Topic
Chemical binding
About: Chemical binding is a research topic. Over the lifetime, 1822 publications have been published within this topic receiving 52516 citations.
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TL;DR: In this article, the nitrogen functional groups introduced into a carbon support appear to influence at least three aspects of the catalyst/support system: modified nucleation and growth kinetics during catalyst nanoparticle deposition, which results in smaller catalyst particle size and increased catalyst particle dispersion, increased support/catalyst chemical binding (or "tethering"), and catalyst particle electronic structure modification, which enhances intrinsic catalytic activity.
Abstract: Insufficient catalytic activity and durability are key barriers to the commercial deployment of low temperature polymer electrolyte membrane (PEM) and direct-methanol fuel cells (DMFCs). Recent observations suggest that carbon-based catalyst support materials can be systematically doped with nitrogen to create strong, beneficial catalyst-support interactions which substantially enhance catalyst activity and stability. Data suggest that nitrogen functional groups introduced into a carbon support appear to influence at least three aspects of the catalyst/support system: 1) modified nucleation and growth kinetics during catalyst nanoparticle deposition, which results in smaller catalyst particle size and increased catalyst particle dispersion, 2) increased support/catalyst chemical binding (or “tethering”), which results in enhanced durability, and 3) catalyst nanoparticle electronic structure modification, which enhances intrinsic catalytic activity. This review highlights recent studies that provide broad-based evidence for these nitrogen-modification effects as well as insights into the underlying fundamental mechanisms.
584 citations
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TL;DR: This analysis will stimulate studies which will provide, for a given series of bio types, the total information on carbon gain, use, and loss, so that quantitative models can be derived relating to shortand long-term environmental influences.
Abstract: There has been considerable recent interest in the assessment of the en ergy allocation of plants (38, 50, 52). It is likely that through a quantitative understanding of how different plants gain and allocate their resources it will be possible to make predictions as to their success in any given physical envi ronment in combination with any competitor and predator. We are still far from this reality. However, as a contribution toward this goal, this review seeks to gather the available. information on the various evolutionary strate gies which plants have evolved to gain energy and to account for the numer ous ways in which this energy is utilized to meet the demands of the environ ment, as well as to successfully produce progeny. To date, studies which have considered allocation have generally been at a rather gross level-e.g., reproductive versus nonreproductive (38), roots versus shoots (117), and photosynthetic versus nonphotosynthetic tissue (86). A study by Harper & Ogden (52) has attempted, however, to account in somewhat more detail for the various sources of energy allocation. To account in more detail for energy gain in allocation and for its even tual loss through a variety of routes, the approach that will be used here is the capture of carbon by plants and its SUbsequent diversion into various products which perform a multiplicity of functions. Carbon is the vehicle by which organisms store and transfer energy by chemical binding. This device enables the utilization of a large reservoir of physiological and ecological data into a single coherent body. However, it becomes rather clear that the total information required for any given plant simply does not exist. Thus, this review unfortunately can represent only a composite picture of the gen realized routes of carbon movement in plants. It does, however, call attention to the continual partitioning of resources and the multiplicity of carbon path ways. Emphasis is placed on the modes of capture of carbon. Hopefully, this analysis will stimulate studies which will provide, for a given series of bio types, the total information on carbon gain, use, and loss, so that quantitative models can be derived relating these to shortand long-term environmental influences.
576 citations
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TL;DR: In this article, a dual-confined flexible Li-S cathode configuration was proposed by encapsulating sulfur in nitrogen-doped double-shelled hollow carbon spheres followed by graphene wrapping, which achieved a high initial discharge capacity of 1360 mA h g−1 at a current rate of C/5.
Abstract: Batteries with high energy and power densities along with long cycle life and acceptable safety at an affordable cost are critical for large-scale applications such as electric vehicles and smart grids, but is challenging. Lithium–sulfur (Li-S) batteries are attractive in this regard due to their high energy density and the abundance of sulfur, but several hurdles such as poor cycle life and inferior sulfur utilization need to be overcome for them to be commercially viable. Li–S cells with high capacity and long cycle life with a dual-confined flexible cathode configuration by encapsulating sulfur in nitrogen-doped double-shelled hollow carbon spheres followed by graphene wrapping are presented here. Sulfur/polysulfides are effectively immobilized in the cathode through physical confinement by the hollow spheres with porous shells and graphene wrapping as well as chemical binding between heteronitrogen atoms and polysulfides. This rationally designed free-standing nanostructured sulfur cathode provides a well-built 3D carbon conductive network without requiring binders, enabling a high initial discharge capacity of 1360 mA h g−1 at a current rate of C/5, excellent rate capability of 600 mA h g−1 at 2 C rate, and sustainable cycling stability for 200 cycles with nearly 100% Coulombic efficiency, suggesting its great promise for advanced Li–S batteries.
453 citations
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TL;DR: An overview of past achievements and present scenario of biosorption studies carried out on the use of some promising biosorbents which could serve as an economical means for recovering precious metals is provided in this paper.
441 citations
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TL;DR: A general phenomenon for binding of alkali and alkaline earth metal atoms with substrates is discovered, which is explained in a unified picture of chemical bonding and allows us to solve the long-standing puzzle of low Na capacity in graphite and predict the trends of battery voltages.
Abstract: It is well known that graphite has a low capacity for Na but a high capacity for other alkali metals. The growing interest in alternative cation batteries beyond Li makes it particularly important to elucidate the origin of this behavior, which is not well understood. In examining this question, we find a quite general phenomenon: among the alkali and alkaline earth metals, Na and Mg generally have the weakest chemical binding to a given substrate, compared with the other elements in the same column of the periodic table. We demonstrate this with quantum mechanics calculations for a wide range of substrate materials (not limited to C) covering a variety of structures and chemical compositions. The phenomenon arises from the competition between trends in the ionization energy and the ion–substrate coupling, down the columns of the periodic table. Consequently, the cathodic voltage for Na and Mg is expected to be lower than those for other metals in the same column. This generality provides a basis for analyzing the binding of alkali and alkaline earth metal atoms over a broad range of systems.
411 citations