02780nas 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-surface01963nas a2200253 4500008004100000022001400041245011500055210006900170260000800239300001400247490000700261520109300268653001501361653001801376653001401394653001801408653002001426100003801446700001801484700002201502700002601524700003001550856012901580 2021 eng d a1867-388000aDurable metalloporphyrin 2D-polymer for photocatalytic hydrogen and oxygen evolution from river and sea waters0 aDurable metalloporphyrin 2Dpolymer for photocatalytic hydrogen a cAPR a1717-17210 v133 a

It is highly imaginary that the outcome of a combination of two complementary resources leads to answer an alarming global issue. One such possible example is the solar seawater splitting for `clean fuel' H-2 generation. Since the catalytic activity and stability of the photocatalysts are substantially challenged in seawater, the design of an efficient and stable photocatalyst is highly desirable. Herein, we demonstrate the solar seawater splitting by a two-dimensional polymer catalyst derived from metalloporphyrin bearing multi-hydroxyl groups. A bimetallic (Co and Ni) porphyrin 2D-polymer exhibits excellent long-term durability of 15 cycles of H-2 and O-2 generation in 200 days from pure water without a considerable decrease in efficiency. Detailed studies using river and seawaters also show the reliable performance of the catalyst over repeated cycles. Here the deactivation modes of catalytic activity have been nullified by the layered metalloporphyrin polymer structure through stable pi-pi stacking, signifying the molecular design of 2D-polymer photocatalyst.

10a2D-polymer10aPhotocatalyst10aporphyrin10aSelf-assembly10awater splitting1 aRanjeesh, Kayaramkodath, Chandran1 aGeorge, Leena1 aMaibam, Ashakiran1 aKrishnamurty, Sailaja1 aBabu, Sukumaran, Santhosh uhttp://library.ncl.res.in/content/durable-metalloporphyrin-2d-polymer-photocatalytic-hydrogen-and-oxygen-evolution-river-and02001nas a2200241 4500008004100000022001400041245010600055210006900161260000800230300001100238490000800249520116900257653002101426653000801447653002101455653003201476653002201508653002901530100002201559700002501581700002901606856012401635 2022 eng d a0169-433200aDoped 2D VX2 (X = S, Se, Te) monolayers as electrocatalysts for ammonia production: a DFT based study0 aDoped 2D VX2 X S Se Te monolayers as electrocatalysts for ammoni cNOV a1544010 v6023 a

Electrocatalytic nitrogen fixation under ambient conditions on vanadium dichalcogenides (VX2) with non-metal dopants has been explored herein. Understanding the interface chemistry, inherent electronic and acute synergistic nature of non-metal dopants on two unique phases of VX2 has been meticulously explored through a scrutiny of several non-metal atoms as catalytic centers. The efficacity of N-2 chemisorption and N-N bond activation has been implemented as crucial parameters to realize boron and carbon doped VX2 monolayers to be electrocatalytically active for nitrogen reduction reaction (NRR). Detailed investigation on the NRR mechanism brings out the pivotal role of thermodynamic favourability for product formation obtained from Gibbs free energy differences. The charge transfer on N and pi-pi* orbital hybridization and electron ``donor-acceptor `` mechanism between the non-metal and N-2 has been found to modulate the electrocatalytic barrier for NRR on VX2 monolayers. This study proposes boron doped VS2 as an efficient chemically feasible, earth abundant sustainable electrocatalyst for NRR with an overpotential as low as 0.06 eV.

10a1T and 2H phases10aDFT10aelectrocatalysts10aNitrogen Reduction Reaction10aNon metal dopants10aVanadium dichalcogenides1 aMaibam, Ashakiran1 aBabaRao, Ravichandar1 aKrishnamurty, Sailaj, A. uhttp://library.ncl.res.in/content/doped-2d-vx2-x-s-se-te-monolayers-electrocatalysts-ammonia-production-dft-based-study02064nas a2200205 4500008004100000022001400041245009100055210006900146260000800215300001200223490000700235520134700242100002401589700002701613700002201640700002601662700003001688700002701718856011301745 2023 eng d a0031-865500aD-A-D-based unsymmetrical thiosquaraine dye for the dye-sensitized solar cells(dagger)0 aDADbased unsymmetrical thiosquaraine dye for the dyesensitized s cMAR a529-5370 v993 a

In dye-sensitized solar cell, modulating the electronic properties of the sensitizer by varying the donor, pi-spacer, acceptor and anchoring groups help optimizing the structure of the dye for better device performance. Here, a donor-acceptor-donor-based unsymmetrical thiosquaraine sensitizer (SQ5S) has been designed and synthesized. Photophysical, electrochemical, theoretical and photovoltaic characterizations of SQ5S dye have been compared with its oxygen analog, SQ5. The incorporation of the sulfur atom in the acceptor unit of SQ5S dye showed an intense peak at 688 nm, which was 38 nm of red-shifted and showed the panchromatic light harvesting response with the onset of 850 nm compared with SQ5 dye. The LUMO and HOMO energy levels are well aligned with the conduction band of TiO2 and the redox potential of electrolyte for the charge injection and the dye-regeneration processes, respectively. Photovoltaic efficiency of 1.51% (V-OC 610 mV, J(SC) 3.07 mA cm(-2), ff 81%) has been achieved for SQ5S dye, whereas SQ5 showed the device performance of 5.43% (V-OC 723 mV, J(SC) 9.3 mA cm(-2), ff 80%). The decreased device performance for the dye SQ5S has been attributed to the favorable intersystem crossing process associated with the photoexcited SQ5S that reduces the driving force for the charge injection process.

1 aJadhav, Avinash, P.1 aSingh, Ambarish, Kumar1 aMaibam, Ashakiran1 aKrishnamurty, Sailaja1 aKrishnamoorthy, Kothandam1 aNithyanandhan, Jayaraj uhttp://library.ncl.res.in/content/d-d-based-unsymmetrical-thiosquaraine-dye-dye-sensitized-solar-cellsdagger