scholarly journals INFLUENCE OF ELECTRICAL CONNECTION BETWEEN METAL ELECTRODES ON CONTIGUOUS SOLUTE-FREE ZONES

2013 ◽  
Vol 4 (1) ◽  
Author(s):  
Binghua Chai ◽  
Amrita G. Mahtani ◽  
Gerald H. Pollack
Keyword(s):  
Metal Surfaces ◽  
Aqueous Media ◽  
Exclusion Zone ◽  
Metal Electrodes ◽  
Electrical Connection ◽  
Underlying Mechanisms

Earlier, we reported solute-free “exclusion zones” in aqueous media next to various metal surfaces. Here we explore the effect of connecting zinc, which ordinarily shows a large exclusion zone, to platinum, which ordinarily does not. We found the connecting the two metals diminished the exclusion zone next to zinc, while it increased the exclusion zone next to platinum. Disconnecting resulted in return to control values. These effects were largest when the metals were juxtaposed relatively closely, and became smaller with increasing separation. The underlying mechanisms are considered.

The importance of the active states of surface atoms with regard to the electrocatalytic behaviour of metal electrodes in aqueous media

2000 ◽  
Vol 45 (25-26) ◽  
pp. 4127-4134 ◽  
Author(s):  
L.D Burke ◽  
J.A Collins ◽  
M.A Horgan ◽  
L.M Hurley ◽  
A.P O'Mullane
Keyword(s):  
Aqueous Media ◽  
Metal Electrodes ◽  
Electrocatalytic Behaviour

scholarly journals Formation of negative ions at metal surfaces

1938 ◽  
Vol 168 (932) ◽  
pp. 19-42 ◽  
Keyword(s):  
Kinetic Energy ◽  
Metal Surfaces ◽  
Neutral Atom ◽  
Negative Ions ◽  
Excess Energy ◽  
Negative Ion ◽  
Initial Kinetic Energy ◽  
Theoretical Treatment ◽  
Metal Electrodes ◽  
Recent Experimental Work

In a previous paper (Massey and Smith 1936) a theoretical treatment of various processes of formation of negative ions in gases has been given. The recent experimental work of Arnot (1936, 1937) has, however, shown the importance of formation taking place at the surface of metal electrodes. The purpose of this paper is to give a theoretical treatment of the formation of negative ions at metal surfaces and to indicate where further experimental research is necessary in order to understand more fully the processes taking place. When a neutral atom captures an electron to form a negative ion, excess energy equal to the sum of the initial kinetic energy of the electron and the electron affinity of the atom must be disposed of. The method of disposal largely determines the probability with which a process will take place. These processes may be divided into two classes, radiative and non-radiative. In the former the excess energy is given off as radiation.

scholarly journals Adsorbed Cobalt Porphyrins Act like Metal Surfaces in Electrocatalysis

2021 ◽  
Author(s):  
Corey J. Kaminsky ◽  
Sophia Weng ◽  
Joshua Wright ◽  
Yogesh Surendranath
Keyword(s):  
Electron Transfer ◽  
Metal Surfaces ◽  
Active Sites ◽  
Aqueous Media ◽  
Modified Electrodes ◽  
Outer Sphere ◽  
Carbon Electrodes ◽  
H2 Evolution ◽  
Reaction Sequence ◽  
Substrate Activation

Carbon electrodes chemically modified with molecular active sites are potent catalysts for key energy conver-sion reactions. Generally, it is assumed that these molecularly modified electrodes operate by the same redox mediation mechanisms observed for soluble molecules, in which electron transfer and substrate activation occur in separate elementary steps. Here, we uncover that, depending on the solvent, carbon-bound cobalt porphyrin can carry out electrolysis by the non-mediated mechanisms of metal surfaces in which electron transfer and substrate activation are concerted. We chemically modify glassy carbon electrodes with cobalt tetraphenylpor-phyrin units that are anchored by flexible aliphatic linkages to form CH-CoTPP. In acetonitrile, CH-CoTPP dis-plays a clear outer-sphere Co(II/I) process which catalyzes the H2 evolution reaction by a step-wise, redox-mediated reaction sequence. In contrast, clear surface redox waves are not observed for CH-CoTPP in aqueous media and H2 evolution proceeds via a non-mediated, concerted proton-electron transfer reaction sequence over a wide pH range. The data suggest that, in aqueous electrolyte, the CoTPP fragments reside inside the electro-chemical double layer and are electrostatically coupled to the surface. This coupling allows CH-CoTPP to carry out catalysis without being pinned to the redox potential of the molecular fragment. These studies highlight that the simple adsorption of molecules can lead to reaction mechanisms typically reserved for metal surfaces, ex-posing new principles for the design of molecularly-modified electrodes.

scholarly journals Effect of Humid Air Exposed to IR Radiation on Enzyme Activity

2022 ◽  
Vol 23 (2) ◽  
pp. 601
Author(s):  
Olga I. Yablonskaya ◽  
Vladimir L. Voeikov ◽  
Kirill N. Novikov ◽  
Ekaterina V. Buravleva ◽  
Valeriy A. Menshov ◽  
...  
Keyword(s):  
Aqueous Media ◽  
Radiant Energy ◽  
Chemical Properties ◽  
Infrared Light ◽  
Heat Inactivation ◽  
Electromagnetic Spectrum ◽  
Exclusion Zone ◽  
Humid Air ◽  
Ir Radiation ◽  
Partial Unfolding

Water vapor absorbs well in the infra-red region of the electromagnetic spectrum. Absorption of radiant energy by water or water droplets leads to formation of exclusion zone water that possesses peculiar physico-chemical properties. In the course of this study, normally functioning and damaged alkaline phosphatase, horseradish peroxidase and catalase were treated with humid air irradiated with infrared light with a wavelength in the range of 1270 nm and referred to as coherent humidity (CoHu). One-minute long treatment with CoHu helped to partially protect enzymes from heat inactivation, mixed function oxidation, and loss of activity due to partial unfolding. Authors suggest that a possible mechanism underlying the observed effects involves altering the physicochemical properties of aqueous media while treatment of the objects with CoHu where CoHu acts as an intermediary.

