01430nas a2200193 4500008004100000022001500041245012700056210006900183260000800252300001600260490000700276520071800283100001801001700002501019700002601044700002701070700001601097856012301113 2018 eng d a 1463-907600aDissociative chemisorption of hydrogen molecules on defective graphene-supported aluminium clusters: a computational study0 aDissociative chemisorption of hydrogen molecules on defective gr cNOV a26506-265120 v203 a

Using periodic density functional theory-based calculations, in the present study, we address the chemical bonding between aluminium clusters (Al-n, n = 4-8 and 13) and monovacant defective graphene. The adsorption strength of the above-mentioned aluminium clusters is fivefold (approximate to 3 to 5 eV) higher on defective graphene as compared to the earlier reported values on non-defective graphene and BN-doped graphene. The Bader charge analysis and different charge densities reveal that this adsorption is driven by significant charge transfer from the Al clusters to defective graphene. Thus, chemisorbed Al clusters demonstrate high activity towards dissociative adsorption of molecular hydrogen.

1 aKumar, Deepak1 aGovindaraja, Thillai1 aKrishnamurty, Sailaja1 aKaliaperumal, Selvaraj1 aPal, Sourav uhttp://library.ncl.res.in/content/dissociative-chemisorption-hydrogen-molecules-defective-graphene-supported-aluminium02780nas a2200181 4500008004100000022001400041245011100055210006900166260000800235300001600243490000800259520210000267100002202367700002502389700002702414700002602441856013102467 2019 eng d a1932-744700aDinitrogen activation on graphene anchored single atom catalysts: local site activity or surface phenomena0 aDinitrogen activation on graphene anchored single atom catalysts cNOV a27492-275000 v1233 a

Catalysis on two-dimensional (2D) substrates with metal clusters or centers is generally dealt with as a surface phenomenon under the conjecture that the delocalized electron density is the driving force. When single atom catalysts (SACs) are anchored on such materials with delocalized electron density, for instance graphene, the stimulant for catalysis may be either the d-electrons on the metal or the system altogether. To understand the contributing factors of catalysis on such systems, a case study of dinitrogen (N-2) activation on Mo anchored graphene has been made by employing periodic and finite models of graphene. The periodic model represents a continuum of SACs anchored periodically on graphene, while the finite models are graphene nanoflakes of varying sizes and edge orientations. In addition to the physical aspects, such as size/finiteness of graphene, the influence of varying chemical compositions of the substrate on the activity is also evaluated by doping graphene with different B and N concentrations. This study, while clearly bringing out the connotation of regulating atomic composition of graphene substrate for dinitrogen activation, also surprisingly unveils the relative insignificance of varying the size and edge effects of the substrate. These features are highlighted through an analysis of red shift in the N-N stretching frequency, charge transfer to dinitrogen from the catalytic system, and structural and electronic characteristics of the catalytic system. The total and projected density of states plots reveal hybridization between the metal d orbitals and the p orbitals of carbon and nitrogen in the valence band. On the other hand, the frontier molecular orbital analysis also depicts a strong chemisorption of dinitrogen with the metal-graphene supports on account of direct hybridization between the d orbitals of the supported metal atom and the p orbitals of dinitrogen. The Bader and Lowdin charge distribution on the adsorbed dinitrogen in periodic and finite models shows the preeminence of local site over the surface activity.

1 aMaibam, Ashakiran1 aGovindaraja, Thillai1 aSelvaraj, Kaliaperumal1 aKrishnamurty, Sailaja uhttp://library.ncl.res.in/content/dinitrogen-activation-graphene-anchored-single-atom-catalysts-local-site-activity-or-surface02700nas a2200265 4500008004100000022001400041245016000055210006900215260000800284300001100292490000800303520172400311653003002035653003202065653001702097653001902114653003702133100002202170700001902192700001702211700002502228700002602253700002702279856012802306 2020 eng d a0304-389400aUnravelling the distinct surface interactions of modified graphene nanostructures with methylene blue dye through experimental and computational approaches0 aUnravelling the distinct surface interactions of modified graphe cAPR a1217550 v3883 a

Nanoscopic modifications leading to multi-dimensional graphene structures are known to significantly influence their candidature for several applications including catalysis, energy storage, molecular sensing and most significantly adsorption and remediation of harmful materials such as dyes. The present work attempts to identify the key trajectories that connect the structural qualification with a chosen application, viz., the interactive forces in dye remediation. Various physico-chemically Modified Graphene Nanostructures (MGNs) such as 2 dimensional Graphite, Graphene Oxide (GO), reduced GO (rGO), holey rGO, and 3 dimensional GO hydrogel and Holey GO hydrogel are chosen and synthesised herein. These represent varieties of physicochemical features with respect to their dimensionality, surface features such as oxygen functionality, nanoscopic holes etc., that contribute to their characteristic overall surface interactions. Methylene Blue (MB), a popular industrial effluent posing major environmental concern is chosen to be a probe adsorbate in this case study. An exclusive real time in-situ UV visible spectral experiment provides the revealing reasons behind the outstanding performance of 2D GO sheets with an adsorption capacity of greater than 92 % even at high MB concentrations (>2000 ppm). A complex dependency of various factors such as surface oxygen, morphology, nanoporosity etc. on the unique overall interaction with an adsorbent such as MB by all these adsorbates is demonstrated using experimental and DFT based computational studies. Electrostatics and hydrogen bonding are understood to be the two dominant forces driving the MB adsorption on the best performing GO here.

10aDensity functional theory10aIn-situ UV-vis spectroscopy10aInteractions10aMethylene blue10aModified Graphene Nanostructures1 aManappadan, Zinoy1 aKumar, Shubham1 aJoshi, Krati1 aGovindaraja, Thillai1 aKrishnamurty, Sailaja1 aSelvaraj, Kaliaperumal uhttp://library.ncl.res.in/content/unravelling-distinct-surface-interactions-modified-graphene-nanostructures-methylene-blue