Hydrogen generation and related energy applications heavily rely on the hydrogen evolution reaction (HER), which faces challenges of slow kinetics and high overpotential. Efficient electrocatalysts, particularly single-atom catalysts (SACs) on two-dimensional (2D) materials, are essential. This study presents a few-shot machine learning (ML) assisted high-throughput screening of 2D septuple-atomic-layer Ga2CoS4−x supported SACs to predict HER catalytic activity. Initially, density functional theory (DFT) calculations showed that 2D Ga2CoS4 is inactive for HER. However, defective Ga2CoS4−x (x = 0–0.25) monolayers exhibit excellent HER activity due to surface sulfur vacancies (SVs), with predicted overpotentials (0–60 mV) comparable to or lower than commercial Pt/C, which typically exhibits an overpotential of around 50 mV in the acidic electrolyte, when the concentration of surface SV is lower than 8.3%. SVs generate spin-polarized states near the Fermi level, making them effective HER sites. We demonstrate ML-accelerated HER overpotential predictions for all transition metal SACs on 2D Ga2CoS4−x. Using DFT data from 18 SACs, an ML model with high prediction accuracy and reduced computation time was developed. An intrinsic descriptor linking SAC atomic properties to HER overpotential was identified. This study thus provides a framework for screening SACs on 2D materials, enhancing catalyst design.@en

Finding an appropriate new anode material with high electrochemical performance for lithium-ion batteries (LIBs) is considered one of the significant challenges for both the academic and industrial research communities. Herein, we propose to explore the efficiency of a newly designed two-dimensional (2D) material, named orthorhombic dialuminium dinitride (o-Al₂N₂), as an alternative anode material for LIB systems through first-principles calculations and ab initio molecular dynamics (AIMD) simulations. The obtained results show that orthorhombic-Al₂N₂ exhibits a high specific capacity of 1144.2913 mAhg⁻¹, an operating voltage around 0.575 V, and a low kinetic diffusion barrier of 0.26 eV. These results prove the suitability of the o-Al₂N₂ monolayer as a promising anode material for LIBs with high structural stability, strong binding energy towards lithium adsorbent, fast lithium diffusion, and a high theoretical capacity. These features rank the 2D o-Al₂N₂ monolayer among the best choices for the anode part of the next-generation rechargeable LIBs.

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Two-dimensional (2D) Janus monolayers, distinguished by their intrinsic vertical electric fields, emerge as highly efficient and eco-friendly materials for advancing the field of hydrogen evolution reactions (HER). In this study, we explore, for the first time, the potential viability of the oxygenation phase of two-dimensional Janus transition metal dichalcogenides MoOX (X = S, Se, and Te) monolayers as an exceptionally efficient photocatalyst for hydrogen production. Based on first-principles computations, we demonstrate that all three monolayers exhibit semiconductor behavior, characterized by a band gap ranging from 0.66 to 1.55 eV. This narrow band gap renders the proposed materials highly efficient at absorbing light within the visible region. Excitingly, the introduction of an electrostatic potential difference ΔΦ has granted us the ability to surpass the conventional bandgap limit (E_g≥1.23). Consequently, all monolayers exhibit favorable band alignment with respect to the vacuum level. Moreover, the calculated solar-to-hydrogen efficiency for the envisaged monolayer exceeds the established theoretical limit. Particularly, the MoOTe monolayer emerges as an infrared-light-driven photocatalyst, demonstrating a remarkable solar-to-hydrogen efficiency limit of up to 25,21% when considering the entire solar spectrum. A thorough examination of the Gibbs free energy differences across these monolayers has revealed that the values during the oxygenation phase are significantly smaller and approach the optimum, in contrast to the parental two-dimensional Janus transition metal dichalcogenides. Our results conclusively establish that the proposed materials exhibit exceptional efficiency as photocatalysts for hydrogen evolution reactions. Notably, their efficacy is demonstrated even in the lack of co-catalysts or sacrificial agents.

