The InSe/g-CN van der Waals hybrid heterojunction as a photocatalyst for water splitting driven by visible light

The Role of Photo in Oxygen Evolution Reaction: A Review

Photo enhanced oxygen evolution reaction has recently emerged as an advanced strategy with great application prospects for highly efficient energy conversion and storage. In the course of photo enhanced oxygen evolution reactions, the other works focus has predominantly centered on catalysts while inadvertently overlooking the pivotal role of photo. Consequently, this manuscript embarks upon a comprehensive review of recent advancements in photo-driven, aiming to illuminate this critical dimension. A detailed introduction to the photothermal effect, photoelectronic effect, photon-induced surface plasmon resonance, photo and heterojunction, photo-induced reversible geometric conversion, photo-induced energy barrier reduction, photo-induced chemical effect, photo-charging, and the synthesis of laser/photo-assisted catalysts, offering prospects for the development of each case is provided. A detailed introduction to the photothermal effect, photoelectronic effect, photon-induced surface plasmon resonance, photo and heterojunction, photo-induced reversible geometric conversion, photo-induced energy barrier reduction, photo-induced chemical effect, photo-charging, and the synthesis of laser/photo-assisted catalysts is provided. At the same time, the overpotential and Tafel slope of some catalysts mentioned above at 10 mA cm-2 is collected, and calculated the lifting efficiency of light on them, offering prospects for the development of each case.

Review on Microreactors for Photo-Electrocatalysis Artificial Photosynthesis Regeneration of Coenzymes

In recent years, with the outbreak of the global energy crisis, renewable solar energy has become a focal point of research. However, the utilization efficiency of natural photosynthesis (NPS) is only about 1%. Inspired by NPS, artificial photosynthesis (APS) was developed and utilized in applications such as the regeneration of coenzymes. APS for coenzyme regeneration can overcome the problem of high energy consumption in comparison to electrocatalytic methods. Microreactors represent a promising technology. Compared with the conventional system, it has the advantages of a large specific surface area, the fast diffusion of small molecules, and high efficiency. Introducing microreactors can lead to more efficient, economical, and environmentally friendly coenzyme regeneration in artificial photosynthesis. This review begins with a brief introduction of APS and microreactors, and then summarizes research on traditional electrocatalytic coenzyme regeneration, as well as photocatalytic and photo-electrocatalysis coenzyme regeneration by APS, all based on microreactors, and compares them with the corresponding conventional system. Finally, it looks forward to the promising prospects of this technology.

Z-scheme Al2SeTe/GaSe and Al2SeTe/InS van der Waals heterostructures for photocatalytic water splitting

Designing Z-scheme van der Waals (vdW) heterostructured photocatalysts is a promising strategy for developing highly efficient overall water splitting. Herein, by employing density functional theory calculations, we systematically investigated the stability, electronic structures, photocatalytic and optical properties of Al2SeTe, GaSe, and InS monolayers and their corresponding vdW heterostructures. Interestingly, electronic structures show that all vdW heterostructures have direct band gaps, which is conducive to the transition of electrons from the valence band to the conduction band. Notably, Al2TeSe/GaSe and Al2TeSe/InS vdW heterostructures possess large overpotentials for Z-scheme photocatalytic water splitting, as proved by the results of band edge positions and band structure bending. Moreover, these vdW heterostructures exhibit good optical absorption in ultraviolet and visible light regions. We believe that our findings will open a new avenue for the modulation and development of Al2TeSe/GaSe and Al2TeSe/InS vdW heterostructures for photocatalytic water splitting.

Bilayer and Trilayer C3N/Blue-Phosphorene Heterostructures as Potential Anode Materials for Potassium-Ion Batteries

Two-dimensional (2D) van der Waals heterostructures outperform conventional anode materials for postlithium-ion batteries in terms of mechanical, thermal, and electrochemical properties. This study systemically investigates the performance of bilayer and trilayer C3N/blue phosphorene (C3N/BlueP) heterostructures as anode materials for potassium-ion batteries (KIBs) using first-principles density functional theory calculations. This study reveals that the adsorption and diffusion of K ions on bilayer and trilayer C3N/BlueP heterostructures are markedly superior to those of their monolayer counterparts. A bilayer heterostructure (C3N/BlueP) effectively reduces the bandgap of the BlueP monolayer (1.98 eV) to 0.02 eV, whereas trilayer heterostructures (bilayer-C3N/BlueP and C3N/bilayer-BlueP) exhibit metallic behavior with no bandgap. Additionally, the theoretical capacity of the bilayer and trilayer heterostructures ranges from 636.7 to 755.5 mA h g-1, considerably higher than the theoretical capacity of other prospective 2D heterostructures for KIBs investigated in the literature. This study also shows that the heterostructures exhibit K-ion diffusion barriers as low as 0.042 eV, ensuring the relatively fast diffusion of K ions.

