Edge Position Research Articles

The structural, electronic, optical and photocatalytic properties of two-dimensional ZrIN monolayer: A first-principles study

This study presents a comprehensive investigation of the structural stability, electronic and optical properties of two-dimensional ZrIN using first-principles calculations. The stability of two-dimensional (2D) ZrIN was confirmed through investigation of thermodynamic, mechanical, dynamic and thermal criteria. The ZrIN monolayer is predicted to be an indirect bandgap semiconductor with a gap value of 2.28 eV. Notably, it exhibits significant transmittance in the violet region of the visible spectrum. Furthermore, the photocatalytic attributes of 2D ZrIN are examined under varying pH conditions (0 and 7) by assessing band edge positions. The efficacy of ZrIN in electrocatalytic water decomposition is confirmed through simulations of the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). The influence of mechanical strain on the band structure and photocatalytic performance is also investigated. It is observed that compressive strain restricts the photocatalytic operational range of the ZrIN monolayer, while tensile strain broadens this range. Nevertheless, excessive tensile strain leads to a reduction in the effective catalytic operational region. These results offer valuable insights into the potential applications of 2D ZrIN in optoelectronics and catalysis.

Geometrical features, stability and electronic properties of (Cu3Sn)n clusters

Recently, significant advancements have been made in low-entropy Cu3Sn catalysts, showcasing their efficient catalytic CO oxidation capabilities. Hence, the atomic models of the Cu3Sn are worth established to further investigate their catalytic mechanisms. Here, the structural features and stability of (Cu3Sn)n clusters (n = 1–6) are investigated using the genetic algorithm combined with the density functional theory (DFT). The results reveal the structural evolution of these clusters from hollow cages to compact icosahedrons, where Cu atoms predominantly tend to grow together, while Sn atoms are dispersed at the edge positions. The Eb, Ef and Δ2E analyses show that the icosahedral (Cu3Sn)3 has a higher stability than that of its neighbors. The molecular dynamics simulations demonstrates its stability even at 1000 K. The molecular orbitals and density of states reveal that the (Cu3Sn)3 has an 1S21P61D102S21F1 superatomic electronic configuration. Electrostatic potential surfaces show that (Cu3Sn)n clusters have significant σ-hole regions at the Cu atomic sites, which can make the CO stretching frequency and bond length have a large red-shift. Moreover, the adsorption energy between the (Cu3Sn)3 and CO is the largest, reaching 1.17 eV. Our work provides inferences to the structural characteristics and adsorptions of the CuSn alloys at the atomic level.

Direct Z-scheme ZrS2/InP heterostructure as an efficient photocatalyst for overall water-splitting under acidic, alkaline and neutral environments

Photocatalytic water-splitting for hydrogen production by building heterostructure is an efficient approach to resolve the current environmental pollution problem. Here, the ZrS2/InP heterostructure with a direct Z-scheme have been constructed, and the first-principles calculations with Heyd-Scuseria-Ernzerhof (HSE06) hybrid function and density functional dispersion correction (DFT-D3) have been used to study their structural stabilities, electronic properties, photocatalytic mechanisms and optical features. The findings reveal that the ZrS2/InP heterostructure is a direct bandgap semiconductor having a type-II energy band alignment, where electrons mobilize from InP to ZrS2 monolayer at the interface of the heterostructure, leading to the creation of a build-in electric field pointing from InP to ZrS2. The ZrS2/InP heterostructure is competent for photocatalytic water-splitting owing to its advantageous band edge positions. In addition, the ZrS2/InP heterostructure possesses superior visible light absorption properties than the two monolayers structures, with a solar-to-hydrogen (STH) efficiency of 7.11 % and useable in acidic, alkaline and neutral environments. These excellent properties enable ZrS2/InP heterostructure to be an efficient photocatalyst for overall water-splitting. This effort not only proves the possibility of applying heterostructure in photocatalytic water-splitting but also has important implications for designing efficient direct Z-scheme photocatalysts.

