02298nas a2200253 4500008004100000022001400041245014600055210006900201260007500270300001400345490000700359520131800366653002001684653002001704653003001724653002001754653001701774100002901791700002401820700002601844700002001870700002401890856013001914 2016 eng d a1616-301X00aNanoporous graphene enriched with Fe/Co-N active sites as a promising oxygen reduction electrocatalyst for anion exchange membrane fuel cells0 aNanoporous graphene enriched with FeCoN active sites as a promis aPOSTFACH 101161, 69451 WEINHEIM, GERMANYbWILEY-V C H VERLAG GMBHcAPR a2150-21620 v263 a

Here, a simple but efficient way is demonstrated for the preparation of nanoporous graphene enriched with Fe/Co-nitrogen-doped active sites (Fe/Co-NpGr) as a potential electrocatalyst for the electrochemical oxygen reduction reaction (ORR) applications. Once graphene is converted into porous graphene (pGr) by a controlled oxidative etching process, pGr can be converted into a potential electrocatalyst for ORR by utilizing the created edge sites of pGr for doping nitrogen and subsequently to utilize the doped nitrogens to build Fe/Co coordinated centers (Fe/Co-NpGr). The structural information elucidated using both XPS and TOF-SIMS study indicates the presence of coordination of the M-N (M = Fe and Co)-doped carbon active sites. Creation of this bimetallic coordination assisted by the nitrogen locked at the pore openings is found to be helping the system to substantially reduce the overpotential for ORR. A 30 mV difference in the overpotential () with respect to the standard Pt/C catalyst and high retention in half wave potential after 10 000 cycles in ORR can be attained. A single cell of an anion exchange membrane fuel cell (AEMFC) by using Fe/Co-NpGr as the cathode delivers a maximum power density of approximate to 35 mWcm(-2) compared to 60 mWcm(-2) displayed by the Pt-based system.

10aelectrocatalyst10anitrogen doping10aoxygen reduction reaction10aporous grapheme10aquantum dots1 aPalaniselvam, Thangavelu1 aKashyap, Varchaswal1 aBhange, Siddeswar, N.1 aBaek, Jong-Beom1 aKurungot, Sreekumar uhttp://library.ncl.res.in/content/nanoporous-graphene-enriched-feco-n-active-sites-promising-oxygen-reduction-electrocatalyst02820nas a2200349 4500008004100000022001400041245018300055210006900238260000800307300001400315490000600329520162200335653002201957653002001979653001201999653001402011653002402025653002402049653002402073653002102097653002002118653001702138653003002155653001602185653001402201653002702215653003402242100002402276700002302300700002402323856012302347 2017 eng d a2365-654900aActivity tuning of cobalt ferrite nanoparticles anchored on N-doped reduced graphene oxide as a potential oxygen reduction electrocatalyst by Zn substitution in the spinel matrix0 aActivity tuning of cobalt ferrite nanoparticles anchored on Ndop cSEP a7845-78530 v23 a

Development of highly efficient and durable ORR catalysts by using non-platinum group metals (such as Co, Fe, Mn, and Zn) is a challenging task in the forward path towards the realization of low-cost energy devices in the commercial stream. The present work deals with an effective strategy wherein an efficient Pt-free electrocatalyst for oxygen reduction reaction (ORR) is prepared by stoichiometrically substituting some fraction of Fe with Zn in cobalt ferrite and anchoring these spinel nanoparticles on nitrogen doped reduced graphene oxide (N-rGO). Zn substitution is found to be significantly altering the ratio of Fe2+/Fe3+ in the cobalt ferrite nanocrystal system with a concomitant promotional influence on its electrocatalytic activity towards ORR. The nanoparticle composition with a Co, Fe and Zn molar ratio of 1.0:1.7:0.3, represented by the formula CoFe1.7Zn0.3O4(CFZn(0.3)), supported over N-rGO has shown 10 mV and 20 mV positive shift in the onset and half-wave potentials, respectively, for ORR in 0.1 M KOH in comparison to the nanoparticles of CoFe2O4 supported over N-rGO (CF/N-rGO). The optimum Zn substitution is found to be narrowing down the difference with the state-of-the-art Pt/C for ORR by 100 and 110 mV in terms of the onset and half-wave potentials, respectively. Most significantly, the homemade catalyst is found to be clearly outperforming the Pt catalyst in terms of the limiting current density and electrochemical durability.

