Enhanced photocatalytic activity for water splitting of blue-phase GeS and GeSe monolayers via biaxial straining

Two-Dimensional Polarized Blue P/SiS Heterostructures as Promising Photocatalysts for Water Splitting

Two-dimensional (2D) polarized heterostructures with internal electric fields are potential photocatalysts for high catalytic performance. The Blue P/SiS van der Waals heterostructures were formed from monolayer Blue P and polar monolayer SiS with different stacking interfaces, including Si-P and P-S interfaces. The structural, electronic, optical and photocatalytic properties of the Blue P/SiS heterostructures were studied via first-principle calculations. The results showed that the Si-P-2 or P-S-4 stacking order contributes to the most stable heterostructure with the Si-P or P-S interface. The direction of the internal electric field is from the 001 surface toward the 001¯ surface, which is helpful for separating photo-generated electron-hole pairs. The bandgap and electrostatic potential differences in the Si-P-2(P-S-4) heterostructures are 1.74 eV (2.30 eV) and 0.287 eV (0.181 eV), respectively. Moreover, the Si-P-2(P-S-4) heterostructures possess suitable band alignment and wide ultraviolet and visible light spectrum regions. All results suggest that 2D polarized Blue P/SiS heterostructures are potential novel photocatalysts for water splitting under a wide ultraviolet and visible light spectrum region.

Two-dimensional Janus monolayers SPtAZ2 (A = Si and Ge; Z = N, P, and As): insight into their photocatalytic properties via first-principles calculations

As a derivative of the two-dimensional material family, two-dimensional Janus materials have garnered widespread attention in recent years. Consequently, in this work, we systematically investigated the stability, electronic properties, photocatalytic properties, optical properties, and carrier mobility of SPtAZ2 (A = Si and Ge; Z = N, P, and As) monolayers using first-principles calculations. In the equilibrium state, we identified four stable structures that exhibited the properties of indirect band gap semiconductors using the HSE06 hybrid functional. Through the exploration of the photocatalytic and optical properties of these four stable structures, we observed that SPtSiN2, SPtSiP2, and SPtGeAs2 monolayers possess favorable band edge positions, high solar-to-hydrogen efficiency (up to 30.74%), and light absorption efficiency, thus endowing these three structures with commendable photocatalytic and light absorption performance. We additionally calculated the carrier mobility of these three structures and identified significant differences in electron and hole mobilities in the same direction, facilitating the effective separation of electrons and holes. Finally, we explored the effects of biaxial strain on the electronic properties, photocatalysis, and light absorption of stable SPtAZ2 monolayers. Our research results not only expand the 2D Janus material family, but also successfully predict a type of photocatalyst capable of utilizing visible light for overall water splitting.

Strong Vertical Piezoelectricity and Broad-pH-Value Photocatalyst in Ferroelastic Y2Se2BrF Monolayer

With the development of miniaturized devices, there is an increasing demand for 2D multifunctional materials. Six ferroelastic semiconductors, Y2Se2XX' (X, X' = I, Br, Cl, or F; X ≠ X') monolayers, are theoretically predicted here. Their in-plane anisotropic band structure, elastic and piezoelectric properties can be switched by ferroelastic strain. Moderate energy barriers can prevent the undesired ferroelastic switching that minor interferences produce. These monolayers exhibit high carrier mobilities (up to 104 cm2 V-1 s-1) with strong in-plane anisotropy. Furthermore, their wide bandgaps and high potential differences make them broad-pH-value and high-performance photocatalysts at pH value of 0-14. Strikingly, Y2Se2BrF possesses outstanding d33 (d33 = -405.97 pm/V), greatly outperforming CuInP2S6 by 4.26 times. Overall, the nano Y2Se2BrF is a hopeful candidate for multifunctional devices to generate a direct current and achieve solar-free photocatalysis. This work provides a new paradigm for the design of multifunctional energy materials.

