02872nas a2200253 4500008004100000022001400041245010000055210006900155260000800224300001400232490000600246520202700252653002002279653002002299653001402319653003002333653001602363100002802379700001502407700001902422700002302441700002402464856013002488 2020 eng d a2574-097000aFeNx/FeSx-anchored carbon sheet-carbon nanotube composite electrocatalysts for oxygen reduction0 aFeNxFeSxanchored carbon sheetcarbon nanotube composite electroca cMAR a2234-22450 v33 a

Even though various Pt-free electrocatalysts for oxygen reduction reaction (ORR) have been introduced, many of them are found to be active only in alkaline conditions. Considering Nafion, phosphoric acid-doped polybenzimidazole (PBI), and so on as the prominent ionomer membranes, used in the commercially available polymer electrolyte membrane fuel cells (PEMFCs), it becomes important that any development on the Pt-free catalysts should ensure the better ORR performance under acidic conditions. The present work effectively tackles this issue, where an ORR-based catalyst could be prepared with simultaneous incorporation of both Fe-N and Fe-S active sites on in situ generated carbon sheets which are spatially separated by the carbon nanotube (CNT) network. This catalyst shows ability to perform under both acidic and basic conditions. This has been achieved by growing a polyethylenedioxythiophene polymer network in the presence of CNT and melamine followed by its pyrolysis under an inert atmosphere. The catalyst formed at 900 degrees C (PMCNT-900) displays 0.94 V onset potential for ORR under acidic electrolyte conditions, which corresponds to 60 mV overpotential compared to its 40 wt % Pt/C counterpart. Interestingly, in single cell demonstration of Nafion-based PEMFC with PMCNT-900 as the cathode catalyst, the system delivered a maximum power density (PD) of 500 and 275 mW/cm(2) at 60 degrees C under H-2-O-2 and H-2-air feed conditions, respectively. On the other hand, in a single cell test in the anion exchange membrane fuel cell (AEMFC) mode, a maximum power density of 65 mW/cm(2) at 50 degrees C could be achieved with the same cathode catalyst, which is a comparable value obtained while employing Pt/C as the cathode. These results, thus, infer to the efficiency of the catalyst to facilitate ORR under the extreme pH conditions, and particularly its performance under acidic condition reveals its prospect as a potential Pt-free electrocatalyst to serve in the Nafion-based systems.

10acarbon nanotube10aelectrocatalyst10afuel cell10aoxygen reduction reaction10aPt-free ORR1 aBhange, Siddheshwar, N.1 aSoni, Roby1 aSingla, Gourav1 aAjithkumar, T., G.1 aKurungot, Sreekumar uhttps://library.ncl.res.in/content/fenxfesx-anchored-carbon-sheet-carbon-nanotube-composite-electrocatalysts-oxygen-reduction02395nas a2200301 4500008004100000022001400041245013200055210006900187260000800256300001200264490000800276520136300284653001501647653002201662653001901684653003401703653003401737653002901771100001801800700001801818700001801836700001901854700001901873700001401892700003001906700002501936856013201961 2020 eng d a0008-622300aRoom temperature processed in-situ carbon-coated vanadium carbide (VC@C) as a high capacity robust Li/Na battery anode material0 aRoom temperature processed insitu carboncoated vanadium carbide  cMAY a108-1160 v1613 a

3D carbide systems with their robust physical and mechanical properties have always attracted multiple application interests. In this report, we have synthesized a three-dimensional in-situ carbon coated cubic carbide, Vanadium Carbide (VC@C), by a very simple, scalable and cost-effective room temperature mechano-chemical ball-milling procedure and researched its promise as effective anode material for Li and Na ion batteries. We have demonstrated that VC@C shows an impressive initial discharge/lithiation capacity of 1165 mAh g(-1) with a high reversible capacity of 640 mAh g(-1) after 100 charge-discharge cycles at an applied current density of 0.1 A g(-1). We have also found that this material renders a very promising rate performance with significantly low capacity drop after exposing it to variable current densities ranging from 0.05 A g(-1) to 2 A g(-1) with an excellent stability up to 1000 cycles owing to its structural robustness, as verified by post-cycling characterizations. A Li-ion full cell study using LiCoO2 as cathode also showed excellent promise in terms of practical application demonstrating a reversible capacity of 95 mAh g(-1) after 100 cycles. Even for Na insertion/de-insertion VC@C shows a clear promise in terms of capacity, cyclic stability and rate performance. (C) 2020 Elsevier Ltd. All rights reserved.

