Electrocatalysts oxides

The overpotentials for oxygen reduction and evolution on carbon-based bifunctional air electrodes for rechargeable Zn/air batteries are reduced by utilizing metal oxide electrocatalysts. Besides enhancing the electrochemical kinetics of the oxygen reactions, the electrocatalysts serve to reduce the overpotential to minimize... 

Thus indeed CH4 oxidation in a SOFC with a Ni/YSZ anode results into partial oxidation and the production of synthesis gas, instead of generation of C02 and H20 as originally believed. The latter happens only at near-complete CH4 conversion. However the partial oxidation overall reaction (3.12) is not the result of a partial oxidation electrocatalyst but rather the result of the catalytic reactions (3.9) to (3.11) coupled with the electrocatalytic reaction (3.8). From a thermodynamic viewpoint the partial oxidation reaction (3.12) is at least as attractive as complete oxidation to C02 and H20. 

Nickel oxide anodes are another example for a relatively simple oxide electrocatalyst used rather widely in the oxidation of organic substances (alcohols, amines, etc.) in alkaline solutions at relatively low anodic potentials (about +0.6 V RHE). These processes, which occur at an oxidized nickel surface, are rather highly selective. As an example, we mention the industrial oxidation of diacetone-L-sorbose to the corresponding acid in vitamin C synthesis. This reaction occurs at nickel oxide electrodes with chemical yields close to 100%. 

Chen GY, Delafuente DA, Sarangapani S, Mallouk TE. 2001. Combinatorial discovery of bifunctional oxygen reduction-water oxidation electrocatalysts for regenerative fuel cells. Catal Today 67 341-355. 

Chemical system, 32 278-283 Chemisorbed intermediates, 38 1-135 see also Oxide electrocatalysts cathodic hydrogen evolution, 38 58-66 chemical identity, 38 16-23 species from dissociative or associative chemisorption, 38 20-23 species from electrochemical discharge steps, 38 16-20... 

XAS studies of, table, 34 276 Oxide electrocatalysts, 38 122-135 atom superposition and electron delocalization molecular orbital approach, 38 133-135... 

In the case of ethanol, Pd-based electrocatalysts seem to be slightly superior to Pt-based catalysts for electro-oxidation in alkaline medium [87], whereas methanol oxidation is less activated. Shen and Xu studied the activity of Pd/C promoted with nanocrystalline oxide electrocatalysts (Ce02, C03O4, Mn304 and nickel oxides) in the electro-oxidation of methanol, ethanol, glycerol and EG in alkaline media [88]. They found that such electrocatalysts were superior to Pt-based electrocatalysts in terms of activity and poison tolerance, particularly a Pd-NiO/C electrocatalyst, which led to a negative shift of the onset potential ofthe oxidation of ethanol by ca 300 mV compared... 

A Detailed Study of Kn[Mti" (0H2)SiWn039]( -">- as Oxidation Electrocatalyst Pope and coworkers [112] were the first to identify that the chemical or electrochemical oxidation of Mn(I I) center within K [Mn"(0H2)SiWii039]( -">-yields a Mn (OH) complex rather than a Mn (O) complex. Tkn electrochemical confirmation of the formation of the complex... 

The historical development of electro-organic chemistry is well documented by several authors, e.g. in refs. 514 and 521-527, and therefore will not be repeated here. Much of the pioneering work in the field was carried out at Pt, i.e. Pt covered with an oxide film of monolayer dimensions in the case of anodic reactions. Electro-organic reactions at Pt have been analyzed in considerable detail by Conway [517] and will not be discussed here. Rather, attention will be focussed on oxide electrocatalysts and metal anodes covered with oxide films of multilayer dimensions, e.g. Ni and Pb. However, before commencing with a discussion of such oxide catalysts, some important factors in electroorganic chemistry will be briefly reviewed. 

