Enhanced Thermoelectric Performance of Nanostructured 2D Tin Telluride.

A lot of experimental studies are conducted on theoretically predicted thermoelectric 2D materials. Such materials can pave the way for charging ultra-thin electronic devices, self-charging wearable devices, and medical implants. This study systematically explores the thermoelectric attributes of bulk and 2D nanostructured Tin Telluride (SnTe), employing experimental investigations and theoretical analyses based on semiclassical Boltzmann transport theory. The bulk SnTe is synthesized through flame melting, while the 2D SnTe is produced via liquid phase exfoliation. The comprehensive assessment of thermoelectric properties integrated experimental measurements utilizing a Physical Property Measurement System and theoretical calculations from the BoltzTraP code. Experimental thermoelectric studies show a high ZT of 0.17 for 2D SnTe when compared to bulk (0.005) at room temperature. This rise in ZT is due to the high Seebeck coefficient and low thermal conductivity of nanostructured 2D SnTe. Density functional theory (DFT) studies reveal the contribution of the density of states (DOS) and energy bandgap in enhancing the Seebeck coefficient and lowering thermal conductivity by interface scattering.

Gd3+ Encapsulation on 2D-g-C3N4 Nanostructure for Spintronics and Ultrasound Assisted Photocatalytic Applications: First-Principles and Experimental Studies.

Atomically thin two-dimensional (2D) semiconductors have high potential in optoelectronics and magneto-optics appliances due to their tunable band structures and physicochemical stability. The work demonstrates that Gd3+ incorporated 2D-g-C3N4 nanosheet (Gd3+/2D-g-C3N4 NS) is synthesized through chemisorption methodology for defect enrichment. The material characterizations reveal that the ion decoration enhances the surface area and defect concentration of the 2D sheet. The experimental observations have been further corroborated with the help of density functional theory (DFT) simulation. Spin asymmetry polarizations near the Fermi level, obtained through the partial density of states (PDOS) analyses, reveal the magnetic nature of the synthesized material, validating the room temperature ferromagnetism obtained through a vibrating-sample magnetometer (VSM). Gd3+/2D-g-C3N4 NS shows significant enhancement in saturation magnetization (Ms) experimentally and computationally compared to the pristine one. The magnetic catalyst shows 98% remediation efficiency for ultrasound-assisted visible-light-driven photodegradation of methyl orange (MO). The synergistic approach of liquid chromatography-mass spectrometry (LC-MS) analyses and DFT studies elucidates reaction intermediates and unveils the degradation mechanism. Post-characterization studies assure the stability of the magnetic catalyst through optical, chemical, magnetic, and microscopic analyses. So, the synthesized material can be proficiently used as a magnetic nanocatalyst in wastewater treatments and spin-electronics applications.

A comprehensive diffusion-induced stress coupled multiscale modeling and analysis in hard-carbon electrodes of Li-ion batteries.

Particle fracture due to diffusion-induced stress (DIS) in electrodes is a key factor for lithium-ion battery (LIB) failure. Among many ways to minimize DIS, optimization of particle size and C-rates using state of charge (SOC) dependent varying properties can be a noble approach. Herein, a comprehensive multiscale modeling approach has been proposed to optimize the particle size by studying the DIS in hard carbon (HC) particles as the potential anode materials for high-energy LIBs. To accomplish this, density functional theory (DFT) was used to calculate the SOC dependent coefficient of volume expansion (CVE). Similarly, SOC dependent diffusivity and elastic modulus are calculated via molecular dynamics (MD) simulations. These results are transferred to a continuum model to examine the evolution of concentrations and DISs in hard carbon particles of radius 100-1000 nm lithiated at various C-rates (1C, 2C, 5C, and 10C). Our model successfully incorporates the variation of Li+ diffusivity and elastic modulus with SOC and tracks stress relaxation and volume expansion in the particles during lithiation. An optimized particle size has been recommended for hard carbon, considering both stresses for different C-rates. Our study provides a more realistic multiscale modeling framework for optimizing the DIS and can act as a guiding method towards achieving an optimum particle size so that capacity fading due to cracking can be avoided.

Lithium and phosphorus-functionalized graphitic carbon nitride monolayer for efficient hydrogen storage: A DFT study.

We have explored the consequence of lithium and phosphorous functionalization on the graphitic carbon nitride (g-C3N4) monolayer for hydrogen storage using density functional theory. Both pristine and Li and P decorated g-C3N4 show a semiconductor nature. The substantial overlap between the s orbital of Li and the p orbital of nitrogen near the Fermi level shows the binding between Li and the g-C3N4. The repositioning of HOMO and LUMO is noticed in the Li and P decorated g-C3N4. The Bader charge analysis indicates the charge allocation from the Li and P atom to the g-C3N4, which results in the adsorption of H2 by electrostatic interaction. The hydrogen storage capacity of 5.78 wt% is obtained after functionalizing Li and P into the g-C3N4. The obtained adsorption energies for the H2 adsorption and the H2 desorption temperature confirm that Li and P functionalized g-C3N4 is a fascinating candidate for the reversible loading of H2 at ambient conditions.

