Transition metal single‐atom catalysts (SACs) are currently a hot area of research in the field of electrocatalytic oxygen reduction reaction (ORR). In this review, the recent advances in transition ...metal single‐atom supported by 2D materials as catalysts for ORR with high performance are reported. Due to their large surface area, uniformly exposed lattice plane, and adjustable electronic state, 2D materials are ideal supporting materials for exploring ORR active sites and surface reactions. The rational design principles and synthetic strategies of transition metal SACs supported by 2D materials are systematically introduced while the identification of active sites, their possible catalytic mechanisms as well as the perspectives on the future of transition metal SACs supported by 2D materials for ORR applications are discussed. Finally, according to the current development trend of ORR catalysts, the future opportunities and challenges of transition metal SACs supported by 2D materials are summarized.
In this review, the rational design and synthesis of transition metal single‐atom catalysts supported by 2D materials are systematically summarized while the identification of active sites, their possible catalytic mechanisms, and the future perspectives for the oxygen reduction reaction (ORR) are provided. Finally, the opportunities and challenges are also discussed according to the current development trends in ORR catalysts.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Facial action units (AUs) analysis plays an important role in facial expression recognition (FER). Existing deep spectral convolutional networks (DSCNs) have made encouraging performance for FER ...based on a set of facial local regions and a predefined graph structure. However, those regions do not have close relationships to AUs, and DSCNs cannot model the dynamic spatial dependencies of these regions for estimating different facial expressions. To tackle these issues, we propose a novel Double Dynamic Relationships Graph Convolutional Network (DDRGCN) to learn the strength of the edges in the facial graph by a trainable weighted adjacency matrix. We construct facial graph data by 20 regions of interest (ROIs) guided by different facial AUs. Furthermore, we devise an efficient graph convolutional network in which the inherent dependencies of vertices in the facial graph can be learned automatically during network training. Notably, the proposed model only has 110K parameters and 0.48MB model size, which is significantly less than most existing methods. Experiments on four widely-used FER datasets demonstrate that the proposed dynamic relationships graph network achieves superior results compared to existing light-weight networks, not just in terms of accuracy but also model size and speed.
Surface passivation of metal halide perovskites (MHPs) is essential for their stability and various properties as well as functionalities, including optical and electronic. Passivation is important ...for both stabilizing intrinsic defects and preventing extrinsic damaging species from reaching the perovskite (PVK), such as water and oxygen. Because of the ternary nature of their chemical composition, multiple surface defects exist for both bulk and nanostructured PVKs, with the latter particularly prominent because of their extremely large surface-to-volume ratio. To effectively passivate the different surface defects, a multitude of different ligands are necessary because each type of defect likely requires a different ligand for optimal passivation, as has been successfully demonstrated in a number of systems in essentially a “cocktail” approach. Characteristics of the ligands that affect effectiveness of passivation include size, shape, charge and charge distribution, orientation, conductivity, and interligand interaction. Examples of ligands for MHPs include both cationic and anionic or zwitterionic species with varied valences. The challenge is to identify the most effective ligand for each type of defect, and addressing this will require further experimental and theoretical study.
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IJS, KILJ, NUK, PNG, UL, UM
Metallic lithium anodes are highly promising for revolutionizing current rechargeable batteries because of their ultrahigh energy density. However, the application of lithium metal batteries is ...considerably impeded by lithium dendrite growth. Here, a biomacromolecule matrix obtained from the natural membrane of eggshell is introduced to control lithium growth and the mechanism is motivated by how living organisms regulate the orientation of inorganic crystals in biomineralization. Specifically, cryo-electron microscopy is utilized to probe the structure of lithium at the atomic level. The dendrites growing along the preferred < 111 > crystallographic orientation are greatly suppressed in the presence of the biomacromolecule. Furthermore, the naturally soluble chemical species in the biomacromolecules can participate in the formation of solid electrolyte interphase upon cycling, thus effectively homogenizing the lithium deposition. The lithium anodes employing bioinspired design exhibit enhanced cycling capability. This work sheds light on identifying substantial challenges in lithium anodes for developing advanced batteries.
Two multifunctional, ether-bridged tricarboxylic acids, 2-(4-carboxylphenoxy)terephthalic acid (H3cpta) and 2-(3,5-dicarboxylatobenzyloxy)benzoic acid (H3dbba), were used as unexplored and highly ...versatile building blocks for the hydrothermal generation of a novel series of cadmium(ii) metal-organic architectures. These were formulated as Cd(μ-Hcpta)(phen)(py)n (1), {Cd3(μ5-cpta)2(phen)3·8H2O}n (2), {Cd3(μ5-cpta)2(2,2'-bipy)3·6H2O}n (3), {Cd(μ3-cpta)(Hbpa)·2H2O}n (4), {Cd6(μ4-cpta)2(μ6-cpta)2(H2biim)2(H2O)6·5H2O}n (5), Cd3(μ4-cpta)2(μ-prz)(H2O)4n (6), {Cd3(μ4-dbba)2(phen)3·H2O}n (7), and {Cd3(μ3-dbba)2(2,2'-bipy)3(H2O)3·2H2O}n (8) on the basis of single-crystal X-ray diffraction, elemental analysis, FTIR, PXRD, and TGA data. Products 1-8 were assembled in the presence of N-donor crystallization mediators selected from pyridine (py), 1,10-phenanthroline (phen), 2,2'-bipyridine (2,2'-bipy), bis(4-pyridyl)amine (bpa), 2,2'-biimidazole (H2biim), or piperazine (prz). The nature of the crystallization mediator and/or the type of principal tricarboxylate building block have a significant effect on the structural diversity, dimensionality, and topology of the resulting cadmium-organic architectures. These span from 1D (1, 8) and 2D (7) coordination polymers to 3D metal-organic frameworks (2-6) with intricate topologies (3,4,5T64 in 2 and 3, utp (103)-d in 4, 3,4,4T9 in 6) that also include unprecedented types in 5 and 7. Besides, MOF 6 features a 3D + 3D two-fold interpenetrated framework. Luminescent and photocatalytic properties of selected materials were investigated, showing that coordination polymer 7 is a promising photocatalyst for the UV-light-driven degradation of methylene blue as a model organic dye pollutant. Moreover, products 7 and 8 are the first examples of structurally characterized coordination compounds derived from H3dbba.