First-Principles Computational Screening of Two-Dimensional Polar Materials for Photocatalytic Water Splitting

The band gap constraint of the photocatalyst for overall water splitting limits the utilization of solar energy. A strategy to broaden the range of light absorption is employing a two-dimensional (2D) polar material as photocatalyst, benefiting from the deflection of the energy level due to their intrinsic internal electric field. Here, by using first-principles computational screening, we search for 2D polar semiconductors for photocatalytic water splitting from both ground- and excited-state perspectives. Applying a unique electronic structure model of polar materials, there are 13 photocatalyst candidates for the hydrogen evolution reaction (HER) and 8 candidates for the oxygen evolution reaction (OER) without barrier energies from the perspective of the ground-state free energy variation calculation. In particular, Cu2As4Cl2S3 and Cu2As4Br2S3 can catalyze HER and OER simultaneously, becoming promising photocatalysts for overall water splitting. Furthermore, by combining ground-state band structure calculations with excited-state charge distribution and transfer calculated by linear-response time-dependent density functional theory (LR-TDDFT) and time-dependent ab initio nonadiabatic molecular dynamics (NAMD), respectively, the rationality of the 2D polar material model has been manifested. The intrinsic built-in electric field promotes the separation of charge carriers while suppressing their recombination. Therefore, our computational work provides a high-throughput method to design high-performance photocatalysts for water splitting.

2D Free-Standing GeS1-xSex with Composition-Tunable Bandgap for Tailored Polarimetric Optoelectronics

Germanium-based monochalcogenides (i.e., GeS and GeSe) with desirable properties are promising candidates for the development of next-generation optoelectronic devices. However, they are still stuck with challenges, such as relatively fixed electronic band structure, unconfigurable optoelectronic characteristics, and difficulty in achieving free-standing growth. Herein, it is demonstrated that two-dimensional (2D) free-standing GeS1-xSex (0 ≤ x ≤ 1) nanoplates can be grown by low-pressure rapid physical vapor deposition (LPRPVD), fulfilling a continuously composition-tunable optical bandgap and electronic band structure. By leveraging the synergistic effect of composition-dependent modulation and free-standing growth, GeS1-xSex-based optoelectronic devices exhibit significantly configurable hole mobility from 6.22 × 10-4 to 1.24 cm2V-1s⁻1 and tunable responsivity from 8.6 to 311 A W-1 (635 nm), as x varies from 0 to 1. Furthermore, the polarimetric sensitivity can be tailored from 4.3 (GeS0.29Se0.71) to 1.8 (GeSe) benefiting from alloy engineering. Finally, the tailored imaging capability is also demonstrated to show the application potential of GeS1-xSex alloy nanoplates. This work broadens the functionality of conventional binary materials and motivates the development of tailored polarimetric optoelectronic devices.

Theoretical Study of the Ternary Compound Monolayer CuP2Se for Photocatalytic Water Splitting with Efficient Optical Absorption

Utilizing photocatalytic method to produce hydrogen by splitting water is an efficient strategy to solve the hotspot issues of energy crisis and environmental pollution. Herein, we systematically investigate the corresponding properties of the reported Cu-bearing ternary compound monolayer CuP2Se by using the first-principle calculations. The monolayer CuP2Se has quite small cleavage energy of 0.51 J/m2, indicating it can be easily produced by the mechanical exfoliation method experimentally. In addition, it is an indirect bandgap semiconductor material which has a moderate value of 1.91 eV. The conduction band minimum (CBM) and valence band maximum (VBM) can perfectly straddle the redox potentials of water when a biaxial strain of -4% to 4% is applied, unveiling the high photocatalytic thermodynamic stability of monolayer CuP2Se in response to the effect of solvent tension. Remarkably, the monolayer CuP2Se also demonstrates significant sunlight capturing ability in the visible region. The outstanding electronic and optical properties suggest that the monolayer CuP2Se is undoubtedly a viable material for photocatalytic water splitting.

