Piezoelectric, Thermoelectric, and Photocatalytic Water Splitting Properties of Janus Arsenic Chalcohalide Monolayers
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PROVIDER: S-EPMC11308028 | biostudies-literature | 2024 Jul
REPOSITORIES: biostudies-literature
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Project description:Chevrel non-van der Waals crystals are promising candidates for the fabrication of novel 2D materials due to their versatile crystal structure formed by covalently bonded (Mo6X8) clusters (X-chalcogen atom). Here, we present a comprehensive theoretical study of the stability and properties of Mo-based Janus 2D structures with Chevrel structures consisting of chalcogen and halogen atoms via density functional theory calculations. Based on the analysis performed, we determined that the S2Mo3I2 monolayer is the most promising structure for overall photocatalytic water-splitting application due to its appropriate band alignment and its ability to absorb visible light. The modulated Raman spectra for the representative structures can serve as a blueprint for future experimental verification of the proposed structures.
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Project description:Single-atom nickel catalysts hold great promise for photocatalytic water splitting due to their plentiful active sites and cost-effectiveness. Herein, we adopt a reactive-group guided strategy to prepare atomically dispersed nickel catalysts on red phosphorus. The hydrothermal treatment of red phosphorus leads to the formation of P-H and P-OH groups, which behave as the reactive functionalities to generate the dual structure of single-atom P-Ni and P-O-Ni catalytic sites. The produced single-atom sites provide two different functions: P-Ni for water reduction and P-O-Ni for water oxidation. Benefitting from this specific Janus structure, Ni-red phosphorus shows an elevated hydrogen evolution rate compared to Ni nanoparticle-modified red phosphorus under visible-light irradiation. The hydrogen evolution rate was additionally enhanced with increased reaction temperature, reaching 91.51 μmol h-1 at 70 °C, corresponding to an apparent quantum efficiency of 8.9 % at 420 nm excitation wavelength.
| S-EPMC9400897 | biostudies-literature
Project description:On the basis of first-principles calculations and non-adiabatic molecular dynamics (NAMD) simulations, we explore the photocatalytic water splitting properties of PtSSe/ζ-Phosphorene heterostructure. This heterostructure possess semiconducting nature with high carrier mobility (≈ 103 cm2V- 1s- 1). The calculated high value of electron-hole recombination rate as compared to electron transfer rate and hole transfer rate, establish the Type-II mechanism more favorable for PtSSe/ζ-Phosphorene heterostructure. Further, the calculated value of solar-to-hydrogen (STH) conversion efficiency of PtSSe/ζ-Phosphorene exceeds to 10%, which makes it the potential candidate for commercial production of hydrogen for industrial use. STH conversion efficiency is further tunable on rotating one monolayer over other with specific angles in the heterostructure. Our study demonstrates PtSSe/ζ-Phosphorene heterostructure to be efficient Type II-scheme photocatalyst for water splitting.
| S-EPMC11405408 | biostudies-literature
Project description:Janus monolayers with breaking out-of-plane structural symmetries and spontaneous electric polarizations offer new possibilities in the field of two-dimensional materials. Due to the depletion of fossil fuels and serious environmental problems, there has been a growing interest in the conversion of water and solar energy into H2 fuels in recent years. In this research, Janus XGaInY (X, Y = S, Se and Te) monolayers are predicted as promising solar-water-splitting photocatalysts. Based on first-principles calculations, the electronic, mechanical, optical and photocatalytic properties of Janus XGaInY (X, Y = S, Se and Te) monolayers are investigated. These Janus monolayers are structurally stable semiconductors with indirect bandgaps, except for SGaInSe, SGaInTe, TeGaInS and SeGaInTe. Their energy bandgaps extend from 0.74 to 2.66 eV at a hybrid density functional level, which is crucial for broadband photoresponses. Moreover, these Janus monolayers not only show strong light absorption coefficients greater than 104 cm-1 in the visible and ultraviolet regions but possess suitable band edge positions for water splitting. Our findings reveal that these Janus monolayers have a potential for application in the fields of optoelectronic and photocatalysis.
