li, X. Enhanced water splitting photocatalyst enabled by two-dimensional GaP/GaAs van der Waals heterostructure. Appl. Surf. Sci.
**2022**, 591, 153198. [Google Scholar] [CrossRef] - Fu, C.; Sun, J.; Luo, Q.; Li, X.; Hu, W.; Yang, J. Intrinsic Electric Fields in Two-dimensional Materials Boost the Solar-to-Hydrogen Efficiency for Photocatalytic Water Splitting. Nano Lett.
**2018**, 18, 6312–6317. [Google Scholar] [CrossRef] [PubMed] - Li, X.; Li, Z.; Yang, J. Proposed photosynthesis method for producing hydrogen from dissociated water molecules using incident near-infrared light. Phys. Rev. Lett.
**2014**, 112, 018301. [Google Scholar] [CrossRef] [PubMed] - Li, Z.; Zhang, L.; Liu, Y.; Shao, C.; Gao, Y.; Fan, F.; Wang, J.; Li, J.; Yan, J.; Li, R.; et al. Surface polarity-induced spatial charge separation boosting photocatalytic overall water splitting on GaN nanorod arrays. Angew. Chem. Int. Ed.
**2019**, 59, 935–942. [Google Scholar] [CrossRef] [PubMed] - Peng, R.; Ma, Y.; Huang, B.; Dai, Y. Two-dimensional Janus PtSSe for photocatalytic water splitting under the visible or infrared light. J. Mater. Chem.A
**2019**, 7, 603–610. [Google Scholar] [CrossRef] - Ji, Y.; Yang, M.; Dong, H.; Hou, T.; Wang, L.; Li, Y. Two-dimensional germanium monochalcogenide photocatalyst for water splitting under ultraviolet, visible to near-infrared light. Nanoscale
**2017**, 9, 8608–8615. [Google Scholar] [CrossRef] - Gu, D.; Tao, X.; Chen, H.; Ouyang, Y.; Zhu, W.; Du, Y. Two-dimensional polarized MoTe
_{2}/GeS heterojunction with an intrinsic electric field for photocatalytic water-splitting. RSC Adv.**2021**, 11, 34048–34058. [Google Scholar] [CrossRef] - Gu, D.; Tao, X.; Chen, H.; Zhu, W.; Ouyang, Y.; Du, Y.; Peng, Q. Highly Efficient Polarized Ge
_{S}/MoSe_{2}van der Waals Heterostructure for Water Splitting from Ultraviolet to Near-Infrared Light. Physica Status Solidi (RRL)–Rapid Res. Lett.**2020**, 14, 1900582. [Google Scholar] [CrossRef] - Gu, D.; Tao, X.; Chen, H.; Zhu, W.; Ouyang, Y.; Peng, Q. Enhanced photocatalytic activity for water splitting of blue phase GeS and GeSe monolayers via biaxial straining. Nanoscale
**2019**, 11, 2335–2342. [Google Scholar] [CrossRef] [PubMed] - Abid, A.; Idrees, M.; Din, H.U.; Alam, Q.; Amin, B.; Haneef, M. Structural, electronic, optical, thermoelectric and photocatalytic properties of SiS/MXenes van der Waals heterostructures. Mater. Today Commun.
**2021**, 26, 101702. [Google Scholar] [CrossRef] - Alam, Q.; Muhammad, S.; Idrees, M.; Hieu, N.V.; Binh NT, T.; Nguyen, C.; Amin, B. First-principles study of the electronic structures and optical and photocatalytic performances of van der Waals heterostructures of SiS, P and SiC monolayers. RSC Adv.
**2021**, 11, 14263–14268. [Google Scholar] [CrossRef] - Gu, D.; Chen, X.; Xu, X.; Qin, W.; Tao, X.; Ouyang, Y.; Zhu, W. Polarization Electric Field in 2D Polar Monolayer Silicon Monochalcogenides SiX (X = S, Se) as Potential Photocatalysts for Water Splitting. Physica Status Solidi (RRL)–Rapid Res. Lett.
**2022**, 17, 2200179. [Google Scholar] [CrossRef] - Ding, W.; Zhu, J.; Wang, Z.; Gao, Y.; Xiao, D.; Gu, Y.; Zhang, Z.; Zhu, W. Prediction of intrinsic two-dimensional ferroelectrics in In
_{2}Se_{3}and other III_{2}-VI_{3}van der Waals materials. Nat. Commun.**2017**, 8, 14956. [Google Scholar] [CrossRef] [PubMed][Green Version] - Xiao, J.; Zhu, H.; Wang, Y.; Feng, W.; Hu, Y.; Dasgupta, A.; Han, Y.; Wang, Y.; Muller, D.A.; Martin, L.W.; et al. Intrinsic Two-Dimensional Ferroelectricity with Dipole Locking. Phys. Rev. Lett.
**2018**, 120, 227601. [Google Scholar] [CrossRef][Green Version] - Zhao, P.; Ma, Y.; Lv, X.; Li, M.; Huang, B.; Dai, Y. Two-dimensional III
_{2}-VI_{3}materials: Promising photocatalysts for overall water splitting under infrared light spectrum. Nano Energy**2018**, 51, 533–538. [Google Scholar] [CrossRef] - Zhou, Y.; Wu, D.; Zhu, Y.; Cho, Y.; He, Q.; Yang, X.; Herrera, K.; Chu, Z.; Han, Y.; Downer, M.C.; et al. Out-of-Plane Piezoelectricity and Ferroelectricity in Layered alpha-In
