Browsing by Author "Jiang, SP"

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    Controlled one‐pot synthesis of nickel single atoms embedded in carbon nanotube and graphene supports with high loading
    (Wiley, 2020-04-09) Zhao, S; Wang, T; Zhou, G; Zhang, L; Lin, C; Veder, JP; Johannessen, B; Saunders, M; Yin, L; Liu, C; De Marco, R; Yang, SZ; Zhang, Q; Jiang, SP
    Single‐atom catalysts (SACs) have attracted much attentions due to the advantages of high catalysis efficiency and selectivity. However, the controllable and efficient synthesis of SACs remains a significant challenge. Herein, we report a controlled one‐pot synthesis of nickel single atoms embedded on nitrogen‐doped carbon nanotubes (NiSA−N−CNT) and nitrogen‐doped graphene (NiSA−N−G). The formation of NiSA−N−CNT is due to the solid‐to‐solid rolling up mechanism during the high temperature pyrolysis at 800 °C from the stacked and layered Ni‐doped g‐C3N4, g‐C3N4−Ni structure to a tubular CNT structure. Addition of citric acid introduces an amorphous carbon source on the layered g‐C3N4−Ni and after annealing at the same temperature of 800 °C, instead of formation of NiSA−N−CNT, Ni single atoms embedded in planar graphene type supports, NiSA−N−G were obtained. The density functional theory (DFT) calculation indicates the introduction of amorphous carbon source substantially reduces the structure fluctuation or curvature of layered g‐C3N4‐Ni intermediate products, thus interrupting the solid‐to‐solid rolling process and leading to the formation of planar graphene type supports for Ni single atoms. The as‐synthesized NiSA−N−G with Ni atomic loading of ∼6 wt% catalysts shows a better activity and stability for the CO2 reduction reaction (CO2RR) than NiSA−N−CNT with Ni atomic loading of ∼15 wt% due to the open and exposed Ni single atom active sites in NiSA−N−G. This study demonstrates for the first time the feasibility in the control of the microstructure of carbon supports in the synthesis of SACs. © 1999-2024 John Wiley & Sons, Inc or related companies. All rights reserved.
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    High-performance perovskite composite electrocatalysts enabled by controllable interface engineering
    (John Wiley & Sons, Inc, 2021-06-17) Xu, XM; Pan, YL; Ge, L; Chen, YB; Mao, X; Guan, DQ; Li, MR; Zhong, YJ; Hu, ZW; Peterson, VK; Saunders, M; Chen, CT; Zhang, HJ; Ran, R; Du, AJ; Jiang, SP; Zhou, W; Shao, ZP
    Single-phase perovskite oxides that contain nonprecious metals have long been pursued as candidates for catalyzing the oxygen evolution reaction, but their catalytic activity cannot meet the requirements for practical electrochemical energy conversion technologies. Here a cation deficiency-promoted phase separation strategy to design perovskite-based composites with significantly enhanced water oxidation kinetics compared to single-phase counterparts is reported. These composites, self-assembled from perovskite precursors, comprise strongly interacting perovskite and related phases, whose structure, composition, and concentration can be accurately controlled by tailoring the stoichiometry of the precursors. The composite catalyst with optimized phase composition and concentration outperforms known perovskite oxide systems and state-of-the-art catalysts by 1–3 orders of magnitude. It is further demonstrated that the strong interfacial interaction of the composite catalysts plays a key role in promoting oxygen ionic transport to boost the lattice-oxygen participated water oxidation. These results suggest a simple and viable approach to developing high-performance, perovskite-based composite catalysts for electrochemical energy conversion. © 2021 Wiley-VCH GmbH
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    Identification of the hydrogen utilization pathway for the electrocatalytic hydrogenation of phenol
    (Springer Nature, 2021-08-19) Zhou, L; Zhu, XR; Su, H; Lin, HZ; Lyu, YH; Zhao, X; Chen, C; Zhang, N; Xie, C; Li, YY; Lu, Y; Zheng, JY; Johannessen, B; Jiang, SP; Liu, QH; Li, Y; Zou, Y; Wang, SG
    Electrochemical hydrogenation (ECH) of biomass-derived platform molecules is a burgeoning route for the sustainable utilization of hydrogen. However, the noble-metal-catalyzed ECH of phenolic compounds suffers from intense competition with hydrogen evolution reaction. We prepared PtRh bimetallic nanoparticles dispersed on highly ordered mesoporous carbon nanospheres, which improves the utilization efficiency of adsorbed hydrogen (Had) to ECH in H–UPD region (>0 V vs. RHE). Further analysis reveals (i) the strong overlapping between the d-orbitals of Pt and Rh enhances specific adsorption of phenol; (ii)incorporation of Rh devotes an electronic effect on weakening the alloy–Had interaction to increase the FE of ECH. DFT calculations confirm the selectivity difference and the ECH parallel pathways: cyclohexanol and cyclohexanone are formed via hydrogenation/dehydrogenation of the intermediate *C6H10OH. These findings deepen our fundamental understanding of the ECH process, and cast new light on exploration of highly efficient electrocatalysts for biomass upgrading. © 2019 Springer Nature
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    Investigating HPA functionalized mesoporous silica materials for use as high temperature proton exchange membranes
    (Australian Institute of Nuclear Science and Engineering (AINSE), 2012-12-07) Lamb, K; De Marco, R; Jiang, SP; Peterson, VK
    High temperature (>100°C) proton exchange membrane fuel cells (HT-PEMFC) are solid energy conversion devices that electrochemically convert chemical energy (eg. from alcohols) into electricity. HT-PEMFCs are more efficient than low temperature PEMFCs due to elimination of carbon monoxide poisoning and faster oxidation kinetics. Various types of proton exchange membranes have been explored, such as nonfluorinated hydrocarbon polymers, or hybrid Nafion-based membranes. While these materials have their advantages, they dehydrate at high temperatures, leading to a significant reduction in proton conductivity. Recently, we found that heteropolyacids (HPA) such as tungstophosphiric acid (abbreviated as HPW) can be used to functionalize ordered mesoporous silica (MSN) to make nanocomposites PEMs. While these nanocomposites have shown promising preliminary results as HT-PEMs, the ways in which changes to the structure of these materials affect the proton exchange properties are largely unknown. Analysis techniques such as ex- and in-situ HR-FTIR, SAXS, SANS, and QENS will be used to build an understanding of the membrane structure and proton diffusion mechanisms of these HT-PEMs, thereby determining the best performance HPA-MSNs for use in direct alcohol fuel cells.
