Redox

About: Redox is a research topic. Over the lifetime, 26853 publications have been published within this topic receiving 862368 citations. The topic is also known as: reduction-oxidation & reduction-oxidation reaction.

The Path of Carbon in Photosynthesis

Abstract: As knowledge regarding the formation of organic compounds from carbon dioxide and other inorganic materials in green plants accumulates, it becomes increasingly apparent that it is difficult to distinguish which transformations of carbon compounds should be classified as part of the pathway of carbon in photosynthesis and which reactions should be considered as other metabolic processes of the plant. All reactions of a photoautotrophic plant rely ultimately on the energy stored by the photosynthetic process. Therefore, any definition of carbon reduction during photosynthesis based on requirement of energy or equivalents of reducing agents should specify the requirement precisely. Even so, it is questionable whether such a definition can distinguish between carbon reduction reactions of photosynthesis and other metabolic transformations of carbon compounds. It is now believed that energy-carrying compounds such as adenosine triphosphate and reducing agents such as reduced triphosphopyridine nucleotide which are formed during respiratory processes may also be formed directly from products close to the primary photochemical reactions of photosynthesis. Transformations of carbon compounds which require such substances and which take place in the dark may also occur at a greatly accelerated rate during photosynthesis. Furthermore, most, if not all, of the reactions of carbon reduction in photosynthesis are known to occur, although at a diminished rate, in the dark long after the immediate reducing and energy-carrying agents formed from the photochemical reaction have decayed.

Solvent-Dictated Lithium Sulfur Redox Reactions: An Operando UV–vis Spectroscopic Study

Abstract: Fundamental understanding of solvent's influence on Li-S redox reactions is required for rational design of electrolyte for Li-S batteries. Here we employ operando UV-vis spectroscopy to reveal that Li-S redox reactions in high-donor-number solvents, for example, dimethyl sulfoxide (DMSO), undergo multiple electrochemical and chemical reactions involving S8(2-), S6(2-), S4(2-), and S3(•-), where S3(•-) is the most stable and dominant reaction intermediate. In low-donor-number solvents, for example, 1,3-dioxolane:1,2-dimethoxyethane, the dominant reaction intermediate, is found to be S4(2-). The stability of these main polysulfide intermediates determines the reaction rates of the disproportionation/dissociation/recombination of polysulfides and thereby affects the reaction rates of the Li-S batteries. As an example, we show that dimethylformamide, a high-donor-number solvent, which exhibits stronger stabilization of S3(•-) compared with DMSO, significantly reduces Li-S cell polarization compared with DMSO. Our study reveals solvent-dependent Li-S reaction pathways and highlights the role of polysulfide stability in the efficiency of Li-S batteries.