Synergistic N-heterocyclic carbene and C2N integration for efficient and selective metal-free photocatalytic CO reduction to C2H5OH

In the pursuit of sustainable and highly efficient catalysts for the reduction of CO to valuable multi-carbon fuels, this study presents a novel metal-free catalyst, C/C2N, created by integrating N-heterocyclic carbene (NHC) into a C2N monolayer. Utilizing density functional theory, we demonstrate that this integration effectively addresses the individual limitations of C2N and NHC, neither of which can stably adsorb CO molecules on their own. The synergistic effect of C2N and NHC facilitates distinct CO adsorption energies on the C2N surface (−0.08 eV) and at the NHC site (−0.83 eV), leading to an exceptionally low C–C coupling energy barrier of 0.41 eV, surpassing traditional metal-based catalysts. Computational results reveal that C/C2N exhibits outstanding activity and selectivity in reducing CO to C2H5OH, with a remarkably low free energy barrier of only 0.34 eV, further reducible to 0.20 eV under alkaline conditions. Furthermore, the integration of NHC into the C2N monolayer markedly narrows its band gap, enhancing visible light absorption and optimizing band edge positions, suggesting its potential for visible-light-driven reactions. Our findings establish C/C2N as an effective and selective metal-free photocatalyst with a notably low C–C coupling energy barrier, offering a novel avenue for CO conversion to multi-carbon fuels.

HYDROSAFE: A Hybrid Deterministic-Probabilistic Model for Synthetic Appliance Profiles Generation.

Realistic appliance power consumption data are essential for developing smart home energy management systems and the foundational algorithms that analyze such data. However, publicly available datasets are scarce and time-consuming to collect. To address this, we propose HYDROSAFE, a hybrid deterministic-probabilistic model designed to generate synthetic appliance power consumption profiles. HYDROSAFE employs the Median Difference Test (MDT) for profile characterization and the Density and Dynamic Time Warping based Spatial Clustering for appliance operation modes (DDTWSC) algorithm to cluster appliance usage according to the corresponding Appliance Operation Modes (AOMs). By integrating stochastic methods, such as white noise, switch-on surge, ripples, and edge position components, the model adds variability and realism to the generated profiles. Evaluation using a normalized DTW-distance matrix shows that HYDROSAFE achieves high fidelity, with an average DTW distance of ten samples at a 1Hz sampling frequency, demonstrating its effectiveness in producing synthetic datasets that closely mimic real-world data.

Self-catalysed breakdown of titanate nanotubes by graphitic carbon nitride resulting in enhanced hydrogen production

Efficient design of a photocatalyst is an important step in realizing real world applications. In this work, using in-situ catalysis we have prepared and investigated a titanate nanotube (TiNT)/ graphitic carbon nitride nanocomposite, which after optimization shows excellent hydrogen production efficiency of 2.3 mmolg−1h−1, much improved compared to GCN, which achieved a rate of 0.56 mmolg−1h−1. We can conclude that pyrolysis of urea to carbon nitride also self catalyses the breakdown of TiNT into anatase TiO2 nanoparticles, resulting in a nanocomposite material comprising TiO2 and heterojunctions with GCN. After heating and modification the TiO2 shows a conduction band edge with a more negative potential than the H+/H2 potential, which along with the ideal position of the GCN CB edge facilitates hydrogen production under light irradiation. This novel method can be viewed as a general method for improving catalysis synthesis and design, whilst simultaneously reducing the complexity and energy footprint of active catalyst synthesis.

Enhanced Photocatalytic Activity of Direct Z‐Scheme K4Nb6O17/Carbon‐Rich Melon Heterostructures

AbstractMelon (also known as graphitic carbon nitride, g‐C3N4) holds promise for photocatalysis, but challenges such as severe charge recombination, low oxidation potential, and sluggish exciton dissociation hinder its performance. Herein, a series of carbon‐rich, melon‐based photocatalysts are synthesized via one‐pot, temperature‐induced condensation of urea with the addition of a trace amount of citric acid. The addition of citric acid enhances crystallinity, extends melon chains, increases the C/N ratio, and improves π–π layer stacking of heptazine units, thereby enhancing charge transport properties and visible‐light harvesting capacity. These carbon nitride samples are then coupled with molten salt synthesized K4Nb6O17 crystals by a straightforward self‐assembly method to construct 2D/2D heterostructure photocatalysts. Z‐scheme electron transfer from K4Nb6O17 to the melon samples is established based on their work functions and band edge positions. This efficient charge transfer in the Z‐scheme heterostructure facilitates the spatial separation of charge carriers, resulting in a nearly fivefold enhancement in photocatalytic performance compared to the individual constituents.

