[신간의 별자리x] 우리/미술, 그리고 ‘슬픔의 박물관’

Titanium Dioxide Nanomaterials: Synthesis, Properties, Modifications, and Applications

Polydopamine and Its Derivative Materials: Synthesis and Promising Applications in Energy, Environmental, and Biomedical Fields

The recent advances in electrocatalysis for oxygen reduction reaction (ORR) for proton exchange membrane fuel cells (PEMFCs) are thoroughly reviewed. This comprehensive Review focuses on the low- and non-platinum electrocatalysts including advanced platinum alloys, core–shell structures, palladium-based catalysts, metal oxides and chalcogenides, carbon-based non-noble metal catalysts, and metal-free catalysts. The recent development of ORR electrocatalysts with novel structures and compositions is highlighted. The understandings of the correlation between the activity and the shape, size, composition, and synthesis method are summarized. For the carbon-based materials, their performance and stability in fuel cells and comparisons with those of platinum are documented. The research directions as well as perspectives on the further development of more active and less expensive electrocatalysts are provided.

http://repository.ust.hk/ir/bitstream/1783.1-77094/1/acs.chemrev.5b00462_withlink.pdf

Recent Advances in Electrocatalysts for Oxygen Reduction Reaction

TiO(2) is one of the most studied compounds in materials science. Owing to some outstanding properties it is used for instance in photocatalysis, dye-sensitized solar cells, and biomedical devices. In 1999, first reports showed the feasibility to grow highly ordered arrays of TiO(2) nanotubes by a simple but optimized electrochemical anodization of a titanium metal sheet. This finding stimulated intense research activities that focused on growth, modification, properties, and applications of these one-dimensional nanostructures. This review attempts to cover all these aspects, including underlying principles and key functional features of TiO(2), in a comprehensive way and also indicates potential future directions of the field.

TiO2 nanotubes: synthesis and applications.

1D tubular micro-nano structural materials have been attracting extensive attention in the microwave absorption (MA) field for their anisotropy feature, outstanding impedance matching, and electromagnetic energy loss capability. Herein, unique double-shelled Sn@Mo2 C/C tubes with porous Sn inner layer and 2D Mo2 C/C outer layer are successfully designed and synthesized via a dual-template method. The composites possess favorable MA performance with an effective absorption bandwidth of 6.76 GHz and a maximum reflection loss value of -52.1 dB. Specifically, the rational and appropriate construction of Sn@Mo2 C/C tubes promotes the multi-path electron transfer in the composites to optimize the dielectric constant and consequently to enhance the capacity of electromagnetic wave energy dissipation. Three mechanisms dominate the MA process: i) the conductive loss resulted from the rapid electron transmission due to the novel 1D hollow coaxial multi-shelled structure, especially the metallic Sn inner layer; ii) the polarization loss caused by abundant heterogeneous interfaces of Sn-Mo2 C/C and Mo2 CC from the precise double-shelled structure; iii) the capacitor-like loss by the potential difference between Mo2 C/C nanosheets. This work hereby sheds light on the design of the 1D hierarchical structure and lays out a profound insight into the MA mechanism.

Multi‐Path Electron Transfer in 1D Double‐Shelled Sn@Mo 2 C/C Tubes with Enhanced Dielectric Loss for Boosting Microwave Absorption Performance

Dielectric polarization and magnetic resonance associated with intrinsic constituent and extrinsic structure are two kinds of fundamental attenuation mechanisms for microwave absorbers, but remain extremely challenging in revealing the composition‐morphology‐performance correlation. Herein, hierarchical MXene/metal‐organic framework derivatives with coherent boundaries and magnetic units below critical grain size are constructed to realize synergistic dielectric–magnetic enhancement by phase‐evolution engineering and dynamic magnetic resonance. Specifically, phase‐evolution induced inseparable interfaces, diverse incompatible phases, and defects/vacancies contribute to dielectric polarization, while closely distributed magnetic units simultaneously realize nanoscale multi‐domain coupling and long‐range magnetic interaction. As results, the hierarchical derivatives promise an exceptional reflection loss of −59.5 dB and an effective absorption bandwidth of 6.1 GHz. Both experimental results and theoretical calculations indicate that phase‐evolution engineering and dynamic magnetic resonance maximize the absorption capability and demonstrate a versatile methodology for manipulating microwave attenuation. More importantly, the proposed multi‐domain coupling and long‐range magnetic interaction theories innovatively offer dynamic magnetic resonance mechanism for magnetic loss within critical grain size.