10aCarbon Nano-fiber10aCathod Catalyst10aCoFe2O410aEvolution10aMagnetic-properties10aMembrane fuel- Cell10aMetal-Air Batteries10aN-doped graphene10aNanocrystalline10ananocrystals10aoxygen reduction reaction10aperformance10aPlatinium10asolvothermal synthesis10aZn substituted cobalt ferrite1 aKashyap, Varchaswal1 aSingh, Santosh, K.1 aKurungot, Sreekumar uhttp://library.ncl.res.in/content/activity-tuning-cobalt-ferrite-nanoparticles-anchored-n-doped-reduced-graphene-oxide02900nas a2200301 4500008004100000022001400041245013800055210006900193260000800262300001400270490000600284520183300290653003802123653002502161653002402186653003002210653002802240653001902268100002302287700002402310700002102334700002802355700001502383700002302398700002202421700002502443856013002468 2017 eng d a2155-543500aEfficient and durable oxygen reduction electrocatalyst based on CoMn alloy oxide nanoparticles supported over N-doped porous graphene0 aEfficient and durable oxygen reduction electrocatalyst based on  cOCT a6700-67100 v73 aTransition metal oxide derived materials are very important for various applications, such as electronics, magnetism, catalysis, electrochemical energy conversion, and storage. Development of efficient and durable catalysts for the oxygen reduction reaction (ORR), an important reaction in fuel cells and metal air batteries, is highly desirable. Moreover, the futuristic catalysts for these applications need to be costeffective in order to ensure a competitive edge for these devices in the energy market. This article describes the synthesis of a cost-effective and efficient electrocatalyst for ORR It is based on supporting CoMn alloy oxide nano particles on N-doped porous graphene through a simple and scalable microwave irradiation method. Microwave irradiation was found to be very crucial for the fast creation of pores in the graphene framework with a concomitant formation of the CoMn alloy oxide nanoparticles. A series of catalysts have been synthesized by varying the Co:Mn ratio, among which, the one with the Co:Mn ratio of 2:1 [designated as CoMn/pNGr(2:1)] displayed remarkably higher ORR activity in 0.1 M KOH solution. It showed a similar to 60 mV potential shift with a low Tafel slope of 74 mV/decade, which is comparable to that derived from the commercial Pt/C catalyst. This high activity of CoMn/pNGr(2:1) has been credited to the cooperative effect arising from the metal entities and the defects present in the N-doped porous graphene. Finally, real system-level validations of the use of CoMn/pNGr(2:1) as cathode catalyst could be performed by fabricating and testing single-cells of an anion-exchange membrane fuel cell (AEMFC) and a primary Zn-air battery, which successfully demonstrated the efficiency of the catalyst to facilitate ORR in real integrated systems of the single-cell assemblies.10aanion-exchange membrane fuel cell10acooperativity effect10amicrowave synthesis10aoxygen reduction reaction10aporous N-doped graphene10aZn-air battery1 aSingh, Santosh, K.1 aKashyap, Varchaswal1 aManna, Narugopal1 aBhange, Siddheshwar, N.1 aSoni, Roby1 aBoukherroub, Rabah1 aSzunerits, Sabine1 aKurungot, Sreekurnar uhttp://library.ncl.res.in/content/efficient-and-durable-oxygen-reduction-electrocatalyst-based-comn-alloy-oxide-nanoparticles03125nas a2200205 4500008004100000022001400041245017200055210006900227260000800296300001400304490000600318520228000324653003502604653003002639653003002669653004102699100002402740700002402764856013102788 2018 eng d a2155-543500aZirconium-substituted cobalt ferrite nanoparticle supported n-doped reduced graphene oxide as an efficient bifunctional electrocatalyst for rechargeable Zn-air battery0 aZirconiumsubstituted cobalt ferrite nanoparticle supported ndope cAPR a3715-37260 v83 a

