九州大学超顕微解析研究センター
微細構造解析プラットフォーム「ナノマテリアル開発のための超顕微解析共用拠点」

第 227 回ＨＶＥＭ研究会のお知らせ
令和元年 12 月 5 日

インド工科大学マンディー校より Aditi Halder 准教授 と Viswanath Balakrishnan 准教
授をお招きし、下記のご講演をいただきます。皆様、奮ってご参加ください。

【日時】令和元年 12 月 25 日（水）13 時 30 分 ～ 15 時 30 分

【会場】九州大学 鉄鋼リサーチセンター（EN40 棟）（〒819-0395 福岡県福岡市西区元岡 744）

２階 セミナー室【講 演 １】 Viswanath Balakrishnan 氏

インド工科大学マンディー校
工学部准教授“Stabilizing unstable phases in 2D materials and heterostructures”【講 演 ２】 Aditi Halder 氏

インド工科大学マンディー校
理学部准教授“Materials for Hydrogen Evolution Using Earth-abundant Elements”*********************************************************************
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ＨＶＥＭ研究会世話人：波多 聰・安田和弘・佐藤幸生
連絡先：佐藤幸生（九州大学 大学院工学研究院 材料工学部門）
Tel: 092-802-2971 E-mail: sato@zaiko.kyushu-u.ac.jp

Abstract【講演１】“Stabilizing unstable phases in 2D materials and heterostructures”
Two dimensional materials offer unique opportunities to control defects and stabilize polymorphic
phases towards optoelectronic and energy applications to great extent. Growth of 2D materials withability to control the co-existing polymorph assembly in single domain provides unique platform toproduce seamless homojunctions with different properties. We achieved large area of chemical vapour
deposited (CVD) growth of 2D monolayer WS2 having their two polymorphs (1H/1T or 1H/1T’) forming
homojunctions in single domain. We have identified CVD grown homojunctions with different phases of
WS2 monolayers using detailed microscopic as well spectroscopic techniques. Formation of in-plane
heterostructures with 1H and 1T’ polymorphs have been extensively analysed using variety ofspectroscopic as well as microscopic techniques, along with the lifetime luminescence imaging. Atomic
resolution scanning transmission electron microscope have been used to identify the lateral glided Scolumn in hexagonal WS2 arrangement, causing intrinsic lattice distortion dominated polymorphic
phase (1H, 1T’ and 1T) formation. In situ Raman spectroscope and microscope observations revealthat the formation of heterophases in WS2 cancel competing thermal mismatch and lattice strains andstabilize crack free monolayer heterostrutures while homophase WS2 monolayer suffers from severe
cracking. Further we investigated the evolution of point defects induced void formation during thegrowth and their role on crack propagation in WS2 monolayer. Owing to other interesting properties ofmetastable 1T phase, we also investigated in- situ phase transition characteristics and developedstrategies to stabilize 1T phase in WS2 monolayer. The formation and stability of in plane
heterostructures involving polymorphic phases and heteroatomic interfaces have been explored. The
investigated 2D materials and their heterostructures show interesting optical, electrical and energy
storage properties.

【講演２】“Materials for Hydrogen Evolution Using Earth-abundant Elements”
The state-of the art catalyst for polymer-electrolyte-membrane fuel cell and electrolyzer suffers theproblems associated with higher cost and durability. The less expensive first row transition metals basedoxides are found to be the suitable alternatives. Water electrolysis is one of the effective strategies toproduce hydrogen with the help of an efficient electrocatalyst. Nickel, tungsten and molybdenum are
few of the transition metals and their oxides which found to be very efficient on electrochemicalhydrogen production. In the first part of the presentation, we will show how the incorporation of oxygen
vacancies or oxygen doping in transition metal oxides (TMOs) and sulphides are found to be very
beneficial for the production of hydrogen.
In the second part of the work, we will show our work on single atom catalysts (SAC) which is a newkind of material which has emerged as newer alternative with the view “ATOM ECONMOY”. SACs
are basically isolated metal atoms dispersed on solid supports, ideally having on spatial ordering or any
other types of notable interaction among the other isolated individual atoms. A suitable support material
strongly anchors the metal species -preventing them to aggregate and creating stable, finely dispersed
metal clusters with a high catalytic activity. In our group we are aiming to design low cost SACs or
pseudo-SAC materials made of transition metal and metal oxides for energy conversion.

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