_{2}Se_{3}Nanoflakes. Nano Lett.**2017**, 17, 5508–5513. [Google Scholar] [CrossRef][Green Version] - Haman, Z.; Khossossi, N.; Kibbou, M.; Bouziani, I.; Singh, D.; Essaoudi, I.; Ainane, A.; Ahuja, R. Janus Aluminum Oxysulfide Al
_{2}OS: A promising 2D direct semiconductor photocatalyst with strong visible light harvesting. Appl. Surf. Sci.**2022**, 589, 152997. [Google Scholar] [CrossRef] - Ju, L.; Shang, J.; Tang, X.; Kou, L. Tunable Photocatalytic Water Splitting by the Ferroelectric Switch in a 2D AgBiP
_{2}Se_{6}Monolayer. J. Am. Chem. Soc.**2020**, 142, 1492–1500. [Google Scholar] [CrossRef] - Ma, X.; Wu, X.; Wang, H.; Wang, Y. A Janus MoSSe monolayer: A potential wide solar-spectrum water–splitting photocatalyst with a low carrier recombination rate. J. Mater. Chem.A
**2018**, 6, 2295–2301. [Google Scholar] [CrossRef] - Zhao, F.; Li, J.; Chen, Y.; Zhang, M.; Zhang, H. Photocatalytic activity of co–doped Janus monolayer MoSSe for solar water splitting: A computational investigation. Appl. Surf. Sci.
**2021**, 544, 148741. [Google Scholar] [CrossRef] - Ji, Y.; Yang, M.; Lin, H.; Hou, T.; Wang, L.; Li, Y.; Lee, S.T. Janus Structures of Transition Metal Dichalcogenides as the Heterojunction Photocatalysts for Water Splitting. J. Phys. Chem. C
**2018**, 122, 3123–3129. [Google Scholar] [CrossRef] - Wang, G.; Tang, W.; Xie, W.; Tang, Q.; Wang, Y.; Guo, H.; Gao, P.; Dang, S.; Chang, J. Type–II CdS/PtSSe heterostructures used as highly efficient water–splitting photocatalysts. Appl. Surf. Sci.
**2022**, 589, 152931. [Google Scholar] [CrossRef] - Wang, G.; Tang, W.; Xu, C.; He, J.; Zeng, Q.; Xie, W.; Gao, P.; Chang, J. Two–dimensional CdO/PtSSe heterojunctions used for Z–scheme photocatalytic water–splitting. Appl. Surf. Sci.
**2022**, 599, 153960. [Google Scholar] [CrossRef] - Shen, H.N.; Zhang, Y.; Wang, G.Z.; Ji, W.X.; Xue, X.M.; Zhang, W. Janus PtXO (X = S, Se) monolayers: The visible light driven water splitting photocatalysts with high carrier mobilities. Phys. Chem. Chem. Phys. PCCP
**2021**, 23, 21825–21832. [Google Scholar] [CrossRef] - Jamdagni, P.; Pandey, R.; Tankeshwar, K. First principles study of Janus WSeTe monolayer and its application in photocatalytic water splitting. Nanotechnol.
**2022**, 33, 025703. [Google Scholar] [CrossRef] [PubMed] - Chen, F.; Huang, H.; Guo, L.; Zhang, Y.; Ma, T. The Role of Polarization in Photocatalysis. Angew. Chem. Int. Ed.
**2019**, 58, 10061–10073. [Google Scholar] [CrossRef] [PubMed] - Liang, Y.; Li, J.; Jin, H.; Huang, B.; Dai, Y. Photoexcitation Dynamics in Janus–MoSSe/WSe
_{2}Heterobilayers: Ab Initio Time-Domain Study. J. Phys. Chem. Lett.**2018**, 9, 2797–2802. [Google Scholar] [CrossRef] [PubMed] - Liu, L.; Huang, H. Ferroelectrics in Photocatalysis. Chemistry
**2022**, 28, e202103975. [Google Scholar] [CrossRef] [PubMed] - Yin, W.; Wen, B.; Ge, Q.; Zou, D.; Xu, Y.; Liu, M.; Wei, X.; Chen, M.; Fan, X. Role of intrinsic dipole on photocatalytic water splitting for Janus MoSSe/nitrides heterostructure: A first-principles study. Prog. Nat. Sci.: Mater. Int.
**2019**, 29, 335–340. [Google Scholar] [CrossRef] - Jiang, X.X.; Gao, Q.; Xu, X.H.; Xu, G.; Li, D.M.; Cui, B.; Liu, D.S.; Qu, F.Y. Design of a noble-metal-free direct Z-scheme photocatalyst for overall water splitting based on a SnC/SnSSe van der Waals heterostructure. Phys. Chem. Chem. Phys. PCCP
**2021**, 23, 21641–21651. [Google Scholar] [CrossRef] - Zhu, Y.L.; Yuan, J.H.; Song, Y.Q.; Wang, S.; Xue, K.H.; Xu, M.; Cheng, X.M.; Miao, X.S. Two-dimensional silicon chalcogenides with high carrier mobility for photocatalytic water splitting. J. Mater. Sci.
**2019**, 54, 11485–11496. [Google Scholar] [CrossRef][Green Version] - Chen, Y.; Sun, Q.; Jena, P. SiTe monolayers: Si-based analogues of phosphorene. Journal of Materials Chemistry C
**2016**, 4, 6353–6361. [Google Scholar] [CrossRef] - Bhattarai, R.; Shen, X. Optical and electronic properties of SiTe
_{x}(x = 1, 2) from first-principles. J. Appl. Phys.**2021**, 129, 224305. [Google Scholar] [CrossRef] - Kamal, C.; Chakrabarti, A.; Ezawa, M. Direct band gaps in group IV-VI monolayer materials: Binary counterparts of phosphorene. Phys. Rev. B