10a3D carbide10aIn-situ synthesis10aLi-ion battery10aPost cycling characterization10aRoom temperature ball milling10aWilliamson-Hall analysis1 aMahajan, Mani1 aRoy, Kingshuk1 aParmar, Swati1 aSingla, Gourav1 aPandey, O., P.1 aSingh, K.1 aVaidhyanathan, Ramanathan1 aOgale, Satishchandra uhttps://library.ncl.res.in/content/room-temperature-processed-situ-carbon-coated-vanadium-carbide-vcc-high-capacity-robust-lina02285nas a2200181 4500008004100000022001400041245014300055210006900198260000800267300001400275490000700289520159000296100001901886700002801905700001801933700002401951856012801975 2021 eng d a2040-336400aFacile synthesis of CNT interconnected PVP-ZIF-8 derived hierarchically porous Zn/N co-doped carbon frameworks for oxygen reduction dagger0 aFacile synthesis of CNT interconnected PVPZIF8 derived hierarchi cMAR a6248-62580 v133 a

In this work, a strategy has been adopted to construct an architecture through the coordination of polyvinylpyrrolidone (PVP) and a monodisperse zeolitic imidazolate framework (ZIF-8), which was entwined by carbon nanotubes (CNTs) firstly, followed by a pyrolysis process to obtain the hybrid catalyst. The meticulous design of the hybrid material using CNTs to interconnect the PVP assisted ZIF-8 derived porous carbon frameworks together produces a hierarchical pore structure and dual-heteroatom (Zn/N) doping (Zn-N/PC@CNT). Without further acid treatment, the hybrid material prepared after pyrolysis at 900 degrees C (PVP-ZIF-8@CNT-900) has been demonstrated as an efficient non-precious metal catalyst for the oxygen reduction reaction (ORR) with its superior stability compared to the commercial 20 wt% Pt/C catalyst in alkaline media. The catalyst shows better performance towards the ORR, with its more positive onset and half-wave potentials (E-onset = 0.960 V vs. RHE and E-1/2 = 0.795 V vs. RHE) than the counterpart system which is free of both CNT and PVP. The high performance of the hybrid catalyst can be ascribed to the co-existence of dual-active sites with hierarchical pore structures originating from the synergistic effects between Zn/N co-doped porous carbon and CNTs. We further demonstrated the single-cell performance by using the homemade system as the cathode catalyst for the Alkaline Exchange Membrane Fuel Cell (AEMFC) system, which showed a maximum power density of 45 mW cm(-2) compared to 60 mW cm(-2) obtained from the 40 wt% Pt/C catalyst.

1 aSingla, Gourav1 aBhange, Siddheshwar, N.1 aMahajan, Mani1 aKurungot, Sreekumar uhttps://library.ncl.res.in/content/facile-synthesis-cnt-interconnected-pvp-zif-8-derived-hierarchically-porous-znn-co-doped03178nas a2200217 4500008004100000022001400041245013800055210006900193260000900262300001600271490000700287520239300294100002402687700002402711700001902735700002302754700001602777700001802793700002402811856012502835 2022 eng d a2040-336400aUnravelling faradaic electrochemical efficiencies over Fe/Co spinel metal oxides using surface spectroscopy and microscopy techniques0 aUnravelling faradaic electrochemical efficiencies over FeCo spin cNOV  a15928-159410 v143 a