Solar-driven photocatalytic nitrogen fixation on transition metal-doped covalent organic frameworks: First-principles study

Designing highly efficient single-atom catalysts for converting nitrogen into ammonia under ambient temperature conditions holds significant importance. Current research predominantly focuses on electrocatalytic nitrogen fixation, but compared to that, photocatalytic nitrogen fixation requires only sunlight as an energy source, making it more environmentally friendly and cost-effective. Developing efficient nitrogen reduction reaction (NRR) photocatalysts presents a promising yet highly challenging task. Two-dimensional (2D) covalent organic frameworks (COFs) have garnered interest because of their elevated surface area and regular pore structure. This study employs density functional theory calculations to investigate the potential of NRR photocatalysts using the 2D COF TMT-TFPT-COF (TT-COF) supported with 18 different transition metal atoms (TM = Rh, Nb, Os, Mo, Ru, Pt, Ni, Co, V, Cu, Fe, Re, W, Cr, Ta, Mn, Pd, Ti). Through a four-step selection process, the most promising photocatalyst is identified. The results indicate that a single Re atom loaded onto TT-COF (Re@TT-COF) displays the optimal nitrogen fixation performance, demonstrating excellent catalytic activity and selectivity with a limiting potential of only −0.30 V. Furthermore, its good light absorption efficiency, suitable band edge position, and significant photo-generated electron potential enable spontaneous nitrogen fixation. Our study provides useful guidance for the rational design of COF-based NRR photocatalysts with high activity, stability, and selectivity.

Strain-Driven Phase Transitions in Delafossite Cu1-xAxAlO2: A Key to Enhanced Photo(electro)catalytic Performance.

This study investigates the impact of intrinsic strain and phase transitions on the thermodynamic stability and electronic properties of Cu1-xAxAlO2 solid solutions, which are key to their photocatalytic performance. It is demonstrated that Cu1-xAxAlO2 with A = Ag, Au, Pt can form continuous isostructural solid solutions due to relatively small compressive strain, while a substantial increase strain restricts Cu1-xPdxAlO2 to forming only limited solutions. For A = Li, Na, the formation of heterostructural solid solutions is facilitated by structural motif alterations, accommodating significant differences in ionic radii and A-O bond characteristics. Specifically, Cu1-xLixAlO2 exhibits a phase transition at x ≈ 0.333, whereas Cu1-xNaxAlO2 undergoes three distinct phase transitions. Electronic structure analysis indicates that in Cu1-xAxAlO2 (A = Ag, Au), d10-d10 closed-shell interactions dominate, enabling tunable band gaps with varying solubility. Nevertheless, increased intrinsic strain in metal sublattices, as seen in A = Pd and Pt, shifts antibonding states to the Fermi level, inducing a semiconductor-to-metal transition. Experimental evidence confirms that Ag+ ions modulate the band gaps and carrier dynamics in Cu1-xAgxAlO2, with Cu0.75Ag0.25AlO2 exhibiting heightened photoelectrochemical activity and a 38.5-fold enhancement in H2 production rate over CuAlO2. Additionally, the coordination environment changes between alkali metals and O, induced by phase transitions, effectively tune the band edge positions and carrier dynamics of Cu1-xAxAlO2 (A = Li, Na) heterostructural solid solutions. Therefore, 3R-Cu0.97Li0.03AlO2 with asymmetric nonlinear dumbbell O-Cu-O demonstrates the highest photocatalytic H2 production activity, 72.9 times greater than CuAlO2. In contrast, α-Cu1-xAxAlO2 with a smaller CuO6 octahedral splitting energy exhibits increased band gaps, resulting in diminished photocatalytic activity. This research underscores that strain-driven phase transition provides an additional control factor and new mechanism for regulating the photo(electro)catalytic activity of Cu1-xAxAlO2 solid solutions.