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Lithium–sulfur (Li–S) batteries, renowned for their potential high energy density, have attracted attention due to their use of earth-abundant elements. However, a significant challenge lies in developing suitable materials for both lithium-based anodes, which are less prone to lithium dendrite formation, and sulfur-based cathodes. This obstacle has hindered their widespread commercial viability. In this study, we present a novel sulfur host material in the form of a two-dimensional semiconductor boron nitride framework, specifically the 2D orthorhombic diboron dinitride (o-B2N₂). The inherent conductivity of o-B2N₂ mitigates the insulating nature often observed in sulfur-based electrodes. Notably, the o-B2N₂ surface demonstrates a high binding affinity for long-chain Li-polysulfides, leading to a significant reduction in their dissolution into the DME/DOL electrolytes. Furthermore, the preferential deposition of Li2S on the o-B2N₂ surface expedites the kinetics of the lithium polysulfide redox reactions. Additionally, our investigations have revealed a catalytic mechanism on the o-B2N₂ surface, significantly reducing the free energy barriers for various sulfur reduction reactions. Consequently, the integration of o-B2N₂ as a host cathode material for Li–S batteries holds great promise in suppressing the shuttle effect of lithium polysulfides and ultimately enhancing the overall battery performance. This represents a practical advancement for the application of Li–S batteries.

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The present study highlights the efficiency of Ag₃PO₄ photocatalyst with a band gap of 2.25 eV, synthesized by a green and one-pot simple mechanochemical method, towards photodegradation of orange G under visible irradiation. The phase structure, morphology, and optical properties of mechano-synthesized Ag₃PO₄ were investigated using X-ray diffraction, Scanning Electron Microscopy, Thermogravimetric Analysis, Fourier Transform Infrared, the Brunauer-Emmet-Teller surface area, and UV–vis diffuse reflectance spectroscopy. DFT calculations were also conducted for band gap energy prediction. The photocatalytic activity of the sample was evaluated using a central composite design for surface response methodology (CCD-RSM) to determine the optimal conditions for Orange G (OG) removal. The photocatalytic activity of Ag₃PO₄ was approximately 93 % within 20 min of reaction under irradiation for 24.6 mg/L and 11 mg/L of Ag₃PO₄ and Orange G, respectively. Trapping experiments confirmed that peroxides and hydroxyl radicals are the dominant active species in the photodegradation process.

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This study aims to identify photo-/electrocatalysts that can enhance the oxygen evolution reaction (OER), hydrogen evolution reaction (HER), and oxygen reduction reaction (ORR), which are of utmost importance in electro-/photochemical energy systems, such as solar energy, fuel cells, water electrolyzers, or metal-air batteries. Our study focused on investigating the 2D Ge₂Se₂P₄ monolayer and found that it exhibits a bifunctional photocatalyst with a very high solar-to-hydrogen efficiency. The two-dimensional (2D) Ge₂Se₂P₄ monolayer has superior HER activity compared to that of most 2D materials, and it also outperforms the reference catalysts IrO₂(110) and Pt(111) in terms of low overpotential values for ORR and OER mechanisms. Such superior catalytic performance in the 2D Ge₂Se₂P₄ monolayer can be attributed to its electron states, charge transfer process, and suitable band alignments referring to normal hydrogen electrodes. Overall, the study suggests that the Ge₂Se₂P₄ monolayer could be an excellent bifunctional catalyst for advancing photo-/electrochemical energy systems.

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A primary concern towards achieving a robust and sustainable water-splitting strategy consists in the development and designing of non-precious hydrogen evolution electrocatalysts capable of operating at relatively high current densities. In the present density functional theory (DFT) based study, we explored and identified α-NbB₂-based catalysts consisting of Borophene as graphene-like noble metal-free networks in Niobium-metal based networks, as promising catalysts for the hydrogen-evolution reaction (HER). Our results unveiled that Fe/Co covalent doping in α-NbB₂ {001} surface provides high-efficiency HER activity sites, namely, T_Nb-sites in Nb-terminated Fe/Co-NbB₂ {001} surface with the lowest ΔG_H^∗ Gibbs free energy value of about 0.264/0.278 eV, which further drops to a very optimal value in the range of ΔG_H^∗ ≤ ± 0.10 eV upon the implementation of an external electric field. Furthermore, it was also revealed that in contrast to the extensively used Pt-based surface catalysts, both α-NbB₂ and Fe/Co-NbB₂ catalysts can sustain consistently high catalytic activity for HER over a very large hydrogen coverage and thus ensure a large density of effective catalytic free sites.