Cobalt and iron metal-based oxide catalysts play a significant role in energy devices. To unravel some interesting parameters, we have synthesized metal oxides of cobalt and iron (i.e. Fe2O3, Co3O4, Co2FeO4 and CoFe2O4), and measured the effect of the valence band structure, morphology, size and defects in the nanoparticles towards the electrocatalytic hydrogen evolution reaction (HER), the oxygen evolution reaction (OER) and the oxygen reduction reaction (ORR). The compositional variations in the cobalt and iron precursors significantly alter the particle size from 60 to <10 nm and simultaneously the shape of the particles (cubic and spherical). The Tauc plot obtained from the solution phase ultraviolet (UV) spectra of the nanoparticles showed band gaps of 2.2, 2.3, 2.5 and 2.8 eV for Fe2O3, Co3O4, Co2FeO4 and CoFe2O4, respectively. Further, the valence band structure and work function analysis using ultraviolet photoelectron spectroscopy (UPS) and core level X-ray photoelectron spectroscopy (XPS) analyses provided better structural insight into metal oxide catalysts. In the Co3O4 system, the valence band structure favors the HER and Fe2O3 favors the OER. The composites Co2FeO4 and CoFe2O4 show a significant change in their core level (O 1s, Co 2p and Fe 2p spectra) and valence band structure. Co3O4 shows an overpotential of 370 mV against 416 mV for Fe2O3 at a current density of 2 mA cm(-2) for the HER. Similarly, Fe2O3 shows an overpotential of 410 mV against the 435 mV for Co3O4 at a current density of 10 mA cm(-2) for the OER. However, for the ORR, Co3O4 shows 70 mV improvement in the half-wave potential against Fe2O3. The composites (Co2FeO4 and CoFe2O4) display better performance compared to their respective parent oxide systems (i.e., Co3O4 and Fe2O3, respectively) in terms of the ORR half-wave potential, which can be attributed to the presence of the oxygen vacancies over the surface in these systems. This was further corroborated in density functional theory (DFT) simulations, wherein the oxygen vacancy formation on the surface of CoFe2O4(001) was calculated to be significantly lower (similar to 50 kJ mol(-1)) compared to Co3O4 (001). The band diagram of the nanoparticles constructed from the various spectroscopic measurements with work function and band gap provides in-depth understanding of the electrocatalytic process.

1 aKashyap, Varchaswal1 aPandikassala, Ajmal1 aSingla, Gourav1 aKhan, Tuhin, Suvra1 aHaider, Ali1 aVinod, C., P.1 aKurungot, Sreekumar uhttps://library.ncl.res.in/content/unravelling-faradaic-electrochemical-efficiencies-over-feco-spinel-metal-oxides-using01981nas a2200181 4500008004100000022001400041245013300055210006900188260000800257300001600265490000700281520129500288100001901583700001801602700002801620700002401648856012701672 2025 eng d a1144-054600aFabrication of a 3D iron-modified NiCo2S4 structure on nickel foam as a bifunctional electrocatalyst for overall water splitting0 aFabrication of a 3D ironmodified NiCo2S4 structure on nickel foa cJUN a10056-100640 v493 a

The development of highly efficient bifunctional electrocatalysts that operate effectively in strong electrolytes, with low overpotentials at defined current densities and excellent durability, has become a central focus in research on overall water splitting. In this study, a three-dimensional (3D) sheet-wrapped wire electrocatalyst, composed of Fe-doped NiCo2S4 on nickel foam (NF), was fabricated. This material demonstrated excellent durability for both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in an alkaline medium. The uniform distribution of Ni, Co, Fe, and S elements significantly enhanced the electro-catalytic performance. The incorporation of Fe improved activity, with the Fe2.5%-NiCo2S4/NF electrocatalyst achieving overpotentials of 310 mV and 260 mV for the HER and OER, respectively, at a current density of 100 mA cm-2. These results were superior to those of both bare nickel foam and NiCo2S4/NF. The 3D configuration facilitated efficient ion transport and contributed to the remarkable catalytic performance. As a water-splitting electrolyzer in an alkaline electrolyte of 1.0 M KOH, the system delivered a current density of 20 mA cm-2 at a cell voltage of 1.66 V, highlighting the effectiveness of this design strategy.

1 aSingla, Gourav1 aMahajan, Mani1 aBhange, Siddheshwar, N.1 aKashyap, Varchaswal uhttps://library.ncl.res.in/content/fabrication-3d-iron-modified-nico2s4-structure-nickel-foam-bifunctional-electrocatalyst