XIX. Electronic and Structural Features of Oxide Electrocatalysts for Chlorine and Oxygen Evolution... 

Studies of perovskite and other oxide electrocatalysts continue to be of great interest [115-118]. The high activities of perovskite catalysts for the oxidation of organic substances [119,120] has stimulated related electrocatalytic studies [121-123]. Perovskites are also convenient inactive substrates for electroanalytical purposes [124]. These investigations are intrinsically related to the electrochemistry of HTSC and serve therefore to extend the circle of well-characterized electrode materials. 

Jung, S. McCrory, C. Ferrer, I. M. Peters, J. C. Jaramillo, T. F. Benchmarking Nanoparticulate Metal Oxide Electrocatalysts for the Alkaline Water Oxidation Reaction. J. Mater. Chem. A, 2015, DOI 10.1039/C5TA07586F... 

Three decades ago, Bockris et al. reported enhancement of the efficiency of methanol oxidation with a platinum-ruftienium alloy electrocatalyst. Two decades ago, another promising approach to electrocatalysis of methanol oxidation was presented. That was the platinum-ruthenium oxide electrocatalyst proposed by Watanabe and Motoo [24]. 

With regard to Eq. (9-20) a steady state coverage with NiO(OH) will be attained, i.e. continuous oxidation reaction with a continuous current flow will be observed under potentiostatic conditions. All this means that the nickel oxide catalyst is turned into a nickel oxide electrocatalyst, that can be used in electrosynthesis. The most important synthetic reactions emplo)dng such electrodes are as follows ... 

Fig. 10.1 A schematic illustration of a reversible Li-O battery, in which lithium reacts with oxygen to form lithium oxide discharge products on the surface of porous carbon electrode (with or without metal oxide electrocatalysts). Ideally, the reverse charging process is to decompose lithium oxide into Li and O2 gas...

Baturina OA, Garsany Y, Zega T, Stroud R, Schull E, Swider-Lyonsa KE (2008) Oxygen reduction reaction on platinum/tantalum oxide electrocatalysts for PEM fuel cells. J Electrochem Soc 155 B1314—B1321... 

Among the oxygen reduction catalysts, Pt, Pt-based catalyst, or Ag dispersed in carbon is the most powerful catalyst. However, there are some problems such as the cost for the material, cohesion of the metals, and deactivation from dropping out of the catalyst from the base electrode. Nano-sized perovskite-type oxide electrocatalyst, which could be synthesized by a wet chemical route, is one of the most... 

Maillard F, Gloaguen F, Leger JM. Preparation of methanol oxidation electrocatalysts ruthenium deposition on carbon-supported platinum nanoparticles. J Appl Electrochem 2003 33 1-8. 

Whitelocke, S. A. and Kalu, E. E. 2008. Catalytic activity and stabihty of tungsten oxide electrocatalyst for fuel cell apphcations. AIChE Annual Meeting Conference Proceedings, Philadelphia, PA, Nov. 16-21,2008 117/1-/8. 

Barnett SM, Goldberg KI, Mayer JM. A soluble copper-bipyridine water-oxidation electrocatalyst. Nat Chem. 2012 4 498-502. 

Benbow EM, Kelly SP, Zhao L, Reutenauer JW, Suib SL (2011) Oxygen reduction properties of bifunctional a-manganese oxide electrocatalysts in aqueous and organic electrolytes. J Phys Chem C 115(44) 22009-22017... 

Minowa H, Hayashi M, Hayashi K, Kobayashi R, Takahashi K (2013) Mn-Fe-based oxide electrocatalysts for air electrodes of lithium-air batteries. J Power Sources 244 17-22... 

Figure 4.2 Current-potential curves comparing the activity of PtRhSn02/C with that of several other catalysts for ethanol oxidation. Electrocatalyst compositions - PtRhSnOj/C ...

Electrocatalysts One can screen arrays for electrochemical activity using SECM. This rapid screening along with rapid array preparation is an excellent way to test very rapidly a large number of compositions. As described in Chapter 16, several different SECM modes can be employed. This approach has been used, for example, with oxygen reduction, water oxidation, and methanol oxidation electrocatalysts. 

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