| S-EPMC9033172 | biostudies-literature
Project description:Photoelectrochemical devices could play a crucial role toward fuel production in a circular economy. Yet, light absorption suffers losses from thermalization and the inability to use low-energy photons. Here, we demonstrate that photoelectrochemical reactors can utilize this waste heat by integrating thermoelectric modules, which provide additional voltage under concentrated light irradiation. While most single semiconductors require external bias, we already accomplish unassisted water splitting under 2 sun irradiation by wiring a BiVO4 photoanode to a thermoelectric element, whereas the photocurrent of a perovskite-BiVO4 tandem system is enhanced 1.7-fold at 5 sun. This strategy is particularly suitable for photoanodes with more positive onset potentials like hematite, with thermoelectric-perovskite-Fe2O3 systems achieving a 29.7× overall photocurrent increase at 5 sun over conventional perovskite-Fe2O3 devices without light concentration. This thermal management approach provides a universal strategy to facilitate widespread solar fuel production, as light concentration increases output, reduces the reactor size and cost, and may enhance catalysis.
| S-EPMC10311528 | biostudies-literature
Project description:Janus structures that include different functional compartments have attracted significant attention due to their specific properties in a diverse range of applications. However, it remains challenge to develop an effective strategy for achieving strong interfacial interaction. Herein, a Janus nanoreactor consisting of TiO2 2D nanocrystals integrated with Prussian blue analog (PBA) single crystals is proposed and synthesized by mimicking the planting process. In situ etching of PBA particles induces nucleation and growth of TiO2 nanoflakes onto the concave surface of PBA particles, and thus enhances the interlayer interaction. The anisotropic PBA-TiO2 Janus nanoreactor demonstrates enhanced photocatalytic activities for both water reduction and oxidation reactions compared with TiO2 and PBA alone. As far as it is known, this is the first PBA-based composite that serves as a bifunctional photocatalyst for solar water splitting. The interfacial structure between two materials is vital for charge separation and transfer based on the spectroscopic studies. These results shed light on the elaborate construction of Janus nanoreactor, highlighting the important role of interfacial design at the microscale level.
| S-EPMC8024990 | biostudies-literature
Project description:Recent studies have demonstrated the feasibility of synthesizing two-dimensional (2D) Janus materials which possess intrinsic structural asymmetry. Hence, we performed a systematic first-principles study of 2D Janus transition metal dichalcogenide (TMD) monolayers based on PtXY (X,Y = S, Se, or Te). Our calculated formation energies show that these monolayer Janus structures retain the 1T phase. Furthermore, phonon spectral calculations confirm that these Janus TMD monolayers are thermodynamically stable. We found that PtSSe, PtSTe, and PtSeTe exhibit an insulating phase with indirect band gaps of 2.108, 1.335, and 1.221 eV, respectively, from hybrid functional calculations. Due to the breaking of centrosymmetry in the crystal structure, the spin-orbit coupling (SOC)-induced anisotropic Rashba splitting is observed around the M point. The calculated Rashba strengths from M to Γ (α M-Γ R) are 1.654, 1.103, and 0.435 eV Å-1, while the calculated values from M to K (α M-K R) are 1.333, 1.244, and 0.746 eV Å-1, respectively, for PtSSe, PtSTe, and PtSeTe. Interestingly, the spin textures reveal that the spin-splitting is mainly attributed to the Rashba effect. However, a Dresselhaus-like contribution also plays a secondary role. Finally, we found that the band gaps and the strength of the Rashba effect can be further tuned through biaxial strain. Our findings indeed show that Pt-based Janus TMDs demonstrate the potential for spintronics applications.