**2016**, 93, 125428. [Google Scholar] [CrossRef][Green Version] - Chen, X.; Han, W.; Jia, M.; Ren, F.; Peng, C.; Gu, Q.; Wang, B.; Yin, H. A direct Z-scheme MoSi
_{2}N_{4}/BlueP vdW heterostructure for photocatalytic overall water splitting. J. Phys. D: Appl. Phys.**2022**, 55, 215502. [Google Scholar] [CrossRef] - Gu, D.; Tao, X.; Chen, H.; Ouyang, Y.; Zhu, W.; Peng, Q.; Du, Y. Strain Enhanced Visible–Ultraviolet Absorption of Blue Phosphorene/MoX
_{2}(X = S, Se) Heterolayers. Physica Status Solidi (RRL)–Rapid Res. Lett.**2019**, 13, 1800659. [Google Scholar] [CrossRef] - Zhao, H.Y.; Li, E.L.; Liu, C.; Shen, Y.; Shen, P.F.; Cui, Z.; Ma, D.M. DFT computation of two-dimensional CdO/GaS van der Waals heterostructure: Tunable absorption spectra for water splitting application. Vacuum
**2021**, 192, 110434. [Google Scholar] [CrossRef] - Ren, K.; Shu, H.B.; Huo, W.Y.; Cui, Z.; Yu, J.; Xu, Y.J. Mechanical, electronic and optical properties of a novel B
_{2}P_{6}monolayer: Ultrahigh carrier mobility and strong optical absorption. Phys. Chem. Chem. Phys. PCCP**2021**, 23, 24915–24921. [Google Scholar] [CrossRef] [PubMed] - Ren, K.; Yu, J.; Tang, W. Two–dimensional ZnO/BSe van der waals heterostructure used as a promising photocatalyst for water splitting: A DFT study. J. Alloys Compd.
**2020**, 812, 152049. [Google Scholar] [CrossRef] - Yang, X.; Zhou, Y.; He, J. Two unexplored two–dimensional MSe
_{2}(M = Cd, Zn) structures as the photocatalysts of water splitting and the enhancement of their performances by strain. Vacuum**2020**, 182, 109728. [Google Scholar] [CrossRef] - Xu, F.Y.; Zhou, Y.; Zhang, T.; Zeng, Z.Y.; Chen, X.R.; Geng, H.Y. An ab initio study of two-dimensional anisotropic monolayers ScXY (X = S and Se; Y = Cl and Br) for photocatalytic water splitting applications with high carrier mobilities. Phys. Chem. Chem. Phys. PCCP
**2022**, 24, 3770–3779. [Google Scholar] [CrossRef] - Nørskov, J.K.; Rossmeisl, J.; Logadottir, A.; Lindqvist, L.; Kitchin, J.R.; Bligaard, T.; Jónsson, H. Origin of the Overpotential for Oxygen Reduction at a Fuel-Cell Cathode. J. Phys. Chem. B
**2004**, 108, 17886–17892. [Google Scholar] [CrossRef] - Tauc, J.; Grigorovici, R.; Vancu, A. Optical Properties and Electronic Structure of Amorphous Germanium. Phys. Status Solidi (B)
**1966**, 15, 627–637. [Google Scholar] [CrossRef] - Kresse, G.; Furthmüller, J. Efficient iterative schemes forab initiototal-energy calculations using a plane-wave basis set. Phys. Rev. B
**1996**, 54, 11169–11186. [Google Scholar] [CrossRef] - Blochl, P.E. Projector augmented-wave method. Phys. Rev. B
**1994**, 50, 17953–17979. [Google Scholar] [CrossRef][Green Version] - Perdew, J.P.; Burke, K.; Ernzerhof, M. Generalized gradient approximation made simple. Phys. Rev. Lett.
**1996**, 77, 3865–3868. [Google Scholar] [CrossRef][Green Version] - Grimme, S. Semiempirical GGA-type density functional constructed with a long-range dispersion correction. J. Comput. Chem.
**2006**, 27, 1787–1799. [Google Scholar] [CrossRef] [PubMed] - Klimeš, J.; Bowler, D.R.; Michaelides, A. Chemical accuracy for the van der Waals density functional. J. Phys. Condens. Matter
**2009**, 22, 022201. [Google Scholar] [CrossRef] [PubMed] - Klimeš, J.; Bowler, D.R.; Michaelides, A. Van der Waals density functionals applied to solids. Phys. Rev. B
**2011**, 83, 195131. [Google Scholar] [CrossRef][Green Version] - Paier, J.; Marsman, M.; Hummer, K.; Kresse, G.; Gerber, I.C.; Angyan, J.G. Screened hybrid density functionals applied to solids. J. Chem. Phys.
**2006**, 124, 154709. [Google Scholar] [CrossRef][Green Version] - Monkhorst, H.J.; Pack, J.D. Special points for Brillouin-zone integrations. Phys. Rev. B
**1976**, 13, 5188–5192. [Google Scholar] [CrossRef] - Martyna, G.J.; Klein, M.L.; Tuckerman, M. Nosé-Hoover chains: The canonical ensemble via continuous dynamics. J. Chem. Phys.
**1992**, 97, 2635–2643. [Google Scholar] [CrossRef] - Wang, V.; Xu, N.; Liu, J.C.; Tang, G.; Geng, W.T. VASPKIT: A user-friendly interface facilitating high-throughput computing and analysis using VASP code. Comput. Phys. Commun.
**2021**, 267, 108033. [Google Scholar] [CrossRef]