Dimensionality effects of g-C3N4 from wettability to solar light assisted self-cleaning and electrocatalytic oxygen evolution reaction.

Unique interfacial properties of 2D materials make them more functional than their bulk counterparts in a catalytic application. In the present study, bulk and 2D graphitic carbon nitride nanosheet (bulk g-C3N4 and 2D-g-C3N4 NS) coated cotton fabrics and nickel foam electrode interfaces have been applied for solar light-driven self-cleaning of methyl orange (MO) dye and electrocatalytic oxygen evolution reaction (OER), respectively. Compared to bulk, 2D-g-C3N4 coated interfaces show higher surface roughness (1.094 > 0.803) and enhanced hydrophilicity (θ âˆ¼ 32° < 62° for cotton fabric and θ âˆ¼ 25° < 54° for Ni foam substrate) due to oxygen defect induction as confirmed from morphological (HR-TEM and AFM) and interfacial (XPS) characterizations. The self-remediation efficiencies for blank and bulk/2D-g-C3N4 coated cotton fabrics are estimated through colorimetric absorbance and average intensity changes. The self-cleaning efficiency for 2D-g-C3N4 NS coated cotton fabric is 87%, whereas the blank and bulk-coated fabric show 31% and 52% efficiency. Liquid Chromatography-Mass Spectrometry (LC-MS) analysis determines the reaction intermediates for MO cleaning. 2D-g-C3N4 shows lower overpotential (108 mV) and onset potential (1.30 V) vs. RHE for 10 mA cm-2 OER current density in 0.1 M KOH. Also, the decreased charge transfer resistance (RCT = 12 Ω) and lower Tafel's slope (24 mV dec-1) of 2D-g-C3N4 make it the most efficient OER catalyst over bulk-g-C3N4 and state-of-the-art material RuO2. The pseudocapacitance behavior of OER governs the kinetics of electrode-electrolyte interaction through the electrical double layer (EDL) mechanism. The 2D electrocatalyst demonstrates long-term stability (retention ∼94%) and efficacy compared to commercial electrocatalysts.

A facile and green synthesis of Mn and P functionalized graphitic carbon nitride nanosheets for spintronics devices and enhanced photocatalytic performance under visible-light.

Manganese and phosphorus co-doped, graphitic carbon nitride (g-C3N4) nanosheet (Mn/P-g-C3N4) is prepared by facile and green calcination process of melamine (C3H6N6), manganese chloride tetrahydrate (MnCl2·4H2O), and ammonium dihydrogen phosphate ((NH4)H2PO4). The Mn/P co-doping significantly enhances magnetic values compared to pristine-g-C3N4, phosphorus-doped g-C3N4 (P-g-C3N4), and manganese-doped g-C3N4 (Mn-g-C3N4). We find that Mn/P-g-C3N4 is a half-metallic ferromagnetic material having a magnetic moment and Curie temperature of 4.51 µB and âˆ¼ 800 K, respectively. The ultraviolet-visible (UV-vis) absorption spectrum of Mn/P-g-C3N4 reveals superior absorption in broader wavelength compared to pristine-g-C3N4, P-g-C3N4, and Mn-g-C3N4. The methyl orange degradation efficiency of Mn/P-g-C3N4 photocatalyst is 94 %, which is three times more than that of pristine-g-C3N4 (29 %) and more significant than the P-g-C3N4 (46 %) and Mn-g-C3N4 (58 %). Furthermore, density functional theory (DFT) calculation explains the origin of high magnetic behavior, the boosted photocatalytic efficiency of Mn/P-g-C3N4, and the essential material properties like structure, bandgap, the density of states (DOS), and atomic level interaction. This work may be helpful for reasonably designing ferromagnetic material for spintronics devices and boosting visible-light (VL) photocatalytic performance for environmental remediation.

Density functional theory-based analyses on selective gas separation by ß-PVDF-supported ionic liquid membranes.