The regulation of the withstand voltage performance of ZnO/GaN vertical heterostructures using external electric field and vacancy defects

The band gap of the heterostructure determines the withstand voltage. It is very important to regulate the band gap of heterojunctions and to investigate their electrical properties by applying external electric field. Based on density functional theory (DFT), ZnO/GaN vertical heterostructures with two stacking configurations (AB/BA and AB/AB, named H₁ and H₂, respectively) are constructed. The external electric field and vacancy defects of Zn, Ga, O and N atoms (V_Zn, V_Ga, V_O and V_N) are applied to analyze the electrical properties. The band gap can be tuned from 2.07 eV to 0 eV in H₁ and 1.53 eV-0 eV in H₂. As the electric field increases, H₁ has stronger withstand voltage (-0.84-0.56 V/Å) than H₂ (-0.26-0.26 V/Å). In addition, the structures deform obviously with the effect of vacancy defects, but remain stable. The presence of V_Ga and V_N enables H₁ and H₂ to exhibits metal conductivity and V_O change the band types of H₁ and H₂ from direct to indirect. The results of charge density difference (CDD) prove that a zero potential region and a weak electric field occur at the position of V_Zn and V_O, respectively. Likewise, the external electric field is applied to the defective heterostructures. The bandgap also exhibits strong tunability, and the heterostructure with V_O has the largest electric field modulation width. The above results indicate that ZnO/GaN exhibits excellent electrical properties with the influence of V_O, which represents potential applications in electronic devices.

A Cr2O3-doped graphene sensor for early diagnosis of liver cirrhosis: a first-principles study

Liver cirrhosis is among the leading causes of death worldwide. Because of its asymptomatic evolution, timely diagnosis of liver cirrhosis via non-invasive techniques is currently under investigation. Among the diagnostic methods employing volatile organic compounds directly detectable from breath, sensing of limonene (C₁₀H₁₆) represents one of the most promising strategies for diagnosing alcohol liver diseases, including cirrhosis. In the present work, by means of state-of-the-art Density Functional Theory calculations including the U correction, we present an investigation on the sensing capabilities of a chromium-oxide-doped graphene (i.e., Cr₂O₃-graphene) structure toward limonene detection. In contrast with other structures such as g-triazobenzol (g-C₆N₆) monolayers and germanane, which revealed their usefulness in detecting limonene via physisorption, the proposed Cr₂O₃-graphene heterostructure is capable of undergoing chemisorption upon molecular approaching of limonene over its surface. In fact, a high adsorption energy is recorded (∼-1.6 eV). Besides, a positive Moss-Burstein effect is observed upon adsorption of limomene on the Cr₂O₃-graphene heterostructure, resulting in a net increase of the bandgap (∼50%), along with a sizeable shift of the Fermi level toward the conduction band. These findings pave the way toward the experimental validation of such predictions and the employment of Cr₂O₃-graphene heterostructures as sensors of key liver cirrhosis biomarkers.

Modulating the Schottky barrier of MXenes/2D SiC contacts via functional groups and biaxial strain: a first-principles study

Two-dimensional (2D) graphene-like SiC has attracted intense interest recently due to its unique electrical and physical properties. In implementing 2D semiconductors in device applications, one of the main challenges so far has been the formation of a high-quality Schottky barrier owing to the strong Fermi level pinning (FLP) at the interface of traditional metal-2D semiconductor contacts. In this paper, the 2D MXenes Ti₃C₂T₂ (T = F, O, OH) are proposed to serve as electrodes for 2D SiC. The structural and barrier properties of the Ti₃C₂T₂/SiC contacts were systematically investigated based on first-principles calculations combined with the GGA-PBE and HSE06 functionals. It is found that Ti₃C₂T₂ can be bonded with 2D SiC by van der Waals (vdW) interactions. Weak FLP is exhibited at Ti₃C₂T₂/SiC vdW contacts. The type of contact can be tuned by changing the functional T group of Ti₃C₂T₂. Ti₃C₂F₂/SiC and Ti₃C₂O₂/SiC contacts exhibit a p-type Schottky contact and p-type Ohmic contact, respectively, whereas an n-type Ohmic contact occurs in the Ti₃C₂(OH)₂/SiC contact. In addition, the calculated tunneling possibility (T_B) is ∼20% between Ti₃C₂T₂ and SiC, indicating weak bonding at the Ti₃C₂T₂/SiC vdW junctions. Furthermore, the Schottky barrier height and T_B of the Ti₃C₂(OH)₂/SiC contacts can be modulated via the biaxial strain. The controllable contact type and barrier in Ti₃C₂T₂/SiC contacts provide guidelines for developing high-performance 2D SiC optoelectronic and electronic devices.