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    Iron single atoms on graphene as nonprecious metal catalysts forhHigh‐temperature polymer electrolyte membrane fuel cells
    (Wiley, 2019-03-13) Cheng, Y; He, S; Lu, SF; Veder, JP; Johannessen, B; Thomsen, L; Saunders, MJ; Becker, T; De Marco, R; Li, QF; Yang, SZ; Jiang, SP
    Iron single atom catalysts (Fe SACs) are the best‐known nonprecious metal (NPM) catalysts for the oxygen reduction reaction (ORR) of polymer electrolyte membrane fuel cells (PEMFCs), but their practical application has been constrained by the low Fe SACs loading (<2 wt%). Here, a one‐pot pyrolysis method is reported for the synthesis of iron single atoms on graphene (FeSA‐G) with a high Fe SAC loading of ≈7.7 ± 1.3 wt%. The as‐synthesized FeSA‐G shows an onset potential of 0.950 V and a half‐wave potential of 0.804 V in acid electrolyte for the ORR, similar to that of Pt/C catalysts but with a much higher stability and higher phosphate anion tolerance. High temperature SiO2 nanoparticle‐doped phosphoric acid/polybenzimidazole (PA/PBI/SiO2) composite membrane cells utilizing a FeSA‐G cathode with Fe SAC loading of 0.3 mg cm−2 delivers a peak power density of 325 mW cm−2 at 230 °C, better than 313 mW cm−2 obtained on the cell with a Pt/C cathode at a Pt loading of 1 mg cm−2. The cell with FeSA‐G cathode exhibits superior stability at 230 °C, as compared to that with Pt/C cathode. Our results provide a new approach to developing practical NPM catalysts to replace Pt‐based catalysts for fuel cells. © 1999-2024 John Wiley & Sons, Inc or related companies. © 2019 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
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    Neutron and synchrotron characterisation techniques for hydrogen fuel cell materials
    (Australian Nuclear Science and Technology Organisation, 2021-11-24) Lamb, K; Kirby, N; Bartlett, JR; Peterson, VK; Appadoo, D; Jiang, SP; De Marco, R
    Hydrogen fuel cells and other renewable energy technologies have specific materials and functional needs which can be more fully understood using neutron and synchrotron characterisation techniques. In this presentation, a materials which has applications in proton exchange membranes is studied with a variety to techniques to develop a comprehensive understanding of the functional-structural relationship. The materials used here is phosphotungstic acid (HPWA) stabilised in an ‘inert’ mesoporous silica host material. This aim of this research is to develop an understanding of the interaction between the HPWA and the silica and whether different structures or surface chemistries have advantageous or detrimental effects. Two silica symmetries used were Ia3 ̅d (face centred cubic bi-continuous) and P6mm (2D hexagonal with cylindrical pores) which were vacuum impregnated with solutions of HPWA in a range of concentrations. The resulting powder samples were then analysed using small angle x-ray scattering (SAXS), inductively coupled plasma emissions spectroscopy (ICP-OES), nitrogen gas adsorption/desorption, near edge X-ray absorption fine structure (NEXAFS/X-ray absorption near edge structure/XANES) of the O and Si k-edges, Fourier transform infra-red spectroscopy (FTIR), Raman spectroscopy, and then formed into a disk using polyethylene as the binder for electrical impedance spectroscopy (EIS). The insights gained from this systematic study indicate that the surface chemistry of the silica host has a significant effect on the performance, uptake and interactions with the HPWA anions, where lower concentrations of HPWA result in stronger host:HPWA interactions but lower conductivity. © The Authors