Finding proper candidates for polymer-supported ionic liquid (IL)-based gas separating membranes is a challenge. The current article elucidates the quantum chemical perspective of the selective gas adsorption efficiency, from a mixture of CO2, CO, CH4, and H2, of α- and ß-polyvinylidene fluoride (PVDF)-supported imidazolium- and pyridinium-based six ionic liquid membranes. Although IL-based membrane efficiency mainly depends on the gas solubility of ILs, IL/support binding and gas adsorption on the support material are also studied to describe the overall gas adsorption properties of the PVDF/IL complexes. ß-PVDF exhibits better binding with the ILs, and better gas affinity, thus, qualified as a more suitable membrane component as compared to α-PVDF. Dispersion-corrected density functional calculations are performed to provide a detailed insight into the energetic interactions, nonbonding intermolecular interactions based on symmetry adapted perturbation theory (SAPT), natural bond orbitals (NBO), Bader's quantum theory of atoms in molecules (QTAIM), reduced density gradient (RDG), frontier orbital interactions, density of states (DOS), and thermochemical analyses of the gas-adsorbed systems. Gas molecules interact with the membrane components through weak hydrogen bonds and exhibit low interaction energies, indicating physisorption of the gases. Gas adsorption energies are more negative than the mutual interaction energies of the gas molecules, ensuring effective gas adsorption by the membrane components. All the ß-PVDF/IL systems have shown the highest and lowest affinity for CO2 and H2, respectively, leading to effective separation of CO2 and H2 from the other gases.

Lanthanum ions decorated 2-dimensional g-C3N4 for ciprofloxacin photodegradation.

The low band gap energy and high surface area two-dimensional materials allow it to tune its basic properties using surface decoration. Here, La3+ are decorated on two-dimensional graphitic carbon nitride using a simple and easily scalable chemisorption process with an adsorption capacity of 657.32 mg g-1. In the X-ray diffraction (XRD) study, the positive slope of the W-H plot elucidates the tensile strain generation (0.103) in La3+ ions decorated 2D-g-C3N4 (La3+-2D-g-C3N4). The high-resolution transmission electron microscope (HR-TEM) study and the higher ID/IG ratio (0.82) in the Raman spectroscopy study confirm the more defects intensification in La3+-2D-g-C3N4. The reduction in band gap energy for La3+-2D-g-C3N4 (from 2.83 eV to 2.21 eV) has shown a good correspondence with the band structures study as obtained from the DFT study. In the DFT study, the significant contributions of N atoms in charge transfer validate the N 1s findings from the X-ray photoelectron spectroscopy (XPS) study for La3+-2D-g-C3N4. La3+-2D-g-C3N4 shows the photodegradation efficiency (93%) of ciprofloxacin under UV irradiation, which is superior to pristine 2D-g-C3N4 (82%) as well as other g-C3N4 based nanocatalysts. Also, La3+ decoration results in enhancement (32.3%) in photodegradation kinetics rate. The degradation and kinetics studies in the presence of different scavengers ensure that the O2- and OH- radicals are mostly responsible for the ciprofloxacin photodegradation. The Liquid chromatographic-mass spectroscopy and the high-performance liquid chromatography studies confirm the photodegradation. The reusability of La3+-2D-g-C3N4 is tested up to the fifth cycle. FTIR and UV-visible absorption spectroscopy confirm the stability of the used photocatalyst.

Density functional theory based studies on the adsorption of rare-earth ions from hydrated nitrate salt solutions on g-C3N4 monolayer surface.

This article represents density functional theory (DFT) based comparative analysis on six trivalent rare-earth ions (RE3+; RE: Y, La, Ce, Sm, Eu and Gd) absorption, from the respective nitrate-hexahydrate salts, on graphitic carbon nitride (g-C3N4) 2D monolayer, and the photocatalytic properties of the RE3+ adsorbed g-C3N4 systems (g-C3N4/RE3+) based on the ground-state electronic structure calculations. Structure, stability and coordination chemistry of two configurations of each hydrated RE-salt system are discussed in detail. Both DFT (B3LYP/SDD) and semi-empirical (Sparkle/PM7) calculations identify the central N6 vacancy of pristine g-C3N4 as the most suitable site for RE3+ adsorption. Bader's QTAIM, Mayer bond order and charge population analyses (ADCH, CHELPG and DDEC) are performed to describe the bond characteristics within the systems under study. Thermochemical calculations suggest that the adsorption process is thermodynamically more feasible for higher atomic number (Z) RE3+ [Sm3+, Eu3+ and Gd3+], compared to lower-Z RE3+ [Y3+, La3+ and Ce3+] ions. Besides, the better photocatalytic properties of higher-Z RE3+ adsorbed g-C3N4 systems are revealed from better HOMO-LUMO delocalization, decreased HOMO-LUMO gap, increased softness, higher electrophilicity and electron transfer parameter, compared to pristine or lower-Z RE3+ adsorbed g-C3N4 systems, as obtained from Hirshfeld orbital compositions, density of states and condensed Fukui function analyses.