Hydrogen production from photocatalytic water splitting in the hBNC/MoS2 heterojunction: First-principles calculations

Photocatalytic water splitting for hydrogen production is a kind of hydrogen production method with less pollution and low cost. We designed the hBNC/MoS2 heterojunction as a photocatalyst for hydrogen production. This investigation is based on the first-principles. The results show that hBNC/MoS2 heterojunction has type-II band alignment. Moreover, the built-in electric field makes the photo-generated carries transfer along Z-scheme path. The hBNC/MoS2 has suitable band edge positions for hydrogen evolution reaction and oxidation evolution reaction. The reduction reaction overpotential is 2.27 eV (χH2 = 2.27 eV) in hBNC/MoS2. Meanwhile, the visible light absorption is improved in this heterojunction compared with the monolayer hBNC and MoS2. In addition, the Gibbs free energy calculation confirmed that the HER under the light irradiation in hBNC/MoS2 is an exothermic and spontaneous process. This investigation indicates that the hBNC/MoS2 heterojunction has potential application prospect in photocatalytic hydrogen production.

Relevance of the Iron Distribution in Natural Smectite Clays for the Thermal Stability of PMMA-Clay Nanocomposites.

Polymer-clay nanocomposites have greater thermal stability compared to the pristine polymer matrix. This can be attributed to the physical barrier provided by the inclusion of 2D clay nanoparticles (especially of the smectite group), together with radical trapping related to the distribution of specific 3d atoms in the inorganic phase. To elucidate the relevance of the Fe3+ distribution in this synergic effect, the iron atoms present in octahedral sheets of natural nontronite clay (Non, 5.6 wt % Fe) or in maghemite (M) nanoparticles (γ-Fe2O3) were incorporated in a poly(methyl methacrylate) (PMMA) matrix. Na-laponite (Lap) clay was used to evaluate the contribution of the diffusion barrier effect to the increased thermal stability of a PMMA-Lap nanocomposite, as evidenced by the upshift of the thermogravimetric (TGA) curve compared to that for PMMA. The contribution of radical trapping to the thermal stability of the PMMA-Non nanocomposite was evidenced by a significant shift of the Fe K-edge rising edge position by -4.5 eV after iron reduction by heating in N2, while similar treatment of pristine nontronite did not lead to a significant rising edge shift in the X-ray absorption spectra (XAS). This downshift demonstrated the reduction of Fe3+ to Fe0, induced by the sequestration of radicals formed by PMMA depolymerization. Raman spectroscopy analysis evidenced the formation of graphitic char deposits above 400 °C, further improving the thermal stability of PMMA-Non by providing an additional physical barrier to mass transport. A fourth contribution of well-dispersed iron was the abstraction of carbon from the char by the iron carburization reaction, which hindered CO2 formation by oxidative coking. In contrast, no relevant contribution of graphitic layer deposition was observed for the PMMA-M-Lap nanocomposite, where its improved thermal stability was only due to the combined contributions of the gas diffusion barrier effect and radical trapping by iron atoms. The maghemite effectively captured the radicals confined by the clay sheets, resulting in significant stabilization of the nanocomposite, with a shift of the mass loss of the PMMA-M-Lap nanocomposite compared to PMMA-Lap.

Mechanical strain effect on the optoelectronic properties and photocatalysis applications of layered AlN/GaN nanoheterostructure.