Solvothermal synthesis of zirconium-substituted cobalt ferrite nanoparticles was accomplished by the introduction of zirconium (Zr) in the spinel matrix to obtain a cost-effective and robust electrocatalyst that does not use noble metals. A variation in the cobalt ferrite structure CoFe2−xZrxO4 with Zr (0.1−0.4) substitution has significantly altered the overpotential for the electrocatalytic oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), leading to an optimum composition of CFZr(0.3). The incorporation of the foreign Zr4+ ion in the cobalt ferrite spinel lattices has effectively enhanced the oxygen evolution reaction (OER) activity in comparison to the parent cobalt ferrite (CF) nanocrystals. However, a nominal change in the ORR current density has been observed due to Zr incorporation. For the OER, the Zr-substituted catalyst has shown a 40 mV negative shift in the overpotential in comparison with the CF nanoparticles at 10 mA/cm2 current density. Interestingly, the in situ grafting of Zr-substituted cobalt ferrite nanoparticles over N-doped reduced graphene oxide (CFZr(0.3)/N-rGO) results in remarkably enhanced performance during the ORR and moderately favored the OER with an overall potential difference (ΔE) of 0.840 V. The enhanced bifunctional electrocatalytic activity of the material is crucial for the fabrication of high-performance rechargeable Zn−air batteries (ZABs). The prepared catalyst exhibited an overpotential of 80 mV for the ORR in comparison with the state-of-the-art (Pt/C) catalyst and an overpotential of 340 mV at 10 mA/cm2 current density for the OER from the standard value (1.23 V vs RHE). This potential bifunctional electrocatalyst has been employed as an electrode material for the fabrication of a primary ZAB, where it exhibited discharge capacities of 727 and 730 mAh/g at current densities of 20 and 30 mA/cm2 , respectively, under ambient conditions. The notable performance of the catalyst as a bifunctional material is observed during the cycling of the rechargeable ZAB. The prepared catalyst showed an increase of 200 mV in the overall operating overpotential after cycling for 10 cycles at 15 mA/cm2 in comparison to the 350 mV increase shown by the Pt/C catalyst.

10aN-doped reduced graphene oxide10aOxygen Evolution Reaction10aoxygen reduction reaction10azirconium-substituted cobalt ferrite1 aKashyap, Varchaswal1 aKurungot, Sreekumar uhttp://library.ncl.res.in/content/zirconium-substituted-cobalt-ferrite-nanoparticle-supported-n-doped-reduced-graphene-oxide-002394nas a2200241 4500008004100000022001400041245009700055210006900152260000900221300001400230490000600244520158800250653001901838653002401857653001401881653003001895653002101925100002401946700001601970700001501986700002402001856012702025 2019 eng d a2196-021600aMedium modulated oxygen reduction activity of Fe/Co active centre-engrafted electrocatalysts0 aMedium modulated oxygen reduction activity of FeCo active centre cJUN  a2956-29640 v63 a

Iron and cobalt metal atoms are effective active centers for the synthesis of carbon-based noble-metal-free catalysts for the oxygen reduction reaction (ORR) owing to their cost-effective intrinsic activity and tunable properties. Annealing of the active center with the conducting carbon enhances the ORR activity significantly. Herein, we have engrafted Fe and Co active centers in the homemade conducting carbon and the ORR performance has been closely observed under acidic and basic pH conditions to understand the influence of the medium and participating moieties towards the performance. In the half-cell reaction, the onset potential and half-wave potential for ORR are governed by the surface intermediates and concomitantly driven by the adsorption energies of the intermediates over the active centers. The iron and cobalt active center-engrafted carbon catalyst behaves differently in acidic and basic electrolytes owing to the dissociation of the surface intermediates. The iron-based catalyst shows improved onset potential against the cobalt-based one. Similarly, the cobalt-based catalyst shows improved half-wave potential against the iron active-center-grafted catalyst. The combined synergistic effect of the two catalysts is realized in the composition represented as Fe/2Co-N-GVC, where improved onset and half-wave potentials are noted in basic medium. A significant variation in the activity of the catalyst is observed as the medium changes from acidic to basic and the effect is directly associated with the surface adsorption of the intermediates.

10aactive centers10ahalf-wave potential10aMechanism10aoxygen reduction reaction10atransition state1 aKashyap, Varchaswal1 aAnand, Aljo1 aSoni, Roby1 aSreekumar, Kurungot uhttp://library.ncl.res.in/content/medium-modulated-oxygen-reduction-activity-feco-active-centre-engrafted-electrocatalysts