Synergistic Dielectric–Magnetic Enhancement via Phase‐Evolution Engineering and Dynamic Magnetic Resonance

Dielectric composites constructed using carbon and metal oxides have become a hot research topic; however, the strategy to strengthen the coupling of components still needs to be optimized to enhance dielectric loss. Herein, ultra-fine ZnO derived from ZIF-8 was uniformly distributed and tightly embedded in multi-wall carbon nanotubes (C-ZnO@CNTs) via a novel confined space synthesis. Due to the presence of a polypyrrole coating, ZnO nanocrystals could be formed in the space of the original polyhedron and inserted into the CNTs, promoting the generation of polarized CNTs and providing abundant polarization centers on the CNTs. The composites exhibited superior microwave absorption capacity with a reflection loss value of up to -48.2 dB at 6.0 GHz, and the effective bandwidth reached 14.9 GHz by adjusting their thickness. According to the geometric phase analysis, the strain driven by the tight-coupling between ZnO-CNTs was confirmed to exist in the interfaces, boosting their inherent electromagnetic properties. The improved dielectric loss was caused by the strong interfacial polarization among ZnO-ZnO or ZnO-CNTs and the conductive loss among intertwined CNTs network, as revealed by electron holography. Therefore, the overall electrical properties could be improved by the polarized C-ZnO@CNTs with high electron conductivity. The confined space strategy may have promising potential for the synthesis of new composites of polarized carbon materials tightly coupled with metal oxides nanocrystals.

Enhanced microwave absorption performance from abundant polarization sites of ZnO nanocrystals embedded in CNTs via confined space synthesis.

A New Sodium Calcium Cyclotetravanadate Framework: “Zero-Strain” during Large-Capacity Lithium Intercalation

In this paper, we report an air-exposed and room-temperature immersion reaction for synthesis of novel Au nanoparticles decorated Ag(Cl,Br) [Ag(Cl,Br)–Au] micro-necklaces from the AgBr template for efficient and stable photocatalytic degradation and SERS detection of food contaminant Sudan I (SDI) molecules. Amazingly, as the photocatalyst, the partial substitution of bromine atoms by chlorine in crystalline lattices and decoration of Au nanoparticles on the surface have synergistically ensured these Ag(Cl,Br)–Au micro-necklaces of enhanced degradation efficiency of SDI from 65.1% achieved by AgBr to 100% after 18 min of visible light irradiation, along with significantly promoted efficiency maintenance after 12 cycles of the photocatalytic reaction. Meanwhile, due to the designed decoration of Au nanoparticles on surfaces of semiconducting micro-necklaces, these Ag(Cl,Br)–Au micro-necklaces also exhibited the ability to offer sensitive SERS signals for trace detection of SDI molecules with the limit of detection as low as 10−10 M being achieved. Hence, in consideration of the novel structures, facile preparation as well as attractive applications in both SERS detection and photocatalytic degradation of SDI dye of these Ag(Cl,Br)–Au micro-necklaces, it is believable that such bifunctional substrate materials hold great potential for various environmental and health-related applications.

Renchao Che

Papers

Multi‐Path Electron Transfer in 1D Double‐Shelled Sn@Mo 2 C/C Tubes with Enhanced Dielectric Loss for Boosting Microwave Absorption Performance

Synergistic Dielectric–Magnetic Enhancement via Phase‐Evolution Engineering and Dynamic Magnetic Resonance

Enhanced microwave absorption performance from abundant polarization sites of ZnO nanocrystals embedded in CNTs via confined space synthesis.

A New Sodium Calcium Cyclotetravanadate Framework: “Zero-Strain” during Large-Capacity Lithium Intercalation

Gold nanoparticles decorated Ag(Cl,Br) micro-necklaces for efficient and stable SERS detection and visible-light photocatalytic degradation of Sudan I