The aim of this work is to use first principles calculations to examine the effects of different mechanical strains on the optoelectronic and photocatalytic capabilities of the 2D/2D nanoheterostructure of AlN/GaN. By utilizing the lmBJ (Meta-GGA) and PBEsol (GGA) functional, the bandgap of the nanoheterostructure is calculated and found to be 4.89eV and 3.24eV. Simulated 2D AlN/GaN nanoheterostructure exhibits exceptional optical and electronic characteristics under applied biaxial tensile and compressive strains. The band gap changes from 4.89 to 3.77eV, while the energy gap nature transitions from direct to indirect during tensile strain fluctuations of 0% to 8%. Strain is also found to have a significant effect on the optical absorption peaks. And a 0-8% rise in tensile strain causes the initial absorption peak of the 2D AlN/GaN nanoheterostructure to shift from 4.88 to 4.20eV, which results in a 14% red shift in photon energy for every 2% change in strain. Furthermore, the optimum bandgap and band edge positions of the 2D AlN/GaN nanoheterostructure enable the water redox process to produce hydrogen and oxygen for wide range of pH. Thus, modification via strain may be an effective method for altering the optical as well as electronic characteristics of a 2D AlN/GaN nanoheterostructure, and this study may pave the way for new applications of this material in optoelectronic devices in the future. In the current work, density functional theory is used to explore every attribute of the 2D AlN/GaN nanoheterostructure. To characterize the electronic exchange-correlation, we used the PBEsol functional. In order to prevent any interlayer contact between periodicity of images, a vacuum is produced along the z-direction of approximately 10 Å. To increase the precision of bandgap prediction, the electronic and optical characteristics were computed using the meta-GGA lmBJ functional. To account for interlayer van der Waals interactions, nanoheterostructure computations were performed using the DFT-D3 functional.

New Insights into the ORR Catalysis on Pt Alloy Nanoparticles from an Element Specific d-Band Analysis.

Bolstered by their unique atomic structures and tailored compositions, nanoalloys exhibit extraordinary properties making them ideal materials to solve challenges in energy storage and conversion catalysis. However, a quantitative description of the structure-property relationships using an accurate descriptor-based model for nanoalloys, ranging from bimetallic to multimetallic compositions, is needed to drive efficient material design toward high-performance catalysis. In this work, we highlight the electronic property and catalytic activity relationship from an element specific d-band analysis of Pt-based alloy catalysts using X-ray absorption near-edge spectroscopy (XANES). Using a series of L10-MPt/Pt (M = Fe, Co, Ni) core/shell alloy catalysts with well-defined atomic structures, we quantified subtle differences in the Pt d-electron states and correlated the Pt d-band structure to their superior catalytic activity toward the oxygen reduction reaction (ORR). Our analysis used the upper d-band edge position as a predictive descriptor for the mass activity toward the ORR instead of the commonly used d-band center position. Together with density functional theory calculations and Nørskov d-band theory, the upper d-band edge position for the Pt states, derived from experimental measurements, elucidates new physical insights into the ORR performance of the L10-MPt/Pt core/shell catalysts. An element specific Pt d-band analysis using XANES overcomes challenges in traditional X-ray photoelectron spectroscopy-based valence d-band analysis, which cannot distinguish signals from independent elements in nanoalloys. Thus, the insights from the element specific d-band analysis presented in this work are a promising approach to determine structure-property relationships in a variety of transition metal nanoalloys and will be useful in the design of future high-performance catalysts.

A study on the formulation of process parameters for soft finger-assisted fabric stitching

PurposeTo reduce the difficulty of the sewing process and promote the automation process of fabric sewing, a soft finger-assisted feeding method is proposed to investigate the effect of sewing process parameters on the quality of automatic sewing.Design/methodology/approachTaking cotton woven fabrics as an example, the causes of sewing deviation are firstly investigated from three aspects: fabric properties, sewing speed and sewing edge position. By simulating the sewing action of human hands, the method of reducing sewing deviation by using soft fingers to press and feed the fabric is proposed. Then, four sewing process factors, namely, robot arm end pressure, sewing machine speed, sewing needle gauge and stitch density, were selected, and three levels were set for each factor to design orthogonal sewing experiments. The sewing deviation of 1# sample under different sewing processes was measured, and the optimal parameter matching for automatic sewing of this specimen was derived.FindingsThe findings demonstrate that, while sewing cloth automatically, the sewing deviation is significantly influenced by the robotic arm's end pressure, sewing speed, and stitch density, whereas the sewing deviation is not significantly impacted by the needle number.Originality/valueThe findings offer fundamental information for the development of an automated sewing procedure using soft fingers, which has theoretical and real-world application value to speed up the intelligent modernization and transformation of the apparel industry.