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

A two-dimensional (2D) polar monolayer with a polarization electric field can be used as a potential photocatalyst. In this work, first principle calculations were used to investigate the stability and photocatalytic properties of 2D polar monolayer SiTe as a potential promising catalyst in water-splitting. Our results show that the 2D polar monolayer SiTe possesses an indirect band gap of 2.41 eV, a polarization electric field from the (001) surface to the (001¯) surface, a wide absorption region, and a suitable band alignment for photocatalytic water-splitting. We also discovered that the photocatalytic activity of 2D polar monolayer SiTe could be effectively tuned through strain engineering. Additionally, strain engineering, particularly compressive strain in the range from −1% to −3%, can enhance the photocatalytic activity of 2D polar monolayer SiTe. Overall, our findings suggest that 2D polar monolayer SiTe has the potential to be a promising catalyst for photocatalytic water-splitting using visible light.

Fast Intercalation of Lithium in Semi-Metallic γ-GeSe Nanosheet: A New Group-IV Monochalcogenide for Lithium-Ion Battery Application

Existence of van der Waals gaps renders two-dimensional (2D) materials ideal passages of lithium for being used as anode materials. However, the requirement of good conductivity significantly limits the choice of 2D candidates. So far, only graphite is satisfying due to its relatively high conductivity. Recently, a new polymorph of layered germanium selenide (γ-GeSe) was proven to be semimetal in its bulk phase with a higher conductivity than graphite while its monolayer behaves semiconducting. In this work, by using first-principles calculations, the possibility was investigated of using this new group-IV monochalcogenide, γ-GeSe, as anode in Li-ion batteries (LIBs). The studies revealed that the Li atom would form an ionic adsorption with adjacent selenium atoms at the hollow site and exist in cationic state (lost 0.89 e to γ-GeSe). Results of climbing image-nudged elastic band showed the diffusion barrier of Li was 0.21 eV in the monolayer limit, which could activate a relatively fast diffusion even at room temperature on the γ-GeSe surface. The calculated theoretical average voltages ranged from 0.071 to 0.015 V at different stoichiometry of Li_x GeSe with minor volume variation, suggesting its potential application as anode of LIBs. The predicted moderate binding energy, a low open-circuit voltage (comparable to graphite), and a fast motion of Li suggested that γ-GeSe nanosheet could be chemically exfoliated via Li intercalation and is a promising candidate as the anode material for LIBs.

Strain Engineering: A Boosting Strategy for Photocatalysis

Whilst the photocatalytic technique is considered to be one of the most significant routes to address the energy crisis and global environmental challenges, the solar-to-chemical conversion efficiency is still far from satisfying practical industrial requirements, which can be traced to the suboptimal bandgap and electronic structure of photocatalysts. Strain engineering is a universal scheme that can finely tailor the bandgap and electronic structure of materials, hence supplying a novel avenue to boost their photocatalytic performance. Accordingly, to explore promising directions for certain breakthroughs in strained photocatalysts, an overview on the recent advances of strain engineering from the basics of strain effect, creations of strained materials, as well as characterizations and simulations of strain level is provided. Besides, the potential applications of strain engineering in photocatalysis are summarized, and a vision for the future controllable-electronic-structure photocatalysts by strain engineering is also given. Finally, perspectives on the challenges for future strain-promoted photocatalysis are discussed, placing emphasis on the creation and decoupling of strain effect, and the modification of theoretical frameworks.