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All-solid electrolytes could lead to a technological breakthrough in the performance of all-solid-state batteries when combined with a lithium-metal anode. However, the use of a lithium-metal anode presents several challenges, such as dendrite growth, interface electrochemical stability, formation and propagation of cracks, and delamination of the electrode/electrolyte interfaces. This work aims to explore the effectiveness of using newly synthesized 2D graphyne-based membranes (namely graphyne, graphdiyne, and graphtriyne) for electrode protection in a solid polymer electrolyte battery through first-principle calculations, nudged elastic band method, and classical molecular dynamics simulation. Specifically, we aim to investigate the effectiveness of these membranes in mitigating the aforementioned challenges. A high external electric field of up to 0.5 V/Å, 0.75 V/Å, and 1 V/Å was applied to accelerate the ions diffusion process. The adsorption energies, charge transfer, and in-plane/out-plane diffusion of single lithium on graphyne-based surfaces were investigated. Afterward, we calculated and compared the Li⁺ permeability, the electrolyte molecules’ rejection efficiency, and the intrinsic properties of graphyne-based nanoporous membranes. Our findings show that both graphyne and graphdiyne surfaces effectively permit Li⁺ intercalation while preventing other electrolyte molecules from reaching the electrodes.

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Owing to their ecological integrity, non-toxicity, and outstanding performances, Double-Halide perovskites have been vigorously promoted as sustainable alternatives for thermoelectric and photovoltaic applications. In this context, we have systematically explored the structural and mechanical strength characteristics of Cs₂AgGa(Cl,Br)₆ materials through the tolerance factor analyses and Born stability criteria. Subsequently, a detailed study of their electronic, optical, and thermoelectric properties has been performed. As results, both Cs₂AgGaCl₆ and Cs₂AgGaBr₆ show semiconducting nature with a direct bandgap of about 2.57 eV and 1.42 eV, respectively. Additionally, with such desirable band gaps, the optical properties were examined based on the complex dielectric function. It has been derived that both materials exhibit a very high absorption spectrum in the order of 10⁵ cm⁻¹ and a low reflectivity not exceeding more than 18% in the visible and UV region. Furthermore, the Cs₂AgGaBr₆ has been taken into account as absorber to construct the planar p-intrinsic-n structure (FTO/TiO₂/Cs₂AgGaBr₆/Spiro-OMeTAD/Au) and a high-record efficiency of 32.57% has been reached. The thermoelectric performance was also studied and revealed a very high Seebeck coefficient (thermo-power) and a sufficient figure of merit (ZT). Based on these results, we believe that the studied double-halide perovskites present outstanding performance for both optoelectronic and thermoelectric engineering devices.

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Through a density functional theory-driven survey, a comprehensive investigation of two-dimensional (2D) Janus aluminum-based monochalcogenides (Al₂XY with X/Y = S, Se, and Te) has been performed within this study. To begin with, it is established that the examined phase, in which the Al-atoms are located at the two inner planes while the (S, Se, and Te)-atoms occupy the two outer planes in the unit cell, are energetically, mechanically, dynamically, and thermally stable. To address the electronic and optical properties, the hybrid function HSE06 has been employed. It is at first revealed that all three monolayers display a semiconducting nature with an indirect band gap ranging from 1.82 to 2.79 eV with a refractive index greater than 1.5, which implies that they would be transparent materials. Furthermore, the monolayers feature strong absorption spectra of around 10⁵ cm⁻¹ within the visible and ultraviolet regions, suggesting their potential use in optoelectronic devices. Concerning the photocatalytic performance, the conduction band-edge positions straddle the hydrogen evolution reaction redox level. Also, it is observed that the computed Gibbs free energy is around 1.15 eV, which is lower and comparable to some recently reported 2D-based Janus monolayers. Additionally, the thermoelectric properties are further investigated and found to offer a large thermal power as well as a high figure of merit (ZT) around 1.03. The aforementioned results strongly suggest that the 2D Janus Al-based monochalcogenide exhibits suitable characteristics as a potential material for high-performance optoelectronic and thermoelectric applications.

