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Pd Nanocluster/Monolayer MoS₂ Heterojunctions for Light-Induced Room Temperature Hydrogen Sensing
Hien Duy Mai,Sangmin Jeong,Ki-Joon Jeon 한국대기환경학회 2021 한국대기환경학회 학술대회논문집 Vol.2021 No.10
Developing sensing approaches that can exploit visible light for the detection of low-concentration hydrogen at room temperatures has become increasingly important for the safe use of hydrogen in many applications. Heterostructures composed of monolayer MoS₂ and Pd nanoclusters functioning as photo- and hydrogen-sensitizers were successfully fabricated in a facile and reproducible manner. The Pd/MoS₂ heterostructure as an active hydrogen-sensing layer enables the utilization of visible light for enhancing the sensing performance threefold relative to dark conditions. Visible light radiation can also improve the sensing reversibility and reproducibility in the obtained sensor. This proof-of-concept opens a new avenue for visible light-induced hydrogen gas sensing at room temperature.
Hien Duy Mai,Suncheol Kim,Hyojong Yoo 한국공업화학회 2020 Journal of Industrial and Engineering Chemistry Vol.82 No.-
Oxygen evolution reaction (OER) is considered a major challenge in the production of efficientelectrochemical water splitting devices. To overcome the challenge, the development of inexpensiveelectrochemical catalysts with high energy conversion efficiencies is vital. Nanohybrids composed ofnoble metal nanoparticles and transition metal hydroxides often possess catalytically active sites that arebeneficial for OER performance. In this study, we report a successful synthesis of Ni(OH)2 nanoflowerswith a high degree of crystallinity and uniformity. The as-prepared Ni(OH)2 nanoflowers are employed astemplates for effective and controllable loading of Au nanodots to obtain Ni(OH)2@Au nanohybrids. Anexamination of the OER activity reveals that Ni(OH)2@Au nanohybrids exhibit a considerably loweroverpotential (h) value (390 mV) at a current density of 5 mA cm–2 and a smaller Tafel slope (120 mV dec–1) than those of Ni(OH)2 nanoflowers (540 mV and 324 mV dec–1, respectively). The OER enhancementeffect is mainly attributed to the decoration of Au nanodots, inducing charge transfer from Ni to Au andthereby stabilizing the Ni species at high oxidation levels. Moreover, the uniform loading of Au nanodotson the anisotropic Ni(OH)2 nanoflowers provides more active interfacial surfaces, which are expedient toOER.
Multilevel coordination-driven assembly for metallosupramolecules with hierarchical structures
Mai, Hien Duy,Tran, Ngoc Minh,Yoo, Hyojong Elsevier 2019 Coordination chemistry reviews Vol.387 No.-
<P><B>Abstract</B></P> <P>Despite recent advances toward understanding metallosupramolecular platforms, structural classification remains a challenge because of the high multiplicity and diversity originating from the variety of three-dimensional binding modes of metal ions and multifunctional ligands. In this review, multilevel coordination-driven assembly and its potential implementation in the analysis of a variety of structurally complicated metallosupramolecules are demonstrated. The classification of coordination-driven structures with their respective hierarchy levels is summarized based on the ability of each structural unit to construct ordered molecular platforms. Multilevel assembly is composed of (i) primary, (ii) secondary, (iii) tertiary, or higher-order assembly. The coordination-driven binding modes should differ by levels in a complex. In particular, tertiary assembly involves the use of predefined, well-organized secondary supramolecules as basic modules to build discrete or polymeric structures. Using the suggested concept, coordination-driven metallosupramolecular platforms can be readily classified depending on their respective hierarchical structures. We expect that this simple analytical approach will provide researchers with a more effective understanding of coordination-driven assembly and facilitate the design of new complexes for specialized applications.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Systematic classification of metallosupramolecules based on their hierarchical level is demonstrated. </LI> <LI> Multilevel coordination-driven assembly as an effective analysis for metallosupramolecules. </LI> <LI> Multilevel assembly is composed of primary, secondary, tertiary, or higher-order assembly. </LI> <LI> The simple analysis could be helpful for the design of new complexes for specific applications. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Mai, Hien Duy,Lee, Inme,Yoo, Hyojong Wiley (John WileySons) 2018 Chemistry - An Asian Journal Vol.13 No.15