Fractional-Order Boosted Hybrid Young's Double-Slit Experimental Optimizer for Truss Topology Engineering Optimization.

Inspired by classical experiments that uncovered the inherent properties of light waves, Young's Double-Slit Experiment (YDSE) optimization algorithm represents a physics-driven meta-heuristic method. Its unique search mechanism and scalability have attracted much attention. However, when facing complex or high-dimensional problems, the YDSE optimizer, although striking a good balance between global and local searches, does not converge as fast as it should and is prone to fall into local optimums, thus limiting its application scope. A fractional-order boosted hybrid YDSE, called FYDSE, is proposed in this article. FYDSE employs a multi-strategy mechanism to jointly address the YDSE problems and enhance its ability to solve complex problems. First, a fractional-order strategy is introduced into the dark edge position update of FYDSE to ensure more efficient use of the search potential of a single neighborhood space while reducing the possibility of trapping in a local best. Second, piecewise chaotic mapping is constructed at the initial stage of the population to obtain better-distributed initial solutions and increase the convergence rate to the optimal position. Moreover, the low exploration space is extended by using a dynamic opposition strategy, which improves the probability of acquisition of a globally optimal solution. Finally, by introducing the vertical operator, FYDSE can better balance global exploration and local exploitation and explore new unknown areas. The numerical results show that FYDSE outperforms YDSE in 11 (91.6%) of cec2022 sets. In addition, FYDSE performs best in 8 (66.6%) among all algorithms. Compared with the 11 methods, FYDSE obtains the optimal best and average weights for the 20-bar, 24-bar, and 72-bar truss problems, which proves its efficient optimization capability for difficult optimization cases.

Systematic investigation on the rational design and optimization of bi-based metal oxide semiconductors in photocatalytic applications

To address the global energy shortage and mitigate greenhouse gas emissions on a massive scale, it is critical to explore novel and efficient photocatalysts for the utilization of renewable resources. Bi-based metal oxide (Bi x MO y ) semiconductors composed of bismuth, transition metal, and oxygen atoms have demonstrated improved photocatalytic activity and product selectivity. The vast number of element combinations available for Bi x MO y materials provides a huge compositional space for the rational design and isolation of promising photocatalysts for specific applications. In this study, we have systematically investigated the electronic and optical properties over Bi2O3 and a series of selected Bi x MO y group materials (BiVO4, BiFeO3, BiCoO3, and BiCrO3) by calculating band structure, basic optical property features, mobility and separation of charge carriers. It is clearly noted that the band gap and band edge position of the Bi x MO y group materials can be tuned in a wide range in comparison to Bi2O3. Similarly, the light response of Bi x MO y also can be broadened from the ultraviolet to the visible light region by adjusting the selection of transition metals. Additionally, the analysis of the effective mass of charge carriers of these materials further confirms their possibility in photocatalytic reaction applications because of the appropriate separation efficiency and mobility of carriers. A selection of experimental investigations on the crystal structure, composition, and optical properties of Bi2O3, BiVO4, and BiFeO3 as well as their catalytic performance in the degradation of methylene blue over was also conducted, which agree well with the theoretical predictions.

Co‐Solvent Assisted Optimization of the CuSCN Hole Transport Layer for Enhancing the Efficiency of Ambient Processable Perovskite Solar Cells with Carbon Counter Electrodes

In recent perovskite solar cell (PSC) research, copper(I) thiocyanate (CuSCN) is an emerging inorganic hole transport layer (HTL) due to its suitable band gap, matched band edge positions with the perovskite and high stability under ambient conditions. However, being a coordination polymer typically requires sulfide‐based solvents that strongly interact with Cu(I) for dissolution. Dipropyl sulfide (DPS) is generally used where it is very sparingly soluble of about 10–12 mg mL−1, which leads to low surface coverage with pin‐holes on the surface responsible for the generation of defects at the perovskite–HTL interface. In this study, addition of the optimized amount 100 μL of co‐solvent Acetonitrile (ACN) increased the CuSCN dissolution from 10 to 35 mg mL−1. ACN can act as a Lewis‐base making it capable of donating electrons to a Lewis‐acid like Cu+ from CuSCN. ACN is a polar aprotic solvent due to its highly polar CN bond and by adding CuSCN the dipole–dipole interactions can stabilize the CuSCN molecules in solution. The device with architecture (FTO/c‐TiO2/mp‐TiO2/MAPbI3/CuSCN/carbon) showed the higher power conversion efficiency (PCE) of ≈11% with Voc of 1.01 V and Isc 24.65 mA cm−2 showing excellent stability stored under ambient atmosphere which retains 80% of its initial efficiency after 10 days.

