[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.

Recently, 2D ferromagnetic materials have aroused wide interest for their magnetic properties and potential applications in spintronic and topological devices. However, their actual applications have been severely hindered by intricate challenges such as the unclear spin arrangement. In particular, the evolution of spin texture driven by high-density electron current, which is an essential condition for fabricating devices, remains unclear. Herein, the current-pulse-driven spin textures in 2D ferromagnetic material Fe3GeTe2 have been thoroughly investigated by in situ Lorentz transmission electron microscopy. The dynamic experiments reveal that the stripe domain structure in the AB and AC planes can be broken and rearranged by the high-density current. In particular, the density of domain walls can be modulated, which offers an avenue to achieve a high-density domain structure. This phenomenon is attributed to the weak interlayer exchange interaction in 2D metallic ferromagnetic materials and the strong disturbance from the high-density current. Therefore, a bubble domain structure and random magnetization in Fe3GeTe2 can be acquired by synchronous current pulses and magnetic fields. These achievements reveal domain structure transitions driven by the current in 2D metallic magnetic materials and provide references for the practical applications.

Anomalous Spin Behavior in Fe3GeTe2 Driven by Current Pulses

We report an in-situ Lorentz transmission electron microscopy (LTEM) investigation to study the thermal effects on the generation of magnetic skyrmions within a nanobelt. Under an action of a moderate current pulse, magnetic skyrmions appear even in the temperature range far below the critical temperature and even at zero field. Finite element simulation reveals that the Joule heating plays an essential role in this behavior. Our results also uncover the importance of the cooling conditions in the current-related in situ LTEM research.

Thermal effects on current-related skyrmion formation in a nanobelt

While metal-based electrocatalysts have garnered extensive attention owing to the large variety of enzyme-mimic properties, the search for such highly-efficient catalysts still relies on empirical explorations, owing to the lack of predictive indicators as well as the ambiguity of structure-activity relationships. Notably, surface electronic structures play a crucial role in metal-based catalysts yet remain unexplored in enzyme-mimics. Herein, the authors investigate the electronic structure as a possible indicator of electrocatalytic activities of H2 O2 decomposition and glucose oxidation using Pd@Pt core-shell nanocrystals as a well-defined platform. The electron densities of the Pd@Pt are modulated with the correlation of strain through precise control of surface orientation and the number of atomic layers. The close relationships between the electrocatalytic activities and the surface charge accumulation are found, in which the increase of the electron accumulation can enhance both the enzyme-mimic activities. As a result, the Pd@Pt3L icosahedra with compressive strain in Pt shells exhibit the highest electrocatalytic activities for H2 O2 decomposition and glucose oxidation. Such systematic and comprehensive study provides the structure-activity relationships and paves a new way for the rational design of metal-based electrocatalysts. Especially, the charge accumulation degrees may serve as a general performance indicator for metal-based catalysts.

Understanding of Strain-Induced Electronic Structure Changes in Metal-Based Electrocatalysts: Using Pd@Pt Core-Shell Nanocrystals as an Ideal Platform.

Intercalation electrode materials store Na by incorporation into their framework structure without phase transformation and substantial large volume, resulting in the excellent cycling stability during electrochemical cycling. However, challenges arise due to a low capacity of intercalation electrode for sodium‐ion batteries (SIBs). Here, a perovskite oxide (Ce1/3NbO3 (CNO)) as an intercalation anode with dual functions of high capacity and excellent cycling stability is explored. The Na+ storage capacity of CNO (141.3 mAh g‐1) originates from not only sufficient cation vacancies but also the interfacial space charge storage of Na+ in the surface of CNO particles. Additionally, CNO exhibits excellent cycling stability with 90.2% capacity retention after 1000 cycles at 1 C, 99.4% capacity retention after 2000 cycles at 5 C, and 96.5% capacity retention after 10 000 cycles at 10 C. The cycling performance can be explained by the “zero‐stain” Na+ storage characteristic, where the maximal unit cell volume variation induced by Na+ insertion/extraction is calculated to be only 0.38%. Hence, CNO is a promising alternative for long‐life SIBs. The mechanisms that enable the storage of Na+ with negligible volume variation will guide new insights for the rational design of ultra‐stable electrode materials for SIBs.

Renchao Che

Papers

Anomalous Spin Behavior in Fe3GeTe2 Driven by Current Pulses

Thermal effects on current-related skyrmion formation in a nanobelt

Understanding of Strain-Induced Electronic Structure Changes in Metal-Based Electrocatalysts: Using Pd@Pt Core-Shell Nanocrystals as an Ideal Platform.

Interfacial Space Charge Enhanced Sodium Storage in a Zero‐Strain Cerium Niobite Perovskite Anode

Recyclable magnetic carbon foams possessing voltage-controllable electromagnetic shielding and oil/water separation