Robert J. Rees

Lithium–sulfur batteries—the solution is in the electrolyte, but is the electrolyte a solution?

At first glance, the combination of the lightest, most electropositive metal (lithium) with a safe, abundant (and reasonably light) non-metal (sulfur) makes good sense as a prospective battery. However, while the lithium–sulfur battery offers a very high theoretical specific energy (∼2600 W h kg−1) the actual performance delivered is proving to be severely limited—in many cases, this is directly related to the role of the electrolyte. The fundamental issue is that the reduction of sulfur proceeds through a series of polysulfide species, which are for the most part soluble in common organic solvents, including those employed in battery electrolyte solutions. So, despite the fact that the ultimate product (Li2S) is essentially insoluble, the intermediate stages of discharge see a migration of redox-active species out of the cathode, from where they can react with the lithium anode, which sets in train a series of equilibria that cause both a loss of charging efficiency and a gradual loss of discharge capacity. In the last decade, a major stream of the research to overcome this complex situation has focused on minimizing the solubility of polysulfides. From this we now have a range of media in which the lithium–sulfur system can operate with much improved charge–discharge characteristics: ionic liquids (and blends with organic media); super-saturated salt-solvent mixtures; polymer-gelled organic media; solid polymers; solid inorganic glasses. Underlining the multi-faceted nature of interactions within the lithium–sulfur cell, though, none of these improved electrolytes has been able to bring the performance of this system up to the levels of reliability and capacity maintenance (without sacrificing high specific energy) that are benchmarks in energy storage applications. Our survey indicates that only by combining particular electrolytes with cathode materials that are designed to actively retain sulfur and its reduction products, have a relatively few studies been able to obtain the desired levels of performance. Ultimately the successful development of the lithium–sulfur battery requires careful coordination of the choice of modified electrolyte with the specific nature of the cathode material, underpinned by the assumption that the resulting electrolyte composition will meet established criteria for compatibility with the lithium anode.

Computational Modeling and Simulation of CO2 Capture by Aqueous Amines

We review the literature on the use of computational methods to study the reactions between carbon dioxide and aqueous organic amines used to capture CO2 prior to storage, reuse, or sequestration. The focus is largely on the use of high level quantum chemical methods to study these reactions, although the review also summarizes research employing hybrid quantum mechanics/molecular mechanics methods and molecular dynamics. We critically review the effects of basis set size, quantum chemical method, solvent models, and other factors on the accuracy of calculations to provide guidance on the most appropriate methods, the expected performance, method limitations, and future needs and trends. The review also discusses experimental studies of amine-CO2 equilibria, kinetics, measurement and prediction of amine pKa values, and degradation reactions of aqueous organic amines. Computational simulations of carbon capture reaction mechanisms are also comprehensively described, and the relative merits of the zwitterion, termolecular, carbamic acid, and bicarbonate mechanisms are discussed in the context of computational and experimental studies. Computational methods will become an increasingly valuable and complementary adjunct to experiments for understanding mechanisms of amine-CO2 reactions and in the design of more efficient carbon capture agents with acceptable cost and toxicities.

How Dirhodium Catalyst Controls the Enantioselectivity of [3 + 2]-Cycloaddition between Nitrone and Vinyldiazoacetate: A Density Functional Theory Study.

The origin of enantioselectivity in the dirhodium-catalyzed [3 + 2]-cycloaddition of nitrone and vinyldiazoacetate has been investigated using dispersion-corrected density functional theory. Taking a more realistic account of bulky ligands in models of the dirhodium catalyst when investigating its catalytic behavior is crucial for describing the effects resulting from a high level of asymmetric induction. More than one active site can be located and the extra reactivity is provided by an electron-donation interaction between the substrate and an additional Rh2L4 catalyst.

The use of analytic continuation to increase the accuracy in modelling fluid–surface interactions in cylindrical nanopores

In this paper, the mathematical formulation of a rigid/smooth-walled semi-empirical fluid–surface interaction potential is discussed. Potentials of this type may be used to model the adsorption of simple fluids in cylindrical nanopores, for example, cavities in a solid material or free standing single- or multi-wall nanotubes. Analysis of the properties of the hypergeometric series functions used to evaluate these potentials indicates that modelling of the fluid–surface interactions for particles very near to the surface is improved with analytically continuous series. The derivation and implementation of a potential representing a cylindrical cavity within a continuous solid material are also presented.

Guest Editorial Introduction

Pope Benedict XVI recently invited Christian believers and theologians to interrogate research on the historical Jesus with the question, “What has Jesus really brought . . . if he has not brought world peace, universal prosperity, and a better world?” The “great question” driving Benedict’s study Jesus of Nazareth (2007) emerges from his confrontation with the charge that Jesus “can hardly be the true Messiah,” since the kingdom of God that biblical exegetes tell us he claimed to inaugurate has “not brought world peace” or “conquered the world’s misery.” This query places the Gospel accounts of the life, death, and resurrection of Jesus Christ in a hermeneutical circle with the hopes and the tragedies of humankind at the dawn of a new millennium. What does Jesus offer to the half of humanity that struggles for life in the face of grinding poverty? to those whose very culture and human dignity are under assault by predatory forms of globalization? to the innocent who yearn for peace amidst endless wars “of choice” like the recent conflagration in Iraq? and to the billions living in the shadow of looming planetary environmental crisis? In this special issue of Theological Studies Catholic theologians from Africa, Asia, Central America, Europe, South America, and the United States respond to the pope’s invitation, focusing on the significance for Christian churches and communities of faith around the globe of what we learned about Jesus of Galilee. This project emerged from events leading up to the 40th anniversary of the option for the poor embraced by the bishops of Latin America at Medellı́n (1968), and the 30th anniversary of Virgilio Elizondo’s groundbreaking dissertation (1978) on the Galilean Jesus in Mexican

The science and life of Ian K. Snook

In your life, you are fortunate indeed to be able to count a close friend as someone who has been your teacher and mentor; Ian Snook was such a friend. He was a talented and internationally recognized scientist, lecturer and research advisor; it was however, Ian’s generosity, humour and above all his humility that those of us privileged to know him most admired. In every sense, Ian was a lateral and innovative thinker. He had considerable and adaptable skills in pure and applied mathematics, which he employed often and with great success in both developing computational methods and condensed matter theory. One only need read his monograph on the application of the Langevin and Generalised Langevin equations to the dynamics of atomic and complex fluids to recognise his mathematical prowess. His skill in recognizing geometrical patterns and resolving them through innovative mathematical methods enabled him to tackle many difficult problems in the area of colloid physics (in the early years) through to nanoscience (more recently). We will not attempt here to describe in detail Ian’s life but will refer the reader to a website dedicated to him iansnook.com