Browsing by Author "Rehman, AU"

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    Enhancing oxygen reduction reaction activity and CO2 tolerance of cathode for low-temperature solid oxide fuel cells by in situ formation of carbonates
    (American Chemical Society, 2019-07-31) Rehman, AU; Li, MR; Knibbe, R; Khan, MS; Peterson, VK; Brand, HEA; Li, ZH; Zhou, W; Zhu, ZH
    Development of low-cost and cobalt-free efficient cathode materials for oxygen reduction reaction (ORR) remains one of the paramount motivations for material researchers at a low temperature (<650 °C). In particular, iron-based perovskite oxides show promise as electrocatalysts for ORR because Fe metal is cheaper and naturally abundant, exhibit matched thermal expansion with contacting components such as electrolytes, and show high tolerance in a CO2-containing atmosphere. Herein, we demonstrated a new mechanism, the in situ formation of alkali metal carbonates at the cathode surface. This new mechanism leads to an efficient and robust cobalt-free electrocatalyst (Sr0.95A0.05Fe0.8Nb0.1Ta0.1O3−δ, SAFNT5, A = Li, Na, and K) for the application of low-temperature solid oxide fuel cells (LT-SOFCs). Our results revealed that the formation of Li\K carbonates boosts the ORR activity with an area-specific resistance as low as 0.12 and 0.18 Ω cm2 at 600 °C, which show the highest performance of the cobalt-free single-phase cathode that has been ever reported so far. We also find that the chemical stability and tolerance of tested cathodes toward CO2 poisoning significantly improved with alkali carbonates, as compared to the pristine SrFe0.8Nb0.1Ta0.1O3−δ (SFNT) at 600 °C. This work demonstrates the conclusive role of alkali carbonates in developing highly efficient and stable cobalt-free cathodes for LT-SOFCs and CO2 neutralization. © 2019 American Chemical Society
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    Low resolution structural studies of Munc18c complexed with a Syntaxin-4/T4- Lysozyme Fusion
    (Australian Institute of Nuclear Science and Engineering, 2016-11-29) Whitten, AE; Rehman, AU; Hu, SH; Tnimov, Z; Christie, MP; King, GJ; Jarrott, RJ; Norwood, S; Alexandrov, K; Collins, BM; Martin, JL
    Soluble N-ethylmaleimide-sensitive factor attachment protein receptors (SNARE) act at every intracellular trafficking pathway. Cognate v-SNAREs (e.g. VAMP) and t-SNAREs (Syntaxin (Sx) and SNAP) form a high affinity SNARE ternary complex (Sx-SNAP-VAMP) that brings the membranes together, triggering fusion. Syntaxins consist of a SNARE motif, and a three-helix bundle. In an open confirmation, the SNARE motif is free to form the SNARE ternary complex (stimulating fusion), but in the closed confirmation fusion is inhibited. Sec1p/Munc18 (SM) proteins bind to Sx, regulating SNARE mediated fusion [1], but their exact role is not well understood [2-4]. In the cell, Sx is bound to the membrane, and it is possible that this tethering may influence the manner in which it interacts with other proteins. As a means of investigating structural changes arising due to tethering, here, we investigate how the addition of a C-terminal T4-Lysozyme (soluble) fusion to Sx4 modulates its interaction with Munc18c. Preliminary low-resolution models of the Munc18c-Sx4T4 complex optimized against small-angle scattering data will be presented.