**Figure 1.**(

**a**) Top view, (

**b**) side view, (

**c**) phonon dispersions, and (

**d**) the total energy fluctuations during AIMD simulations of 2D polar monolayer SiTe.

**Figure 2.**(

**a**) The band structures and (

**b**) the partial density of states (PDOS) of 2D polar monolayer SiTe.

**Figure 4.**(

**a**) The planar average potential of 2D polar monolayer SiTe; (

**b**) an enlarged section of (

**a**); (

**c**) the surface potential difference (ΔΦ) of 2D polar monolayer SiTe at different strains.

**Figure 5.**(

**a**) The band alignment of 2D polar monolayer SiTe; (

**b**) the Band alignment as a function of strain engineering.

**Figure 6.**(

**a**) The Gibbs free energy changes of HER at different strains; (

**b**) the trend of ΔG at different strains.

**Table 1.**Comparison of the calculated values of lattice constant (a), vertical layer distance (d), bond distance (l), and band gap (E

_{g}).

Disclaimer/Publisher’s Note: The statements, opinions and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions or products referred to in the content. |

© 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).

## Share and Cite

**MDPI and ACS Style**

Gu, D.; Qin, W.; Hu, S.; Li, R.; Chen, X.; Tao, X.; Ouyang, Y.; Zhu, W. Enhanced Photocatalytic Activity of Two-Dimensional Polar Monolayer SiTe for Water-Splitting via Strain Engineering. *Molecules* **2023**, *28*, 2971.
https://doi.org/10.3390/molecules28072971

**AMA Style**

Gu D, Qin W, Hu S, Li R, Chen X, Tao X, Ouyang Y, Zhu W. Enhanced Photocatalytic Activity of Two-Dimensional Polar Monolayer SiTe for Water-Splitting via Strain Engineering. *Molecules*. 2023; 28(7):2971.
https://doi.org/10.3390/molecules28072971

**Chicago/Turabian Style**

Gu, Di, Wen Qin, Sumei Hu, Rong Li, Xingyuan Chen, Xiaoma Tao, Yifang Ouyang, and Weiling Zhu. 2023. "Enhanced Photocatalytic Activity of Two-Dimensional Polar Monolayer SiTe for Water-Splitting via Strain Engineering" *Molecules* 28, no. 7: 2971.
https://doi.org/10.3390/molecules28072971