Electrochemical oxygen evolution

Electrochemical Oxygen Evolution. Thermodynamically, the oxygen evolution reaction is favoured over the chlorine evolution reaction in aqueous solutions because the standard reversible potential is 1.23 V for the oxygen evolution reaction and 1.35 V for the chlorine evolution reaction. However, because of the slow kinetics of the oxygen evolution... 

Cheng M-J, Head-Gordon M, Bell AT. How to chemically tailor metal-porphyrin-like active sites on carbon nanotubes and graphene for minimal overpotential in the electrochemical oxygen evolution and oxygen reduction reactions. J Phys Chem C 2014 118 29482-91. 

However, the electrochemical oxygen evolution reaction (OER) from the water in acid solutions is thermodynamically slightly more favorable than the CER given by Eq. 2 (the fP value for the OER is 1.229 V). Bearing in mind that electrocatalysis essentially implies the activity and selectivity of various electrode materials toward a certain electrode reaction [2], the correct choice of electrode material that is of high electrocatalytic activity for the CER and of lower activity for the OER is of extreme importance. Anyhow, CAT is always subjected to current loss due to the OER as a side reaction. This fact sets additional demands toward the anode material for the CER, i.e., its stability toward the OER and consequently its durability in CAT. 

There are other parallel electrochemical reactions that can occur at the electrodes within the cell, lowering the overall efficiency for CIO formation. Oxygen evolution accounts for about 1—3% loss in the current efficiency on noble metal-based electrodes in the pH range 5.5—6.5. 

In normal battery operation several electrochemical reactions occur on the nickel hydroxide electrode. These are the redox reactions of the active material, oxygen evolution, and in the case of nickel-hydrogen and nickel-metal hydride batteries, hydrogen oxidation. In addition there are parasitic reactions such as the corrosion of nickel current collector materials and the oxidation of organic materials from separators. The initial reaction in the corrosion process is the conversion of Ni to Ni(OH)2. 

Dimethyl sulphoxide has also been oxidized electrochemically, using either a platinum anode or a dimensionally stable anode containing iridium and selenium in 1 M sulphuric acid solution158. The former electrode requires a potential close to that required for oxygen evolution whilst the latter needed a potential 0.5 volts lower. Thus the dimension-... 

Ezzaouia H, Heindl R, Parsons R, Tributsch H (1983) Visible light photo-oxidation of water with single-crystal RuS2 electrodes. J Electroanal Chem 145 279-292 Kiihne HM, Tributsch H (1983) Oxygen evolution from water mediated by infrared light on iron doped RuS2 electrodes. J Electrochem Soc 130 1448-1450... 

When the layer has electronic in addition to ionic conductivity, the electrochemical reaction will be partly or completely pushed out to its outer surface. In addition, other electrochemical reactions involving the solution components, particularly anodic oxygen evolution, can occur on top of the layer. 

In this section we treat some electrochemical reactions at interfaces with solid electrolytes that have been chosen for both their technological relevance and their scientific relevance. The understanding of the pecularities of these reactions is needed for the technological development of fuel cells and other devices. Investigation of hydrogen or oxygen evolution reactions in some systems is very important to understand deeply complex electrocatalytic reactions, on the one hand, and to develop promising electrocatalysts, on the other. 

Oxides of Platinum Metals Anodes of platinum (and more rarely of other platinum metals) are used in the laboratory for studies of oxygen and chlorine evolution and in industry for the synthesis of peroxo compounds (such as persulfuric acid, H2S2O8) and organic additive dimerization products (such as sebacic acid see Section 15.6). The selectivity of the catalyst is important for all these reactions. It governs the fraction of the current consumed for chlorine evolution relative to that consumed in oxygen evolution as a possible parallel reaction it also governs the current yields and chemical yields in synthetic electrochemical reactions. 

The character of the oxide layers influences the kinetics and mechanism of the electrochemical reactions occurring on the platinum anode surface. The relation between the rate of oxygen evolution and oxide layer thickness is complex. In the region where the a-oxides exist, the reaction rate decreases with increasing oxide layer thickness. In the region where the P-oxides exist, the reaction rate depends little on oxide layer thickness or, according to some data, increases with increasing oxide layer thickness. 

M. Faraday was the first to observe an electrocatalytic process, in 1834, when he discovered that a new compound, ethane, is formed in the electrolysis of alkali metal acetates (this is probably the first example of electrochemical synthesis). This process was later named the Kolbe reaction, as Kolbe discovered in 1849 that this is a general phenomenon for fatty acids (except for formic acid) and their salts at higher concentrations. If these electrolytes are electrolysed with a platinum or irridium anode, oxygen evolution ceases in the potential interval between +2.1 and +2.2 V and a hydrocarbon is formed according to the equation... 

Lodi, G., Sivieri, E., Debattisti, A., and Trasatti, S., Ruthenium dioxide-based film electrodes. III. Effect of chemical composition and surface morphology on oxygen evolution in acid solutions, /. Appl. Electrochem., 8, 135, 1978. 

Another factor contributing to higher profitability is the fact that should the electrochemical side-reaction of oxygen evolution is reduced by about 1%, the... 

At IREQ, besides the participation in the field tests run by the engineers of Hydro-Quebec (12), the main effort has been to tackle fundamental problems in the field of electrocatalysis (18-22) and of anodic oxidation of different potential fuels (23-26). A careful and extensive study of the electrochemical properties of the tungsten bronze has been carried out (18-20) the reported activity of these materials in acid media for the oxygen reduction could not be reproduced and this claim by other workers has been traced back to some platinum impurities in the electrodes. Some novel techniques in the area of electrode preparation are also under study (21,22) the metallic deposition of certain metals on oriented graphite show some interesting catalytic features for the oxygen reduction and also for the oxygen evolution reaction. 

Akikusa J, Khan SUM (1997) Photo response and AC impedance characterization of n-Ti02 during hydrogen and oxygen evolution in an electrochemical cell. Int J Hydrogen Energy 22 875-882... 

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