Sensitivity Improvement of Surface Plasmon Resonance Biosensors with GeS-Metal Layers

Surface plasmon resonance (SPR) biosensors, with germanium sulfide (GeS) as a sensitive medium and Al/Ag/Au as the metal layers, are reported as we aim to improve the sensitivities of the biosensors. The sensitivities in conventional SPR biosensors, consisting of only metal Al, Ag, and Au layers, are 111°/RIU, 117°/RIU, 139°/RIU, respectively. Additionally, these sensitivities of the SPR biosensors based on the GeS-Al, GeS-Ag, and GeS-Au layers have an obvious improvement, resultant of 320°/RIU, 295°/RIU, and 260°/RIU, respectively. We also discuss the changing sensing medium GeS thickness using layer number to describe the scenario which brought about the diversification on the figure of merit (FOM) and optical absorption (OA) performance of the biosensors. These biosensors show obvious improvement of sensitivity and have strong SPR excitation to analytes; we believe that these kind biosensors could find potential applications in biological detection, chemical examination, and medical diagnosis.

Two-dimensional SiMI4(M = Ge, Sn) monolayers as visible-light-driven photocatalyst of hydrogen production

Two-dimensional (2D) materials of SiMI₄(M = Ge, Sn) monolayers are identified as promising visible-light-driven photocatalyst for hydrogen evolution reaction by DFT calculations. The dynamical and thermal stabilities of the two monolayers are confirmed by the phonon dispersion calculations and ab initiomolecular dynamics (AIMD) simulations, respectively.The results show that the two 2D materials have indirect bandgaps of 2.45 and 2.43 eV, and the band edges can match the hydrogen evolution reaction conditions. Absorption spectra show that the monolayers respond tovisible light and can be tuned by different strains.Besides, the hole and electron mobilitiesare different, which is beneficial for photoelectronic performance. The mechanisms of the hydrogen evolution reaction and the direct water splitting process are also explored. The calculational results support the promising applications of SiMI₄(M = Ge, Sn) monolayers asvisible-light-driven photocatalyst of hydrogen production.

Two-dimensional polarized MoTe2/GeS heterojunction with an intrinsic electric field for photocatalytic water-splitting

The construction of van der Waals heterostructures based on 2D polarized materials is a unique technique to achieve enhanced photocatalytic performance. We have investigated the intrinsic electric field and photocatalytic properties of the MoTe₂/GeS heterostructure via first-principles calculations. The results showed that a dipole-induced electric field induced by the GeS monolayer and an interface-induced electric field induced by the interface between the GeS monolayer and the MoTe₂ monolayer emerge in the 2D polarized MoTe₂/GeS heterostructure. The dipole-induced electric field contributes mainly to the total intrinsic electric field. Moreover, the 2D polarized MoTe₂/GeS heterostructure possesses many excellent and distinguished photocatalytic performance parameters, such as a direct semiconductor bandgap of 1.524 eV, a wide light spectrum ranging from the ultraviolet to near-infrared region with a high absorption coefficient (about 10⁶ cm⁻¹), a total intrinsic electric field, which reduces the probability of the recombination of photo-generated electron–hole pairs effectively, and a suitable band alignment for the water-splitting reaction. These indicate that the 2D polarized MoTe₂/GeS van der Waals heterostructure is a potential novel high-efficient photocatalyst for water-splitting.

The 2D polarized material-based MoTe₂/GeS heterojunction would be a highly efficient photocatalyst for producing hydrogen energy.

Anisotropic Janus SiP2 Monolayer as a Photocatalyst for Water Splitting

The design of materials meeting the rigorous requirements of photocatalytic water splitting is still a challenge. Anisotropic Janus 2D materials exhibit great potential due to outstandingly high photocatalytic efficiency. Unfortunately, these materials are scarce. By means of ab initio swarm-intelligence search calculations, we identify a SiP₂ monolayer with Janus structure (i.e., out-of-plane asymmetry). The material turns out to be semiconducting with an indirect band gap of 2.39 eV enclosing the redox potentials of water. Notably, the oxygen and hydrogen evolution half reactions can happen simultaneously at the Si and P atoms, respectively, driven merely by the radiation-induced electrons and holes. The carrier mobility is found to be anisotropic and high, up to 10^-4 cm² V^-1 s^-1, facilitating fast transport of the photogenerated carriers. The SiP₂ monolayer shows remarkably strong optical absorption in the visible-to-ultraviolet range of the solar spectrum, ensuring efficient utilization of the solar energy.