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An attractive approach to mitigate hydrogen embrittlement (HE) is to use nano-sized particles to immobilize hydrogen. However, the atomic scale relationship between different particle-matrix characteristics in aluminum alloys and the susceptibility to HE is unknown. In this study, the effects of interactions between various interfaces and hydrogen in aluminum alloys are investigated using a comprehensive multiscale experimental and simulation-based approach that includes atomic-scale observations, simulation and advanced hydrogen mapping techniques. Depending on the nature of interfaces, e.g., coherency, size, and crystal structure, some are useful for mitigating HE, others provide hydrogen to sensitive sites, and some act as crack initiation sites.

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Computational design of new two-dimensional materials constitutes an effective and promising approach in the development and exploration of a wide range of emerging applications such as optoelectronics, photocatalysis, energy storage, and conversion. Within the framework of this work, we systematically investigated for the first time, the structural, stability, optoelectronic, and pho-tocatalytic properties of new predicted Al(Ga, In)STe monolayers derived from Janus Aluminium mono-chalcogenides through Density Functional Theory and Ab-Initio molecular dynamic simulations. After a full optimization of both struc-tures, their dynamics and thermal stability was confirmed through the calculations of phonon spectrum and ab-initio molecular dynamics at a chosen temperature, respectively. Subsequently, the electronic and optical properties were explored and findings revealed that both monolayers exhibit a semiconducting characteristic with a direct and indirect electronic band gap of about 2.23 and 2.69 eV using HSE06 hybrid functional for AlGaSTe and AlInSTe monolayers, re-spectively. Furthermore, the optical absorption indicates a strong absorption of light in the range between 3 and 18 eV. More noticeably, Both Janus monolayers considered exhibiting a promising optical absorption in the visible wavelength region with an absorption coefficient greater than 10⁵ cm⁻¹. In addition, the photocatalytic properties of these structures were investigated by plotting the band edge positions straddle the reduction potential of H₂ and the oxidation potential H₂O. Based on our results, we conclude that both monolayers offer good thermodynamic stability allowing them to be processed experimentally and can be used as very appropriate candidates for optoelectronics and photocatalytic applications.

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Motivated by the successful synthesis of 2D C₂F diamanes [Bakharev, P.V. et al., Nat. Nanotechnol. 15, 59–66 (2020)], we have systematically investigated the structural stability, in-plane mechanical, optoelectronic, photocatalytic, piezoelectric, and thermoelectric properties of non-Janus and Janus diamanes monolayers named as C₂H, C₂F, C₂Cl, C₄HF, C₄HCl and C₄FCl. The structural stability is confirmed by cohesive energy, phonon dispersion spectra, and mechanical properties. The electronic properties has been calculated by HSE06 functional and the band gap are found to be 3.85, 5.64, 2.32, 4.16, 0.73 and 1.91 eV for C₂H, C₂F, C₂Cl, C₄HF, C₄HCl and C₄FCl, respectively. The hydrogen-containing non-Janus and Janus diamanes monolayers have a higher negative Poisson's ratio (NPR) and therefore are good auxetic materials. From the Poisson's ratio and Young's modulus of each configuration of non-Janus and Janus diamanes monolayer, anisotropic behavior was displayed. From the optical properties calculations, the refractive index values are around 1.5, which means that it will be a transparent monolayered materials. Also, C₂Cl, C₄HCl and C₄FCl monolayers displayed high absorption spectra with an order of 10⁵ cm⁻¹ in the visible region, which shows great applications in optoelectronic devices. Additionally, the valence and conduction band-edge positions of 2D Janus and non-Janus diamanes of C₂H, C₂F, and C₂Cl and C₄HF monolayers have to straddle the redox potentials of water. It means that the photogenerated electrons and holes are sufficient to drive the overall water splitting. Whereas non-Janus diamanes C₄HCl, and C₄FCl monolayers displayed only water oxidation. The investigated in-plane piezoelectric coefficient has larger in non-Janus diamanes C₄HF, C₄HCl, and C₄FCl monolayers. Therefore, it is very useful in the field of piezoelectric applications. From the thermoelectric properties, the non-Janus and Janus diamanes monolayers have great thermoelectric efficiency and were found to be 10.52 and 10.63% for C₂H and C₂F, respectively. Our results demonstrate the new class of 2D carbon-based monolayers has good auxetic materials as well as a wide range of applications in optoelectronics, piezoelectric, and thermoelectric fields.

