arXiv subjects

Soumendra Kumar Das

Publications and source records attributed to Soumendra Kumar Das.

5 recordsLinked to original sources

arXiv2026

Strain-Driven Electronic and Catalytic Modulation of g-C3N4/GeS van der Waals heterostructure for Photocatalytic Water Splitting

Photocatalytic water splitting offers a viable pathway for sustainable hydrogen production. In this study, first-principles density functional theory calculations were performed to explore the strain-dependent photocatalytic behaviour of a two-dimensional g-C3N4/GeS heterostructure. The heterostructure shows type-II band alignment with an indirect band gap of 2.17 eV, smaller than those of the individual g-C3N4 (2.81 eV) and GeS (3.31 eV) monolayers. Biaxial tensile strain up to 3% effectively modulates the band gap and band edge positions, allowing suitable alignment with water redox potentials. The calculated Gibbs free energy for the hydrogen evolution reaction (ΔGHER) is 0.2 eV for the pristine heterostructure and approaches near-thermoneutral values (-/+ 0.1 eV) under +1% and +2% strain. Meanwhile, the OER overpotential decreases from 2.17 V to 0.97 V with increasing strain. AIMD simulations and optical absorption in the visible region confirm the thermodynamic stability and promising photocatalytic potential of the heterostructure for hydrogen generation.

cond-mat.mtrl-sci↗

arXiv2025

First Principles study of Photocatalytic Water Splitting in BO Monolayer: Effect of Strain and Surface Functionalization

Light element based two dimensional (2D) materials are promising photocatalysts for hydrogen production via water splitting. Boron oxide (BO) is a recently synthesized 2D monolayer which has yet to be thoroughly explored for its potential applications. In this article, using first principles calculations, we report, for the first time, the visible-light photocatalytic activity of a BO monolayer for water splitting under mechanical strain and surface modification with single- and double-atom decorations (C, N, Si, Ge, P, As). The pristine BO monolayer exhibits an indirect band gap of 3.8 eV with band edges spanning the water redox potentials, but its optical absorption lies in the UV region (~ 4.5 eV). Strain engineering tunes the band gap and band alignment with a minimal shifting in the optical absorption (~0.5 eV). Single atom decoration produces a metallic state for elements like N, P, As, and an insulating state for single C, Si, Ge with a partial shifting in optical absorption. In contrast, double atom decoration produces substantial band gap reduction, improved band alignment, a pronounced red-shift in optical absorption into the visible range (1.6 to 3.2 eV) thus satisfying the criteria for water splitting. The stability of all the adsorbed configurations was confirmed by negative formation energy and ab-initio molecular dynamics simulations. These findings suggest BO monolayer functionalization can improve photocatalytic efficiency, providing hydrogen generation insights.

cond-mat.mtrl-sci↗

arXiv2025

Unraveling the Surface Stability and Chemical Reactivity of Aza-Triphenylene Monolayer under O$_2$ and H$_2$O Exposure

Environmental oxidation has a great impact in tuning the physical, chemical and electronic properties of two-dimensional (2D) monolayers which can affect their practical applications in nanoscale engineering devices under ambient conditions. aza-triphenylene is a recently synthesized 2D materials whose practcal applications have not been systematically studied yet. In this study, we report for the first time, the adsorption and dissociation of O$_2$ and H$_2$O molecules on the surface of 2D aza-triphenylene monolayer through first principles calculations in combination with climbing image nudged elastic band (CINEB) method. The results indicates that both the O$_2$ and H$_2$O molecules weakly interact over the monolayer surface with an adsorption energy -0.16 eV and -0.37 eV respectively. In contrast, both the molecules exhibit resistance for dissociation due to the formation of energy barriers. The transition path indicates that molecular oxygen experience two energy barriers (0.16 ev and 1.22 eV) before getting dissociated atomic oxygen. However, the dissociation of H$_2$O requires larger energy barrier (2.3 eV and 0.86 eV) due to breaking of covalent bonds and transfer of hydrogen. The strong chemical adsorption of atomic oxygen and H$^+$/OH$^-$ ions is due to the significant charge transfer from monolayer to the adsorbate as evidenced from the charge density difference and Bader charge analysis. Moreover, the dissociated configuration exhibit a larger band gap as compared to the pristine aza-triphenylene due to the strong hybridization between the p states of carbon and oxygen. our work predicts the robustness of azatriphylene monolayer against oxygen/water exposer thus ensuring their stability for device applications using these materials.

cond-mat.mtrl-sci↗

arXiv2024

Unveiling the Reactivity of Oxygen and Ozone on C2N Monolayer: A First-Principles Study

The process of environmental oxidation is pivotal in determining the physical and chemical properties of two-dimensional (2D) materials. Its impact holds great significance for the practical application of these materials in nanoscale devices functioning under ambient conditions. This study delves into the influence of O2 and O3 exposure on the structural and electronic characteristics of the C2N monolayer, focusing on the kinetics of adsorption and dissociation reactions. Employing first-principles density functional theory calculations alongside climbing image nudged elastic band calculations, we observe that the C2N monolayer exhibits resistance to oxidation and ozonation, evidenced by energy barriers of 0.05 eV and 0.56 eV, respectively. These processes are accompanied by the formation of epoxide (C-O-C) groups. Furthermore, the dissociation mechanism involves charge transfers from the monolayer to the molecules. Notably, the dissociated configurations demonstrate higher bandgaps compared to the pristine C2N monolayer, attributed to robust C-O hybridization. These findings suggest the robustness of C2N monolayers against oxygen/ozone exposures, ensuring stability for devices incorporating these materials.

cond-mat.mtrl-sci↗

arXiv2023

Strain Induced Enhanced Photocatalytic Activities in Layered Two Dimensional C2N/MoS2 Heterostructure: A Meta-GGA Study

The improved photocatalytic water splitting using 2D materials has technological importance for economically viable renewable energy. The present study focuses on the effect of uniaxial, biaxial, and vertical strain on the energy gap and band edge positions of C2N/MoS2 van der Waals heterostructures through first-principles density functional theory using PBE and SCAN functionals. The calculations establish that SCAN functional provides comparatively much better results as compared to the PBE for the band gap and band alignment study. The heterostructure exhibits a type- II band alignment which is beneficial for the efficient separation of charge carriers. For a good photocatalyst, the band edge positions should straddle the water redox potentials. It is observed that for both compressive and tensile vertical strain, the water redox potential values lie within the valence band maximum (VBM) and conduction band minimum (CBM) of the heterostructure. On the other hand, for uniaxial and biaxial strain, the system can be used as a useful photocatalyst only for larger compressive strain, whereas for tensile strain, the energy gap between VBM and CBM keeps on decreasing and lie within the water oxidation/reduction potential. Our study also establishes that the meta-GGA SCAN functional shows similar results as compared to the computationally expensive hybrid HSE functionals. The present work can be extremely useful for experimentalists to design artificial heterostructure devices for better performance in photocatalytic water splitting.

cond-mat.mtrl-sci↗