Fast colloidal synthesis of SnSe2 nanosheets for flexible broad-band photodetection

A new rapid bottom-up colloidal synthetic route has been developed to synthesize SnSe₂ nanosheets within 5 min. A SnSe₂ nanosheet-based flexible photodetector is fabricated for the first time and the resulting device displays a wide photodetection range and high flexibility.

A GeSe micro air brick crystal-based film for the sunlight photodegradation of dye-polluted waters

Pinkish purple rhodamine B polluted water was efficiently photodegraded into colorless by the GeSe MAB crystal-based film under sunlight irradiation.

A Theoretical Analysis on the Oxidation and Water Dissociation Resistance on Group-IV Phosphide Monolayers

Group-IV phosphide monolayers (MP, M=C, Si, Ge and Sn) provide a versatile platform for photocatalysts, as well as optoelectronic and nanoelectronic devices. Herein, comprehensive first-principles calculations and ab initio molecular dynamics (AIMD) simulations were performed to explore their stabilities in the air. We identified that the MP monolayers have excellent mechanical properties and their carrier mobilities are higher than that of phosphorene. The MP monolayers were predicted to possess superior oxidation resistance than the boron phosphide (BP) monolayer based on the proposed donation-backdonation theory. It was observed that the dissociation and chemisorption of a water molecule on the monolayers are kinetically difficult both in the water and in oxygen-water environments involving energy barriers of 1.28-3.48 eV. We also performed AIMD simulations at 300, 1000, 1200 and 1500 K. It is noteworthy that only the carbon phosphide (CP) monolayer can retain an intact structure at 1500 K, while the other three monolayers can just sustain to 1200 K. These results provide a guidance for their practical application and experimental fabrication.

Liquid-Phase Exfoliated GeSe Nanoflakes for Photoelectrochemical-Type Photodetectors and Photoelectrochemical Water Splitting

Photoelectrochemical (PEC) systems represent powerful tools to convert electromagnetic radiation into chemical fuels and electricity. In this context, two-dimensional (2D) materials are attracting enormous interest as potential advanced photo(electro)catalysts and, recently, 2D group-IVA metal monochalcogenides have been theoretically predicted to be water splitting photocatalysts. In this work, we use density functional theory calculations to theoretically investigate the photocatalytic activity of single-/few-layer GeSe nanoflakes for both the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) in pH conditions ranging from 0 to 14. Our simulations show that GeSe nanoflakes with different thickness can be mixed in the form of nanoporous films to act as nanoscale tandem systems, in which the flakes, depending on their thickness, can operate as HER- and/or OER photocatalysts. On the basis of theoretical predictions, we report the first experimental characterization of the photo(electro)catalytic activity of single-/few-layer GeSe flakes in different aqueous media, ranging from acidic to alkaline solutions: 0.5 M H2SO4 (pH 0.3), 1 M KCl (pH 6.5), and 1 M KOH (pH 14). The films of the GeSe nanoflakes are fabricated by spray coating GeSe nanoflakes dispersion in 2-propanol obtained through liquid-phase exfoliation of synthesized orthorhombic (Pnma) GeSe bulk crystals. The PEC properties of the GeSe nanoflakes are used to design PEC-type photodetectors, reaching a responsivity of up to 0.32 AW-1 (external quantum efficiency of 86.3%) under 455 nm excitation wavelength in acidic electrolyte. The obtained performances are superior to those of several self-powered and low-voltage solution-processed photodetectors, approaching that of self-powered commercial UV-Vis photodetectors. The obtained results inspire the use of 2D GeSe in proof-of-concept water photoelectrolysis cells.