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Hydrogen production via solar light-driven water dissociation has been regarded as an artificial and effective process to overcome the environmental problem as well as solving the current energy crisis. In this regard, numerous works have mainly been devoted to developing the appropriate photocatalyst which satisfies the conditions for water splitting and understanding the photocatalysis process. In this study, we propose for the first time the potential application of the two-dimensional Janus aluminum oxysulfide Al₂OS as an efficient photocatalyst material for hydrogen-production H₂ through the first-principles calculations. Janus Al₂OS monolayer has been designed from the parental binary aluminum sulfide AlS by substituting one sub-layer of sulfide atoms (S) to oxygen atoms (O). The electronic properties of the pristine AlS and the derived Janus Al₂OS were computed using GGA-PBE and HSE06 functionals. According to the band structure, AlS monolayer shows a semiconductor behavior with an indirect bandgap of 2.14 eV whereas, the Janus Al₂OS exhibits a direct bandgap of 1.579 eV. Motivated by the desirable bandgap of the Janus Al₂OS, the absorption-coefficient of Janus Al₂OS shows strong visible light harvesting compared to the parental AlS. Furthermore, the photocatalytic performance of Al₂OS has been investigated. Our calculations demonstrate that the band edge position of Al₂OS is suitable for the hydrogen evolution reaction (HER). More importantly, based on the reaction coordinate, it was found that the Gibbs free-energy ΔG_H^∗ of Al₂OS is 0.97 eV which is smaller than of the two-dimensional Janus Ga₂XY (X, Y = S, Se, Te with X ≠ Y) reported recently. Moreover, this value decreases from 0.97 eV to 0.69 eV under 0.5 V/Å of an external electrical field. Our results indicate that Janus Al₂OS fulfills the fundamental requirements for efficient photo-catalyst under visible light and provides new guidance for hydrogen-production via water splitting.

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Organic electrode materials are becoming increasingly important as they reduce the C-footprint as well as the production cost of currently used and studied rechargeable batteries. With increasing demand for high-energy-density devices, over the past few decades, various innovative new materials based on the fundamental structure-property relationships and molecular design have been explored to enable high-capacity next-generation battery chemistries. One critical dimension that catalyzes this study is the building up of an in-depth understanding of the structure-property relationship and mechanism of alkali ion batteries. In this review, we present a critical overview of the progress in the technical feasibility of organic battery electrodes for use in long-term and large-scale electrical energy-storage devices based on the materials designing, working mechanisms, performance, and battery safety. Specifically, we discuss the underlying alkali ion storage mechanisms in specific organic batteries, which could provide the designing requirements to overcome the limitations of organic batteries. We also discuss the promising future research directions in the field of alkali ion organic batteries, especially multivalent organic batteries along with monovalent alkali ion organic batteries.

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To achieve the high-rate efficiency in a electrochemical energy storage technologies, it is vital for the battery anode to be electronically as well as ionically conductive. Such a requirement has boosted the survey of three-dimensional (3D) porous networks made up of light-weight non-metallic elements, like carbon, boron, and nitride. A wide range of 3D porous materials composed of carbon and/or boron for Li/Na-ion batteries have been recently reported, whereas analogous efforts for lightest 3D porous boron nitride are yet to be addressed. In this work, we explore the 3D porous boron nitride network namely sp³-linked zigzag BN nanoribbons (BNNRs) with a width of 1 (lz1-BN) by assembling the 2D zigzag BNNRs and its first ever application as battery anodes for Li and Na ion batteries. Upon a consistent DFT and AIMD computations, It is revealed that the 3D porous lz1-BN material is chemically and thermally stable and yields a high specific capacity of about 539.94 mAh/g with respect to the commercialized graphite (372 mAh/g for LIBs) and recently reported Janus-graphite anode (≈332 mAh/g for SIBs), fast (Li⁺,Na⁺)-ionic diffusion, low potential voltage, and slight volume-expansion. Such puzzling electrochemical characteristics, along with the light-weight and high abundance of B and N elements, strongly support the possibility of 3D porous BN as a desirable candidate for Li and Na-ion battery anodes.

