Si electrode failure mechanisms: (a) Material pulverization. (b) Continuous SEI growth. (c) Morphology and volume change of the entire Si electrode. Display omitted
► We reviewed recent research ...progress on Si based high performance anode for lithium ion batteries. ► We reviewed the fundamental challenges associated with large volume change in Si anode. ► Nanostructured materials design can significantly improve the cycling life of Si anode. ► The nanoscale design principles can also be extended to other battery materials that undergo large volume changes.
High energy lithium ion batteries are in demand for consumer electronics, electric-drive vehicles and grid-scale stationary energy storage. Si is of great interest since it has 10 times higher specific capacity than traditional carbon anodes. However, the poor cyclability due to the large volume change of Si upon insertion and extraction of lithium has been an impediment to its deployment. This review outlines three fundamental materials challenges associated with large volume change, and then shows how nanostructured materials design can successfully address these challenges. There have been three generations of nanostructure design, encompassing solid nanostructures such as nanowires, hollow nanostructures, and clamped hollow structures. The nanoscale design principles developed for Si can also be extended to other battery materials that undergo large volume changes.
Hollow nanostructures have shown great promise for energy storage, conversion, and production technologies. Significant efforts have been devoted to the design and synthesis of hollow nanostructures ...with diverse compositional and geometric characteristics in the past decade. However, the correlation between their structure and energy‐related performance has not been reviewed thoroughly in the literature. Here, some representative examples of designing hollow nanostructure to effectively solve the problems of energy‐related technologies are highlighted, such as lithium‐ion batteries, lithium‐metal anodes, lithium–sulfur batteries, supercapacitors, dye‐sensitized solar cells, electrocatalysis, and photoelectrochemical cells. The great effect of structure engineering on the performance is discussed in depth, which will benefit the better design of hollow nanostructures to fulfill the requirements of specific applications and simultaneously enrich the diversity of the hollow nanostructure family. Finally, future directions of hollow nanostructure design to solve emerging challenges and further improve the performance of energy‐related technologies are also provided.
Hollow nanostructures are promising candidates for various energy‐storage technologies, especially for lithium‐ion batteries, lithium‐metal anodes, lithium–sulfur batteries, supercapacitors, dye‐sensitized solar cells, electrocatalysis, and photoelectrochemical cells. In‐depth understanding about the effect of structure engineering on performance is discussed, by which the design of hollow nanostructures can be improved, to fulfill the requirements of specific applications, and simultaneously enrich the diversity of the hollow nanostructure family.
Eccrine sweat glands help to maintain homoeostasis, primarily by stabilizing body temperature. Derived from embryonic ectoderm, millions of eccrine glands are distributed across human skin and ...secrete litres of sweat per day. Their easy accessibility has facilitated the start of analyses of their development and function. Mouse genetic models find sweat gland development regulated sequentially by Wnt, Eda and Shh pathways, although precise subpathways and additional regulators require further elucidation. Mature glands have two secretory cell types, clear and dark cells, whose comparative development and functional interactions remain largely unknown. Clear cells have long been known as the major secretory cells, but recent studies suggest that dark cells are also indispensable for sweat secretion. Dark cell‐specific Foxa1 expression was shown to regulate a Ca2+‐dependent Best2 anion channel that is the candidate driver for the required ion currents. Overall, it was shown that cholinergic impulses trigger sweat secretion in mature glands through second messengers – for example InsP3 and Ca2+ – and downstream ion channels/transporters in the framework of a Na+‐K+‐Cl− cotransporter model. Notably, the microenvironment surrounding secretory cells, including acid–base balance, was implicated to be important for proper sweat secretion, which requires further clarification. Furthermore, multiple ion channels have been shown to be expressed in clear and dark cells, but the degree to which various ion channels function redundantly or indispensably also remains to be determined.
Homogeneous catalysts generally possess superior catalytic performance compared to heterogeneous catalysts. However, the issue of catalyst separation and recycling severely limits their use in ...practical applications. Single‐atom catalysts have the advantages of both homogeneous catalysts, such as “isolated sites”, and heterogeneous catalysts, such as stability and reusability, and thus would be a promising alternative to traditional homogeneous catalysts. In the hydroformylation of olefins, single‐atom Rh catalysts supported on ZnO nanowires demonstrate similar efficiency (TON≈40000) compared to that of homogeneous Wilkinson's catalyst (TON≈19000). HAADF‐STEM and infrared CO chemisorption experiments identified isolated Rh atoms on the support. XPS and XANES spectra indicate that the electronic state of Rh is almost metallic. The catalysts are about one or two orders of magnitude more active than most reported heterogeneous catalysts and can be reused four times without an obvious decline in activity.
Rhodium single‐atom catalysts supported on ZnO nanowires display olefin hydroformylation efficiency comparable to that of homogeneous Wilkinson's catalyst.
Surface-supported isolated atoms in single-atom catalysts (SACs) are usually stabilized by diverse defects. The fabrication of high-metal-loading and thermally stable SACs remains a formidable ...challenge due to the difficulty of creating high densities of underpinning stable defects. Here we report that isolated Pt atoms can be stabilized through a strong covalent metal-support interaction (CMSI) that is not associated with support defects, yielding a high-loading and thermally stable SAC by trapping either the already deposited Pt atoms or the PtO
units vaporized from nanoparticles during high-temperature calcination. Experimental and computational modeling studies reveal that iron oxide reducibility is crucial to anchor isolated Pt atoms. The resulting high concentrations of single atoms enable specific activities far exceeding those of conventional nanoparticle catalysts. This non defect-stabilization strategy can be extended to non-reducible supports by simply doping with iron oxide, thus paving a new way for constructing high-loading SACs for diverse industrially important catalytic reactions.
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