Two-Dimensional GeTe: Air Stability and Photocatalytic Performance for Hydrogen Evolution

As a key method to convert solar into chemical energy, photocatalytic water decomposition has garnered attention. Moreover, the development of graphene and graphene-like two-dimensional (2D) materials has brought fresh vitality in the field of photocatalysis. Here, we prepared two to four layers of GeTe nanosheets by ultrasonic-assisted liquid-phase exfoliation in argon and air, which we referred to as Ar-GeTe and O-GeTe, respectively. The photocatalytic hydrogen production potential of 2D GeTe was experimentally investigated for the first time. The results indicated that minimally layered GeTe samples are indirect-gap semiconductors with the GeTe band gap increasing after oxidation. All samples have suitable band positions that can drive photocatalytic water splitting into H₂ under mild conditions, providing maximum hydrogen evolution rates of 1.13 mmol g^-1 h^-1 (Ar-GeTe) and 0.54 mmol g^-1 h^-1 (O-GeTe). With density functional theory computations, the structural stability of GeTe in air was discussed, revealing that oxygen atoms could easily combine with Ge to form a more stable structure, thus impacting the photocatalytic performance of 2D GeTe. Therefore, the light requirement and oxygen deficiency of the material give an advantage in the field of energy supply in space.

Two-dimensional few-layered PC3 as a promising photocatalyst for overall water splitting

Recently, 2D carbon phosphides (PCs) have attracted much attention due to their superior electronic and photovoltaic properties suitable for potential applications in field effect transistors and photodetectors. In this work, we systematically investigate the stability, electronic properties, optical absorption and photocatalytic water splitting performance of few-layered PC3 by using the first principles calculation method. Numerical results indicate that both monolayered and bilayered PC3 can serve as efficient photocatalysts for overall water splitting due to their high stability, moderate band gaps, suitable band edge positions, anisotropic high carrier mobilities and strong capacity of solar absorption. Compared with monolayered PC3, bilayered PC3 displays higher carrier mobilities (2500-23 000 cm2 V-1 s-1) and a wider optical absorption spectrum. Moreover, by applying an in-plane biaxial strain, the utilization of solar energy and the pH range suitable for overall water splitting can be improved effectively for both monolayered and bilayered PC3. Our work reliably expands the potential application of 2D few-layered PC3 in the field of nano-electronics and nano-optoelectronics.

Inartificial Two-Dimensional Ge4Se9 Janus Structures with Appropriate Direct Band Gaps and Intrinsic Polarization Boosted Charge Separation for Photocatalytic Water Splitting

Two-dimensional (2D) Janus structures, which are totally different from prevailing 2D structures, are more interesting for photocatalytic water splitting. Here we proposed some inartificial 2D Ge₄Se₉ Janus structures. Excellent photocatalytic properties are revealed: (a) Ge₄Se₉ structures exhibit layer-independent direct gap character with appropriate band gaps of 2.53, 2.22, 2.11, and 2.03 eV for monolayered, bilayered, triple-layered, and four-layered structures, respectively. (b) Band edge positions of these 2D structures are suitable for the driving of the evolution reaction of water splitting. (c) More importantly, owning to intrinsic electric polarization, the charge densities of the valence band maximum (VBM) and the conduction band minimum (CBM) of triple-layered and four-layered Ge₄Se₉ structures can be notably separated. (d) In addition, we also observed that these 2D structures can possess rather pronounced optical absorption in the visible light region. This work discloses some inartificial 2D Janus structures whose fascinating properties render them as promising photocatalysts for water splitting.