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Promising flexible electrochemical energy storage systems (EESSs) are currently drawing considerable attention for their tremendous prospective end-use in portable self-powered electronic devices, including roll-up displays, and “smart” garments outfitted with piezoelectric patches to harvest energy from body movement. However, the lack of suitable battery electrodes that provides a specific electrochemical performance has made further development of these technologies challenging. Two-dimensional (2D) lightweight and flexible materials with outstanding physical and chemical properties, including mechanical strengths, hydrophilic surfaces, high surface metal diffusivity, and good conductivity, have been identified as a potential prospect for battery electrodes. In this study, taking a new 2D boron nitride allotrope, namely 2D orthorhombic diboron dinitride monolayer (o-B₂N₂) as representatives, we systematically explored several influencing factors, including electronic, mechanical, and their electrochemical properties (e.g., binding strength, ionic mobility, equilibrium voltage, and theoretical capacity). Considering potential charge-transfer polarization, we employed a charged electrode model to simulate ionic mobility and found ionic mobility has a unique dependence on the surface atomic configuration influenced by bond length, valence electron number, electrical conductivity, excellent ionic mobility, low equilibrium voltage with excellent stability, good flexibility, and extremely superior theoretical capacity, up to 8.7 times higher than that of widely commercialized graphite (3239.74 mAh g⁻¹ Vs 372 mAh g⁻¹) in case of Li-ion batteries and 2159.83 mAh g⁻¹ in case of Na-ion batteries, indicating that the new predicted 2D o-B₂N₂ monolayer possess the capability to be ideal flexible anode materials for Lithium and Sodium-ion battery. Our finding provides valuable insights for experimental explorations of flexible anode candidates based on 2D o-B₂N₂ monolayer.

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Through density functional theory (DFT)-based computations, a systematic exploration of the newly predicted 2D phosphorene allotrope, namely holey-phosphorene (HP), is carried out. It is revealed that HP shows a semiconducting nature with an indirect bandgap of 0.83 eV upon Perdew-Burke-Ernzerhof (PBE) functional. Then, to survey the optical features, a (G₀W₀)-based approach is employed to solve the Bethe–Salpeter equation to derive the intra-layer excitonic effects. It is derived via the absorption spectrum, that HP presents an excitonic binding strength of 1.47/1.96 eV along the x/y-direction with the first peak of the absorption at 0.92/0.43 eV for the x/y-direction. The thermoelectric properties are also explored in detail and reveal a very high thermal power value along with an enhanced figure of merit (ZT) of about 3.6. The 2D HP monolayer for thermoelectric performance has high thermoelectric conversion efficiency (TCE) and is estimated to be about 22%. All these outstanding findings may be attributed to the quantum confinement effect of the porous geometry of the 2D HP nanosheet, thereby confirming its relevance as a prospect for high-performance optoelectronic and thermoelectric engineering systems.

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We explore the possibility and potential benefit of rolling a Si2BN sheet into single-walled nanotubes (NTs). Using density functional theory (DFT), we consider both structural stability and the impact on the nature of chemical bonding and conduction. The structure is similar to carbon NTs and hexagonal boron-nitride (hBN) NTs and we consider both armchair and zigzag Si2BN configurations with varying diameters. The stability of these Si2BN NTs is confirmed by first-principles molecular dynamics calculations, by exothermal formation, an absence of imaginary modes in the phonon spectra. Also, we find the nature of conduction varies from semiconducting over semimetallic to metallic, reflecting differences in armchair/zigzag-type structures, curvature effects, and the effect of quantum confinement. We present a detailed characterization of how these properties lead to differences in both the bonding nature and electronic structures.

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