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  • 1
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    Online Resource
    Structural Transformations in Ni (Oxy)Hydroxide Host Structures Under Operating Conditions for Oxygen Evolution Electrocatalysts
    The Electrochemical Society ; 2023
    In:  ECS Meeting Abstracts Vol. MA2023-01, No. 36 ( 2023-08-28), p. 2062-2062
    Details
    In: ECS Meeting Abstracts, The Electrochemical Society, Vol. MA2023-01, No. 36 ( 2023-08-28), p. 2062-2062
    Abstract: The incorporation of Fe into the brucite-like Ni(OH) 2 host structure increases significantly the catalytic activity for the oxygen evolution reaction (OER). 1 The resulting hydrotalcite-like crystalline structure is known as NiFe layered double hydroxide (LDH). However, even the most active NiFe LDH catalyst still shows a considerable overpotential for the OER. 2 Understanding the nature of the catalytic active sites and the catalytic mechanism in NiFe LDHs are key challenges to develop better OER electrocatalysts, as well as the fundamental understanding of the role of the Ni-based host structure. In this contribution, atomic-scale details of the catalytic active phase will be presented, showing that NiFe LDHs are oxidized under applied anodic potentials from as-prepared α-phases to activated γ-phases. 3 The interlayer and in-plane lattice parameters of the OER-active γ-phase were obtained by performing wide angle X-ray scattering (WAXS) measurements on NiFe LDH nanoplatelets during operating electrochemical conditions and were characterized by a contraction of about 8%. Operando WAXS was then performed for other selected catalysts belonging to the transition metal LDH family of materials. Structural similarities of the catalytically active phases will be highlighted. In addition, the structural transformations of β-Ni(OH) 2 will be discussed, as potential host structure for novel multi-element catalysts. Also for Ni(OH) 2 , the γ-phase is found to be the catalytically active phase. However, the structural transformations are more complex, involving multiple limiting phases. Their structural stability is presented and the discussion supported by density functional theory calculations. References L. Trotochaud, S. L. Young, J. K. Ranney and S. W. Boettcher, Journal of the American Chemical Society, 2014, 136: 6744-6753. F. Dionigi and P. Strasser, Advanced Energy Materials, 2016, 6 1600621. F. Dionigi, Z. Zeng, I. Sinev, T. Merzdorf, S. Deshpande, M. B. Lopez, S. Kunze, I. Zegkinoglou, H. Sarodnik, D. Fan, A. Bergmann, J. Drnec, J. Ferreira de Araujo, M. Gliech, D. Teschner, J. Zhu, W.-X. Li, J. Greeley, B. Roldan Cuenya and P. Strasser, Nat Commun, 2020, 11 2522.
    Type of Medium: Online Resource
    ISSN: 2151-2043
    URL: Article
    DOI: 10.1149/MA2023-01362062mtgabs
    Language: Unknown
    Publisher: The Electrochemical Society
    Publication Date: 2023
    detail.hit.zdb_id: 2438749-6
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  • 2
    Online Resource
    Online Resource
    Catalyst Support Interactions of Highly Active Nife-LDH Towards the Implementation in Photoelectrochemical and Sea-Water Based Water Splitting Technologies
    The Electrochemical Society ; 2023
    In:  ECS Meeting Abstracts Vol. MA2023-01, No. 37 ( 2023-08-28), p. 2195-2195
    Details
    In: ECS Meeting Abstracts, The Electrochemical Society, Vol. MA2023-01, No. 37 ( 2023-08-28), p. 2195-2195
    Abstract: For the implementation in photoelectrochemical (PEC) and sea-water based water splitting devices it is of utmost importance to find stable substrates that do not degrade under application related potentials and illumination. While PEC devices incorporate an absorber that has to be protected from the harsh conditions in the electrolyte, the prevalence of Cl - ions in sea-water based water splitting devices leads to corrosion of most metallic substrates under application related potentials. Catalyst coated TiO 2 substrates are therefore used as protection layers in PEC devices, while titanium porous transport layers show great stability in anionic exchange membrane sea-water splitting devices. In this study we investigated the interaction between state-of-the-art NiFe-LDH as a catalyst for the OER and titanium substrates. It was shown that the activity of NiFe-LDH on bare Ti/TiO x substrates was very poor. Through the incorporation of thin metal interlayers (Au, Ni) an increase in current density by two orders of magnitude could be observed. Through detailed XPS measurements before and after electrochemical activation of the electrodes we were able to show an improved transformation of the as prepared catalyst into the highly active (oxo)hydroxide phase for the gold and nickel sputtered titanium electrodes. An accelerated stress test performed on these electrodes showed a stable behavior for most electrode assemblies, with Nickel interlayers showing great promise for PEC devices. From our experiments we exclude a pure conductivity enhancement as possible explanation, but instead propose an additional change in the local atomic and electronic structure at the metal-support and metal-catalyst interfaces.
