Browsing by Author "Hu, Huimin"

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    On the Catalytic Activity of Sn Monomers and Dimers at Graphene Edges and the Synchronized Edge Dependence of Diffusing Atoms in Sn Dimers
    (Weinheim : Wiley-VCH, 2021) Yang, Xiaoqin; Ta, Huy Q.; Hu, Huimin; Liu, Shuyuan; Liu, Yu; Bachmatiuk, Alicja; Luo, Jinping; Liu, Lijun; Choi, Jin-Ho; Rummeli, Mark H.
    In this study, in situ transmission electron microscopy is performed to study the interaction between single (monomer) and paired (dimer) Sn atoms at graphene edges. The results reveal that a single Sn atom can catalyze both the growth and etching of graphene by the addition and removal of C atoms respectively. Additionally, the frequencies of the energetically favorable configurations of an Sn atom at a graphene edge, calculated using density functional theory calculations, are compared with experimental observations and are found to be in good agreement. The remarkable dynamic processes of binary atoms (dimers) are also investigated and is the first such study to the best of the knowledge. Dimer diffusion along the graphene edges depends on the graphene edge termination. Atom pairs (dimers) involving an armchair configuration tend to diffuse with a synchronized shuffling (step-wise shift) action, while dimer diffusion at zigzag edge terminations show a strong propensity to collapse the dimer with each atom diffusing in opposite directions (monomer formation). Moreover, the data reveals the role of C feedstock availability on the choice a single Sn atom makes in terms of graphene growth or etching. This study advances the understanding single atom catalytic activity at graphene edges. © 2021 The Authors. Advanced Functional Materials published by Wiley-VCH GmbH
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    Titanium Substitution Facilitating Oxygen and Manganese Redox in Sodium Layered Oxide Cathode
    (Weinheim : Wiley-VCH, 2024) Zhou, Junhua; Hu, Huimin; Wang, Jiaqi; Shi, Qitao; Lian, Xueyu; Liu, Lijun; Bachmatiuk, Alicja; Sun, Jingyu; Yang, Ruizhi; Choi, Jin‐Ho; Rümmeli, Mark H.
    Sodium layered oxide with anion redox activity (SLO-A) stands out as a promising cathode material for sodium-ion batteries due to its impressive capacity and high voltage resulting from Mn- and O-redox processes. However, the SLO-A faces significant challenges in cycling stability and rate performance, primarily due to the poor reversibility and sluggish kinetics of the O-redox. In this study,a novel Ti-doped material, Na2/3Li2/9Mn53/72Ti1/24O2 (NLMTO), exhibiting remarkable characteristics such as a notable rate capacity (130 mAh g−1 at 3C, where 1C equals 200 mA g−1) and excellent cycling retention (85.4% after 100 cycles at 0.5C) is introduced. Employing electrochemical differential analyses, the contributions to the superior performance arising from the Mn- and O-redox processes are quantitatively delineated. The optimized performance of NLMTO is attributed, in part, to the enhanced stability of both bulk and interface structures. The introduction of Ti through substitution not only contributes to this stability but also allows for the fine-tuning of the material's electron configurations. This is achieved by augmenting the density of states near the Fermi energy level, as well as elevating the O 2p and Mn 3d orbits. This research advances sodium-ion battery technology.