Wide Band Gap Chalcogenide Semiconductors

Wide band gap semiconductors are essential for today's electronic devices and energy applications because of their high optical transparency, controllable carrier concentration, and tunable electrical conductivity. The most intensively investigated wide band gap semiconductors are transparent conductive oxides (TCOs), such as tin-doped indium oxide (ITO) and amorphous In-Ga-Zn-O (IGZO), used in displays and solar cells, carbides (e.g., SiC) and nitrides (e.g., GaN) used in power electronics, and emerging halides (e.g., γ-CuI) and 2D electronic materials (e.g., graphene) used in various optoelectronic devices. Compared to these prominent materials families, chalcogen-based (Ch = S, Se, Te) wide band gap semiconductors are less heavily investigated but stand out because of their propensity for p-type doping, high mobilities, high valence band positions (i.e., low ionization potentials), and broad applications in electronic devices such as CdTe solar cells. This manuscript provides a review of wide band gap chalcogenide semiconductors. First, we outline general materials design parameters of high performing transparent semiconductors, as well as the theoretical and experimental underpinnings of the corresponding research methods. We proceed to summarize progress in wide band gap (E_G > 2 eV) chalcogenide materials-namely, II-VI MCh binaries, CuMCh₂ chalcopyrites, Cu₃MCh₄ sulvanites, mixed-anion layered CuMCh(O,F), and 2D materials-and discuss computational predictions of potential new candidates in this family, highlighting their optical and electrical properties. We finally review applications-for example, photovoltaic and photoelectrochemical solar cells, transistors, and light emitting diodes-that employ wide band gap chalcogenides as either an active or passive layer. By examining, categorizing, and discussing prospective directions in wide band gap chalcogenides, this Review aims to inspire continued research on this emerging class of transparent semiconductors and thereby enable future innovations for optoelectronic devices.

Investigation of the mechanism of overall water splitting in UV-visible and infrared regions with SnC/arsenene vdW heterostructures in different configurations

Monolayer arsenene presents good stability and high photogenic carrier mobility. However, a high photogenic electron and hole pair recombination rate seriously reduces its photocatalytic activity. The photocatalytic activity can be effectively improved by building type II heterostructures. In this work, SnC/arsenene heterostructures in three configurations are studied using first-principles calculations. Their structure, stability, and electronic and photocatalytic properties are investigated. It is found that all SnC/arsenene heterostructures are stable, and form type-II band edges, which effectively promote the transfer of photogenerated electrons from the SnC monolayer to the arsenene sheet. The charge transfer between SnC and arsenene leads to a built-in electric field in the interface region, which is favorable for inhibiting photogenic electron and hole pair recombination. Compared with the monolayer arsenene, the photocatalytic activity is greatly improved and the absorption spectrum of SnC/arsenene heterostructures is expanded. Attractively, these three heterostructures present two different photocatalytic mechanisms. H1 and H3 configurations were taken as examples to study their photocatalytic properties for overall water splitting at varying pH values and external strains. We found that alkaline conditions were more favorable for photocatalysis of SnC/arsenene heterostructures. In particular, H3 can still achieve full photocatalytic water decomposition in the near infrared region. These results show that the SnC/arsenene heterostructures are a prospective material for photocatalysis application.

The Electronic and Optical Properties of InSe-GeTe Heterobilayer via Applying Biaxial Strain

A comprehensive insight into the electronic and optical properties of small-lattice-mismatched InSe-GeTe heterobilayer (HBL) is performed based on the density functional theory (DFT) with van der Waals corrections from first-principles perspective. The optimization of most stable geometric stacking mode for the InSe-GeTe HBL is demonstrated. In addition, it is found that the InSe-GeTe HBL forms a type-II heterostructure of staggered-gap band alignment, resulting in an indirect band gap of 0.78 eV, which could be employed as a separator for electron-hole pairs. Moreover, the influence of biaxial strain on the electronic and optical properties of the InSe-GeTe HBL are systematically explored by calculating the band structures, density of states (PDOS), electron density differences, and optical absorption spectra of InSe-GeTe HBL under compressive and tensile biaxial strains. The results indicate that the electronic structures and optical performance of InSe-GeTe HBL could be modulated by changing the biaxial strain conveniently. Our findings provide new opportunities for the novel InSe-GeTe HBL to be applied in the electronic and optoelectronic fields.