<P>Metallosupramolecule-based polymeric platforms with high degrees of hierarchy and tailorable functionalities are of great interests because of their unique morphologies and potential applications. Herein, the controllable synthesis of a highly-ordered polymeric structure, {[M,P-Co-8(PDA)(6)(HIP)(3)(DMF)(5)(H2O)](3)-[Co(DMF)(H2O)(2)]} (1) (PDA=2,6-pyridinedicarboxylate, HIP=5-hydroxyisophthalate, DMF=dimethylformamide) with unique topology is reported. The solid-state structure of 1 reveals that it is alternately and periodically assembled from racemic supramolecular monomers to form a zigzag-shaped polymeric strand. Discrete racemic supramolecules (2) with topologies similar to those of monomeric species of 1 are also controllably synthesized in a separate reaction. Formation of intermolecular hydrogen bonds between supramolecules associated with hydroxyl groups of HIPs are critical for the unique solid-state packing geometries of 1 and 2.</P>
전기화학적 물분해 기반 수소에너지 생산 효율을 증진하기 위한 전략적 전극 설계 및 효율 평가
정상민,Hien Duy Mai,전기준 한국대기환경학회 2021 한국대기환경학회 학술대회논문집 Vol.2021 No.10
최근 몇 년 동안 수소 에너지는 자원 고갈과 환경 오염으로 인해 화석 연료를 대체하기 위해 더욱 중요해지고 있다. 전기화학적 물분해방식(수전해시스템)은 환경오염 없이 청정수소에너지를 생산할 수 있는 방식중 하나로 알려져 있다. 그러나 수전해 시스템은 과전압을 줄이기 위해 전기촉매가 필수적이지만, 귀금속(백금족) 촉매가 가장 높은 효율을 보이기 때문에 대체방안이 필요하다. 따라서 가격 경쟁력을 극복하기 위해서는 백금 함량을 낮추거나 대체 소재 개발하는 등 전극 설계 전략 및 분석기법이 필요하다. 본 연구에서는 화학기상증착법(CVD)을 도입하여, 값싼 스테인리스스틸(SUS) 상에 단일층 그래핀(Graphene)을 성장시킬 수 있는 합성 조건을 최적화하였으며, 합성된 전극은 물 분해에 의해 표면상의 변화를 실시간으로 관측할 수 있는 In-situ Raman 기법이 체계적으로 특성화되었다. 이러한 독특한 기술은 전극표면을 실시간으로 관측함으로써, 메커니즘 규명과 효율적인 전극 설계에 도움을 줄 수 있다.
김선철,( Mai Duy Hien ),유효종 한국공업화학회 2019 한국공업화학회 연구논문 초록집 Vol.2019 No.1
The preparation of multinary metal chalcogenide nanocrystals, particularly those derived from first-row transition metal elements, is of considerable interest since these materials is not only cheap and abundant, but also exhibit improved electrocatalytic performance that would be as comparable as does IrO<sub>2</sub> or RuO<sub>2</sub>. Herein, we develop a facile synthesis of tertiary metal (Ni and Fe)-based selenide (Ni<sub>x</sub>Fe<sub>1-x</sub>Se<sub>2</sub>) nanocrystals with a homogeneous element distribution as well as uniform size and shape. Specifically, Ni<sub>x</sub>Fe<sub>1-x</sub>Se<sub>2</sub> nanocrystals are readily converted from the as-prepared Ni-Fe LDH with unique flower-like morphologies through a solution-based approach. The prepared Ni<sub>x</sub>Fe<sub>1-x</sub>Se<sub>2</sub> nanocrystals can be deposited on a variety of conductive supports, such as carbon fiber or nickel foil, to improve the catalytic performance and durability. Importantly, these materials can be rationally implemented as dual-functional catalysts for overall water-splitting, including HER and OER.
김선철,( Mai Duy Hien ),유효종 한국공업화학회 2019 한국공업화학회 연구논문 초록집 Vol.2019 No.1
Nanohybrids composed of noble metal nanoparticles and transition metal hydroxides often possess catalytically active sites that are beneficial for OER performance. In this study, we report a successful synthesis of Ni(OH)<sub>2</sub> nanoflowers with a high degree of crystallinity and uniformity. The as-prepared Ni(OH)<sub>2</sub> nanoflowers are employed as templates for effective and controllable loading of Au nanodots to obtain Ni(OH)<sub>2</sub>@Au nanohybrids. An examination of the OER activity reveals that Ni(OH)<sub>2</sub>@Au exhibits a considerably lower overpotential value (390 mV) at a current density of 5 mA ㎠ and a smaller Tafel slope (120 mV dec<sup>-1</sup>) than those of Ni(OH)<sub>2</sub> (540 mV and 324 mV dec<sup>-1</sup>, respectively).