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[Display omitted] • S-dopant and S-linkers are exploited to tune the catalytic activity of GQD. • Charge transfer from active sites play an important role to bind the intermediates. • Higher efficiency of sulfurized GQD with double S dopant or in presence of oxygen. • Combined effect of S-linker and N-dopant enhances ORR efficiency of entangled GQDs. To enhance the catalytic efficiency of graphene quantum dot (GQD) for ORR, the role of S-dopant and S-linker is explored here by utilizing the first-principles density functional theory-based approach. The ORR efficiency is found to be changed on different active sites with the variation of dopant position and dopant configuration on the sulfurized GQD. Charge transfer from the dopant site to the active sites and to the intermediates, as well as the binding energy of intermediates on the active sites play an important role to realize the potential determining step, onset potential and the overpotential for ORR. The increase in the doping concentration of S or the presence of oxygen is found to drastically enhance the ORR efficiency of GQD. Furthermore, S-linkers are exploited to connect two GQDs entangled or twisted with each other and resulting in a rather complex system. The combined effect of entangling, S-linkers and presence of a single N dopant at the meta position of the active site resulted in the adsorption of the intermediates with optimum binding strength. Consequently, the ORR activity is found to be enhanced, thereby resulting in a metal-free and cost-effective electrocatalyst with efficiency similar to the Pt-based metal catalysts. [ABSTRACT FROM AUTHOR]

Highlights: [•] IR and Raman analysis could be used to investigate the type of conformer. [•] Shrinkage of lattice parameter, results in blue shift of Raman frequency. [•] Formation of shallow donor level due to hydrogenation. [•] Chair conformer properties are largely differ from Boat and Stirrup conformer. [ABSTRACT FROM AUTHOR]

First principles density functional theory based calculations have been performed to investigate the strain and temperature induced tunability of the thermoelectric properties of monolayer (ML) MoS 2. Modifications in the electronic and phononic transport properties, under two anisotropic uniaxial strains along the armchair (AC) and zigzag (ZZ) directions, have been explored in detail. Considering the intrinsic carrier-phonon scattering, we found that the charge carrier mobility (μ) and relaxation time (τ) increase remarkably for strains along the ZZ direction. Concomitantly, strain along the ZZ direction significantly reduces the lattice thermal conductivity (κ L) of ML-MoS 2. The combined effect of shortened phonon relaxation time and group velocity, and the reduced Debye temperature is found to be the driving force behind the lowering of κ L. The large reduction in κ L and increase in τ , associated with the strains along the ZZ direction, act in unison to result in enhanced efficiency and hence, improved thermoelectric performance. Nearly 150% enhancement in the thermoelectric efficiency can be achieved with the optimal doping concentration. We, therefore, highlight the significance of in-plane tensile strains, in general, and strains along the ZZ direction, in particular, in improving the thermoelectric performance of ML-MoS 2. [Display omitted] • DFT based study on the strain engineered thermoelectric performance of ML-MoS 2. • Tensile strain driven anisotropic enhancement in the thermoelectric efficiency. • Charge carrier mobility and relaxation time increases remarkably with strain. • Significant strain induced reduction in lattice thermal conductivity. • Tensile strain along the zigzag direction in particular results in large increase in ZT. [ABSTRACT FROM AUTHOR]

Using state-of-the-art density functional theory (DFT) based approach; we investigated the catalytic activity of electron doped C 2 N monolayer (O → N) for CO oxidation. Large surface-to-volume ratio and uniformly distributed holes of recently synthesized planar 2D C 2 N have made it a potential candidate as noble metal-free catalyst. However, pristine C 2 N monolayer is chemically inert and hinders the adsorption of O 2 and CO molecule on it. Oxygen doping in C 2 N brings additional electrons to the system and introduces donor state below E F . Thus the reactivity of O-doped C 2 N (2OC 2 N) monolayer gets significantly enhanced, thereby opening up the possibility of its usage as a catalyst. This reactive 2OC 2 N surface adsorbs an incoming O 2 molecule along with the elongation of O O bond, making it chemically active. Presence of this pre-adsorbed active O 2 greatly impedes the adsorption of another incoming CO, favoring Eiley-Rideal (ER) mechanism for CO oxidation. [ABSTRACT FROM AUTHOR]

Abstract: Electronic structure calculations based on density functional theory (DFT) using method are performed in order to investigate the local magnetic behaviour of isolated Fe impurity in dilute alloy. The calculations performed for different near neighbour configurations reveal that the giant magnetic moment of Fe in Pd is drastically suppressed in mainly due to reduction of the induced ferromagnetic polarization of the host Pd atoms and the development of a negative spin moment on the V atoms. The results are compared with experimental data obtained from -ray perturbed angular distribution measurements. [Copyright &y& Elsevier]