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RISS 인기검색어
- 검색키워드
- 저자 : Sougrati, Moulay Tahar (검색결과 3 건)
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Essehli, R.,Ben Yahia, H.,Maher, K.,Sougrati, M.T.,Abouimrane, A.,Park, J.-B.,Sun, Y.-K.,Al-Maadeed, M.A.,Belharouak, I. Elsevier Sequoia 2016 Journal of Power Sources Vol. No.
<P><B>Abstract</B></P> <P>The new compound Na<SUB>1.86</SUB>□<SUB>0.14</SUB>Fe<SUB>3</SUB>(PO<SUB>4</SUB>)<SUB>3</SUB> was successfully synthesized via hydrothermal synthesis and its crystal structure was determined using powder X-ray diffraction data. Na<SUB>1.86</SUB>Fe<SUB>3</SUB>(PO<SUB>4</SUB>)<SUB>3</SUB> was also characterized by operando XRD and Mössbauer spectroscopy, cyclic voltammetry, and galvanostatic cycling. Na<SUB>1.86</SUB>Fe<SUB>3</SUB>(PO<SUB>4</SUB>)<SUB>3</SUB> crystallizes with the alluaudite-type structure with the eight coordinated Na1 and Na2 sodium atoms located within the channels. The combination of the Rietveld- and Mössbauer-analyses confirms that the sodium vacancies in the Na1 site are linked to a partial oxidation of Fe<SUP>2+</SUP> during synthesis. The electrochemical tests indicated that Na<SUB>1.86</SUB>Fe<SUB>3</SUB>(PO<SUB>4</SUB>)<SUB>3</SUB> is a 3 V sodium intercalating cathode. At the current densities of 5, 10, and 20 mA g<SUP>−1</SUP>, the material delivers the specific capacities of 109, 97, and 80 mA h g<SUP>−1</SUP>, respectively. After 100 charge and discharge cycles, Na<SUB>1.86</SUB>Fe<SUB>3</SUB>(PO<SUB>4</SUB>)<SUB>3</SUB> exhibited good sodium removal and uptake behavior although no optimizations of particle size, morphology, and carbon coating were performed.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Na<SUB>1.86</SUB>□<SUB>0.14</SUB>Fe<SUB>3</SUB>(PO<SUB>4</SUB>)<SUB>3</SUB> was synthesized via hydrothermal synthesis method. </LI> <LI> Na<SUB>1.86</SUB>□<SUB>0.14</SUB>Fe<SUB>3</SUB>(PO<SUB>4</SUB>)<SUB>3</SUB> crystallizes with the Alluaudite-type structure. </LI> <LI> Operando in situ XRD and Mössbauer spectroscopy studies were carried on. </LI> <LI> The crystal structure of Na<SUB>1.86</SUB>□<SUB>0.14</SUB>Fe<SUB>3</SUB>(PO<SUB>4</SUB>)<SUB>3</SUB> is stable during cycling. </LI> <LI> Na<SUB>1.86</SUB>□<SUB>0.14</SUB>Fe<SUB>3</SUB>(PO<SUB>4</SUB>)<SUB>3</SUB> is a promising 3 V cathode material for sodium ion batteries. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>Na1.86□0.14Fe3(PO4)3 was synthesized via hydrothermal synthesis method. Na1.86Fe3(PO4)3 crystallizes with the alluaudite-type structure. Na1.86Fe3(PO4)3 is a 3 V sodium intercalating cathode. At the current densities of 5, 10, and 20 mA g<SUP>−1</SUP>, the material delivers the specific capacities of 109, 97, and 80 mA h g<SUP>−1</SUP>, respectively. After 100 charge and discharge cycles, Na1.86Fe3(PO4)3 exhibited good sodium removal and uptake behavior with a stable crystal structure.</P> <P>[DISPLAY OMISSION]</P>
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The Achilles' heel of iron-based catalysts during oxygen reduction in an acidic medium
Choi, Chang Hyuck,Lim, Hyung-Kyu,Chung, Min Wook,Chon, Gajeon,Ranjbar Sahraie, Nastaran,Altin, Abdulrahman,Sougrati, Moulay-Tahar,Stievano, Lorenzo,Oh, Hyun Seok,Park, Eun Soo,Luo, Fang,Strasser, Pete The Royal Society of Chemistry 2018 ENERGY AND ENVIRONMENTAL SCIENCE Vol.11 No.11
<P>For catalysing dioxygen reduction, iron-nitrogen-carbon (Fe-N-C) materials are today the best candidates to replace platinum in proton-exchange membrane fuel cell (PEMFC) cathodes. Despite tremendous progress in their activity and site-structure understanding, improved durability is critically needed but challenged by insufficient understanding of their degradation mechanisms during operation. Here, we show that FeNxCy moieties in a representative Fe-N-C catalyst are structurally stable but electrochemically unstable when exposed in an acidic medium to H2O2, the main oxygen reduction reaction (ORR) byproduct. We reveal that exposure to H2O2 leaves iron-based catalytic sites untouched but decreases their turnover frequency (TOF) <I>via</I> oxidation of the carbon surface, leading to weakened O2-binding on iron-based sites. Their TOF is recovered upon electrochemical reduction of the carbon surface, demonstrating the proposed deactivation mechanism. Our results reveal for the first time a hitherto unsuspected key deactivation mechanism during the ORR in an acidic medium. This study identifies the N-doped carbon surface as the Achilles' heel during ORR catalysis in PEMFCs. Observed in acidic but not in alkaline electrolytes, these insights suggest that durable Fe-N-C catalysts are within reach for PEMFCs if rational strategies minimizing the amount of H2O2 or reactive oxygen species (ROS) produced during the ORR are developed.</P>
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Li- and Na-ion Storage Performance of Natural Graphite via Simple Flotation Process
Laziz, Noureddine Ait,Abou-Rjeily, John,Darwiche, Ali,Toufaily, Joumana,Outzourhit, Abdelkader,Ghamouss, Fouad,Sougrati, Moulay Tahar The Korean Electrochemical Society 2018 Journal of electrochemical science and technology Vol.9 No.4
Natural graphite is obtained from an abandoned open-cast mine and purified by a simple, eco-friendly and affordable beneficiation process including ball milling and flotation process. Both raw graphite (55 wt %) and its concentrate (85 wt %) were electrochemically tested in order to evaluate these materials as anode materials for Li-ion and Na-ion batteries. It was found that both raw and purified graphites exhibit good electrochemical activities with respect to lithium and sodium ions through completely different reaction mechanisms. The encouraging results demonstrated in this work suggest that both raw and graphite concentrates after flotation could be used respectively for stationary and embedded applications. This strategy would help in developing local electrical storage systems with a significantly low environmental footprint.
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