The infant's gut microbiome is generally rich in the
genus. The mother's milk contains natural prebiotics, called human milk oligosaccharides (HMOs), as the third most abundant solid component after ...lactose and lipids, and of the different gut microbes, infant gut-associated bifidobacteria are the most efficient in assimilating HMOs. Indeed, the fecal concentration of HMOs was found to be negatively correlated with the fecal abundance of
in infants. Given these results, two HMO molecules, 2'-fucosyllactose and lacto-
-
tetraose, have recently been industrialized to fortify formula milk. As of now, however, our knowledge about the HMO consumption pathways in infant gut-associated bifidobacteria is still incomplete. The recent studies indicate that HMO assimilation abilities significantly vary among different
species and strains. Therefore, to truly maximize the effects of prebiotic and probiotic supplementation in commercialized formula, we need to understand HMO consumption behaviors of bifidobacteria in more detail. In this review, we summarized how different
species/strains are equipped with varied gene sets required for HMO assimilation. We then examined the correlation between the abundance of the HMO-related genes and bifidobacteria-rich microbiota formation in the infant gut through data mining analysis of a deposited fecal microbiome shotgun sequencing dataset. Finally, we shortly described future perspectives on HMO-related studies.
This paper examines the theory of kernel Fisher discriminant analysis (KFD) in a Hilbert space and develops a two-phase KFD framework, i.e., kernel principal component analysis (KPCA) plus Fisher ...linear discriminant analysis (LDA). This framework provides novel insights into the nature of KFD. Based on this framework, the authors propose a complete kernel Fisher discriminant analysis (CKFD) algorithm. CKFD can be used to carry out discriminant analysis in "double discriminant subspaces." The fact that, it can make full use of two kinds of discriminant information, regular and irregular, makes CKFD a more powerful discriminator. The proposed algorithm was tested and evaluated using the FERET face database and the CENPARMI handwritten numeral database. The experimental results show that CKFD outperforms other KFD algorithms.
Rechargeable silicon anode lithium ion batteries (SLIBs) have attracted tremendous attention because of their merits, including a high theoretical capacity, low working potential, and abundant ...natural sources. The past decade has witnessed significant developments in terms of extending the lifespan and maintaining high capacities of SLIBs. However, the detrimental issue of low initial Coulombic efficiency (ICE) toward SLIBs is causing more and more attention in recent years because ICE value is a core index in full battery design that profoundly determines the utilization of active materials and the weight of an assembled battery. Herein, a comprehensive review is presented of recent advances in solutions for improving ICE of SLIBs. From design perspectives, the strategies for boosting ICE of silicon anodes are systematically categorized into several aspects covering structure regulation, prelithiation, interfacial design, binder design, and electrolyte additives. The merits and challenges of various approaches are highlighted and discussed in detail, which provides valuable insights into the rational design and development of state‐of‐the‐art techniques to deal with the deteriorative issue of low ICE of SLIBs. Furthermore, conclusions and future promising research prospects for lifting ICE of SLIBs are proposed at the end of the review.
The issue of low initial Coulombic efficiency (ICE) in Si anodic lithium ion batteries (LIBs) (SLIBs) is attracting more and more attention in recent years. This review first systematically summarizes the recent progress on the improvement of ICE of SLIBs from different viewpoints. Herein, new insights and useful guidance for designing Si anode based LIBs with better overall performances are provided.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
The ammonia synthesis from nitrogen and water under ambient conditions is one of the most inviting but challenging reaction routes. Although nitrogen is abundant in the atmosphere and the ammonia ...synthesis reaction is exothermic on the thermodynamics, the conversion of N
2
to ammonia is actually hard to proceed owing to the chemical inertness and stability of N
2
molecules. In industry, ammonia synthesis is carried out by the Haber-Bosch process under harsh conditions (300–500 °C, 20–30 MPa) associated with the requirement of substantial energy input and the enormous emission of greenhouse gases (e.g., CO
2
). Recently, a growing number of studies on photo(electro)catalytic and electrocatalytic nitrogen reduction reaction (NRR) in aqueous solution have attracted extensive attention, which holds great promise for nitrogen fixation under room temperature and atmospheric pressure. However, the very low efficiency and ambiguous mechanism still remain as the major hurdles for the development of photochemical and electrochemical NRR systems. Here we provide an overview of the latest progresses, remaining challenges and future prospects in photocatalytic and electrocatalytic nitrogen fixation. Moreover, this review offers a helpful guidance for the reasonable design of photocatalysts and electrocatalysts towards NRR by combining theory predictions and experiment results. We hope this review can stimulate more research interests in the relatively understudied but highly promising research field of NRR.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Palladium-catalyzed enantioselective C(sp
)-H activation of ferrocenyl ketones is achieved through utilizing catalytic, inexpensive l-tert-leucine as a chiral transient directing group. The ...transformation allows rapid access to ferrocene scaffolds simultaneously possessing planar- and stereogenic central chirality, widely applied in the ferrocene-based chiral ligand families.
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