Potential electrocatalyst

To circumvent the problem of methanol crossover in direct oxidation fuel cells, there has been continued effort to identify potential electrocatalysts for oxygen reduction which are insensitive to methanol oxidation, such as metal... 

Zellner MB, Chen JG (2005) Surface science and electrochemical studies of WC and W2C PVD films as potential electrocatalysts. Catal Today 99 299-305... 

In this paper, the electrochemical reduction of cobalt and nickel complexes of the ligand N,N -l,2-phenylenebis(salicylideneiminato] (salophen = L) and its relation to the electrochemical activation of CO2 is discussed. These complexes have been investigated as potential electrocatalysts of CO2 reduction. Indeed, cobalt and nickel complexes containing tetraazamacrocycles or tetradentate Schiff base ligands have been recognized as powerful catalysts in the electrochemical reduction of CO2 [4,5]. Bifunctional fixation of CO2 by nucleophilic CofQ-Schiff base complexes assisted by alkali cations coordinated to the same ligand has oeen reported [6. ... 

CO2 reduction. Therefore, they are potential electrocatalysts for the reduction of CO2 (see Scheme 9.16). Two electrons are transferred from the electrode to the active site (buried inside the insulating protein interior) by the iron-sulfur clusters, to reduce CO2 to formate, forming a C-H bond. Conversely, when formate is oxidized, the two electrons are transferred from the active site to the electrode. 

Fashedemi OO, Ozoemena KI (2011) A facile approach to the synthesis of hydrophobic iron tetrasulfophthalocyanine (FeTSPc) nano-aggregates on multi-walled carbon nanotubes a potential electrocatalyst for the detection of dopamine. Sens Acmators B 160 7-16... 

In recent years, much attention has been focused on electrochemical studies of metalloporphyrins, not only as mimetic compounds of the iron porphyrin unit in heme proteins but also as potential electrocatalysts . Metalloporphyrins have been found to be applicable in both homogeneous and heterogeneous catalysis - and, because oxygen can be reduced directly through a 4-electron pathway on some transition metal porphyrins, catalysis in the heterogeneous electrochemical oxygen reduction reaction has received particular attention The application of metalloporphyrins to heterogeneous electrocatalysis requires their attachment to solid electrodes which can be realized based on chemisorption, chemical reactions with previously functionalized electrodes, chemical reactions with a functionalized polymer, incorporation of the porphyrin with the polymer film and electrochemical polymerization. 

In acid electrolytes, carbon is a poor electrocatalyst for oxygen evolution at potentials where carbon corrosion occurs. However, in alkaline electrolytes carbon is sufficiently electrocatalytically active for oxygen evolution to occur simultaneously with carbon corrosion at potentials corresponding to charge conditions for a bifunctional air electrode in metal/air batteries. In this situation, oxygen evolution is the dominant anodic reaction, thus complicating the measurement of carbon corrosion. Ross and co-workers [30] developed experimental techniques to overcome this difficulty. Their results with acetylene black in 30 wt% KOH showed that substantial amounts of CO in addition to C02 (carbonate species) and 02, are... 

In redox flow batteries such as Zn/Cl2 and Zn/Br2, carbon plays a major role in the positive electrode where reactions involving Cl2 and Br2 occur. In these types of batteries, graphite is used as the bipolar separator, and a thin layer of high-surface-area carbon serves as an electrocatalyst. Two potential problems with carbon in redox flow batteries are (i) slow oxidation of carbon and (ii) intercalation of halogen molecules, particularly Br2 in graphite electrodes. The reversible redox potentials for the Cl2 and Br2 reactions [Eq. (8) and... 

Electrochemical promotion or NEMCA is the main concept discussed in this book whereby application of a small current (1-104 pA/cm2) or potential ( 2 V) to a catalyst, also serving as an electrode (electrocatalyst) in a solid electrolyte cell, enhances its catalytic performance. The phenomenology, origin and potential practical applications of electrochemical promotion, as well as its similarities and differences with classical promotion and metal-support interactions, is the main subject of this book. 

Reaction products can also be identified by in situ infrared reflectance spectroscopy (Fourier transform infrared reflectance spectroscopy, FTIRS) used as single potential alteration infrared reflectance spectroscopy (SPAIRS). This method is suitable not only for obtaining information on adsorbed products (see below), but also for observing infrared (IR) absorption bands due to the products immediately after their formation in the vicinity of the electrode surface. It is thus easy to follow the production of CO2 versus the oxidation potential and to compare the behavior of different electrocatalysts. 

The mechanism of electrooxidation of methanol is now nearly well understood. From the considerable effort made during the past 20 years, it is now possible to propose electrocatalysts with acceptable activities for DMFCs, even though further improvement is still necessary. Despite considerable research efforts, R-Ru alloys are the only acceptable catalysts for the electrooxidation of methanol at low anode potentials. Two questions still remain unanswered ... 

Investigations at Siemens in Erlangen, Germany, have used unsupported platinum-ruthenium anodes (4 mg/cm ) and platinum black cathodes (4 mg/cm ). Their best performances were 0.52 V at 400 mA/cml At Los Alamos National Laboratory in New MexicoJ the electrocatalyst was unsupported R-RuOx at the anode and unsupported R black at the cathode (R loading about 2 mg/cm ). In a subsequent study, the thinner Nafion 112 membrane was used to reduce the ohmic drop. Under pressure at 400 mA/cm cell potentials of 0.57 V with Oj and 0.52... 

Table 4 and Fig. 18 illustrate the performance levels achieved by the active players in DMFC R D. The main goal in DMFC research in the U.S. and European programs is to achieve a stable performance level of 200 mW/cm at a cell potential of 0.5 to 0.6 V. It is because of the relatively low activity of the electrocatalyst for methanol electrooxidation that this power level is less than half that of a PEMFC with Hj as a fuel. A higher power level of the DMFC is essential for a transportation application, but the present power level goal is quite adequate for small portable power sources. 

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%. 

Kinoshita K, Lundquist JT, Stonehart P. 1973. Potential cychng effects on platinum electrocatalyst surfaces. J Electroanal Chem 48 157-166. 

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