    Type of Medium: Online Resource
    ISSN: 2151-2043
    URL: Article
    DOI: 10.1149/MA2023-01372195mtgabs
    Language: Unknown
    Publisher: The Electrochemical Society
    Publication Date: 2023
    detail.hit.zdb_id: 2438749-6
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  • 3
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    Online Resource
    Design of Noble-Metal-Free Membrane Electrode Assemblies Based on Metal Chalcogenides for Electrochemical Hydrogen Production Via Alkaline Seawater Electrolysis
    The Electrochemical Society ; 2023
    In:  ECS Meeting Abstracts Vol. MA2023-01, No. 36 ( 2023-08-28), p. 2060-2060
    Details
    In: ECS Meeting Abstracts, The Electrochemical Society, Vol. MA2023-01, No. 36 ( 2023-08-28), p. 2060-2060
    Abstract: The production of large amounts of green hydrogen (H 2 ) by electrochemical water splitting represents one of the key pillars to reach net-zero by 2050. As one of the major drawbacks, both low-temperature proton-exchange membrane (PEM) as well as anion-exchange membrane (AEM) electrolysis still rely on the utilization of noble metals in the catalyst layers driving the evolution of H 2 and oxygen (O 2 ) on the cathode (HER) and on the anode (OER), respectively. Beyond that, the requirement for highly pure water feeds to prevent degradation of the cell performance over time was previously addressed as one of the main concerns. In particular, this holds true for arid regions located close to the ocean. Advantageously, these coastal arid zones provide essentially unlimited access to seawater, coupled with ample solar irradiation and wind throughout the entire year.[1] One of the major challenges for direct seawater electrolysis lies in the development of selective catalysts, especially for the anode due to the inherently faster reaction kinetics of the competing two-electron chlorine evolution reaction (ClER). Nickel-iron layered double hydroxides (NiFe-LDH) were identified as active and selective OER electrocatalysts in a previous study[2] by our group. Dionigi et al.[3] recently reported a general design principle for selective seawater electrolysis, in which alkaline pH values 〉 7.5 are claimed to favor OER over ClER for overpotentials 〈 480 mV. At the cathode, state-of-the-art electrolyzers utilize Pt-based catalysts for an efficient HER.[2] For direct seawater electrolysis, however, not only the high cost but also the weak stability due to chloride-induced corrosion restrict the applicability of Pt-based electrodes. In our contribution, we thus present noble-metal free catalyst materials based on metal chalcogenides with high HER activity and improved stability in alkaline seawater electrolyte in a single-cell electrolyzer setup. Membrane-electrode assemblies (MEAs) with superior corrosion-resistance by a modification of the porous transport layers (PTLs) for both cathode and anode will be presented, which outperform reference MEAs containing Pt-based cathodes in alkaline seawater electrolysis. The optimized noble-metal-free electrode design (fig. 1) combined with well-controlled electrolyte feeding enables alkaline seawater electrolysis operating at industrially relevant current densities. References [1] S. Dresp, F. Dionigi, M. Klingenhof, P. Strasser, ACS Energy Lett. 2019 , 4 , 933. [2] S. Dresp, T. N. Thanh, M. Klingenhof, S. Brückner, P. Hauke, P. Strasser, Energy Environ. Sci. 2020 , 13 , 1725. [3] F. Dionigi, T. Reier, Z. Pawolek, M. Gliech, P. Strasser, ChemSusChem 2016 , 9 , 962. Figure 1
    Type of Medium: Online Resource
    ISSN: 2151-2043
    URL: Article
    DOI: 10.1149/MA2023-01362060mtgabs
    Language: Unknown
    Publisher: The Electrochemical Society
    Publication Date: 2023
    detail.hit.zdb_id: 2438749-6
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  • 4
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    Online Resource
    Defect‐Promoted Ni‐Based Layer Double Hydroxides with Enhanced Deprotonation Capability for Efficient Biomass Electrooxidation
    Wiley ; 2023
    In:  Advanced Materials
    Details
    In: Advanced Materials, Wiley
    Abstract: Ni‐based hydroxides are promising electrocatalysts for biomass oxidation reactions, supplanting the oxygen evolution reaction (OER) due to lower overpotentials while producing value‐added chemicals. The identification and subsequent engineering of their catalytically active sites are essential to facilitate these anodic reactions. Herein, the proportional relationship between catalysts’ deprotonation propensity and Faradic efficiency of 5‐HMF‐to‐FDCA production (FE FDCA ) is revealed by thorough DFT simulations and atomic‐scale characterizations, including in‐situ synchrotron diffraction and spectroscopy methods. The deprotonation capability of ultrathin layer‐double hydroxides (UT‐LDHs) is regulated by tuning the covalency of metal (M)‐oxygen (O) motifs through defect site engineering and selection of M 3+ co‐chemistry. NiMn UT‐LDHs show an ultrahigh FE FDCA of 99% at 1.37 V versus RHE and retain a high FE FDCA of 92.7% in the OER‐operating window at 1.52 V, about 2x that of NiFe UT‐LDHs (49.5%) at 1.52 V. Ni‐O and Mn‐O motifs function as dual active sites for HMF electrooxidation, where the continuous deprotonation of Mn‐OH sites plays a dominant role in achieving high selectivity while suppressing OER at high potentials. Our results showcase a universal concept of modulating competing anodic reactions in aqueous biomass electrolysis by electronically engineering the deprotonation behavior of metal hydroxides, anticipated to be translatable across various biomass substrates. This article is protected by copyright. All rights reserved
    Type of Medium: Online Resource
    ISSN: 0935-9648 , 1521-4095
    URL: Article
    DOI: 10.1002/adma.202305573
    RVK:
    UA 1538
    Language: English
    Publisher: Wiley
    Publication Date: 2023
    detail.hit.zdb_id: 1474949-X
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