05 Fakultät Informatik, Elektrotechnik und Informationstechnik

Permanent URI for this collectionhttps://elib.uni-stuttgart.de/handle/11682/6

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Author: search.filters.author.Birke, Kai PeterSubject: search.filters.subject.333.7

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    Introducing a concept for designing an aqueous electrolyte with pH buffer properties for Zn-MnO2 batteries with Mn2+/MnO2 deposition/dissolution
    (2023) Fitz, Oliver; Wagner, Florian; Pross-Brakhage, Julia; Bauer, Manuel; Gentischer, Harald; Birke, Kai Peter; Biro, Daniel
    For large-scale energy-storage systems, the aqueous rechargeable zinc–manganese dioxide battery (ARZMB) attracts increasing attention due to its excellent advantages such as high energy density, high safety, low material cost, and environmental friendliness. Still, the reaction mechanism and its influence on the electrolyte's pH are under debate. Herein, a pH buffer concept for ARZMB electrolytes is introduced. Selection criteria for pH buffer substances are defined. Different buffered electrolytes based on a zinc salt (ZnSO4, Zn(CH3COO)2, Zn(CHOO)2), and pH buffer substances (acetic acid, propionic acid, formic acid, citric acid, 4-hydrobenzoic acid, potassium bisulfate, potassium dihydrogen citrate, and potassium hydrogen phthalate) are selected and compared to an unbuffered 2 m ZnSO4 reference electrolyte using titration, galvanostatic cycling with pH tracking, and cyclic voltammetry. By adding buffer substances, the pH changes can be reduced and controlled within the defined operating window, supporting the Mn2+/MnO2 deposition/dissolution mechanism. Furthermore, the potential plateau during discharge can be increased from ≈1.3 V (ZnSO4) to ≈1.7 V (ZnSO4 + AA) versus Zn/Zn2+ and the energy retention from ≈30% after 268 cycles (ZnSO4) to ≈86% after 494 cycles (ZnSO4 + AA). Herein, this work can serve as a basis for the targeted design of long-term stable ARZMB electrolytes.
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    Powering the future : Germany's Wasserstoffstrategie in the transition to climate neutrality : case study on green hydrogen for the chemical industry
    (2024) Seithümmer, Valentin Benedikt; Lutz, Julia Valentina; Kaufmann, Samuel Jaro; Chinnaraj, Haripriya; Rößner, Paul; Birke, Kai Peter
    This article provides a comprehensive insight into Germany's transition to climate neutrality, bringing together the political framework of Germany's Climate Protection Act (CPA), the funding strategy of its key pillar, namely the “Wasserstoffstrategie” and the technical dimensions for non-technical stakeholders through a case study of Germany's largest current hydrogen user, the chemical industry. Increasing complexity of our modern economy and society and a lack of clarity in reporting contribute to misleading conclusions and can facilitate polarised views. To overcome that gap, we aim to draw a clear picture of these complex scientific topics and make them also accessible to non-technical stakeholders. This paper reviews Germany's climate policy, emphasizing the federal constitutional court's pivotal role. By calculating prospective GHG-reduction paths for Germany, we illuminate the gap between aspirational targets and practical strategies, emphasizing the need to translate global targets into actionable national plans. Taking the crucial, often-overlooked CO2-budget into account, potential shortcomings are revealed, even when annual emission goals are met by Germany. Shifting focus of this paper to the German hydrogen strategy, a core part of the Climate Protection Program, we reveal a strong emphasis on international collaboration. This involves a global hydrogen ramp-up and facilitation of hydrogen imports, offering trade opportunities but also introducing dependencies and potential price increases. A scale estimation case study on green hydrogen production for the German chemical industry underscores the rationale behind prioritising imports over domestic production. Calculating a demand of 7840 windmills (78.37 TW h) that require 168 000 football pitches (7000 m2 per pitch) of space, it provides easy to grasp insights into the necessary actions for a climate neutral Germany. This perspective frames Germany's climate goals, the Wasserstoffstrategie, and the technical scale of implementing renewables by conducting a case study on green hydrogen. Hereby, it highlights the magnitude of the climate problem and the immense scale of solutions required for a sustainable technical transition in a clear and sound manner.