Electrocatalytic process of CO selectivity in electrochemical reduction of CO2 at metal electrodes in aqueous media

1994 ◽  
Vol 39 (11-12) ◽  
pp. 1833-1839 ◽  
Author(s):  
Yoshio Hori ◽  
Hidetoshi Wakebe ◽  
Toshio Tsukamoto ◽  
Osamu Koga
Keyword(s):  
Electrochemical Reduction ◽  
Aqueous Media ◽  
Metal Electrodes ◽  
Reduction Of Co2

scholarly journals Adsorbed Cobalt Porphyrins Act like Metal Surfaces in Electrocatalysis

2021 ◽  
Author(s):  
Corey Kaminsky ◽  
Sophia Weng ◽  
Joshua Wright ◽  
Yogesh Surendranath
Keyword(s):  
Electron Transfer ◽  
Metal Surfaces ◽  
Active Sites ◽  
Aqueous Media ◽  
Modified Electrodes ◽  
Outer Sphere ◽  
Carbon Electrodes ◽  
H2 Evolution ◽  
Reaction Sequence ◽  
Substrate Activation

Abstract Carbon electrodes chemically modified with molecular active sites are potent catalysts for key energy conversion reactions. Generally, it is assumed that these molecularly modified electrodes operate by the same redox mediation mechanisms observed for soluble molecules, in which electron transfer and substrate activation occur in separate elementary steps. Here, we uncover that, depending on the solvent, carbon-bound cobalt porphyrin can carry out electrolysis by the non-mediated mechanisms of metal surfaces in which electron transfer and substrate activation are concerted. We chemically modify glassy carbon electrodes with cobalt tetraphenylporphyrin units that are anchored by flexible aliphatic linkages to form CH-CoTPP. In acetonitrile, CH-CoTPP displays a clear outer-sphere Co(II/I) process which catalyzes the H2 evolution reaction by a step-wise, redox-mediated reaction sequence. In contrast, clear surface redox waves are not observed for CH-CoTPP in aqueous media and H2 evolution proceeds via a non-mediated, concerted proton-electron transfer reaction sequence over a wide pH range. The data suggest that, in aqueous electrolyte, the CoTPP fragments reside inside the electrochemical double layer and are electrostatically coupled to the surface. This coupling allows CH-CoTPP to carry out catalysis without being pinned to the redox potential of the molecular fragment. These studies highlight that the simple adsorption of molecules can lead to reaction mechanisms typically reserved for metal surfaces, ex-posing new principles for the design of molecularly-modified electrodes.

Highly efficient and selective photocatalytic CO2 to CO conversion in aqueous solution

2020 ◽  
Vol 56 (27) ◽  
pp. 3851-3854 ◽  
Author(s):  
Xiaomin Chai ◽  
Hai-Hua Huang ◽  
Huiping Liu ◽  
Zhuofeng Ke ◽  
Wen-Wen Yong ◽  
...  
Keyword(s):  
Aqueous Solution ◽  
Photocatalytic Performance ◽  
Aqueous Media ◽  
Highly Efficient ◽  
Co Conversion

A Co-based complex displayed the highest photocatalytic performance for CO2 to CO conversion in aqueous media.

The limits of human performance

2008 ◽  
Vol 44 ◽  
pp. 11-26 ◽  
Author(s):  
Ralph Beneke ◽  
Dieter Böning
Keyword(s):  
Human Performance ◽  
Safety Margin ◽  
Afferent Input ◽  
Metabolic Energy ◽  
Human Organism ◽  
Mechanical Resistance ◽  
As Doping ◽  
Gene And Protein Expression ◽  
Underlying Mechanisms ◽  
Biochemical Research

Human performance, defined by mechanical resistance and distance per time, includes human, task and environmental factors, all interrelated. It requires metabolic energy provided by anaerobic and aerobic metabolic energy sources. These sources have specific limitations in the capacity and rate to provide re-phosphorylation energy, which determines individual ratios of aerobic and anaerobic metabolic power and their sustainability. In healthy athletes, limits to provide and utilize metabolic energy are multifactorial, carefully matched and include a safety margin imposed in order to protect the integrity of the human organism under maximal effort. Perception of afferent input associated with effort leads to conscious or unconscious decisions to modulate or terminate performance; however, the underlying mechanisms of cerebral control are not fully understood. The idea to move borders of performance with the help of biochemicals is two millennia old. Biochemical findings resulted in highly effective substances widely used to increase performance in daily life, during preparation for sport events and during competition, but many of them must be considered as doping and therefore illegal. Supplements and food have ergogenic potential; however, numerous concepts are controversially discussed with respect to legality and particularly evidence in terms of usefulness and risks. The effect of evidence-based nutritional strategies on adaptations in terms of gene and protein expression that occur in skeletal muscle during and after exercise training sessions is widely unknown. Biochemical research is essential for better understanding of the basic mechanisms causing fatigue and the regulation of the dynamic adaptation to physical and mental training.

Sign in / Sign up

Export Citation Format

Share Document