| S-EPMC9419079 | biostudies-literature
Project description:Two-dimensional (2D) Janus transition-metal dichalcogenides (TMDs) (MXY, M = Mo, W; X, Y = S, Se, Te; X ≠ Y) have desirable energy gaps and high stability in ambient conditions, similar to traditional 2D TMDs with potential applications in electronics. But different from traditional 2D TMDs, 2D Janus TMDs possess intrinsic Rashba spin splitting due to out-of-plane mirror symmetry breaking, with promising applications in spintronics. Here we demonstrate a new and effective way to manipulate the Rashba effect in 2D Janus TMDs, that is, charge doping, by using first-principles density functional theory (DFT) calculations. We find that electron doping can effectively strengthen the Rashba spin splitting at the valence band maximum (VBM) and conduction band minimum (CBM) in 2D Janus TMDs without constant energy consumption, superior to traditional techniques (electric fields and strain engineering), but hole doping would weaken the Rashba effect in 2D Janus TMDs. By combining the DFT calculations with the electric-triple-layer model, we also reveal the intrinsic mechanism of tuning the Rashba effect in 2D Janus TMDs by charge doping, and find that the charge transfer plays an important role in tuning the Rashba spin splitting in 2D polar semiconductors. In particular, the Rashba constants are linearly dependent on the charge transfer between X (or Y) and M atoms in 2D Janus TMDs. These results enrich the fundamental understanding of the Rashba effect in 2D semiconductors, which can be promising candidates for spin field-effect transistors (FETs) in experiments.
| S-EPMC9049672 | biostudies-literature
Project description:The photocatalytic characteristics of two-dimensional (2D) GeC-based van der Waals heterobilayers (vdW-HBL) are systematically investigated to determine the amount of hydrogen (H2) fuel generated by water splitting. We propose several vdW-HBL structures consisting of 2D-GeC and 2D-SiC with exceptional and tunable optoelectronic properties. The structures exhibit a negative interlayer binding energy and non-negative phonon frequencies, showing that the structures are dynamically stable. The electronic properties of the HBLs depend on the stacking configuration, where the HBLs exhibit direct bandgap values of 1.978 eV, 2.278 eV, and 2.686 eV. The measured absorption coefficients for the HBLs are over ~ 105 cm-1, surpassing the prevalent conversion efficiency of optoelectronic materials. In the absence of external strain, the absorption coefficient for the HBLs reaches around 1 × 106 cm-1. With applied strain, absorption peaks are increased to ~ 3.5 times greater in value than the unstrained HBLs. Furthermore, the HBLs exhibit dynamically controllable bandgaps via the application of biaxial strain. A decrease in the bandgap occurs for both the HBLs when applied biaxial strain changes from the compressive to tensile strain. For + 4% tensile strain, the structure I become unsuitable for photocatalytic water splitting. However, in the biaxial strain range of - 6% to + 6%, both structure II and structure III have a sufficiently higher kinetic potential for demonstrating photocatalytic water-splitting activity in the region of UV to the visible in the light spectrum. These promising properties obtained for the GeC/SiC vdW heterobilayers suggest an application of the structures could boost H2 fuel production via water splitting.
| S-EPMC8421365 | biostudies-literature
Project description:Janus SeMoS monolayers (MLs) are synthetic 2D materials with unique electronic properties, as theory predicts, but their experimental exploration has been hindered by the low quality of the samples. Here we report a synthesis of high-quality Janus MLs on gold substrates by thermal exchange reaction taking place at the ML/Au(111) interface. The synthesized Janus SeMoS MLs were characterized by complementary techniques, and insights into the topography and electronic properties of the system were obtained. Specifically, due to the lattice mismatch with the Au(111), a moiré pattern with a periodicity of 2.9 nm was observed. A precise experimental determination of the lattice constant of Janus SeMoS of 3.22 ± 0.01 Å was obtained, and the measured spin-orbit splitting at the K point of the valence band was found to be 170 ± 15 meV, matching well the results of the density functional theory calculations.
| S-EPMC11869296 | biostudies-literature