First-principles study on the electronic structure and photocatalytic properties of novel two-dimensional Janus CrXCN4 (X = Si, Ge)

Abundant studies demonstrate the significant role of Janus-structured two dimensional semiconductors as photocatalytic materials, highlighting their substantial advantages and importance in photocatalysis. In this work, CrXCN4 (X = Si, Ge) Janus monolayers were constructed based on CrC2N4, and the thermal stability, thermodynamic stability, mechanical stability, electronic properties, and optical properties of the monolayers were systematically investigated. Furthermore, an investigation was conducted to examine the impact of biaxial strain on their electronic and light absorption properties. The findings reveal that both monolayers exhibit direct band gap characteristics, with high absorption coefficients for visible light owing to their appropriate band gaps (1.44 eV for CrSiCN4 and 1.15 eV for CrGeCN4, respectively). At compressive strains exceeding 3%, the CrSiCN4 monolayer demonstrates an optimal band edge position, suggesting its potential as a photocatalyst for overall water splitting. Furthermore, as the compressive strain increases, the absorption spectra have blue-shifted and the absorption coefficient becomes higher, exceeding 2 × 105 cm−1 under a −3% compressive strain. Our study highlights the potential applications of CrXCN4 monolayers in the field of optoelectronic device, particularly emphasizing the promising candidacy of CrSiCN4 as an efficient photocatalyst.

Calculation of the Activation Energy of Electrical ε2‐Conductivity of Weakly Compensated Semiconductors

A model of tunneling (jumping) migration of charge carriers near their mobility edge in the upper band of neutral states of majority hydrogen‐like impurities is proposed to calculate the energy of thermal activation of electrical ‐conductivity of weakly compensated semiconductors. The difference from the known Hubbard model consists in the scheme of interimpurity transitions of charge carriers and in the method of calculating the position of their tunnel mobility edge. The drift mobility edge of free charge carriers corresponds to the thermal ionization energy of majority impurities , which is located near the c‐band bottom or the v‐band top in n‐ and p‐type semiconductors, respectively, and is due to the overlap of excited states of electrically neutral majority impurities. The position of the tunnel mobility edge for ‐conductivity is determined by taking into account the Coulomb interaction of the majority impurities in the charge states and . It is assumed that doping and compensating impurities form a single simple nonstoichiometric cubic lattice in a crystal matrix. The calculations of the activation energy on the insulator side of the insulator–metal concentration phase transition for weakly compensated p‐Si:B, n‐Si:P, and n‐Ge:Sb crystals quantitatively agree with known experimental data.

InP/PtS2 heterojunctions: Z-scheme photocatalysts with enhanced light absorption for high solar-to-hydrogen conversion efficiency

In this paper, the structure and electronic properties of InP/PtS2 heterojunction as well as the photocatalytic and solar hydrogen production efficiency are studied by first principles. Studies have shown that InP/PtS2 heterojunction is type II band alignment, typical Z heterostructure, has strong light absorption coefficient in the absorption spectrumand, InP/PtS2 heterojunction with an indirect bandgap of 1.97 eV，the band edge positions that meet the energy band prerequisites for water splitting across different pH levels，The band edge positions and light absorption capabilities have been modified through biaxial strain, with tensile strain enhancing the absorption capacity within the visible light spectrum ranging from 450 to 800 nm(nm). The InP/PtS2 heterojunction achieves a solar-to-hydrogen conversion efficiency (ηSTH) of 32.5%, which is higher than that of most heterojunctions. The InP/PtS2 heterojunction is anticipated to emerge as a promising contender for the next generation of photocatalysts.