Superior mechanical flexibility, lattice thermal conductivity and electron mobility of the hexagonal honeycomb carbon nitride monolayer

Nitrogen is the nearest neighbor element of carbon and, thus, the hexagonal honeycomb carbon nitride monolayer (C_xN_y), which consists of a covalent network of carbon and nitrogen atoms, usually has attractive physical and chemical properties similar to those in graphene. Here, we systematically investigate the geometric structure, mechanical properties, thermal transport properties, and plasmon excitation of a new phase, labeled C₃N₂, and make a detailed comparison with other possible C_xN_y allotropes. All C_xN_y have a super-high layer modulus and Young's modulus. But compared with the others, C₃N₂ exhibits excellent mechanical flexibility, and can withstand a relatively high critical strain up to 20% (18%) along the X(Y) direction. Additionally, C₃N₂ also has excellent thermal and electronic transport properties, with a super-high lattice thermal conductivity of ∼110.9 W m^-1 K^-1 and electron mobility of ∼1617.52 cm² V^-1 s^-1 at 300 K. By performing time-dependent density functional theory (TDDFT), we obtain the optical absorptions of C₃N₂ and C₃N, and meanwhile analyze their Fourier transforms of induced charge densities at some resonant frequencies. The main optical absorption peaks of the C₃N₂ nanostructure are located in the ultraviolet region, and its plasmon peaks are far higher than those in C₃N. Its excellent mechanical and optical properties, the larger electronic band gap, and the higher electron mobility suggest that C₃N₂ has great potential for application in nanoelectronics and optoelectronics.

An analysis of Schottky barrier in silicene/Ga2SeS heterostructures by employing electric field and strain

Two-dimensional materials are leading the way in nanodevice applications thanks to their various advantages. Although two-dimensional materials show promise for many applications, they have certain limitations. In the last decade, the increasing demand for the applications of novel two-dimensional materials has accelerated heterostructure studies in this field. Hence, restoring the combination of two-dimensional heterostructured materials has been reported. In this paper, we show that the effect of the external electric field and biaxial strain on the silicene/Ga₂SeS heterostructure has a critical impact on the tuning of the Schottky barrier height. The findings such as the variation of the electronic band gap, interlayer charge transfer, total dipole moment, and n-type/p-type Schottky barrier transitions of the silicene/Ga₂SeS heterostructure under external effects imply that the device performance can be adjusted with Janus 2D materials.

Two-Dimensional Metal/Semiconductor Contact in a Janus MoSH/MoSi2N4 van der Waals Heterostructure

Following the successful synthesis of single-layer metallic Janus MoSH and semiconducting MoSi₂N₄, we investigate the electronic and interfacial features of metal/semiconductor MoSH/MoSi₂N₄ van der Waals (vdW) contact. We find that the metal/semiconductor MoSH/MoSi₂N₄ contact forms p-type Schottky contact (p-ShC type) with small Schottky barrier (SB), suggesting that Janus MoSH can be considered as an efficient metallic contact to MoSi₂N₄ semiconductor with high charge injection efficiency. The electronic structure and interfacial features of the MoSH/MoSi₂N₄ vdW heterostructure are tunable under strain and electric fields, which give rise to the SB change and the conversion from p-ShC to n-ShC type and from ShC to Ohmic contact. These findings could provide a new pathway for the design of optoelectronic applications based on metal/semiconductor MoSH/MoSi₂N₄ vdW heterostructures.

Structural, Electronic and Optical Properties of four α-Se-based Heterostructures with Hyperbolic Characteristics

The physical properties and potential applications of two-dimensional (2D) materials can be effectively modulated and enriched by constructing van der Waals heterostructures (VDWHs) with two or more 2D monolayer materials....

Two-Dimensional Sb/InS van der Waals Heterostructure for Electronic and Optical Related Applications

Stable configurations with excellent optical adsorption are crucial for the photovoltaics or photocatalysis. Two-dimensional materials with intrinsic electric-field have been proposed suitable for electric and optical device. Here, we have...