讲座题目1：应力工程构建二维赝异质结结构
Title：Construction of 2D lateral pseudoheterostructures by strain engineering
报告人：Xun Xu（Professor, Wollongong University, Australia）
时间及地点：2020年11月01日08:00-12:00
报告地点：https://meeting.tencent.com/s/dtkZJKdbTtqo会议ID：845 348 840
Abstract:Two-dimensional (2D) lateral heterostructures host unconventional physical properties due to their controllable band-offset tuning and interfacial sensitive characteristic. The lattice mismatch results in the difficulties to construct the perfect atomic interface in such 2D lateral heterostructures, which in turn limits their desirable properties and performances in applications. In this work, strain-modulated 2D lateral pseudoheterogeneous structures are designed and realized in the single-component 2D BiOBr nanosheets by taking advantage of their strain-sensitive crystal and electronic structures. The pseudoheterogeneous interface without atomic mismatch can be feasibly modulated by local strain distribution, which exhibits similar local electronic band structure of corresponding heterostructures. Significant enhancement in charge separation at the pseudoheterostructure was demonstrated under visible light irradiation, which is given rise to the controllable electronic band alignment across the interface. The construction of the lateral pseudoheterostructure offers a feasible and promising way to build unprecedented 2D systems with exciting properties.
讲座题目2：原子级厚度非层状纳米材料在能量存储及转换中的应用
Title：Atomically thin non-layered nanomaterials for energy storage and conversion
报告人：Xun Xu（Professor, Wollongong University, Australia）
时间及地点：2020年11月01日13:00-17:00
报告地点：https://meeting.tencent.com/s/dtkZJKdbTtqo会议ID：845 348 840
Abstract: Phase transformation of layered structure into spinel structure has been detrimental for most of layered oxide cathodes.1Even if a lot of efforts have been made to relieve this highly irreversible phase transformation, there have been few successful results. However, we firstly observed the possibility to make this irreversible phase transformation extremely reversible by utilizing Na-birnessite (NaxMnO2•yH2O; Na-bir) as a basic structural unit, which has distinctive layered structure containing crystal water. Herein, the crystal water in the structure contributes to generating metastable spinel-like phase, which is the key factor for making this unusual reversibility happen.2The reversible structural rearrangement between layered and spinel-like phases during electrochemical reaction could activate new cation sites and enhance ion diffusion with higher structural stability. This unprecedented reversible phase transformation between spinel and layered structure was deeply analyzed via combinedex situsoft and hard X-ray absorption spectroscopy (XAS) analysis within situX-ray diffraction (XRD). Fundamental mechanism on this reversible phase transformation was theoretically elucidated and confirmed by kinetic investigation using first-principle calculation. These results provide deep insight into novel class of intercalating materials which can deal with highly reversible framework changes, and thus it can pave an innovative way for the development of cathode materials for next-generation rechargeable batteries.
